CN114774949A

CN114774949A - Catalyst for preparing alcohol by methane electrooxidation, preparation method and application thereof

Info

Publication number: CN114774949A
Application number: CN202210584745.1A
Authority: CN
Inventors: 张伟明; 张辰; 栗文龙; 胡雪慧
Original assignee: Shanghai Shengjian Environmental System Technology Co ltd
Current assignee: Shanghai Shengjian Environmental System Technology Co ltd
Priority date: 2022-05-26
Filing date: 2022-05-26
Publication date: 2022-07-22
Anticipated expiration: 2042-05-26
Also published as: CN114774949B

Abstract

The invention discloses a catalyst for preparing alcohol by methane electrooxidation, a preparation method and application thereof, and relates to the technical field of catalysts. The catalyst for preparing alcohol by methane electrooxidation comprises a hydrogel film formed by reducing graphene oxide and zinc oxide colloid, wherein the zinc oxide colloid is dispersed in a film layer of the hydrogel film, and zirconium oxide and nickel are also loaded on the surface of the hydrogel film to obtain a non-noble metal catalyst.

Description

Catalyst for preparing alcohol by methane electrooxidation, preparation method and application thereof

Technical Field

The invention relates to the technical field of catalysts, in particular to a catalyst for preparing alcohol by methane electrooxidation, a preparation method and application thereof.

Background

The earth crust all over the world contains abundant natural gas resources, and the storage amount accounts for about 21 percent of the total energy of the earth. In recent years, unconventional natural gas resources such as shale gas and methane hydrate are continuously explored, so that natural gas becomes an ideal substitute for petroleum resources. Methane is the major component of natural gas (about 70-90% by volume). In view of the very high enthalpy of combustion (-892kJ/mol) and energy density of methane: (>1000kWh/m³) Most natural gas resources are used for heating or catalytic oxidation in fuel cells to produce electrical energy. The greenhouse effect is exacerbated by carbon dioxide emissions and methane leakage from these utilization modes. In contrast, the catalytic conversion of methane into high value-added chemical products has higher economic value and practicability.

Currently, methane thermocatalysis is the most mature methane catalytic conversion technology close to commercialization, and mainly comprises methane steam reforming, methane-carbon dioxide reforming, methane autothermal reforming, methane oxidative coupling, methane dehydroaromatization, methane conversion into olefin, aromatic hydrocarbon and hydrogen, and the like. However, the above thermal catalysis process is a high energy-consuming process involving high temperature and high pressure (700-. The product is mainly deep oxidation products such as carbon dioxide, water and the like except a small amount of short-chain olefin and aromatic hydrocarbon, and does not meet the requirement of low carbon. In contrast, the following features make electrocatalytic oxidation of methane the most promising alternative to thermocatalysis:

(1) the electric field near the electrode surface can effectively activate inert carbon-hydrogen (C-H) bonds of methane;

(2) the evolution and the regeneration of active species on the surface of the catalyst can be realized by adjusting the potential, and the reaction rate and the product selectivity are regulated and controlled;

(3) the continuous flow electrolytic cell and the membrane electrode structure are optimized, and the product selectivity and the reaction rate can be regulated and controlled from the dynamic angle;

(4) the sustainable electric power such as solar energy, wind energy, nuclear energy and the like can obviously reduce the cost of electrocatalytic oxidation.

At present, the catalyst systems for mild methane electrooxidation mainly comprise: phthalocyanine cobalt (CoPc) single-atom catalyst of acid electrolyte, acid/alkali electrolyte and noble metal catalyst of proton-transport solid electrolyteCatalysts (Pt, Au, Pd, Ru, Rh) and noble metal alloy catalysts (Pd-Cu, Pd-Ni, Pd-Mn and Pd-Au-Cu), Ni/Ni (OH) of alkaline electrolyte₂Heterojunction catalyst, composite metal oxide catalyst of neutral or alkaline electrolyte (V)₂O₅/SnO₂，Rh/NiO/V₂O₅，Rh/ZnO，TiO₂/RuO₂，TiO₂/RuO₂/V₂O₅Co-Ni spinel Co₃O₄/ZrO₂，CuO/ZrO₂，CuO/CeO₂Co-Ni spinel/ZrO₂Etc.), homogeneous catalyst (Na) for concentrated sulfuric acid electrolyte₂PtIVCl₆，PdSO₄And (V) -oxo dimer), organic mixed solvent electrolyte "tetrabutylammonium perchlorate/1, 2-difluorobenzene (TBAClO4/1, 2-DFB)" (tetramethylporphyrin rhodium ii radical: (TMP) Rh II), and the like. The electrocatalytic oxidation of methane is mainly carried out at normal temperature and normal pressure (the operating temperature of a fuel cell system based on proton transfer solid electrolyte is 50-200 ℃), and the main products are partial oxidation products with high added values, such as methanol, ethanol, n-propanol, isopropanol, acetone, formic acid, propionic acid and the like. Therefore, the mild reaction system and the effective inhibition of deep oxidation are the main advantages of the electrocatalytic oxidation of methane.

However, most of the above catalysts use precious metals (Pt, Pd, Au, Ru, Rh) as main active components or important doping aids, so that the cost of the catalyst for preparing alcohol by electrooxidation of methane is too high, and the catalyst lacks practical application value. In addition, in general, the catalyst powder is mixed with a conductive agent (carbon black or the like), a binder (Nafion solution or the like), and a solvent (water, ethanol, acetone or the like), and then the mixture is dropped on a conductive base material (carbon paper, carbon fiber cloth, glass carbon fiber, metal foam, conductive glass or the like), and performance deterioration due to the falling of an active component cannot be avoided. Therefore, the development of the catalyst for preparing alcohol by methane electrooxidation, which takes non-noble metal elements as active components, has the advantages that the matrix material is firmly connected with the active components, the deep oxidation can be effectively inhibited at room temperature, and the catalyst mainly generates products with high added values has important significance.

In view of this, the invention is particularly proposed.

Disclosure of Invention

The invention aims to provide a catalyst for preparing alcohol by methane electrooxidation and a preparation method thereof, and aims to prepare a non-noble metal catalyst for preparing alcohol by methane electrooxidation, which has high methanol/isopropanol selectivity at room temperature and can effectively inhibit deep oxidation.

Another object of the present invention is to provide a method for producing alcohol by electrooxidation of methane, which uses the above-mentioned catalyst and has the advantages of low cost and high reaction efficiency.

The invention is realized by the following steps:

in a first aspect, the invention provides a catalyst for preparing alcohol by methane electrooxidation, the catalyst consists of a hydrogel film formed by reducing graphene oxide and zinc oxide, the zinc oxide is dispersed in a film layer of the hydrogel film, and zirconia and nickel are loaded on the surface of the hydrogel film. The non-noble metal catalyst is prepared by uniformly dispersing zinc oxide between layers of a hydrogel film by using the hydrogel film formed by reducing graphene oxide and zinc oxide, and depositing zirconium oxide and nickel on the surface of the hydrogel film, and is a catalyst for preparing alcohol by methane electrooxidation, which has high methanol/isopropanol selectivity and can effectively inhibit deep oxidation at room temperature.

In an optional embodiment, the mass fraction of the reduced graphene oxide and the zinc oxide in the catalyst is 60-95%, and the mass fraction of the zirconium oxide and the nickel in the catalyst is 5-40%;

preferably, the total mass of the reduced graphene oxide and the zinc oxide is 75-85%, and the total mass of the zirconium oxide and the nickel is 15-25%;

preferably, the mass ratio of the zinc oxide to the reduced graphene oxide is 1 (0.5-50); more preferably 4:3 to 3: 4;

preferably, the mass ratio of the zirconium oxide to the nickel is 1 (4-20); more preferably 1 (4-6);

preferably, the hydrogel film is compressed by capillary action.

By optimizing the proportion of each component in the catalyst, the performance of the catalyst is favorably further improved, such as the selectivity of methanol/isopropanol is improved, and the occurrence of deep oxidation is inhibited.

In a second aspect, the present invention provides a method for preparing the catalyst of the previous embodiment, comprising:

preparing a zinc oxide-reduced graphene oxide hydrogel film by taking the reduced graphene oxide dispersion liquid and the zinc oxide colloidal solution as raw materials;

depositing zirconium oxide and nickel on the zinc oxide-reduced graphene oxide hydrogel film.

It should be noted that in the preparation method provided by the embodiment of the present invention, the hydrogel film formed by reducing graphene oxide and zinc oxide is used, so that zinc oxide is uniformly dispersed between layers of the hydrogel film, and zirconium oxide and nickel are deposited on the surface of the hydrogel film, so as to prepare a non-noble metal catalyst, and meanwhile, the catalyst is a catalyst for preparing alcohol by methane electrooxidation, which has high methanol/isopropanol selectivity at room temperature and can effectively inhibit deep oxidation.

In an alternative embodiment, the preparation process of the zinc oxide-reduced graphene oxide hydrogel film comprises: mixing the reduced graphene oxide dispersion liquid and the zinc oxide colloidal solution, and forming a hydrogel film through vacuum filtration, wherein the method for preparing the hydrogel film is simple and easy to implement;

preferably, a mixed cellulose ester microfiltration membrane is adopted for vacuum filtration;

preferably, the formed hydrogel film is peeled off the filter membrane into water to remove residual impurities.

In an alternative embodiment, the preparation process of the reduced graphene oxide dispersion comprises: uniformly mixing the graphene oxide dispersion liquid with ammonia water and hydrazine hydrate, and reacting for 0.5-4 h at 70-100 ℃;

preferably, the concentration of the graphene oxide dispersion liquid is 0.05mg/mL-0.5mg/mL, the ammonia water is an aqueous solution with the ammonia content of 25-28 wt%, the hydrazine hydrate is an aqueous solution with the hydrazine hydrate content of 80-90 wt%, the volume ratio of the ammonia water to the graphene oxide dispersion liquid is 1 (100-;

preferably, the preparation process of the graphene oxide dispersion liquid comprises the following steps: and diluting the graphene oxide with water, ultrasonically stripping, and centrifuging to remove the un-stripped part to obtain the graphene oxide dispersion liquid meeting the concentration requirement.

In the preparation process of the reduced graphene oxide dispersion liquid provided by the embodiment of the invention, the concentration and the dosage of ammonia water and hydrazine hydrate are controlled to promote the reduction of graphene oxide, so that the uniform reduced graphene oxide dispersion liquid is obtained.

