CN115747874B

CN115747874B - Preparation method and application of rare earth element doped 2D RE@Fe-MOF efficient integrated membrane electrode

Info

Publication number: CN115747874B
Application number: CN202211400966.5A
Authority: CN
Inventors: 钱涛; 程煜; 许国栋; 万子秋
Original assignee: Nantong University
Current assignee: Nantong University
Priority date: 2022-11-09
Filing date: 2022-11-09
Publication date: 2023-10-13
Anticipated expiration: 2042-11-09
Also published as: CN115747874A

Abstract

The invention relates to the technical field of catalyst preparation, in particular to a preparation method and application of a rare earth element doped 2DRE@Fe-MOF high-efficiency integrated membrane electrode, which comprises the following steps: firstly, weighing a certain amount of benzimidazole, and dissolving the benzimidazole in absolute ethyl alcohol under the stirring action to obtain an organic ligand solution; secondly, weighing a certain amount of ferric nitrate, dissolving in absolute ethyl alcohol, weighing a certain amount of rare earth element precursor after the ferric nitrate is completely dissolved, adding the rare earth element precursor, and stirring until the rare earth element precursor is completely dissolved to obtain a metal precursor solution; adding a metal precursor solution into an organic ligand solution under the stirring effect, adding a current collector for in-situ modification after full reaction, taking out a reacted sample, cleaning, and vacuum drying to obtain the rare earth element doped 2DRE@Fe-MOF high-efficiency integrated membrane electrode. The 2DRE@Fe-MOF high-efficiency integrated membrane electrode prepared by the method has excellent catalytic performance, shows excellent full water-splitting catalytic activity and stability in alkaline electrolyte, and can achieve high current density under extremely low overpotential.

Description

Preparation method and application of rare earth element doped 2D RE@Fe-MOF efficient integrated membrane electrode

Technical Field

The invention relates to the technical field of catalyst preparation, in particular to a preparation method and application of a rare earth element doped 2D RE@Fe-MOF high-efficiency integrated membrane electrode.

Background

The long-term planning (2021-2035) in the development of the hydrogen energy industry clearly proposes that a hydrogen energy industry system is formed in 2035, and the multi-element hydrogen energy application ecology covering the fields of transportation, energy storage, industry and the like is constructed. However, at present, 95% of industrialized hydrogen production mainly depends on a methane steam method and a water gas method for hydrogen production, so that the use of traditional energy sources and the emission of greenhouse gases such as carbon dioxide are accelerated, and the purity of the produced hydrogen is lower, and ash hydrogen is the main material. The hydrogen production by utilizing the electrolyzed water is an efficient way for producing high-purity hydrogen energy, and can fundamentally solve the problems of energy shortage and environmental pollution. According to the data of the international energy agency, if the global hydrogen production adopts the water electrolysis technology, the electric power up to 3,600TWh can be consumed, the total annual energy generation capacity of European Union is exceeded, and the electric power cost is up to more than 70%. Thus, the industry targets for electrochemical hydrogen production are to meet both sustained high activity output and low overpotential at high current densities.

Two-dimensional metal-organic frameworks (2D MOFs) have specific layered structures, higher specific surface area and more surface active sites, and have great structural controllability, proven to be active for water splitting. Most reported catalysts are only at low current densities [ ]<0.2Acm ^-2 ) The following shows activity and limited stability. How to achieve the ultra-high current density>1Acm ^-2 ) Maintaining high activity of the catalyst to meet industrial steady operation remains a problem to be solved.

