CN113279013A

CN113279013A - Monoatomic alloy nanowire catalyst for carbon dioxide electroreduction and preparation method thereof

Info

Publication number: CN113279013A
Application number: CN202110562519.9A
Authority: CN
Inventors: 吴登峰; 程道建
Original assignee: Beijing University of Chemical Technology
Current assignee: Beijing University of Chemical Technology
Priority date: 2021-05-24
Filing date: 2021-05-24
Publication date: 2021-08-20
Anticipated expiration: 2041-05-24
Also published as: CN113279013B

Abstract

The invention discloses a monatomic alloy nanowire catalyst for carbon dioxide electroreduction and a preparation method thereof, and relates to the technical field of electrocatalyst preparation. The method takes the simple substance copper nanowire after activation and surface modification as a template, adopts one or more than two of noble metal elements (rhodium, palladium, silver, iridium, platinum and gold) as a monoatomic component to prepare the monoatomic alloy nanowire catalyst, and enables the noble metal to be distributed on the surface of the copper nanowire in a monoatomic state. In the monatomic alloy nanowire, the content of the noble metal element is 0.1-10%. The monatomic alloy nanowire catalyst prepared by the method has the characteristics of high carbon dioxide electroreduction catalytic activity, high C2 product selectivity and the like.

Description

Monoatomic alloy nanowire catalyst for carbon dioxide electroreduction and preparation method thereof

Technical Field

The invention relates to the technical field of preparation of electrocatalysts, in particular to a monatomic alloy nanowire catalyst for carbon dioxide electroreduction and a preparation method thereof.

Background

In recent years, the greenhouse effect is increasing, which causes global warming and causes a lot of natural disasters. The greenhouse effect caused by greenhouse gases such as carbon dioxide is the most obvious.

Carbon dioxide is the highest-valence oxide of carbon, the property of the carbon dioxide is very stable, and the carbon dioxide is an abundant carbon resource, if the carbon dioxide can be fixed and further converted into other forms of energy, the influence of greenhouse effect can be greatly reduced, and the energy problem can be fully relieved. The electrocatalytic carbon dioxide reduction reaction plays an important role in the aspects of environmental balance, carbon cycle, sustainable energy conversion and the like. Designing and preparing the high-activity and high-selectivity electrocatalyst is the key point for smoothly carrying out the electrocatalytic carbon dioxide reduction process.

The metal catalyst is the most deeply researched type of carbon dioxide reduction electrocatalyst at present due to the advantages of high catalytic activity, excellent conductivity, simple preparation, easy practical application and the like. The carbon dioxide reduction products of most metal catalysts are primarily carbon monoxide or formic acid. However, among many metal catalysts, only metallic copper can directly reduce carbon dioxide into high value-added hydrocarbons or alcohols at a high current efficiency, and among them, C2 products (such as ethylene and methanol) are important chemical products. As such, research and development on copper catalysts have received much attention. Unfortunately, higher overpotential and poor selectivity in obtaining the C2 product are major obstacles to practical use of copper catalysts. Therefore, the design and preparation of the copper-based electrocatalyst with high activity and high selectivity have important significance for preparing high-added-value chemicals such as C2 compounds by electrocatalysis of carbon dioxide reduction, and breakthrough in the fields of environmental protection, sustainable energy conversion and the like can be brought.

Aiming at the problems of high overpotential and poor selectivity of the copper-based catalyst in the electrocatalytic carbon dioxide reduction process, the copper-based catalyst is from the aspect of morphology and structureThe optimization design is an important strategy for the research and development of the catalyst. Researches show that the metal nanowire with the one-dimensional structure has stronger agglomeration resistance, geometric stability and charge transmission performance compared with a particle type metal nano catalyst in the electrocatalytic reaction process, so that great attention is paid to the metal nanowire. Wang et al (Nano Letters,2015,15:6829-6835) found that high-density copper nanowires showed excellent electrocatalytic carbon dioxide reduction performance with a current density of 1.0mAcm^-2The overpotential required is only 0.3V (vs. rhe). Ma et al (Angewandte Chemie International Edition,2016,128:6792-6796) found in their studies that Cu nanowire arrays had high selectivity for the production of C2 products during the electrocatalytic carbon dioxide reduction process, and also found that the Faraday efficiency increased with increasing aspect ratio of the Cu nanowires. In addition, the method for enhancing and controlling the activity and selectivity of the Cu-based catalyst by using an alloying method is one of the common methods at present, the metal copper and a second transition metal (such as silver, gold, platinum, palladium, tin and the like) are alloyed, and the activity and the selectivity of the Cu-based catalyst can be controlled by utilizing the synergistic effect of the two metals.