In an alternative embodiment, the process for preparing a colloidal solution of zinc oxide comprises: dropwise adding a zinc salt aqueous solution into an alkaline precipitant aqueous solution, reacting for 0.5-5 h at 50-90 ℃, cooling and diluting to 0.05-0.5 mg/mL;

preferably, the concentration of the zinc salt aqueous solution is 1mM-10mM, and the mass ratio of the zinc salt to the alkaline precipitator adopted in the reaction is 1 (2-5);

preferably, the zinc salt is selected from at least one of zinc acetate dihydrate, zinc nitrate hexahydrate, zinc chloride, zinc acetylacetonate hydrate, and zinc sulfate heptahydrate;

preferably, the alkaline precipitant is selected from at least one of sodium hydroxide, potassium hydroxide and ammonia water.

According to the preparation method of the zinc oxide colloidal solution provided by the embodiment of the invention, the zinc salt aqueous solution is dropwise added into the alkaline precipitator aqueous solution to form the zinc oxide colloidal solution, and the reaction is fully performed by controlling the reaction conditions to obtain the uniform colloidal solution.

In an alternative embodiment, the zinc oxide-reduced graphene oxide hydrogel film is subjected to capillary compression prior to depositing the zirconium oxide and nickel on the zinc oxide-reduced graphene oxide hydrogel film; and performing capillary compression on the zinc oxide-reduced graphene oxide hydrogel film to improve the conductivity of the catalyst and improve the catalytic activity of the catalyst.

Preferably, the process of capillary compression comprises: soaking the zinc oxide-reduced graphene oxide hydrogel film in a mixed solution formed by water and N-methyl pyrrolidone for 8-15 h, taking out, and then vacuum-drying at 40-90 ℃ for 4-20h to compress the adhesive film; and soaking the compressed zinc oxide-reduced graphene oxide hydrogel film in water again to replace the residual NMP between layers by H2O to obtain ZnO-rGO hydrogel films with different compression degrees.

Preferably, the volume ratio of water to N-methylpyrrolidone is (0-19): 1;

more preferably, the volume ratio of water to N-methylpyrrolidone is (2-3): 1;

more preferably, the vacuum drying temperature is 50-70 ℃, and the vacuum drying time is 6-10 h.

In an alternative embodiment, the method of electrophoretic deposition is adopted to deposit zirconium oxide and nickel on the zinc oxide-reduced graphene oxide hydrogel film, the method is simple and easy to implement, and zirconium oxide and nickel with higher purity can be obtained by deposition on the zinc oxide-reduced graphene oxide hydrogel film.

Preferably, the process of electrophoretic deposition comprises: dispersing nickel salt, zirconia powder, a surfactant and a buffer in water to form a suspension, taking a zinc oxide-reduced graphene oxide hydrogel film as a cathode, and immersing the cathode and an anode in the suspension for electrophoretic deposition;

preferably, in the suspension, the concentration of the substance of nickel salt is between 0.5M and 5M, and the concentration of zirconia is between 1mg/mL and 20 mg/mL;

preferably, the surfactant is sodium dodecyl sulfate, the buffer is boric acid, the mass ratio of the zirconium oxide to the sodium dodecyl sulfate is (5-50):1, and the mass ratio of the zirconium oxide to the boric acid is 1: (0.5-5);

preferably, the nickel salt is selected from at least one of nickel chloride hexahydrate, nickel nitrate hexahydrate, nickel acetate tetrahydrate, and nickel acetylacetonate dihydrate;

preferably, the zirconia powder has an average particle size of 5nm to 20 nm;

preferably, the anode is a carbon rod.

In an optional embodiment, a direct current pulse power supply deposition method is adopted in the electrophoretic deposition process, the average current density is controlled to be 1A/dm 2-10A/dm 2, the duty ratio is 5% -95%, the pulse frequency is 50Hz-2000Hz, the stirring speed is 200rpm-1000rpm, the temperature of the suspension is 20 ℃ -90 ℃, and the deposition time is 0.5min-40 min;

preferably, the average current density is controlled to be 3A/dm 2-8A/dm 2, the duty ratio is controlled to be 40% -80%, the pulse frequency is 100Hz-1200Hz, the stirring speed is 400rpm-600rpm, the temperature of the suspension is 50 ℃ -70 ℃, and the sedimentation time is 10min-30 min. Through further controlling the parameters of the electrophoretic deposition process, the deposition of nickel carried by zirconium oxide on the cathode is facilitated.

In a third aspect, the present invention provides a method for producing alcohol by electrooxidation of methane, in which the catalyst according to any one of the above embodiments or the catalyst produced by the production method according to any one of the above embodiments is used as an electrocatalytic anode working electrode, has high methanol/isopropanol selectivity, and is effective in suppressing deep oxidation.

Preferably, a graphite carbon rod is used as a cathode counter electrode, a Saturated Calomel Electrode (SCE) is used as a reference electrode, each electrode is placed in an alkaline electrolyte of an H-shaped double-chamber electrolytic cell, methane is introduced into the alkaline electrolyte for electrocatalytic oxidation, and a constant potential reaction is carried out for 2H-4H under the condition that a potential interval is 0.5V-1.0V;

preferably, the alkaline electrolyte is selected from Na₂CO₃、K₂CO₃Any one of NaOH and KOH, the mass concentration of the alkaline electrolyte is 0.3M-1.0M;

preferably, the reaction pressure is normal pressure, the reaction temperature is room temperature, and the methane gas flow rate is 25mL/min-35 mL/min.

The embodiment of the invention has the following beneficial effects: the method comprises the steps of utilizing a hydrogel film formed by reducing graphene oxide and zinc oxide to enable the zinc oxide to be uniformly dispersed among layers of the hydrogel film, and depositing zirconium oxide and nickel on the surface of the hydrogel film to prepare a non-noble metal catalyst.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.

FIG. 1 is a ZnO-rGO hydrogel film;

FIG. 2 shows Ni-ZrO after electrophoretic deposition by DC pulse₂a/ZnO-rGO hydrogel film;

FIG. 3 Ni-ZrO in different atmospheres₂Linear sweep voltammetry when ZnO-rGO is used as a catalyst for preparing alcohol by methane electrooxidation;

FIG. 4 shows the results of tests on the methane oxidation performance of the catalysts prepared in examples 1 and 12 to 15;

FIG. 5 shows the results of the tests for methane oxidation performance of the catalysts prepared in example 1 and examples 16 to 19;

FIG. 6 shows the results of tests on the methane oxidation performance of the catalysts prepared in example 1 and examples 20 to 22;

FIG. 7 is a cyclic voltammogram of the catalyst prepared in comparative example 4.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

The embodiment of the invention provides a preparation method of a catalyst, which can be used for preparing alcohol by methane electrooxidation and comprises the following steps:

s1, preparing reduced graphene oxide dispersion liquid

Uniformly mixing the Graphene Oxide (GO) dispersion liquid with ammonia water and hydrazine hydrate, reacting for 0.5-4 h at 70-100 ℃ to obtain reduced graphene oxide (rGO) dispersion liquid, and keeping stirring in the preparation process.

In order to further control the graphene oxide to be fully reduced, the concentration of the graphene oxide dispersion liquid is 0.05mg/mL-0.5mg/mL (such as 0.05mg/mL, 0.1mg/mL, 0.2mg/mL, 0.3mg/mL, 0.4mg/mL, 0.5mg/mL), the ammonia water is an aqueous solution with the ammonia content of 25-28 wt%, the hydrazine hydrate is an aqueous solution with the hydrazine hydrate content of 80-90 wt%, and the volume ratio of the ammonia water to the graphene oxide dispersion liquid is 1: (100-1000), wherein the volume ratio of hydrazine hydrate to graphene oxide dispersion liquid is 1: (1000-10000), in the preparation process, hydrazine hydrate and ammonia raw materials are both solutions, and the dosage of the two reducing agents is far less than that of the graphene oxide dispersion liquid, so that the concentration of the prepared reduced graphene oxide dispersion liquid is about the same as that of the graphene oxide dispersion liquid.

Specifically, the preparation process of the graphene oxide dispersion liquid comprises the following steps: and diluting the graphene oxide with water, carrying out ultrasonic stripping, and then centrifuging to remove the un-stripped part to obtain the graphene oxide dispersion liquid meeting the concentration requirement.

S2 preparation of colloidal zinc oxide solution

The preparation process of the zinc oxide colloid solution comprises the following steps: and (2) dropwise adding a zinc salt aqueous solution into an alkaline precipitator aqueous solution, reacting for 0.5-5 h at 50-90 ℃, cooling and diluting to 0.05-0.5 mg/mL, wherein the diluted final concentration is approximately the same as that of the reduced graphene oxide dispersion liquid, and the mass ratio of the reduced graphene oxide to the zinc oxide can be determined by controlling the volumes of the two raw materials. Specifically, a zinc salt aqueous solution is added dropwise to an alkaline precipitant aqueous solution to generate a zinc hydroxide precipitate, and a zinc oxide colloid is formed by hydrolytic crosslinking, wherein the zinc oxide colloid is not pure zinc oxide or zinc hydroxide, but is formed by crosslinking with water.

In a preferred embodiment, the concentration of the zinc salt aqueous solution is 1mM-10mM, the mass ratio of the zinc salt to the alkaline precipitant used in the reaction is 1 (2-5), and the zinc oxide colloid is obtained by controlling the amounts of the zinc salt and the alkaline precipitant to promote the hydrolytic crosslinking.

In some embodiments, the zinc salt is selected from zinc acetate dihydrate (Zn (CH)₃COO)₂·2H₂O), zinc nitrate hexahydrate (Zn (NO)₃)₂·6H₂O), zinc chloride (ZnCl)₂) Zinc acetylacetonate hydrate (Zn (C)₅H₇O₂)₂·xH₂O) and Zinc sulfate heptahydrate (ZnSO)₄·7H₂At least one of O), mayOne or more of the above zinc salts can be used. The alkaline precipitant is selected from sodium hydroxide (NaOH), potassium hydroxide (KOH) and ammonia (NH)₃·H₂O, 25% to 28%), one or more.

S3, preparing zinc oxide-reduced graphene oxide hydrogel film

The method comprises the steps of preparing a zinc oxide-reduced graphene oxide hydrogel film by using reduced graphene oxide dispersion liquid and a zinc oxide colloidal solution as raw materials, and controlling the volume ratio of the zinc oxide colloidal solution to the reduced graphene oxide dispersion liquid to be 1 (0.5-50).

In some embodiments, the process for preparing the zinc oxide-reduced graphene oxide hydrogel film comprises: mixing the reduced graphene oxide dispersion liquid and the zinc oxide colloidal solution, and forming a hydrogel film through vacuum filtration; for example, vacuum filtration is carried out by adopting a mixed cellulose ester microfiltration membrane. After the filtration, components such as water and a solvent are filtered, and the reduced graphene oxide and the zinc oxide form a self-supporting ZnO-rGO hydrogel film on the filter membrane.

In some embodiments, the formed hydrogel film is peeled off the filter membrane, transferred to a petri dish, and immersed in deionized water to remove residual impurities.