The electrocatalytic is taken as a highly complex system (complex components, complex phase states and complex reactions), and the performance of the electrocatalytic is finally reflected by the synergy and competition between the active components and the inactive components (electrolyte, binder, gas diffusion electrode and the like) of the internal electrocatalytic layer. The main factors that prevent the catalyst from realizing large current and high activity hydrogen production can be attributed to the electrocatalytic layer, the gas diffusion layer and the interface characteristics of the two. From a kinetic point of view, a poor interface of the catalytic layer/gas diffusion layer will cause a retardation of the reactant/product diffusion kinetics, with an increase in reactant concentration losses. And the physical bonding of the interface between the two leads to the increase of interface contact resistance, which is unfavorable for electron transmission. The traditional noble metal electrocatalyst has the defects of low reserves, high cost and poor cycle stability despite high catalytic activity, and mainly comprises a catalytic layer which is formed by mixing a powdery electrocatalyst and a high polymer binder, so that the full exposure of active sites is hindered, the electrocatalytic reaction is delayed, ohmic loss is easily caused due to poor interface contact, the current density is reduced, and the high-current hydrogen production is difficult to realize.

If the powdery catalyst grows on the surface of the current collector in situ, a high-integration-level integrated membrane electrode is constructed, the use of a high-molecular binder is avoided, the exposure of active sites can be maximized, the contact resistance can be reduced, and the problems are expected to be solved.

At the same time, we note the great potential of rare earth elements in the catalyst field. The rare earth element has a special outer electron layer structure and unique optical and magnetic characteristics, and the properties improve the thermal stability and catalytic activity of the rare earth material catalyst, and can be used as a catalytic auxiliary agent to bear the catalytic function. Especially yttrium element and lanthanum element, can be made into molecular sieve catalyst, and has the advantages of high activity, good selectivity, strong poisoning resistance and the like. The rare earth resources in China are rich, the rare earth materials have high cost performance, and the rare earth materials have good application prospect. The rare earth element is doped and introduced into the 2D Fe-MOF membrane electrode, so that the intrinsic electronic structure of the catalyst is hopefully regulated, and the high-current activity and stability of the catalyst are further improved. The hybridization of rare earth elements and 2D Fe-MOF forms a high-efficiency integrated membrane electrode, and the realization of high-current high-efficiency hydrogen production is not reported at present.

Disclosure of Invention

The invention aims to solve the defects in the prior art, and provides a preparation method and application of a rare earth element doped 2D RE@Fe-MOF high-efficiency integrated membrane electrode.

In order to achieve the above purpose, the present invention adopts the following technical scheme:

a preparation method of a rare earth element doped 2D RE@Fe-MOF high-efficiency integrated membrane electrode comprises the following specific steps:

step 1, preparation of an organic ligand: weighing a certain amount of benzimidazole, and dissolving the benzimidazole in absolute ethyl alcohol under the stirring action to obtain an organic ligand solution;

step 2, preparing a metal precursor: weighing a certain amount of ferric nitrate, dissolving in absolute ethyl alcohol, weighing a certain amount of rare earth element precursor after the ferric nitrate is completely dissolved, adding the rare earth element precursor, and stirring until the rare earth element precursor is completely dissolved to obtain a metal precursor solution;

step 3, preparing a rare earth element doped 2D RE@Fe-MOF high-efficiency integrated membrane electrode: adding a metal precursor solution into the stirred organic ligand solution, stirring, adding a current collector for in-situ modification reaction, taking out a sample after the reaction is finished, cleaning, and vacuum drying to obtain the rare earth element doped 2D RE@Fe-MOF high-efficiency integrated membrane electrode.

Preferably, in the step 1, the benzimidazole is used in an amount of 0.3g to 1.0g, and the volume of the absolute ethyl alcohol is 40mL to 60mL.

Preferably, in step 2, the rare earth element is yttrium or lanthanum, and the precursor is one or two of yttrium nitrate, lanthanum nitrate, yttrium acetate and lanthanum acetate.

Preferably, in step 1, step 2 and step 3, the stirring method is to place on a magnetic stirrer with a rotation speed of 100-300 rad/min.

Preferably, in the step 2, the dosage of ferric nitrate is 0.4 g-0.6 g, the volume of absolute ethyl alcohol is 40 mL-60 mL, and the dosage of precursor of rare earth element is 0.01 g-0.1 g.