With the gradual maturity of the preparation and characterization technology of the monatomic catalyst, the noble metal with high intrinsic catalytic activity is often designed as the monatomic catalyst for the purpose of reducing the noble metal loading and maximizing the atom utilization rate. Furthermore, researchers have derived the concept of monatomic alloys based on the concept of traditional monatomic catalysts using metal oxides, graphene-like materials, and the like as carriers. By monatomic alloy, it is meant that the low content components of the alloy are isolated from each other in the alloy system and exist in a monatomic form. The interaction between solute atoms and the matrix in the metal matrix can effectively change the electronic structures of the solute atoms and the matrix, obtain proper adsorption energy to intermediate products and further obtain good catalytic performance. Furthermore, monatomic alloy catalysts often suffer from overflow of intermediate products between the solute atoms and the substrate during the reaction, which provides a routing possibility for the concerted catalysis between the two metal atoms. However, no transition metal monatomic alloy carbon dioxide reduction electrocatalyst directly taking the Cu nanowire as the substrate is reported.

Based on the current research situation, it can be known that a simple method is found to prepare the monatomic alloy nanowire catalyst, and the monatomic alloy nanowire catalyst has important significance in electrocatalysis of carbon dioxide reduction.

Disclosure of Invention

The invention aims to provide a monatomic alloy nanowire catalyst for carbon dioxide electroreduction and a preparation method thereof, which are used for solving the problems in the prior art and remarkably improving the catalytic conversion efficiency and selectivity of carbon dioxide electroreduction.

In order to achieve the purpose, the invention provides the following scheme:

the invention provides a monatomic alloy nanowire catalyst for carbon dioxide electroreduction, which is prepared by taking a copper nanowire as a template and precious metal as a monatomic component and loading the precious metal on the copper nanowire;

the noble metal is one or more than two of rhodium, palladium, silver, iridium, platinum and gold;

the noble metal accounts for 0.1-10% of the total mass of the monatomic alloy nanowire.

Further, the noble metal is silver and accounts for 0.1-5% of the total mass of the monatomic alloy nanowire.

Further, the diameter of the copper nanowire is 10-100 nm, and the length-diameter ratio is 10-500; the copper nanowire has a quintupled twin structure, namely, the side surface is a <100> crystal plane, and the two ends are <111> crystal planes.

The invention also provides a preparation method of the monatomic alloy nanowire catalyst, which comprises the following steps:

(1) carrying out surface activation treatment on the copper nanowire;

(2) dispersing the copper nanowires subjected to surface activation treatment in an organic solvent containing a surface covering agent to obtain a dispersion liquid A;

the concentration of the surface covering agent in the organic solvent is 0.01 mol/L;

(3) slowly adding the solution B containing the noble metal precursor into the dispersion liquid A, and drying the product after reaction to obtain the monatomic alloy nanowire;

further, the reaction temperature in the step (3) is 25-150 ℃, and the reaction time is 5 min-1 h;

further, the molar ratio of the copper nanowires to the surfactant is 0.05-1mmol:0.01 mol;

further, the surface activation treatment is air heat treatment and acid pickling treatment which are adopted in sequence;

the temperature of the air heat treatment is 50-200 ℃, and the time is 5-30 min; the acid washing treatment is to wash for 10 s-10 min in strong acid solution with the concentration of 0.01-0.1 mol/L or weak acid solution with the concentration of 0.02-1.0 mol/L;

the strong acid is nitric acid or hydrochloric acid; the weak acid is acetic acid, formic acid or hypochlorous acid.