S4, performing capillary compression on the zinc oxide-reduced graphene oxide hydrogel film

Before depositing zirconium oxide and nickel on the zinc oxide-reduced graphene oxide hydrogel film, performing capillary compression on the zinc oxide-reduced graphene oxide hydrogel film so as to improve the conductivity of the catalyst and the catalytic activity of the catalyst.

In some embodiments, the process of capillary compression comprises: soaking the zinc oxide-reduced graphene oxide hydrogel membrane in a mixed solution formed by water and N-methylpyrrolidone (NMP) for 8-15 h to completely replace water in the hydrogel membrane by the mixed solution; taking out, fixing the membrane with two cover slips, vacuum drying at 40-90 deg.C for 4-20H to remove H in mixed solvent₂O is completely volatilized, and NMP remains in the hydrogel film layer, so that the ZnO-rGO film is compressed to different degrees. Reducing the compressed zinc oxide-graphene oxide hydrogel filmSoaking in water again to remove NMP left between layers₂And replacing O again to obtain ZnO-rGO hydrogel films with different compression degrees.

It should be noted that N-methylpyrrolidone may be replaced with a conventional solvent having a viscosity greater than that of water and a volatility less than that of water.

In some embodiments, the volume ratio of water to N-methylpyrrolidone is (0-19): 1; preferably, the volume ratio of the water to the N-methylpyrrolidone is (2-3):1, the vacuum drying temperature is 50-70 ℃, and the vacuum drying time is 6-10 h. By controlling the operating parameters in the capillary compression process, the control of the compression degree is facilitated, so that the compression degree is not too large or too small, and the performance of the catalyst is further improved.

S5 deposition of zirconia and nickel

The zirconium oxide and nickel are deposited on the zinc oxide-reduced graphene oxide hydrogel film, and the specific deposition method is not limited. In some embodiments, electrophoretic deposition can be used to deposit zirconia and nickel on the zinc oxide-reduced graphene oxide hydrogel film, where nickel does not refer to an elemental form, but rather is doped with complex nickel components in a combined state.

Specifically, the process of electrophoretic deposition includes: dispersing nickel salt, zirconia powder, a surfactant and a buffer in water to form a suspension, taking a zinc oxide-reduced graphene oxide hydrogel film as a cathode, and immersing the cathode and an anode in the suspension for electrophoretic deposition. The surfactant may be, but is not limited to, sodium lauryl sulfate and the buffer may be, but is not limited to, boric acid.

In some embodiments, a nickel salt, a zirconium oxide powder, Sodium Dodecyl Sulfate (SDS), and boric acid are dispersed in water to form a suspension in which the species of the nickel salt is present in a concentration of 0.5M to 5M and the zirconium oxide is present in a concentration of 1mg/mL to 20 mg/mL; the mass ratio of the zirconium oxide to the sodium dodecyl sulfate is (5-50):1, and the mass ratio of the zirconium oxide to the boric acid is (0.5-5). The amount of raw materials is controlled to promote the deposition of nickel and zirconium oxide on the hydrogel film.

Specifically, the nickel salt is selected from at least one of nickel chloride hexahydrate, nickel nitrate hexahydrate, nickel acetate tetrahydrate and nickel acetylacetonate dihydrate, and can be one or more, and soluble nickel salts can be selected; the zirconia powder has an average particle size of 5nm-20nm and is a nano-grade powder raw material; the anode may be a carbon rod.

In some embodiments, the electrophoretic deposition process adopts a direct current pulse power source deposition method, the average current density is controlled to be 1A/dm 2-10A/dm 2, the duty ratio is 5% -95%, the pulse frequency is 50Hz-2000Hz, the stirring speed is 200rpm-1000rpm, the temperature of the suspension is 20 ℃ -90 ℃, and the deposition time is 0.5min-40 min; preferably, the average current density is controlled to be 3A/dm 2-8A/dm 2, the duty ratio is 40% -80%, the pulse frequency is 100Hz-1200Hz, the stirring speed is 400rpm-600rpm, the temperature of the suspension is 50 ℃ -70 ℃, and the deposition time is 10min-30 min. By controlling the power supply parameters in the electrophoretic deposition process, the deposition of nickel carried by zirconium oxide on the cathode is facilitated.

The embodiment of the invention also provides a catalyst for preparing alcohol by methane electrooxidation, which is prepared by the preparation method. The catalyst consists of a hydrogel film formed by reducing graphene oxide and zinc oxide, wherein the zinc oxide is dispersed in the film layer of the hydrogel film, and zirconium oxide and nickel are loaded on the surface of the hydrogel film. The catalyst does not contain noble metal, has high methanol/isopropanol selectivity at room temperature, and can effectively inhibit deep oxidation.

Further, in terms of mass fraction, the total mass percentage of the reduced graphene oxide and the zinc oxide in the catalyst is 60-95%, and the total mass percentage of the zirconium oxide and the nickel is 5-40%; preferably, the total mass ratio of the reduced graphene oxide to the zinc oxide is 75-85%, and the total mass ratio of the zirconium oxide to the nickel is 15-25%. The mass ratio of the zinc oxide to the reduced graphene oxide is 1 (0.5-50); preferably 4:3 to 3: 4; the mass ratio of the zirconium oxide to the nickel is 1 (4-20); preferably 1 (4-6). The proportion of each component in the catalyst is optimized, so that the performance of the catalyst is further improved.

The embodiment of the invention also provides a method for preparing alcohol by methane electrooxidation, which takes the catalyst as an electrocatalytic anode working electrode for electrocatalysis.

In the actual operation process, a graphite carbon rod is used as a cathode counter electrode, a Saturated Calomel Electrode (SCE) is used as a reference electrode, each electrode is placed in alkaline electrolyte (the volume of electrolyte in an anode chamber is 60mL) of an H-shaped double-chamber electrolytic cell, methane is introduced into the alkaline electrolyte for electrocatalytic oxidation, and a constant potential reaction is carried out for 2H-4H under the condition that a potential interval is 0.5V-1.0V, so that the reaction is fully carried out.

Specifically, the alkaline electrolyte is selected from Na₂CO₃、K₂CO₃Any one of NaOH and KOH, the mass concentration of the alkaline electrolyte is 0.3M-1.0M; the reaction pressure is normal pressure, the reaction temperature is room temperature, and the flow rate of methane gas is 25mL/min-35 mL/min. Ambient room temperature at atmospheric pressure is conventionally understood to be at one standard atmosphere and at a temperature of 25 ℃.

The features and properties of the present invention are described in further detail below with reference to examples.

Example 1

This example provides a method for preparing a catalyst, including the following steps:

(1) graphene oxide was prepared according to Hummers method, and deionized water was injected into the prepared graphene oxide to obtain a GO dispersion with a concentration of 0.2 mg/mL. 100mL of the GO dispersion is uniformly mixed with ammonia water and hydrazine hydrate. Wherein the volume ratio of ammonia water to GO dispersion liquid is 1:1000, the volume ratio of hydrazine hydrate to GO dispersion liquid is 1:10000, and the rGO dispersion liquid is obtained by reflux heating at 80 ℃ for 1 h.

(2) Slowly injecting the zinc acetate solution into the NaOH solution by using an injection pump, wherein the concentration of the zinc acetate in the mixed solution is 1mM, the mass concentration ratio of the zinc acetate to the NaOH is 1:4, uniformly stirring, heating at 80 ℃ for 1h to obtain a ZnO colloidal solution, and adding deionized water to dilute to the target concentration of 0.2 mg/mL.

Note: the method for measuring the concentration of the ZnO colloidal solution comprises the following steps: taking out one glass slide, weighing the glass slide to obtain a mass m₁Then, 1mL of the above ZnO colloidal solution was drawn by a pipette gun and dropped onto a slide glass. Transferring the glass slide to a 100 ℃ oven until the water is completely evaporated, and weighing the glass slide with the mass m₂The concentration of the ZnO colloidal solution is (m)₂-m₁)mg/mL。

(3) The ZnO colloidal solution and rGO dispersion (100mL) were mixed in a volume ratio of 1:1, and vacuum filtered through a mixed cellulose ester microporous membrane to form a self-supporting ZnO-rGO hydrogel membrane (as shown in FIG. 1). The membrane was peeled off the filter, transferred to a petri dish, and immersed in deionized water to remove residual impurities.

(4) Placing the ZnO-rGO hydrogel film in H₂O/NMP mixed solvent for 12H, wherein H₂The volume ratio of O to NMP was 9:1, and then the membrane was fixed using two coverslips and capillary compressed by vacuum drying at 40 ℃ for 4 h. And soaking the compressed ZnO-rGO film in deionized water for 0.5h to obtain a capillary compression ZnO-rGO hydrogel film.

(5) According to Ni (NO)₃)₂·6H₂The mass concentration of O is 1M, the concentration of nano zirconia powder is 5mg/mL, the concentration ratio of zirconia to SDS is 10:1, and the concentration ratio of zirconia to boric acid is 1: 2. And taking the capillary compressed ZnO-rGO hydrogel film as a cathode, taking a carbon rod as an anode, connecting the carbon rod to a direct current power supply, and immersing the carbon rod in the suspension for direct current pulse electrophoretic deposition. Electrophoretic deposition conditions: average current density of 3A/dm²The duty ratio is 80 percent, the pulse frequency is 1200Hz, the stirring speed is 1000rpm, the electrophoretic deposition suspension liquid is 60 ℃, the deposition time is 40min to obtain the catalyst for preparing the alcohol by methane electrooxidation and the catalyst is named as Ni-ZrO₂the/ZnO-rGO-1 (shown in FIG. 2).

And (4) performance testing: using electrode clamps to bond Ni-ZrO₂the/ZnO-rGO-1 hydrogel film is fixed as an anode working electrode. Graphite carbon rod as cathode counter electrode, Saturated Calomel Electrode (SCE) as reference electrode, and Na with concentration of 0.5M in H-type double-chamber electrolytic cell₂CO₃Alkaline electrolyte (60 mL electrolyte volume in anode chamber). Methane was passed through the cell at 30mL/min and evaluated by potentiostatic method at 0.7V (vs. SCE) for 3 h.

Description of concentration test: taking the reacted electrolyte, and determining the concentrations of methanol and isopropanol by using a gas chromatography FID detector to compare with the signal parameters of the standard substance; CO 2₂As gas phase product: introducing the tail gas after reaction into a gas chromatograph, and contrasting standard substance signal parameters by means of a gas chromatograph TCD detector to obtain the productObtaining CO₂Concentration in the tail gas. CO 2₂Concentration reaction time exhaust gas volume flow rate CO₂Generating volume of CO₂Conversion of volume to CO₂Mass (according to the "volume-mass-quantity relationship), and finally CO₂The mass is divided by the volume of the electrolytic liquid to obtain CO₂The reduced concentration.