Preferably, in step 3, the metal precursor solution is rapidly added with the organic ligand solution under the action of magnetic stirring at a rotation speed of 100-300 rad/min for 2-10 min.

Preferably, in step 3, the current collector is any one of nickel foam, iron foam and copper foam, and the current collector has a size of3×3cm ² ～10×10cm ² 。

Preferably, the current collector is foam nickel. The washing steps of the foam nickel are as follows: the foam nickel (3 cm multiplied by 3cm,0.5 mm) is sequentially washed by 95% ethanol (10 min-30 min), deionized water (5 min-20 min), 15ml acetone (10 min-30 min), 3M HCl solution (5 min-20 min) and deionized water (15 min x 3) by ultrasonic.

Preferably, in the step 3, the reaction time is 5-8 h, the cleaning condition is that deionized water and ethanol are alternately washed, the vacuum drying temperature is 60-80 ℃, and the drying time is 12-24 h.

The invention also provides application of the rare earth element doped 2D RE@Fe-MOF high-efficiency integrated membrane electrode prepared by the preparation method in hydrogen evolution, oxygen evolution and full water dissolution.

The rare earth element doped 2D RE@Fe-MOF high-efficiency integrated membrane electrode prepared by the invention can realize high-efficiency hydrogen evolution under high current density under extremely low overpotential. The two-dimensional 2D MOF material has more surface active sites so that the composite material can fully adjust the intrinsic electronic structure on the two-dimensional MOF material. The invention realizes the 2D Fe-MOF integrated membrane electrode doped with rare earth element (RE) for the first time, the two materials with high catalytic activity are stably combined in the two-dimensional MOF nanosheets, the intrinsic electronic structure of the catalytic material is regulated and controlled, and the reaction energy barrier is reduced, so that the performance of catalytic hydrogen evolution is improved, the high-efficiency hydrogen production under high current density is ensured, and the invention is suitable for large-scale application of hydrogen production.

Compared with the prior art, the invention has the following beneficial effects:

1. the rare earth element (RE) -doped 2D RE@Fe-MOF high-efficiency integrated membrane electrode prepared by the invention has excellent catalytic activity in alkaline medium as an electrocatalyst, and the catalyst grows in situ to form the integrated membrane electrode, so that the use of a high polymer binder is avoided, the full exposure of a large number of active sites is ensured, the high-efficiency hydrogen production (about 248 mV@2Acm) with high current density can be realized under extremely low overpotential, and the high-efficiency hydrogen production has excellent structural stability ^-2 ) And realize high-efficiency hydrogen evolution (-548mV@2Acm) ^-2 ) The current density is 20% Pt/C ([email protected]) of noble metal ^-2 ) Is 2.53 times that of (2); and the full water-splitting catalytic activity of the catalyst is far better than that of a noble metal system under a double-electrode system, and the catalyst has great commercial application prospect.

2. The invention prepares the rare earth element (RE) -doped 2D RE@Fe-MOF high-efficiency integrated membrane electrode by a simple and convenient in-situ solvothermal synthesis method, and the preparation method is simple, safe, green and economic, does not need heating in the preparation process, greatly reduces energy consumption, and simultaneously has the advantages of low-cost and easily-obtained preparation materials and industrial production prospect.

Drawings

FIG. 1 is a scanning electron microscope (left) and a transmission electron microscope (right) of a Y@Fe-MOF sample prepared in example 1 of the present invention;

FIG. 2 is a graph showing the profile of a Y@Fe-MOF sample prepared in example 1 of the present invention;

FIG. 3 shows the Fe-MOF5 prepared in example 4, the Y@Fe-MOF prepared in example 1 and the C prepared in comparative example 1 of the present invention ₇ H ₆ N ₂ HER polarization profile for @ NF, 20% pt/c @ NF prepared in comparative example 3;