The activation treatment of the copper nanowire is divided into two steps, the first step is heat treatment under air, and the activation treatment has three functions: 1. removing volatile impurities on the surface of the copper nanowire; 2. forming an oxide thin layer to reduce the acid resistance of surface layer atoms; 3. the crystallinity of internal atoms is improved, thereby enhancing the thermal stability of the whole material. And the second step is to treat the surface of the copper nanowire by using dilute strong acid or medium strong acid, so as to remove the surface oxide and simultaneously manufacture enough defect sites, thereby providing conditions for capturing the single atom of the noble metal and enhancing the load of the single atom.

Further, the surface covering agent is one or a mixture of more of dimethyl dioctadecyl ammonium chloride, hexadecyl trimethyl ammonium chloride, triphenylphosphine or octadecyl dihydroxyethyl methyl ammonium chloride.

The activated copper nanowire is subjected to surface modification, and the surface covering agent is used for slowing down the rate of galvanic displacement reaction between noble metal ions and copper atoms on the surface of the copper nanowire, so that the noble metal is prevented from being aggregated into particles due to the fact that the reduction deposition rate of the noble metal is greater than the diffusion rate, the noble metal atoms are effectively controlled to be deposited on the surface of the copper nanowire in a monatomic mode, and the monatomic alloy nanowire is formed.

Further, the organic solvent in the step (2) is one or more of ethylene glycol, n-hexane, octadecene, oleic acid or octadecane.

Further, the noble metal precursor is one of nitrate, acetylacetone salt, sulfate or chloride; the concentration of the noble metal precursor in the solution B is 0.01-0.5 mol/L.

Furthermore, the solution B is added into the dispersion liquid A by a micro-injection pump, and the injection rate is 0.1-10 mL/min.

The invention discloses the following technical effects:

1. according to the monatomic alloy nanowire catalyst prepared by the method, noble metal atoms can achieve a complete monatomic distribution state on the surface of the copper nanowire, and the purposes of reducing the consumption of noble metals and reducing the cost of the catalyst are achieved.

2. The preparation method can realize the accurate and controllable adjustment of the single atom load so as to achieve the controllable adjustment of the catalyst performance, and the preparation method is simple.

3. The catalyst has high-efficiency electrocatalytic activity for carbon dioxide electroreduction and high selectivity for C2 products.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

FIG. 1 is an XRD diffractogram of a monatomic alloy nanowire catalyst of example 1;

FIG. 2 is a TEM image of a single atom alloy nanowire catalyst in example 1;

FIG. 3 is CO of monatomic alloy nanowires in example 1₂Electro-reducing the cyclic voltammetry test chart;

fig. 4 is a copper nanowire in which noble metal is dispersed in the form of large-sized particles in comparative example 1.

Detailed Description

Reference will now be made in detail to various exemplary embodiments of the invention, the detailed description should not be construed as limiting the invention but as a more detailed description of certain aspects, features and embodiments of the invention.

It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Further, for numerical ranges in this disclosure, it is understood that each intervening value, between the upper and lower limit of that range, is also specifically disclosed. Every smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in a stated range is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference herein for the purpose of disclosing and describing the methods and/or materials associated with the documents. In case of conflict with any incorporated document, the present specification will control.

It will be apparent to those skilled in the art that various modifications and variations can be made in the specific embodiments of the present disclosure without departing from the scope or spirit of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification. The description and examples are intended to be illustrative only.

As used herein, the terms "comprising," "including," "having," "containing," and the like are open-ended terms that mean including, but not limited to.

The copper nanowire template used in the embodiment of the invention has a quintupled twin structure.

Example 1

1) The copper nanowire with the diameter of 100nm and the length-diameter ratio of 50 is subjected to heat treatment for 5min in air at 100 ℃, and then is subjected to acid cleaning for 10min in 0.01mol/L sulfuric acid.

2) And dispersing the surface-treated 0.1mmol of copper nanowires in a 0.01mol/L glycol solution of dimethyl dioctadecyl ammonium chloride.