The results show that: the methane is oxidized to methanol, isopropanol and a small amount of carbon dioxide (CO), a product of complete oxidation₂). Wherein the methanol and isopropanol concentrations are 12.61 μ g/mL and 8.23 μ g/mL respectively, and CO₂The reduced concentration was 1.73. mu.g/mL. Methanol, isopropanol and CO₂The selectivity of (A) is 46.66%, 48.70% and 4.64%, respectively, which shows that the deep oxidation product CO can be effectively inhibited₂And a high-carbon product with high added value can be obtained.

FIG. 3 shows Ni-ZrO in different atmospheres₂The linear sweep voltammogram of/ZnO-rGO as the catalyst for preparing alcohol by methane electrooxidation can be seen from figure 3: CH in the potential range of 0.55V-0.75V (vs. SCE)₄The current density under the atmosphere is obviously improved compared with that under the He atmosphere, which shows that the catalyst has methane electrooxidation activity. And potential interval greater than 0.75V (vs. SCE), CH₄The current density is reduced under the atmosphere, which can be attributed to that the methane electrooxidation reaction on the surface of the catalyst inhibits the oxygen evolution reaction. Through calculation: the methane conversion rate was 270.67. mu.g/h.

Introduction of He atmosphere in the test provided a blank by comparison with CH₄And (3) detecting whether the catalyst has oxidation activity and active potential interval on methane or not by virtue of the difference of linear scanning voltammetry curves in the atmosphere and the He atmosphere. FIG. 3 shows He atmosphere and CH₄Ni-ZrO under atmosphere₂Linear sweep voltammograms of/ZnO-rGO catalysts. Fig. 3 is explained as follows:

under He atmosphere:

potential interval of 0V-0.55V (vs. sce): no obvious current signal and no reactivity;

potential interval of 0.55V-0.75V (vs. sce): an oxidation peak is present and the following reaction occurs:

ni oxidation reaction on the surface of the catalyst:

Ni+OH-→Ni-OH_ads+e^-；

Ni-OH_ads→(OH-Ni)；

(OH-Ni)+OH-→Ni(OH)_2,ads+e^-；

Ni(OH)₂+OH-→NiOOH+H₂O+e^-；

0.75V (vs. sce): oxygen evolution reaction: 4OH- → O₂+2H₂O+4e^-。

In CH₄Under the atmosphere:

potential interval of 0.55V-0.75V (vs. sce): ni oxidation reaction on the surface of the catalyst:

Ni+OH-→Ni-OH_ads+e^-；

Ni-OH_ads→(OH-Ni)；

(OH-Ni)+OH-→Ni(OH)_2,ads+e^-；

Ni(OH)₂+OH-→NiOOH+H₂O+e^-。

the methane oxidation reaction occurs at an increased current compared to He atmosphere:

CH₄+CO₃ ^2-→CH₃OH+CO₂+2e^-(methanol);

CH₃OH+CO₃ ^2-→HCHO+CO₂+H₂O+2e^-；

CH₄+CH₃OH+CO₃ ^2-→CH₃CH₂OH+CO₂+H₂O+2e^-；

CH₃CH₂OH+CO₃ ^2-→CH₃CHO+CO₂+H₂O+2e^-；

CH₄+HCHO+CO₃ ^2-→CH₃CHO+CO₂+H₂O+2e^-；

CH₃OH+HCHO→CH₃CHO+H₂O；

CH₃CHO+CH₄→CH₃CH(OH)CH₃(isopropyl alcohol).

0.75V (vs. sce): oxygen evolution reaction: 4OH- → O₂+2H₂O+4e-；

Deep oxidation reaction of methane: CH (CH)₄+8OH-→CO₂+6H₂O+4e-。

Obviously, CH is present in the same number of transport electrons₄The deep oxidation reaction needs to consume more OH^-And the above OH^-Instead of free hydroxide anions in the electrolyte, the catalyst surface adsorbs the activated OH^-. Thus, OH is on the catalyst surface^-In the case of a limited and identical number, in the introduction of CH₄Resulting in a part of the surface OH^-Participating in CH₄Deep oxidation reactions, rather than oxygen evolution reactions, result in a reduction in the number of transferred electrons. This is in comparison with the case where the potential interval is greater than 0.75V (vs. SCE), CH₄The current density in the atmosphere was lower than that in the He atmosphere.

Example 2

(1) 100mL of GO dispersion with a concentration of 0.2mg/mL was mixed uniformly with ammonia and hydrazine hydrate. Wherein the volume ratio of ammonia water to GO dispersion liquid is 2.8:1000, the volume ratio of hydrazine hydrate to GO dispersion liquid is 5.1:10000, and the rGO dispersion liquid is obtained by reflux heating at 90 ℃ for 0.5 h.

(2) Slowly injecting the zinc acetate solution into the NaOH solution by using a syringe pump, wherein the concentration of the zinc acetate in the mixed solution is 7.5mM, the mass concentration ratio of the zinc acetate to the NaOH is 1:4, uniformly stirring, heating at 60 ℃ for 2h to obtain ZnO colloidal solution, and adding deionized water to dilute to the target concentration of 0.2 mg/mL.

(3) And (3) mixing the ZnO colloidal solution and the rGO dispersion liquid (100mL) according to the volume ratio of 2:1, and performing vacuum filtration through a mixed cellulose ester microporous filter membrane to form a self-supporting ZnO-rGO hydrogel membrane. The membrane was peeled off the filter, transferred to a petri dish and immersed in deionized water to remove residual impurities.

(4) Placing the ZnO-rGO hydrogel film in H₂In O/NMP mixed solvent for 12H, wherein H₂O to NMP volume ratio of 7:3, followed by two blocksThe membrane was fixed with a cover slip and capillary compressed by vacuum drying at 50 ℃ for 8 h. And soaking the compressed ZnO-rGO film in deionized water for 0.5h to obtain a capillary compression ZnO-rGO hydrogel film.

(5) According to Ni (NO)₃)₂·6H₂The mass concentration of O is 0.5M, the concentration of nano zirconia powder is 10mg/mL, the concentration ratio of zirconia to SDS is 20:1, and the concentration ratio of zirconia to boric acid is 1:1, and preparing electrophoresis deposition suspension. And (3) taking the ZnO-rGO hydrogel film subjected to capillary compression as a cathode, taking a carbon rod as an anode, connecting the carbon rod to a direct current power supply, and immersing the carbon rod in the suspension for direct current pulse electrophoretic deposition. Electrophoretic deposition conditions: average current density of 5A/dm²The duty ratio is 80 percent, the pulse frequency is 2000Hz, the stirring speed is 1000rpm, the electrophoretic deposition suspension liquid is 30 ℃, the deposition time is 10min to obtain the catalyst for preparing the alcohol by methane electrooxidation, and the catalyst is named as Ni-ZrO₂/ZnO-rGO-2。

And (3) performance testing: using electrode clamps to bond Ni-ZrO₂the/ZnO-rGO-2 hydrogel film is fixed as an anode working electrode. Graphite carbon rod as cathode counter electrode, Saturated Calomel Electrode (SCE) as reference electrode, and Na with concentration of 0.5M in H-type double-chamber electrolytic cell₂CO₃In an alkaline electrolyte. Methane was passed through the cell at a rate of 30mL/min and potentiostatic evaluation was carried out for 3 hours at a potential of 1.0V (vs. SCE). The results show that: the methane is oxidized to methanol, isopropanol and a small amount of carbon dioxide (CO), a product of complete oxidation₂). Wherein the methanol and isopropanol concentrations are 1.93 μ g/mL and 1.35 μ g/mL respectively, and CO₂Reduced concentration of 0.52. mu.g/mL methanol, isopropanol and CO₂Selectivity of (a) was 43.19%, 48.33%, and 8.48%, respectively calculated: the methane conversion rate was 44.75. mu.g/h.

Example 3

(1) 100mL of 0.2mg/mL GO dispersion was mixed with ammonia and hydrazine hydrate. Wherein the volume ratio of ammonia water to GO dispersion liquid is 5.6:1000, the volume ratio of hydrazine hydrate to GO dispersion liquid is 1.7:10000, and the rGO dispersion liquid is obtained by reflux heating at 100 ℃ for 2 hours.

(2) Slowly injecting the zinc acetate solution into the NaOH solution by using a syringe pump, wherein the concentration of the zinc acetate in the mixed solution is 1mM, the mass concentration ratio of the zinc acetate to the NaOH is 1:2, uniformly stirring, heating at 90 ℃ for 0.5h to obtain ZnO colloidal solution, and adding deionized water to dilute the ZnO colloidal solution to the target concentration of 0.2 mg/mL.

(3) And (3) mixing the ZnO colloidal solution and the rGO dispersion liquid (100mL) according to the volume ratio of 1:50, and performing vacuum filtration through a mixed cellulose ester microporous filter membrane to form a self-supporting ZnO-rGO hydrogel membrane. The membrane was peeled off the filter, transferred to a petri dish, and immersed in deionized water to remove residual impurities.

(4) Placing the ZnO-rGO hydrogel film in H₂In O/NMP mixed solvent for 12H, wherein H₂The volume ratio of O to NMP was 7:3, and then the membranes were fixed using two coverslips and capillary compressed by vacuum drying at 75 ℃ for 8 h. And soaking the compressed ZnO-rGO membrane in deionized water for 0.5h to obtain the capillary compression ZnO-rGO hydrogel membrane.

(5) According to Ni (NO)₃)₂·6H₂The mass concentration of O is 1M, the concentration of nano zirconia powder is 20mg/mL, the concentration ratio of zirconia to SDS is 40:1, and the concentration ratio of zirconia to boric acid is 1: 1. And taking the capillary compressed ZnO-rGO hydrogel film as a cathode, taking a carbon rod as an anode, connecting the carbon rod to a direct current power supply, and immersing the carbon rod in the suspension for direct current pulse electrophoretic deposition. Electrophoretic deposition conditions: average current density of 5A/dm²The duty ratio is 40 percent, the pulse frequency is 1200Hz, the stirring speed is 200rpm, the electrophoretic deposition suspension is 90 ℃, the deposition time is 40min to obtain the catalyst for preparing the alcohol by methane electrooxidation and the catalyst is named as Ni-ZrO₂/ZnO-rGO-3。

And (4) performance testing: using electrode clamps to bond Ni-ZrO₂the/ZnO-rGO-3 hydrogel film is fixed as an anode working electrode. Graphite carbon rod as cathode counter electrode, Saturated Calomel Electrode (SCE) as reference electrode, and Na with concentration of 0.5M in H-type double-chamber electrolytic cell₂CO₃In an alkaline electrolyte. Methane was passed through the cell at 30mL/min and evaluated by potentiostatic method at 0.5V (vs. SCE) for 3 h. The results show that: the methane is oxidized to methanol, isopropanol and a small amount of carbon dioxide (CO), a product of complete oxidation₂). Wherein the methanol and isopropanol concentrations are 4.82 μ g/mL and 3.28 μ g/mL respectively, and CO₂Reduced concentration0.35. mu.g/mL. methanol, isopropanol and CO₂Selectivity of 46.70%, 50.82% and 2.48%, respectively, was calculated: the methane conversion rate was 103.37. mu.g/h.