FIG. 4 shows the Fe-MOF5 prepared in example 4, the Y@Fe-MOF prepared in example 1 and the C prepared in comparative example 1 of the present invention ₇ H ₆ N ₂ Tafel slope plot corresponding to @ NF, 20% pt/c @ NF prepared in comparative example 3;

FIG. 5 is a graph of HER stability test of Y@Fe-MOF prepared in example 1 of the present invention;

FIG. 6 is a graph showing the variation of in situ Raman spectrum of Y@Fe-MOF prepared in example 1 of the present invention at different potentials;

FIG. 7 Y@Fe-MOF prepared in example 1, fe-MOF prepared in example 4, C prepared in comparative example 1 according to the present invention ₇ H ₆ N ₂ IrO prepared in comparative example 2 @ NF ₂ OER polarization profile at NF;

FIG. 8 shows Y@Fe-MOF prepared in example 1, fe-MOF prepared in example 4, C prepared in comparative example 1 of the present invention ₇ H ₆ N ₂ IrO prepared in comparative example 2 @ NF ₂ A Tafil diagram corresponding to @ NF;

FIG. 9 Y@Fe-MOF prepared in example 1 of the present invention was measured at 0.01Acm ^-2 ～2Acm ^-2 I-t stability plot at current density;

FIG. 10 shows OER polarization curves of the Fe-MOF (3) prepared in example 2, the Fe-MOF (10) prepared in example 3, and the Fe-MOF (5) prepared in example 4 according to the present invention;

FIG. 11 is a graph showing the HER polarization curves of the Fe-MOF (3) prepared in example 2, the Fe-MOF (10) prepared in example 3, and the Fe-MOF (5) prepared in example 4 according to the present invention;

FIG. 12 is a graph showing the overall water stability of Y@Fe-MOF|KOH (aq) |Y@Fe-MOF prepared in example 5 of the present invention under a two-electrode system;

FIG. 13 is a graph showing the result of comparative example 4 of Y@Fe-MOF|KOH (aq) |Y@Fe-MOF prepared in example 5 of the present inventionPrepared 20% Pt/C@NF|KOH (aq) |IrO ₂ Full water dissociation polarization plot for NF.

Detailed Description

The following technical solutions in the embodiments of the present invention will be clearly and completely described with reference to the accompanying drawings, so that those skilled in the art can better understand the advantages and features of the present invention, and thus the protection scope of the present invention is more clearly defined. The described embodiments of the present invention are intended to be only a few, but not all embodiments of the present invention, and all other embodiments that may be made by one of ordinary skill in the art without inventive faculty are intended to be within the scope of the present invention.

Example 1:

preparation of rare earth element (RE) -doped 2D Fe-MOF efficient integrated membrane electrode (Y@Fe-MOF):

step 1, preparation of an organic ligand: weighing 0.5g of benzimidazole, and dissolving in 40ml of absolute ethyl alcohol under the stirring action to obtain 2D-MOFs organic ligand;

step 2, preparing a metal precursor: 0.4g of ferric nitrate is weighed and dissolved in 40ml of absolute ethyl alcohol, after the ferric nitrate is completely dissolved, 0.01g of yttrium nitrate is weighed and added into the absolute ethyl alcohol, and the absolute ethyl alcohol is stirred until the yttrium nitrate is completely dissolved, so that a metal precursor can be obtained;

step 3, placing the organic ligand solution prepared previously on a magnetic stirrer, adjusting the rotating speed to 100rad/min, rapidly adding the prepared precursor solution into the organic ligand solution under the stirring action, and stirring for 2min;

step 4, ultrasonically cleaning foam nickel (3.0 cm multiplied by 3.0cm,0.5 mm) with 95% ethanol (30 min), deionized water (15 min), 15ml acetone (30 min), 3M HCl solution (15 min) and deionized water (15 min x 3) in sequence, and then vertically placing the foam nickel into a reaction solution for 5h. After the reaction is finished, washing the sample by using clear water, and then placing the sample in a vacuum drying oven for drying at 60 ℃ for 12 hours, and taking out the sample to obtain a final product (Y@Fe-MOF).