3) 10mL of a 0.01mol/L silver nitrate solution (a mixed solution of ethylene glycol and water in a ratio of 1: 1) was injected into the dispersion by a micro syringe pump at a rate of 0.10mL/min, and the resulting solution was heated to 100 ℃ to react for 30 min.

4) And centrifuging, washing and drying the product to obtain the monatomic alloy nanowire.

The monatomic alloy nanowire catalyst obtained in example 1 was subjected to a composition test using an inductively coupled plasma spectrometer (ICP), and the results of the obtained composition data are shown in table 1, and it can be seen from table 1 that the mass fraction of silver monatomic in the catalyst of example 1 was 1.53%.

Fig. 1-2 are XRD diffractograms and TEM images of the monatomic alloy nanowire catalyst of example 1, respectively.

As can be seen from fig. 1, the main diffraction peaks of the product are (111), (100) and (110) crystal planes mainly corresponding to elemental copper, which proves that no noble metal nanoparticles exist, and the noble metal on the copper nanowire is in a monoatomic state.

As can be seen from fig. 2, the morphology of the product remains that of the nanowire, confirming the absence of the noble metal nanoparticles.

The performance of electrocatalytic carbon dioxide reduction of the product is tested on an electrochemical workstation, a catalyst is utilized to modify an electrode, and CO of the monatomic alloy nanowire is obtained by cyclic voltammetry scanning in a solution saturated by carbon dioxide₂And (3) an electroreduction cyclic voltammetry test chart as shown in figure 3.

From fig. 3, the performance of the material in electrocatalysis of carbon dioxide reduction can be seen, and the faradaic efficiency of the C2 product is obtained by combining a gas chromatographic analysis means, so that the selectivity of the catalyst is evaluated. It can be found that the faradaic efficiency of the C2 product of the product obtained in example 1 can reach 55.23%.

Example 2

1) The copper nanowire with the diameter of 10nm and the length-diameter ratio of 500 is subjected to heat treatment in air at 50 ℃ for 30min, and then is subjected to acid washing in 0.02mol/L acetic acid for 8 min.

2) And dispersing the surface-treated 0.05mmol of copper nanowires in a 0.01mol/L glycol solution of dimethyl dioctadecyl ammonium chloride.

3) 10mL of a silver nitrate solution (solvent of ethylene glycol and water 4: 1) was injected into the above dispersion using a micro syringe pump at an injection rate of 10mL/min, and the resulting solution was heated to 25 ℃ to react for 5 min.

Example 3

1) The copper nanowire with the diameter of 100nm and the length-diameter ratio of 50 is subjected to heat treatment in air at 200 ℃ for 20min, and then is subjected to acid washing in nitric acid of 0.01mol/L for 10 s.

2) The copper nanowires with 1mmol of surface treatment are dispersed in n-hexane solution containing 0.01mol/L of surface covering agent (mixture of cetyltrimethylammonium chloride, triphenylphosphine and the like).

3) 10mL of a silver nitrate solution containing a concentration of 0.1mol/L (solvent: ethylene glycol and water 5: 1) was injected into the above dispersion a using a micro syringe pump at an injection rate of 5mL/min, and the resulting solution was heated to 150 ℃ to react for 1 hour.

Example 4

The preparation method is the same as that of example 1, except that the organic solvent in the step 2) is a mixture of n-hexane, octadecene and oleic acid.

Example 5

The preparation method is the same as that of example 1, except that the metal salt in the step 3) is silver acetylacetonate.

Example 6

The preparation method is the same as that of example 1, except that the metal salt in the step 3) is a mixture of silver nitrate and palladium acetylacetonate in a molar ratio of 1: 1.

Example 7

The preparation method is the same as that of example 1, except that the metal salt in the step 3) is a mixture of silver nitrate and potassium chloroplatinate in a molar ratio of 1: 1.

Example 8

The preparation method is the same as that of example 1, except that the metal salt in the step 3) is a mixture of silver nitrate and ruthenium acetylacetonate in a molar ratio of 1: 1.

Example 9

The preparation method is the same as that of example 1, except that the metal salt in the step 3) is a mixture of silver nitrate and rhodium acetylacetonate in a molar ratio of 1: 1.