Example 4

(1) 100mL of GO dispersion liquid with the concentration of 0.2mg/mL is uniformly mixed with ammonia water and hydrazine hydrate, wherein the volume ratio of the ammonia water to the GO dispersion liquid is 5.6:1000, the volume ratio of the hydrazine hydrate to the GO dispersion liquid is 7:10000, and the rGO dispersion liquid is obtained by reflux heating at 80 ℃ for 1 h.

(2) Slowly injecting the zinc acetate solution into the NaOH solution by using an injection pump, wherein the concentration of the zinc acetate in the mixed solution is 5mM, the mass concentration ratio of the zinc acetate to the NaOH is 1:4.5, uniformly stirring, heating at 60 ℃ for 0.5h to obtain a ZnO colloidal solution, and adding deionized water to dilute to the target concentration of 0.2 mg/mL.

(3) And (3) mixing the ZnO colloidal solution and the rGO dispersion liquid (100mL) according to the volume ratio of 1:25, and performing vacuum filtration through a mixed cellulose ester microporous filter membrane to form a self-supporting ZnO-rGO hydrogel membrane. The membrane was peeled off the filter, transferred to a petri dish, and immersed in deionized water to remove residual impurities.

(4) Placing the ZnO-rGO hydrogel film in H₂In O/NMP mixed solvent for 12H, wherein H₂The volume ratio of O to NMP was 19:1, and then the membrane was fixed using two coverslips and capillary compressed by vacuum drying at 60 ℃ for 12 h. And soaking the compressed ZnO-rGO film in deionized water for 0.5h to obtain a capillary compression ZnO-rGO hydrogel film.

(5) According to Ni (NO)₃)₂·6H₂The mass concentration of O is 5M, the concentration of nano zirconia powder is 15mg/mL, the concentration ratio of zirconia to SDS is 50:1, and the concentration ratio of zirconia to boric acid is 3: 2. And (3) taking the ZnO-rGO hydrogel film subjected to capillary compression as a cathode, taking a carbon rod as an anode, connecting the carbon rod to a direct current power supply, and immersing the carbon rod in the suspension for direct current pulse electrophoretic deposition. Electrophoretic deposition conditions: average current density of 10A/dm²Duty ratio of 80%, pulse frequency of 1200Hz, stirring speed of 500rpm, electrophoretic deposition of suspension liquid at 60 ℃, deposition time of 10min to obtain methane electro-oxidationCatalyst for preparing alcohol and named Ni-ZrO₂/ZnO-rGO-4。

And (4) performance testing: Ni-ZrO Using electrode Clamp₂the/ZnO-rGO-4 hydrogel film is fixed as an anode working electrode. Graphite carbon rod as cathode counter electrode, Saturated Calomel Electrode (SCE) as reference electrode, and Na with concentration of 0.5M in H-type double-chamber electrolytic cell₂CO₃In an alkaline electrolyte. Methane was passed through the cell at 30mL/min and evaluated by potentiostatic method at 0.65V (vs. SCE) for 3 h. The results show that: the methane is oxidized to methanol, isopropanol and a small amount of carbon dioxide (CO), a product of complete oxidation₂). Wherein the methanol and isopropanol concentrations are 25.14 μ g/mL and 18.64 μ g/mL respectively, and CO₂Reduced concentration of 2.99. mu.g/mL, methanol, isopropanol and CO₂The selectivities of (a) were 44.01%, 52.19% and 3.80%, respectively. Through calculation: the methane conversion rate was 572.07. mu.g/h.

Example 5

(1) 100mL of GO dispersion liquid with the concentration of 0.2mg/mL is uniformly mixed with ammonia water and hydrazine hydrate, wherein the volume ratio of the ammonia water to the GO dispersion liquid is 8.4:1000, the volume ratio of the hydrazine hydrate to the GO dispersion liquid is 1:10000, and the rGO dispersion liquid is obtained by reflux heating at 70 ℃ for 3 hours.

(2) Slowly injecting the zinc acetate solution into the NaOH solution by using a syringe pump, wherein the concentration of the zinc acetate in the mixed solution is 1mM, the mass concentration ratio of the zinc acetate to the NaOH is 1:4.5, uniformly stirring, heating at 80 ℃ for 0.5h to obtain ZnO colloidal solution, and adding deionized water to dilute the ZnO colloidal solution to the target concentration of 0.2 mg/mL.

(3) And (3) mixing the ZnO colloidal solution and the rGO dispersion liquid (100mL) according to the volume ratio of 1:1, and performing vacuum filtration through a mixed cellulose ester microporous filter membrane to form a self-supporting ZnO-rGO hydrogel membrane. The membrane was peeled off the filter, transferred to a petri dish, and immersed in deionized water to remove residual impurities.

(4) Placing the ZnO-rGO hydrogel film in H₂O/NMP mixed solvent for 12H, wherein H₂The volume ratio of O to NMP was 3:7, and then the membranes were fixed using two coverslips and capillary compressed by vacuum drying at 90 ℃ for 4 h. Soaking the compressed ZnO-rGO membraneAnd (3) obtaining the capillary compression ZnO-rGO hydrogel film in deionized water for 0.5 h.

(5) According to Ni (NO)₃)₂·6H₂The mass concentration of O is 0.5M, the concentration of nano zirconia powder is 5mg/mL, the concentration ratio of zirconia to SDS is 5:1, and the concentration ratio of zirconia to boric acid is 1: 5. And (3) taking the ZnO-rGO hydrogel film subjected to capillary compression as a cathode, taking a carbon rod as an anode, connecting the carbon rod to a direct current power supply, and immersing the carbon rod in the suspension for direct current pulse electrophoretic deposition. Electrophoretic deposition conditions: average current density of 8A/dm²The duty ratio is 40 percent, the pulse frequency is 2000Hz, the stirring speed is 600rpm, the electrophoretic deposition suspension is 30 ℃, the deposition time is 20min to obtain the catalyst for preparing the alcohol by methane electrooxidation and the catalyst is named as Ni-ZrO₂/ZnO-rGO-5。

And (4) performance testing: Ni-ZrO Using electrode Clamp₂the/ZnO-rGO-5 hydrogel film is fixed as an anode working electrode. Graphite carbon rod as cathode counter electrode, Saturated Calomel Electrode (SCE) as reference electrode, and Na with concentration of 0.5M in H-type double-chamber electrolytic cell₂CO₃In an alkaline electrolyte. Methane was passed through the cell at 30mL/min and potentiostatic evaluation was carried out for 3 hours at a potential of 0.6V (vs. SCE). The results show that: the methane is oxidized to methanol, isopropanol and a small amount of carbon dioxide (CO), a product of complete oxidation₂). Wherein the methanol and isopropanol concentrations are respectively 9.51. mu.g/mL and 5.61. mu.g/mL, and CO₂The reduced concentration was 0.87. mu.g/mL. Methanol, isopropanol and CO₂Selectivity of 49.74%, 46.94% and 3.32%, respectively calculated: the methane conversion rate was 191.45. mu.g/h.

Example 6

(1) 100mL of GO dispersion liquid with the concentration of 0.2mg/mL is uniformly mixed with ammonia water and hydrazine hydrate, wherein the volume ratio of the ammonia water to the GO dispersion liquid is 5.6:1000, the volume ratio of the hydrazine hydrate to the GO dispersion liquid is 5.1:10000, and the rGO dispersion liquid is obtained by reflux heating at 90 ℃ for 2 hours.

(2) Slowly injecting the zinc acetate solution into the NaOH solution by using an injection pump, wherein the concentration of the zinc acetate in the mixed solution is 7.5mM, the mass concentration ratio of the zinc acetate to the NaOH is 1:5, uniformly stirring, heating at 50 ℃ for 3.5h to obtain a ZnO colloidal solution, and adding deionized water to dilute to the target concentration of 0.2 mg/mL.

(4) Placing the ZnO-rGO hydrogel film in H₂In O/NMP mixed solvent for 12H, wherein H₂The volume ratio of O to NMP was 7:3, and then the membrane was fixed using two coverslips and capillary compressed by vacuum drying at 50 ℃ for 12 h. And soaking the compressed ZnO-rGO film in deionized water for 0.5h to obtain a capillary compression ZnO-rGO hydrogel film.

(5) According to Ni (NO)₃)₂·6H₂The mass concentration of O is 2.5M, the concentration of nano zirconia powder is 20mg/mL, the concentration ratio of zirconia to SDS is 20:1, and the concentration ratio of zirconia to boric acid is 1: 1. And (3) taking the ZnO-rGO hydrogel film subjected to capillary compression as a cathode, taking a carbon rod as an anode, connecting the carbon rod to a direct current power supply, and immersing the carbon rod in the suspension for direct current pulse electrophoretic deposition. Electrophoretic deposition conditions: average current density of 8A/dm²The duty ratio is 95 percent, the pulse frequency is 50Hz, the stirring speed is 500rpm, the electrophoretic deposition suspension is 70 ℃, the deposition time is 20min to obtain the catalyst for preparing the alcohol by methane electrooxidation and the catalyst is named as Ni-ZrO₂/ZnO-rGO-6。

And (4) performance testing: Ni-ZrO Using electrode Clamp₂the/ZnO-rGO-6 hydrogel film is fixed as an anode working electrode. Graphite carbon rod as cathode counter electrode, Saturated Calomel Electrode (SCE) as reference electrode, and Na with concentration of 0.5M in H-type double-chamber electrolytic cell₂CO₃In an alkaline electrolyte. Methane was passed through the cell at 30mL/min and evaluated by potentiostatic method at 0.7V (vs. SCE) for 3 h. The results show that: the methane is oxidized to methanol, isopropanol and a small amount of carbon dioxide (CO), a product of complete oxidation₂). Wherein the methanol and isopropanol concentrations are 17.64. mu.g/mL and 14.29. mu.g/mL, respectively, and CO₂The reduced concentration was 2.79. mu.g/mL. Methanol, isopropanol and CO₂Has a selectivity of 41.49%, 53.75% and4.76%. calculated: the methane conversion rate was 425.81. mu.g/h.

Example 7

(1) 100mL of GO dispersion liquid with the concentration of 0.2mg/mL is uniformly mixed with ammonia water and hydrazine hydrate, wherein the volume ratio of the ammonia water to the GO dispersion liquid is 1:1000, the volume ratio of the hydrazine hydrate to the GO dispersion liquid is 1:10000, and the rGO dispersion liquid is obtained by reflux heating at 70 ℃ for 4 hours.