Example 2:

the preparation method of the 2D Fe-MOF high-efficiency integrated membrane electrode (Fe-MOF) without rare earth element doping comprises the following steps:

step 1, preparation of an organic ligand: weighing 0.3g of benzimidazole, and dissolving in 40ml of absolute ethyl alcohol under the stirring action to obtain 2D-MOFs organic ligand;

step 2, preparing a metal precursor: weighing 0.4g of ferric nitrate, dissolving in 40ml of absolute ethyl alcohol, and stirring until the ferric nitrate is completely dissolved to obtain a metal precursor;

step 4, ultrasonically cleaning foam nickel (3.0 cm multiplied by 3.0cm,0.5 mm) with 95% ethanol (30 min), deionized water (15 min), 15ml acetone (30 min), 3M HCl solution (15 min) and deionized water (15 min x 3) in sequence, and then vertically placing the foam nickel into a reaction solution for 5h. After the reaction, washing the sample with clear water, placing the sample in a vacuum drying oven for drying at 60 ℃ for 12 hours, and taking out the sample to obtain a final product (2D Fe-MOF).

Example 3:

to find the optimal benzimidazole content, a 2D Fe-MOF efficient integrated membrane electrode (Fe-MOF (10)) was prepared:

example 3 differs from example 2 only in the amount of benzimidazole added, and example 3 added 1.0g.

Example 4:

to find the optimal benzimidazole content, a 2D Fe-MOF efficient integrated membrane electrode (Fe-MOF (5)) was prepared:

example 4 differs from example 2 only in the amount of benzimidazole added, example 4 adding 0.5g.

Example 5:

full water decomposition under a two-electrode system is constructed by utilizing yttrium doped 2D Fe-MOF high-efficiency integrated membrane electrode (Y@Fe-MOF) prepared in example 1, and Y@Fe-MOF|KOH _(aq) Y@Fe-MOF. Two membrane electrodes with the same size are cut by adopting a traditional double-electrode system and respectively used as an anode and a cathode of the battery for performance test analysis.

The Y@Fe-MOF was scanned at 200nm using a field emission scanning electron microscope (model ZEISS Gemini SEM 300, manufactured by Karl ZEISS Co.) and the resulting scanning electron microscope image was shown in FIG. 1, from which it was seen that the ultra-thin nanoplatelets had a smooth-surfaced two-dimensional structure, which grew tightly on the foamed nickel, with more surface active sites.

The morphology analysis of Y@Fe-MOF was performed using a transmission electron microscope (model FEI Talos F200X, manufactured by FEI Co., U.S.A.), and the sample was found to be a two-dimensional nanofilm, confirming successful synthesis of the 2D MOF. According to the energy spectrum surface distribution test, as shown in fig. 2, C, N, O, ni, Y, fe elements are uniformly distributed in the whole system, no obvious agglomeration or fracture phenomenon exists, and the fact that rare earth yttrium is successfully doped on the surface of the nano-sheet is confirmed, and the morphology of the doped nano-sheet is not changed obviously.

Comparative example 1:

preparation of C from undoped Metal of 2D Fe-MOF framework ₇ H ₆ N ₂ @NF：

Step 1, weighing 0.5g of benzimidazole, dissolving in 40ml of absolute ethyl alcohol under the stirring action, and placing on a magnetic stirrer to adjust the rotating speed to 100rad/min.