Example 10

The preparation method is the same as that of example 1, except that the metal salt in the step 3) is silver nitrate, palladium acetylacetonate and platinum acetylacetonate in a molar ratio of 1: 0.5: 0.5 of a mixture.

TABLE 1

As can be seen from Table 1, the content of Ag in the monatomic alloy nanowires obtained by the preparation method is relatively close in examples 1-5, and the Faraday efficiencies of the C2 products are relatively high. While the loading of the single atom is significantly reduced when other noble metals are introduced and the faradaic constant of the C2 product is also significantly reduced.

Comparative example 1

The preparation method is the same as that of the example 1, except that the surface covering agent is not added in the step 2) to modify the copper nanowires.

The negative effect is that the proportion of noble metal monoatomic atoms on the copper nanowire is very small, and the noble metal is dispersed on the copper nanowire in the form of large-sized particles (as shown in fig. 4).

Comparative example 2

The preparation method is the same as example 1, except that the acid treatment is not performed in step 1).

The negative effect is that the proportion of the noble metal single atoms on the copper nano wire is very small, and the noble metal is dispersed in the solution in the form of particles or ions.

Comparative example 3

The preparation method is the same as example 1, except that air heat treatment is not performed in step 1).

The negative effect is that the proportion of the noble metal single atoms on the copper nano-wire is very small, and the noble metal is dispersed on the copper nano-wire in the form of cluster or particle.

The products prepared in comparative examples 1-3 were subjected to compositional testing using an inductively coupled plasma spectrometer (ICP) and the results are shown in Table 2.

TABLE 2

Comparing the data results in tables 1-2, it can be seen that the faradaic constant of the C2 product of comparative examples 1-3 is significantly reduced compared to examples 1-3, and although the metal loading is improved, the single atom content is very small due to the presence of most of the particles, which may be the main reason for the low faradaic coefficient of the C2 product.

The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are within the scope of the present invention defined by the claims.

Claims

1. A monatomic alloy nanowire catalyst for carbon dioxide electroreduction is characterized in that the catalyst is prepared by taking a copper nanowire as a template and precious metal as a monatomic component and loading the precious metal on the copper nanowire;

2. The monatomic alloy nanowire catalyst of claim 1, wherein the noble metal is silver and is present in an amount of 0.1 to 5% by weight of the monatomic alloy nanowire.

3. The monatomic alloy nanowire catalyst of claim 1, wherein the copper nanowire has a diameter of 10 to 100nm and an aspect ratio of 10 to 500; the copper nanowire is of a quintupled twin structure.

4. The method of preparing the monatomic alloy nanowire catalyst of any of claims 1-3, wherein the method of preparing comprises the steps of:

(1) carrying out surface activation treatment on the copper nanowire;

(3) slowly adding the solution B containing the noble metal precursor into the dispersion liquid A, and drying the product after reaction to obtain the monatomic alloy nanowire.

5. The production method according to claim 4, wherein the surface activation treatment is a heat treatment with air and an acid washing treatment in this order;

the temperature of the air heat treatment is 50-200 ℃, and the time is 5-30 min; the acid washing treatment is to wash for 10 s-10 min in strong acid solution with the concentration of 0.01-0.1 mol/L or weak acid solution with the concentration of 0.02-1.0 mol/L.

6. The preparation method according to claim 4, wherein the surface covering agent is one or more of dimethyldioctadecylammonium chloride, cetyltrimethylammonium chloride, triphenylphosphine or octadecyl dihydroxyethylmethylammonium chloride.

7. The preparation method according to claim 4, wherein the organic solvent in the step (2) is one or more of ethylene glycol, n-hexane, octadecene, oleic acid or octadecane.

8. The preparation method according to claim 4, wherein the noble metal precursor is one of a nitrate, an acetylacetonate, a sulfate, and a chloride; the concentration of the noble metal precursor in the solution B is 0.01-0.5 mol/L.

9. The method according to claim 4, wherein the solution B is added to the dispersion A by a micro-syringe pump at a rate of 0.1-10 mL/min.