(2) Slowly injecting the zinc acetate solution into the NaOH solution by using a syringe pump, wherein the concentration of the zinc acetate in the mixed solution is 7.5mM, the mass concentration ratio of the zinc acetate to the NaOH is 1:3, uniformly stirring, heating at 50 ℃ for 2h to obtain ZnO colloidal solution, and adding deionized water to dilute to the target concentration of 0.2 mg/mL.

(3) And (3) mixing the ZnO colloidal solution and the rGO dispersion liquid (100mL) according to the volume ratio of 1:1, and performing vacuum filtration through a mixed cellulose ester microporous filter membrane to form a self-supporting ZnO-rGO hydrogel membrane. The membrane was peeled off the filter, transferred to a petri dish and immersed in deionized water to remove residual impurities.

(4) Placing the ZnO-rGO hydrogel film in H₂In O/NMP mixed solvent for 12H, wherein H₂The volume ratio of O to NMP was 0:10, and then the membrane was fixed using two coverslips and capillary compressed by vacuum drying at 50 ℃ for 8 h. And soaking the compressed ZnO-rGO membrane in deionized water for 0.5h to obtain the capillary compression ZnO-rGO hydrogel membrane.

(5) According to Ni (NO)₃)₂·6H₂The mass concentration of O is 0.5M, the concentration of nano zirconia powder is 10mg/mL, the concentration ratio of zirconia to SDS is 40:1, and the concentration ratio of zirconia to boric acid is 2: 1. And (3) taking the ZnO-rGO hydrogel film subjected to capillary compression as a cathode, taking a carbon rod as an anode, connecting the carbon rod to a direct current power supply, and immersing the carbon rod in the suspension for direct current pulse electrophoretic deposition. Electrophoretic deposition conditions: average current density of 3A/dm²The duty ratio is 40 percent, the pulse frequency is 2000Hz, the stirring speed is 500rpm, the electrophoretic deposition suspension liquid is at 50 ℃, the deposition time is 0.5min, and the catalyst for preparing alcohol by methane electrooxidation is obtained and named as Ni-ZrO₂/ZnO-rGO-7。

And (3) performance testing: Ni-ZrO Using electrode Clamp₂the/ZnO-rGO-7 hydrogel film is fixed as an anode working electrode. Graphite carbon rod as cathode counter electrode, Saturated Calomel Electrode (SCE) as reference electrode, and Na with concentration of 0.5M in H-type double-chamber electrolytic cell₂CO₃In an alkaline electrolyte. Methane was passed through the cell at 30mL/min and evaluated by potentiostatic method at 0.5V (vs. SCE) for 3 h. The results show that: the methane is oxidized to methanol, isopropanol and a small amount of carbon dioxide (CO), a product of complete oxidation₂). Wherein the methanol concentration and the isopropanol concentration are respectively 3.37 mu g/mL and 2.22 mu g/mL, and the CO concentration is₂The reduced concentration was 0.29. mu.g/mL. Methanol, isopropanol and CO₂The selectivities were 47.25%, 49.79% and 2.96%, respectively. Through calculation: the methane conversion rate was 71.42. mu.g/h.

Example 8

(1) 100mL of GO dispersion liquid with the concentration of 0.2mg/mL is uniformly mixed with ammonia water and hydrazine hydrate, wherein the volume ratio of the ammonia water to the GO dispersion liquid is 1:100, the volume ratio of the hydrazine hydrate to the GO dispersion liquid is 5.1:10000, and the rGO dispersion liquid is obtained by reflux heating at 95 ℃ for 0.5 h.

(2) Slowly injecting the zinc acetate solution into the NaOH solution by using a syringe pump, wherein the concentration of the zinc acetate in the mixed solution is 3mM, the mass concentration ratio of the zinc acetate to the NaOH is 1:3, uniformly stirring, heating at 70 ℃ for 0.5h to obtain ZnO colloidal solution, and adding deionized water to dilute the ZnO colloidal solution to the target concentration of 0.2 mg/mL.

(3) And (3) mixing the ZnO colloidal solution and the rGO dispersion liquid (100mL) according to the volume ratio of 1:5, and performing vacuum filtration through a mixed cellulose ester microporous filter membrane to form a self-supporting ZnO-rGO hydrogel membrane. The membrane was peeled off the filter, transferred to a petri dish and immersed in deionized water to remove residual impurities.

(4) Placing the ZnO-rGO hydrogel film in H₂In O/NMP mixed solvent for 12H, wherein H₂The volume ratio of O to NMP was 7:3, and then the membrane was fixed using two coverslips and dried under vacuum at 75 ℃ for 16h for capillary compression. And soaking the compressed ZnO-rGO film in deionized water for 0.5h to obtain a capillary compression ZnO-rGO hydrogel film.

(5) According to Ni (NO)₃)₂·6H₂The mass concentration of O is 5M, the concentration of nano zirconia powder is 10mg/mL, the concentration ratio of zirconia to SDS is 40:1, and the concentration ratio of zirconia to boric acid is 2:1, and the electrophoresis deposition suspension is prepared. And taking the capillary compressed ZnO-rGO hydrogel film as a cathode, taking a carbon rod as an anode, connecting the carbon rod to a direct current power supply, and immersing the carbon rod in the suspension for direct current pulse electrophoretic deposition. Electrophoretic deposition conditions: average current density 1A/dm²The duty ratio is 5 percent, the pulse frequency is 50Hz, the stirring speed is 500rpm, the electrophoretic deposition suspension is 50 ℃, the deposition time is 10min to obtain the catalyst for preparing the alcohol by methane electrooxidation and the catalyst is named as Ni-ZrO₂/ZnO-rGO-8。

And (3) performance testing: using electrode clamps to bond Ni-ZrO₂the/ZnO-rGO-8 hydrogel film is fixed as an anode working electrode. Graphite carbon rod as cathode counter electrode, Saturated Calomel Electrode (SCE) as reference electrode, and Na with concentration of 0.5M in H-type double-chamber electrolytic cell₂CO₃In an alkaline electrolyte. Methane was passed through the cell at 30mL/min and potentiostatic evaluation was carried out for 3 hours at a potential of 0.65V (vs. SCE). The results show that: the methane is oxidized to methanol, isopropanol and a small amount of carbon dioxide (CO), a product of complete oxidation₂). Wherein the methanol and isopropanol concentrations are 22.77. mu.g/mL and 17.98. mu.g/mL respectively, and CO₂The reduced concentration was 2.80. mu.g/mL. Methanol, isopropanol and CO₂The selectivities of (a) were 42.51%, 53.69% and 3.80%, respectively. Calculated as follows: the methane conversion rate was 536.41. mu.g/h.

Example 9

(1) uniformly mixing 100mL of GO dispersion liquid with the concentration of 0.2mg/mL with ammonia water and hydrazine hydrate, wherein the volume ratio of the ammonia water to the GO dispersion liquid is 5.6:1000, the volume ratio of the hydrazine hydrate to the GO dispersion liquid is 1.7:10000, and carrying out reflux heating at 100 ℃ for 4 hours to obtain the rGO dispersion liquid.

(2) Slowly injecting the zinc acetate solution into the NaOH solution by using an injection pump, wherein the concentration of the zinc acetate in the mixed solution is 3mM, the mass concentration ratio of the zinc acetate to the NaOH is 1:4, uniformly stirring, heating at 60 ℃ for 1h to obtain a ZnO colloidal solution, and adding deionized water to dilute to the target concentration of 0.2 mg/mL.

(4) Placing the ZnO-rGO hydrogel film in H₂O/NMP mixed solvent for 12H, wherein H₂The volume ratio of O to NMP was 5:5, and then the membrane was fixed using two coverslips and capillary compressed by vacuum drying at 90 ℃ for 8 h. And soaking the compressed ZnO-rGO film in deionized water for 0.5h to obtain a capillary compression ZnO-rGO hydrogel film.

(5) According to Ni (NO)₃)₂·6H₂The mass concentration of O is 0.5M, the concentration of nano zirconia powder is 15mg/mL, the concentration ratio of zirconia to SDS is 10:1, and the concentration ratio of zirconia to boric acid is 1: 1. And (3) taking the ZnO-rGO hydrogel film subjected to capillary compression as a cathode, taking a carbon rod as an anode, connecting the carbon rod to a direct current power supply, and immersing the carbon rod in the suspension for direct current pulse electrophoretic deposition. Electrophoretic deposition conditions: average current density of 3A/dm²The duty ratio is 80%, the pulse frequency is 1200Hz, the stirring speed is 1000rpm, the electrophoretic deposition suspension is 70 ℃, the deposition time is 40min to obtain the catalyst for preparing alcohol by methane electrooxidation, and the catalyst is named as Ni-ZrO₂/ZnO-rGO-9。

And (3) performance testing: using electrode clamps to bond Ni-ZrO₂the/ZnO-rGO-9 hydrogel film is fixed as an anode working electrode. Graphite carbon rod as cathode counter electrode, Saturated Calomel Electrode (SCE) as reference electrode, and Na with concentration of 0.5M in H-type double-chamber electrolytic cell₂CO₃In an alkaline electrolyte. Methane was passed through the cell at 30mL/min and evaluated by potentiostatic method at 0.8V (vs. SCE) for 3 h. The results show that: the methane is oxidized to methanol, isopropanol and a small amount of carbon dioxide (CO), a product of complete oxidation₂). Wherein the methanol and isopropanol concentrations are 5.23 μ g/mL and 4.29 μ g/mL respectively, and CO₂The reduced concentration was 1.08. mu.g/mL. Methanol, isopropanol and CO₂The selectivities of (a) were 40.62%, 53.30% and 6.08%, respectively. Through calculation: the methane conversion rate was 128.93. mu.g/h.

Example 10

(1) 100mL of GO dispersion liquid with the concentration of 0.2mg/mL is uniformly mixed with ammonia water and hydrazine hydrate, wherein the volume ratio of the ammonia water to the GO dispersion liquid is 2.8:1000, the volume ratio of the hydrazine hydrate to the GO dispersion liquid is 5.1:10000, and the rGO dispersion liquid is obtained by reflux heating at 95 ℃ for 4 hours.

(2) Slowly injecting the zinc acetate solution into the NaOH solution by using a syringe pump, wherein the concentration of the zinc acetate in the mixed solution is 10mM, the mass concentration ratio of the zinc acetate to the NaOH is 1:4.5, uniformly stirring, heating at 70 ℃ for 2h to obtain ZnO colloidal solution, and adding deionized water to dilute the ZnO colloidal solution to the target concentration of 0.2 mg/mL.

(3) And (3) mixing the ZnO colloidal solution and the rGO dispersion liquid (100mL) according to the volume ratio of 1:25, and performing vacuum filtration through a mixed cellulose ester microporous filter membrane to form a self-supporting ZnO-rGO hydrogel membrane. The membrane was peeled off the filter, transferred to a petri dish and immersed in deionized water to remove residual impurities.