Step 2, ultrasonically cleaning foam nickel (3.0 cm multiplied by 3.0cm,0.5 mm) with 95% ethanol (30 min), deionized water (15 min), 15ml acetone (30 min), 3M HCl solution (15 min) and deionized water (15 min×3) in sequence, and then vertically placing the foam nickel into a benzimidazole solution for 5h. After the reaction, washing the sample with clear water, drying the sample in a vacuum drying oven at 60 ℃ for 12 hours, and taking out the sample to obtain a final product (C) ₇ H ₆ N ₂ @NF)。

Comparative example 2:

IrO using commercial catalysts ₂ Preparation of IrO in place of the Y@Fe-MOF catalyst of example 1 ₂ @NF：

Step 1, 15.8mg IrO ₂ The catalyst was added to a mixed solution of 920. Mu.L of isopropyl alcohol and 80. Mu.L of LNafion solution, and the mixture was ultrasonically dispersed for 1 hour to obtain a uniformly dispersed slurry.

Step 2, nickel foam (3.0 cm. Times.3.0 cm,0.5 mm) was successively treated with 95% ethanol (30 min), deionized water (15 min), 15ml acetone (30 min), 3M HCl solution (15 min) and deionized water (15 min x 3) were ultrasonically cleaned, and then the solution of step 1 was coated on nickel foam with a loading level that was guaranteed to be comparable to the Y@Fe-MOF system (0.88 mg/cm ² ) And drying to obtain a sample.

Comparative example 3:

20% Pt/C@NF was prepared using a commercial catalyst Pt/C instead of the Y@Fe-MOF catalyst of example 1:

step 1, adding 4mg of 20% Pt/C catalyst into a mixed solution of 920 mu L of isopropyl alcohol and 80 mu LNafion solution, and performing ultrasonic dispersion for 1h to obtain uniformly dispersed slurry;

step 2, ultrasonically cleaning foam nickel (0.5 cm multiplied by 0.5cm,0.5 mm) with ethanol (30 min), acetone (30 min multiplied by 30), 3M HCl solution (15 min) and deionized water (15 min multiplied by 3) in sequence, and then coating the solution in step 1 on the foam nickel, wherein the load is ensured to be equivalent to that of a Y@Fe-MOF system (0.88 mg/cm) ² ) And drying to obtain a sample.

Comparative example 4:

IrO prepared in comparative example 2 using a conventional two electrode system ₂ The @ NF catalyst was positive, and the 20% Pt/C @ NF catalyst prepared in comparative example 3 was negative, KOH _(aq) Construction of a cell 20% Pt/C@NF|KOH for electrolyte _(aq) |IrO ₂ And @ NF, performing performance test analysis.

Electrochemical testing:

a three-electrode system was used with a 1.0mol/LKOH solution as electrolyte, and with a Y@Fe-MOF prepared in example 1, a Fe-MOF prepared in example 2, a Fe-MOF10 prepared in example 3, a Fe-MOF5 prepared in example 4, a Y@Fe-MOF|KOH prepared in example 5 _(aq) Y@Fe-MOF, C prepared in comparative example 1 ₇ H ₆ N ₂ IrO prepared in comparative example 2 @ NF ₂ @NF, 20% Pt/C@NF prepared in comparative example 3, 20% Pt/C@NF|KOH prepared in comparative example 4 _(aq) |IrO ₂ The @ NF was used as the working electrode, the mercury/oxidized mercury electrode was used as the reference electrode, and the graphite electrode was used as the counter electrode to measure Y @ Fe-MOF, fe-MOF10, fe-MOF5, Y @ Fe-MOF|KOH _(aq) |Y@Fe-MOF、C ₇ H ₆ N ₂ @NF、IrO ₂ @NF、20％Pt/C@NF、20％Pt/C@NF|KOH _(aq) |IrO ₂ Linear sweep voltammogram of @ NF.

The electrochemical performance is tested by an electrochemical workstation, and the electrochemical workstation is a Chenhua electrochemical workstation, and the model is CHI660E.