(4) Placing the ZnO-rGO hydrogel film in H₂In O/NMP mixed solvent for 12H, wherein H₂The volume ratio of O to NMP was 5:5, and then the membrane was fixed using two coverslips and capillary compressed by vacuum drying at 90 ℃ for 20 h. And soaking the compressed ZnO-rGO film in deionized water for 0.5h to obtain a capillary compression ZnO-rGO hydrogel film.

(5) According to Ni (NO)₃)₂·6H₂The mass concentration of O is 3.5M, the concentration of nano zirconia powder is 10mg/mL, the concentration ratio of zirconia to SDS is 10:1, and the concentration ratio of zirconia to boric acid is 1:2 to prepare electrophoretic deposition suspension. And taking the capillary compressed ZnO-rGO hydrogel film as a cathode, taking a carbon rod as an anode, connecting the carbon rod to a direct current power supply, and immersing the carbon rod in the suspension for direct current pulse electrophoretic deposition. Electrophoretic deposition conditions: average current density of 1A/dm²The duty ratio is 95 percent, the pulse frequency is 600Hz, the stirring speed is 1000rpm, the electrophoretic deposition suspension liquid is 60 ℃, the deposition time is 10min to obtain the catalyst for preparing the alcohol by methane electrooxidation and the catalyst is named as Ni-ZrO₂/ZnO-rGO-10。

And (3) performance testing: Ni-ZrO Using electrode Clamp₂Fixing of/ZnO-rGO-10 hydrogel filmIs an anode working electrode. Graphite carbon rod as cathode counter electrode, Saturated Calomel Electrode (SCE) as reference electrode, and Na with concentration of 0.5M in H-type double-chamber electrolytic cell₂CO₃In an alkaline electrolyte. Methane was passed through the cell at 30mL/min and potentiostatic evaluation was carried out for 3 hours at a potential of 0.7V (vs. SCE). The results show that: the methane is oxidized to methanol, isopropanol and a small amount of carbon dioxide (CO), a product of complete oxidation₂). Wherein the methanol and isopropanol concentrations are respectively 19.48 μ g/mL and 9.93 μ g/mL, and CO₂Reduced concentration of 2.69. mu.g/mL methanol, isopropanol and CO₂The selectivities of (a) were 52.20%, 42.56% and 5.24%, respectively. Through calculation: the methane conversion rate was 373.72. mu.g/h.

Example 11

(1) 100mL of GO dispersion liquid with the concentration of 0.2mg/mL is uniformly mixed with ammonia water and hydrazine hydrate, wherein the volume ratio of the ammonia water to the GO dispersion liquid is 8.4:1000, the volume ratio of the hydrazine hydrate to the GO dispersion liquid is 1:1000, and the rGO dispersion liquid is obtained by reflux heating at 80 ℃ for 3 hours.

(2) Slowly injecting the zinc acetate solution into the NaOH solution by using an injection pump, wherein the concentration of the zinc acetate in the mixed solution is 10mM, the mass concentration ratio of the zinc acetate to the NaOH is 1:5, uniformly stirring, heating at 70 ℃ for 3.5h to obtain a ZnO colloidal solution, and adding deionized water to dilute to the target concentration of 0.2 mg/mL.

(3) And (3) mixing the ZnO colloidal solution and the rGO dispersion liquid (100mL) according to the volume ratio of 1:5, and performing vacuum filtration through a mixed cellulose ester microporous filter membrane to form a self-supporting ZnO-rGO hydrogel membrane. The membrane was peeled off the filter, transferred to a petri dish, and immersed in deionized water to remove residual impurities.

(4) Placing the ZnO-rGO hydrogel film in H₂O/NMP mixed solvent for 12H, wherein H₂The volume ratio of O to NMP was 7:3, and then the membrane was fixed using two coverslips and capillary compressed by vacuum drying at 60 ℃ for 8 h. And soaking the compressed ZnO-rGO membrane in deionized water for 0.5h to obtain the capillary compression ZnO-rGO hydrogel membrane.

(5) According to Ni (NO)₃)₂·6H₂O mass concentration of 1M, nano oxygenThe concentration of zirconium oxide powder is 10mg/mL, the concentration ratio of zirconium oxide to SDS is 50:1, and the concentration ratio of zirconium oxide to boric acid is 1: 2. And taking the capillary compressed ZnO-rGO hydrogel film as a cathode, taking a carbon rod as an anode, connecting the carbon rod to a direct current power supply, and immersing the carbon rod in the suspension for direct current pulse electrophoretic deposition. Electrophoretic deposition conditions: average current density of 8A/dm²The duty ratio is 80 percent, the pulse frequency is 100Hz, the stirring speed is 600rpm, the electrophoretic deposition suspension is 50 ℃, the deposition time is 20min to obtain the catalyst for preparing the alcohol by methane electrooxidation and the catalyst is named as Ni-ZrO₂/ZnO-rGO-11。

And (4) performance testing: Ni-ZrO Using electrode Clamp₂the/ZnO-rGO-11 hydrogel film is fixed as an anode working electrode. Graphite carbon rod as cathode counter electrode, Saturated Calomel Electrode (SCE) as reference electrode, and Na with concentration of 0.5M in H-type double-chamber electrolytic cell₂CO₃In an alkaline electrolyte. Methane was passed through the cell at a rate of 30mL/min and potentiostatic evaluation was carried out for 3 hours at a potential of 0.9V (vs. SCE). The results show that: the methane is oxidized to methanol, isopropanol and a small amount of carbon dioxide (CO), a product of complete oxidation₂). Wherein the methanol and isopropanol concentrations are 3.11 μ g/mL and 2.21 μ g/mL, respectively, and CO₂Reduced concentration of 0.69 μ g/mL, methanol, isopropanol and CO₂The selectivities were 43.51%, 49.45% and 7.04%, respectively. Calculated as follows: the methane conversion rate was 71.58. mu.g/h.

Example 12

The only difference from example 1 is: step (4) H₂O and NMP are replaced by the same amount of NMP, i.e. the mixed solvent does not contain water.

The results show that: the methane is oxidized to methanol, isopropanol and a small amount of carbon dioxide (CO), a product of complete oxidation₂) Wherein the methanol and isopropanol concentrations are 3.73. mu.g/mL and 2.41. mu.g/mL, respectively, CO₂The reduced concentration was 3.01. mu.g/mL. Methanol, isopropanol and CO₂The selectivities of (a) were 38.16%, 39.44% and 22.40%, respectively. Calculated as follows: the methane conversion rate was 97.88. mu.g/h.

Example 13

The only difference from example 1 is: step (4) H₂The volume ratio of O to NMP was 20: 1.

The results show that: the methane is oxidized to methanol, isopropanol and a small amount of carbon dioxide (CO), a product of complete oxidation₂). Wherein the methanol and isopropanol concentrations are 7.45 μ g/mL and 8.03 μ g/mL respectively, and CO₂The reduced concentration was 2.27. mu.g/mL. Methanol, isopropanol and CO₂The selectivities of (a) were 33.95%, 58.53% and 7.52%, respectively. Through calculation: the methane conversion rate was 219.75. mu.g/h.

Example 14

The only difference from example 1 is: step (4) H₂The volume ratio of O to NMP is 2: 1.

The results show that: the methane is oxidized to methanol, isopropanol and a small amount of carbon dioxide (CO), a product of complete oxidation₂) Wherein the methanol and isopropanol concentrations are 15.13. mu.g/mL and 11.74. mu.g/mL, respectively, CO₂The reduced concentration was 0.43. mu.g/mL. Methanol, isopropanol and CO₂The selectivities of (a) were 44.21%, 54.87% and 0.92%, respectively. Calculated as follows: the methane conversion rate was 342.72. mu.g/h.

Example 15

The only difference from example 1 is: step (4) H₂The volume ratio of O to NMP is 3: 1.

The results show that: the methane is oxidized to methanol, isopropanol and a small amount of carbon dioxide (CO), a product of complete oxidation₂) Wherein the methanol and isopropanol concentrations were 23.94. mu.g/mL and 12.04. mu.g/mL, respectively, CO₂The reduced concentration was 2.12. mu.g/mL. Methanol, isopropanol and CO₂Selectivity of 53.51%, 43.05% and 3.44%, respectively calculated: the methane conversion rate was 448.01. mu.g/h.

Combining example 1 with examples 12-15, it can be seen that: preferred range H₂Catalyst of O/NMP volume ratio (H)₂O/NMP 2/1-3/1) has higher methane conversion rate and can inhibit the complete oxidation product CO₂Generation of (CO in the preferred range in FIG. 4)₂A significant reduction in selectivity).

Example 16

The only difference from example 1 is: and (3) mixing the ZnO colloidal solution and the rGO dispersion liquid (100mL) in the step (3) according to the volume ratio of 2: 1.

The results show that: oxidation of methane to methanolIsopropanol and a small amount of carbon dioxide (CO), a product of complete oxidation₂) Wherein the methanol and isopropanol concentrations were 8.42. mu.g/mL and 7.17. mu.g/mL, respectively, CO₂The reduced concentration was 1.55. mu.g/mL. Methanol, isopropanol and CO₂The selectivities of (a) were 40.07%, 54.57% and 5.36%, respectively. Calculated as follows: the methane conversion rate was 210.45. mu.g/h.

Example 17

The only difference from example 1 is: and (3) mixing the ZnO colloidal solution and the rGO dispersion liquid (100mL) in the step (3) according to the volume ratio of 1: 50.

The results show that: the methane is oxidized to methanol, isopropanol and a small amount of carbon dioxide (CO), a product of complete oxidation₂) Wherein the methanol and isopropanol concentrations are 6.89. mu.g/mL and 1.25. mu.g/mL, respectively, CO₂The reduced concentration was 2.72. mu.g/mL. Methanol, isopropanol and CO₂The selectivities were 63.40%, 18.40% and 18.20%, respectively. Through calculation: the methane conversion rate was 108.83. mu.g/h.

Example 18

The only difference from example 1 is: and (4) mixing the ZnO colloidal solution and the rGO dispersion liquid (100mL) in the step (3) according to a volume ratio of 4: 3.

The results show that: the methane is oxidized to methanol, isopropanol and a small amount of carbon dioxide (CO), a product of complete oxidation₂) Wherein the methanol and isopropanol concentrations were 10.25. mu.g/mL and 7.98. mu.g/mL, respectively, CO₂The reduced concentration was 1.71. mu.g/mL. Methanol, isopropanol and CO₂The selectivities were 42.26%, 52.62% and 5.12%, respectively. Through calculation: the methane conversion rate was 242.90. mu.g/h.

Example 19

The only difference from example 1 is: and (4) mixing the ZnO colloidal solution and the rGO dispersion liquid (100mL) in the step (3) according to a volume ratio of 3: 4.

The results show that: the methane is oxidized to methanol, isopropanol and a small amount of carbon dioxide (CO), a product of complete oxidation₂). Wherein the methanol concentration and the isopropanol concentration are respectively 12.41 mu g/mL and 6.27 mu g/mL, and the CO concentration is₂Reduced concentration of 2.04. mu.g/mL methanol, isopropanol and CO₂Selectivity of 51.88%, 41.92% and 6.20%, respectively, was calculated: the methane conversion rate was 239.56. mu.g/h.

Combining example 1 with examples 16-19, it can be seen that: catalysts with ZnO/rGO volumetric ratios in the preferred range (ZnO/rGO ═ 4:3-3:4) have higher methane conversion rates, contributing to the production of high value added products, especially methanol (see figure 5).

Example 20

The only difference from example 1 is: ni (NO) in step (5)₃)₂·6H₂The mass concentration of O is 0.5M, and the concentration of nano zirconia powder is 20 mg/mL.

The results show that: the methane is oxidized to methanol, isopropanol and a small amount of carbon dioxide (CO), a product of complete oxidation₂). Wherein the methanol and isopropanol concentrations are 2.72 μ g/mL and 3.16 μ g/mL, respectively, and CO₂The reduced concentration was 0.01. mu.g/mL. Methanol, isopropanol and CO₂The selectivities of (a) were 34.96%, 64.96% and 0.08%, respectively. Calculated as follows: the methane conversion rate was 77.92. mu.g/h.

Example 21

The only difference from example 1 is: ni (NO) in step (5)₃)₂·6H₂The mass concentration of O is 3M, and the concentration of the nano zirconia powder is 15 mg/mL.

The results show that: the methane is oxidized to methanol, isopropanol and a small amount of carbon dioxide (CO), a product of complete oxidation₂). Wherein the methanol and isopropanol concentrations are 1.68 μ g/mL and 0.39 μ g/mL respectively, and CO₂The reduced concentration was 4.32. mu.g/mL. Methanol, isopropanol and CO₂The selectivities of (a) were 30.86%, 11.46% and 57.68%, respectively. Calculated as follows: the methane conversion rate was 54.52. mu.g/h.

Example 22

The only difference from example 1 is: ni (NO) in step (5)₃)₂·6H₂The mass concentration of O is 5M, and the concentration of the nano zirconia powder is 1 mg/mL.

The results show that: the methane is oxidized to methanol, isopropanol and a small amount of carbon dioxide (CO), a product of complete oxidation₂). Wherein the methanol and isopropanol concentrations are 18.31 μ g/mL and 23.29 μ g/mL respectively, and CO₂The reduced concentration was 0.99. mu.g/mL. Methanol, isopropanol and CO₂The selectivities were 32.53%, 66.19% and 1.28%, respectively.Through calculation: the methane conversion rate was 563.63. mu.g/h.

By combining example 1 with examples 20 to 22, it is known that: ZrO (zirconium oxide)₂Helps to inhibit the complete oxidation product CO₂Formation of excessive ZrO₂The methane conversion rate will be reduced. While Ni has higher oxidation activity, excessive Ni will cause CO₂The selectivity was significantly increased (see figure 6). Therefore, only suitable Ni and ZrO₂The ratio can compromise catalytic activity and selectivity.

Comparative example 1

The only difference from example 1 is: mixing Ni (NO)₃)₂·6H₂Substitution of O for Cu (NO) of equal quantity₃)₂·3H₂O.

The results show that: the methane is oxidized to methanol, isopropanol and a small amount of carbon dioxide (CO), a product of complete oxidation₂). Wherein the methanol and isopropanol concentrations are 4.79 μ g/mL and 0.41 μ g/mL, respectively, and CO₂The reduced concentration was 1.80. mu.g/mL. Methanol, isopropanol and CO₂The selectivities were 70.89%, 9.71% and 19.40%, respectively. Through calculation: the methane conversion rate was 67.66. mu.g/h.

Comparative example 2

The only difference from example 1 is: zirconia is not introduced, i.e. the raw material in step (5) is free of nano zirconia powder.

The results show that: the methane is oxidized to the fully oxidized product carbon dioxide (CO)₂)，CO₂Reduced concentration of 6.70. mu.g/mL, CO₂The selectivity was about 100.00%. Calculated as follows: the methane conversion rate was 48.73. mu.g/h.

Comparative example 3

The only difference from example 1 is: without nickel incorporation, i.e. without Ni (NO) in the feedstock of step (5)₃)₂·6H₂O。

The results show that: methane is oxidized to completely oxidize the product carbon dioxide (CO)₂)，CO₂Reduced concentration of 0.41. mu.g/mL, CO₂The selectivity was about 100.00%. Calculated as follows: the methane conversion rate was 2.98. mu.g/h.

Comparative example 4

The only difference from example 1 is: step (5) was not performed, i.e., nickel and zirconia were not introduced.

The results show that: the catalyst is inactive, and liquid products of methanol and isopropanol and complete oxidation products of CO cannot be detected₂. Methane (CH) in FIG. 7₄) The cyclic voltammetry curves are basically overlapped under the atmosphere and the helium (He) atmosphere, and the catalyst is proved to have no catalytic activity under the methane atmosphere.

The test data for examples 1-22 and comparative examples 1-4 are summarized as shown in Table 1:

TABLE 1 summary of the electrooxidation properties of methane for the examples and comparative examples

The present invention has been described in terms of the preferred embodiment, and it is not intended to be limited to the embodiment. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. The catalyst for preparing alcohol by methane electrooxidation is characterized by consisting of a hydrogel film formed by reducing graphene oxide and zinc oxide, wherein the zinc oxide is dispersed in a film layer of the hydrogel film, and zirconium oxide and nickel are loaded on the surface of the hydrogel film.

2. The catalyst according to claim 1, wherein the total mass ratio of the reduced graphene oxide to the zinc oxide in the catalyst is 60 to 95% and the total mass ratio of the zirconium oxide to the nickel is 5 to 40% in terms of mass fraction;

preferably, the total mass ratio of the reduced graphene oxide to the zinc oxide is 75-85%, and the total mass ratio of the zirconium oxide to the nickel is 15-25%;

preferably, the mass ratio of the zirconia to the nickel is 1 (4-20); more preferably 1 (4-6);

preferably, the hydrogel film is subjected to capillary compression.

3. A process for preparing a catalyst as claimed in claim 1 or 2, comprising:

4. The preparation method according to claim 3, wherein the preparation process of the zinc oxide-reduced graphene oxide hydrogel film comprises the following steps: mixing the reduced graphene oxide dispersion liquid and the zinc oxide colloidal solution, and forming a hydrogel film through vacuum filtration;

preferably, the formed hydrogel film is peeled off from the filter membrane into water to remove residual impurities.

5. The preparation method according to claim 3, wherein the preparation process of the reduced graphene oxide dispersion liquid comprises: uniformly mixing the graphene oxide dispersion liquid with ammonia water and hydrazine hydrate, and reacting for 0.5-4 h at 70-100 ℃;

preferably, the concentration of the graphene oxide dispersion liquid is 0.05mg/mL-0.5mg/mL, the ammonia water is an aqueous solution with the ammonia content of 25-28 wt%, the hydrazine hydrate is an aqueous solution with the hydrazine hydrate content of 80-90 wt%, the volume ratio of the ammonia water to the graphene oxide dispersion liquid is 1 (100-10000), and the volume ratio of the hydrazine hydrate to the graphene oxide dispersion liquid is 1 (1000-10000);

6. The method according to claim 3, wherein the preparation of the zinc oxide colloidal solution comprises: dropwise adding a zinc salt aqueous solution into an alkaline precipitator aqueous solution, reacting for 0.5-5 h at 50-90 ℃, cooling and diluting to 0.05-0.5 mg/mL;

7. The method of claim 3, wherein the zinc oxide-reduced graphene oxide hydrogel film is subjected to capillary compression prior to depositing zirconium oxide and nickel on the zinc oxide-reduced graphene oxide hydrogel film;

preferably, the process of capillary compression comprises: soaking the zinc oxide-reduced graphene oxide hydrogel film in a mixed solution formed by water and N-methylpyrrolidone for 8-15 h, taking out the zinc oxide-reduced graphene oxide hydrogel film, drying the zinc oxide-reduced graphene oxide hydrogel film in vacuum for 4-20h at 40-90 ℃ to compress an adhesive film, and soaking the compressed zinc oxide-reduced graphene oxide hydrogel film in water again;

preferably, the volume ratio of water to N-methylpyrrolidone is (0-19): 1;

more preferably, the volume ratio of water to N-methylpyrrolidone is (2-3): 1;

8. The preparation method according to claim 3, wherein zirconium oxide and nickel are deposited on the zinc oxide-reduced graphene oxide hydrogel film by an electrophoretic deposition method;

preferably, the process of electrophoretic deposition comprises: dispersing nickel salt, zirconia powder, a surfactant and a buffer in water to form a suspension, taking the zinc oxide-reduced graphene oxide hydrogel film as a cathode, and immersing the cathode and an anode in the suspension for electrophoretic deposition;

preferably, in the suspension, the concentration of the substance of nickel salt is 0.5M-5M, and the concentration of zirconia is 1mg/mL-20 mg/mL;

preferably, the zirconia powder has an average particle size of 5nm to 20 nm;

preferably, the anode is a carbon rod.

9. The method according to claim 8, wherein the average current density is controlled to be 1A/dm by using a DC pulse power deposition method in the electrophoretic deposition process²-10A/dm²The duty ratio is 5-95%, the pulse frequency is 50Hz-2000Hz, the stirring speed is 200rpm-1000rpm, the temperature of the suspension is 20-90 ℃, and the deposition time is 0.5-40 min;

preferably, the average current density is controlled to be 3A/dm²-8A/dm²The duty ratio is 40-80%, the pulse frequency is 100-1200 Hz, the stirring speed is 400-600 rpm, the suspension temperature is 50-70 ℃, and the deposition time is 10-30 min.

10. A method for preparing alcohol by methane electrooxidation, which is characterized in that the catalyst prepared by any one of the catalysts of claims 1-2 or the preparation method of any one of claims 3-9 is used as an electrocatalytic anode working electrode;

preferably, a graphite carbon rod is used as a cathode counter electrode, a Saturated Calomel Electrode (SCE) is used as a reference electrode, each electrode is placed in an alkaline electrolyte of an H-shaped double-chamber electrolytic cell, methane is introduced into the alkaline electrolyte for electrocatalytic oxidation, and a constant potential reaction is carried out for 2-4H under the condition that a potential interval is 0.5-1.0V;

preferably, the reaction pressure is normal pressure, the reaction temperature is room temperature, and the flow rate of the methane gas is 25mL/min-35 mL/min.