Characterization of HER performance of the present product:

(1) Fe-MOF5, Y@Fe-MOF, C by linear sweep voltammetry ₇ H ₆ N ₂ HER performance tests were performed at @ NF and at 20% pt/c @ NF, resulting in HER polarization profile (LSV plot) and tafel slope plot, as shown in fig. 3 and 4, showing better performance than the iron-based 2D-MOF membrane electrode with the rare earth yttrium doping at the same time. Y@Fe-MOF at 0.01A/cm ² Has a minimum overpotential of 192mV at the current density of (a); and has a larger current density at a lower potential (508 mV over potential up to 2A/cm) ² ) The method comprises the steps of carrying out a first treatment on the surface of the Y@Fe-MOF has a minimum Tafil slope of 128.27mV dec ^-1 Proved by the feasibility of electrocatalytic hydrogen evolution under high current by adopting the rare earth element (RE) doped 2D Fe-MOF high-efficiency integrated membrane electrode.

(2) HER stability test was performed on y@fe-MOF using a current-time curve, as shown in fig. 5. HER stability test current Density was set at-0.45 mA/cm ² And-2 mA/cm ² . The results show that the Y@Fe-MOF has excellent hydrogen evolution and oxygen evolution stability under different current densities, and the current density is not obviously attenuated within 10 hours.

(3) To further verify the evolution of the structure and composition of the Y@Fe-MOF during HER, in situ Raman spectroscopy was performed in a 1M KOH medium, as shown in FIG. 6, the more negative the overpotential, the less the peaks of v (Ni-OH) and v (Ni-O) Raman can be seen in the active range of HER activity, belonging to the characteristic peaks exposed by the nickel base foam, indicating that the water on the catalyst surface is decomposed into hydrogen. At the end of the test all peaks described above were completely restored to the original state at the same time, indicating that in 1M KOH, the whole process of HER was reversible. This will give the catalyst good cycle stability.

Characterization of OER performance of the present product:

(1) Y@Fe-MOF, fe-MOF5, C by linear sweep voltammetry ₇ H ₆ N ₂ @NF、IrO ₂ OER performance test is carried out on @ NF, and an OER polarization curve graph (LSV graph) and a tafel slope graph are obtained, and as shown in fig. 7 and 8, the rare earth yttrium doped 2D Fe-MOF membrane electrode is found to show better electrocatalytic performance in comparison. Y@Fe-MOF at 0.01A/cm ² Has a minimum overpotential of 301mV at the current density of (a); and has a greater current density at very low overpotential (up to 2A/cm at an overpotential of 548 mV) ² ) The method comprises the steps of carrying out a first treatment on the surface of the And Y@Fe-MOF has a minimum Tafil slope of 72.1mV dec ^-1 Proved by the feasibility of electrocatalytic oxygen evolution under high current by adopting the rare earth element (RE) doped 2D Fe-MOF high-efficiency integrated membrane electrode.

(2) OER stability tests were performed on y@fe-MOF using a current-time scan method, as shown in fig. 9, respectively. HER stability test current Density was set to 0.01mA/cm ² 、0.1mA/cm ² 、1mA/cm ² And 2mA/cm ² . The results show that the Y@Fe-MOF has excellent hydrogen evolution and oxygen evolution stability under different current densities, and the current density is not obviously attenuated within 10 hours.

Comparison of the properties of different amounts of benzimidazole products:

to find the optimum benzimidazole content, the Fe-MOF3 prepared in example 2, the Fe-MOF10 prepared in example 3 and the Fe-MOF5 prepared in example 4 were tested for OER and HER properties by linear sweep voltammetry, respectively, to obtain OER and HER polarization profiles (LSV profiles) as shown in FIGS. 10 and 11, respectively, 2D Fe-MOF catalysts with benzimidazole content of 0.3g showed better properties, fe-MOF3 at 0.01A/cm ² With a minimum overpotential (OER: 264mV; HER:101 mV) and a relatively large current density at lower potentials (OER: 444mV overpotential up to 2A/cm) ² The method comprises the steps of carrying out a first treatment on the surface of the HER:631mV overpotential reaches 2A/cm ² ) The 2D Fe-MOF catalyst with benzimidazole content of 0.3g has the optimal electrocatalytic performance.

Characterization of the full water-splitting property of the product:

(1) By means of electric current-The time-scanning method was used for the full water stability test of Y@Fe-MOF|KOH (aq) |Y@Fe-MOF, as shown in FIG. 12. HER stability test current density was set at 1mA/cm ² . The result shows that Y@Fe-MOF|KOH (aq) |Y@Fe-MOF has excellent hydrogen evolution and oxygen evolution stability, and the current density is only attenuated by 4.8% after 5 hours.

(2) Y@Fe-MOF|KOH (aq) |Y@Fe-MOF, 20% Pt/C@NF|KOH (aq) |IrO were measured by linear sweep voltammetry ₂ The @ NF was tested for full water-splitting performance of the double working electrode, respectively, and the obtained full water-splitting polarization graph (LSV graph) was shown in FIG. 13, which shows that the current commercial noble metal catalyst 20% Pt/C @ NF|KOH (aq) |IrO under the same overpotential of 2.2V ₂ The @ NF can only reach 0.62A/cm ² And Y@Fe-MOF|KOH (aq) |Y@Fe-MOF can reach 1A/cm ² The current density is 1.613 times that of the noble metal system, indicating that Y@Fe-MOF|KOH (aq) |Y@Fe-MOF has significantly better electrolytic water catalytic activity than the noble metal system.

In conclusion, the rare earth element (RE) -doped 2D Fe-MOF high-efficiency integrated membrane electrode prepared by the invention has far better performance than noble metal catalyst (Pt/C, irO) ₂ ) The electrocatalytic full water-splitting performance is excellent in catalytic activity and cycle stability under high current density, and is beneficial to commercial application.

The description and practice of the invention disclosed herein will be readily apparent to those skilled in the art, and may be modified and adapted in several ways without departing from the principles of the invention. Accordingly, modifications or improvements may be made without departing from the spirit of the invention and are also to be considered within the scope of the invention.

Claims

1. A preparation method of a rare earth element doped 2D RE@Fe-MOF high-efficiency integrated membrane electrode is characterized by comprising the following specific steps:

step 3, preparing a rare earth element doped 2D RE@Fe-MOF high-efficiency integrated membrane electrode: adding a metal precursor solution into a stirred organic ligand solution, stirring, adding a current collector for in-situ modification reaction, taking out a sample after the reaction is finished, cleaning, and vacuum drying to obtain a rare earth element doped 2D RE@Fe-MOF high-efficiency integrated membrane electrode;

in the step 1, the dosage of benzimidazole is 0.3 g-1.0 g, and the volume of absolute ethyl alcohol is 40 mL-60 mL;

in the step 2, the rare earth element is yttrium or lanthanum, and the precursor is one or two of yttrium nitrate, lanthanum nitrate, yttrium acetate and lanthanum acetate;

in the step 1, the step 2 and the step 3, the stirring method is that the stirring method is placed on a magnetic stirrer, and the rotating speed is 100-300 rad/min;

in the step 2, the dosage of ferric nitrate is 0.4 g-0.6 g, the volume of absolute ethyl alcohol is 40 mL-60 mL, and the dosage of precursor of rare earth element is 0.01 g-0.1 g;

in the step 3, the metal precursor solution is rapidly added with the organic ligand solution under the action of magnetic stirring, the rotating speed is 100-300 rad/min, and the stirring time is 2-10 min;

in step 3, the current collector has a size of3×3cm ² ~10×10 cm ² ；

The current collector is foam nickel;

in the step 3, the reaction time is 5-8 h, the cleaning condition is that deionized water and ethanol are alternately washed, the vacuum drying temperature is 60-80 ℃, and the drying time is 12-24 h.

2. The application of the rare earth element doped 2D RE@Fe-MOF high-efficiency integrated membrane electrode prepared by the preparation method of claim 1 in hydrogen evolution, oxygen evolution and full water dissolution.