CN110180552B

CN110180552B - Copper/cuprous oxide/molybdenum dioxide electrocatalytic material and preparation method and application thereof

Info

Publication number: CN110180552B
Application number: CN201910575475.6A
Authority: CN
Inventors: 喻发全; 童晶; 薛亚楠; 王建芝; 谌伟民; 蔡宁
Original assignee: Wuhan Institute of Technology
Current assignee: Wuhan Institute of Technology
Priority date: 2019-06-28
Filing date: 2019-06-28
Publication date: 2022-05-10
Anticipated expiration: 2039-06-28
Also published as: CN110180552A

Abstract

本发明涉及一种铜/氧化亚铜/二氧化钼电催化材料及其制备方法和在电解水析氢方面的应用。首先对泡沫镍进行清洗处理，然后将其置于含铜和钼的酸性溶液中水热反应，最后将其置于还原气氛中高温还原即可。该材料通过金属氢氧根和金属结合产生的协同作用提高了其在碱性条件下的催化析氢效果和耐久性，其中氢氧根促进了水的离解，附近的金属原子促进了氢中间体对H₂分子的吸附和结合。The invention relates to a copper/cuprous oxide/molybdenum dioxide electrocatalytic material, a preparation method thereof, and an application in the aspect of electrolysis of water for hydrogen evolution. First, the foamed nickel is cleaned, then placed in an acidic solution containing copper and molybdenum for hydrothermal reaction, and finally placed in a reducing atmosphere for high temperature reduction. The material enhances its catalytic hydrogen evolution effect and durability under alkaline conditions through the synergistic effect of metal hydroxide and metal binding, where hydroxide promotes water dissociation and nearby metal atoms promote hydrogen intermediate pairing Adsorption and binding of H _molecules .

Description

Copper/cuprous oxide/molybdenum dioxide electrocatalytic material and preparation method and application thereof

Technical Field

The invention relates to the technical field of composite functional materials, in particular to a copper/cuprous oxide/molybdenum dioxide electrocatalytic material, a preparation method thereof and application thereof in hydrogen evolution by electrolysis of water.

Background

The hydrogen is a clean and flexible energy carrier, is expected to play a key role in a sustainable energy system in the future, and the electrochemical water cracking technology provides a sustainable development approach for producing the hydrogen. The technology can convert electric energy from renewable energy sources into chemical energy, is a hydrogen conversion technology with a very promising prospect, and has profound significance for effectively and widely utilizing the renewable energy sources. The renewable energy source is characterized by variable and intermittent output, and the key point for realizing high-efficiency water cracking lies in developing a high-activity and durable electrocatalyst for hydrogen evolution reaction.

The alkaline water splitting technology provides a strong support for the commercial production of cost-effective hydrogen. To achieve higher reaction rates, negligible overpotentials are required. Platinum (Pt) is a recognized reference catalyst for the catalytic hydrogen evolution from electrolyzed water, however, due to the scarcity and high cost of platinum, the large-scale industrial application of platinum is severely limited. Therefore, it is of great significance to further explore and develop a high-efficiency and low-cost catalyst for hydrogen evolution by electrolysis of water under alkaline conditions.

The inventor team and other researchers have previously disclosed a number of metal foam-based composites and their use in the catalytic hydrogen evolution from electrolyzed water. In CN108950585A, the copper foam is not used as a support material, it participates in the reaction at the later stage and is transformed into a part of active substances of the catalyst, and the generated sulfide substance is brittle and lacks toughness. The preparation method of the electrochemical material disclosed in CN108754532A is complicated, the generated LDH itself has relatively weak electronic conductivity, and although the electronic conductivity is improved by the post carbon coating treatment, the structure of the LDH may be damaged by the high-temperature carbonization treatment to cover the original active sites. The composite material disclosed in CN106702425A has excellent catalytic activity only in acidic solution, and in addition, the preparation process is complicated, and the electrolytic water reaction requires water molecules to be in full contact with the catalyst. Moreover, the scheme is that the copper electroplating layer on the surface of the formed molybdenum disulfide covers a part of active sites, and the catalytic efficiency of the material is reduced. The catalyst disclosed in CN109468662A is in powder or granule form, and needs to be supported on a glassy carbon electrode by means of an adhesive for electrochemical test and reaction, and active substances may fall off under a high current density state, which affects the catalytic performance.

In conclusion, the existing similar electrocatalytic materials have some problems in the performances, preparation methods and use processes.

Disclosure of Invention

The invention aims to solve the problems of the existing electrolytic water catalytic hydrogen evolution catalytic material, and the non-precious Cu-Mo-O type electrocatalytic material is prepared by combining a hydrothermal method with a high-temperature reduction reaction. The material shows extremely high activity and excellent stability when water is electrolyzed in an alkaline solution for catalyzing hydrogen evolution, and has good application prospect. In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

the preparation method of the copper/cuprous oxide/molybdenum dioxide electrocatalytic material specifically comprises the following steps: (a) pretreating the three-dimensional foam metal for later use; (b) preparing a mixed solution by using a copper salt and a molybdenum salt, and adding the treated three-dimensional foam metal to perform a hydrothermal reaction to obtain a copper-molybdenum bimetal oxide precursor; (c) and (3) placing the copper-molybdenum bimetal oxide precursor in a reducing atmosphere for reduction.

Further, the three-dimensional foam metal is specifically foam nickel, the porosity of the foam nickel is more than 90%, and the purity of the foam nickel is more than 98%.

Further, the pretreatment of the step (a) comprises soaking and cleaning the three-dimensional foam metal by using at least one of deionized water, an acid solution and an alcohol solvent, wherein the soaking and cleaning temperature does not exceed 200 ℃, and ultrasonic treatment is applied during the soaking and cleaning process so as to enhance the cleaning effect.

Further, the preparation method of the mixed solution in the step (b) is as follows: adding copper salt and molybdenum salt into water, stirring and dissolving, and adjusting the pH value to 2-5 by using dilute hydrochloric acid aqueous solution.

Further, the copper salt is selected from one of copper nitrate, copper chloride, copper sulfate and copper acetate, and is preferably copper nitrate; the molybdenum salt is selected from one of sodium molybdate and ammonium molybdate, and sodium molybdate is preferred. The molar ratio of the copper salt to the molybdenum salt is 0.25-4: 1.

Further, the hydrothermal reaction temperature in the step (b) is 100-200 ℃, and the hydrothermal reaction time is within 24 h.

Further, in the step (c), the reducing atmosphere is hydrogen, the reducing reaction temperature is 200-600 ℃, and the reducing reaction time is within 6 h.

Another object of the present invention is to provide a copper/cuprous oxide/molybdenum dioxide electrocatalytic material prepared according to the above method, which can be used for the catalytic hydrogen evolution of electrolyzed water in alkaline solution.

The catalytic activity of most of the catalysts for catalyzing hydrogen evolution by electrolyzed water under alkaline conditions is usually obviously lower than that under acidic conditions, and the phenomenon can be possibly combined with electrolyzed water in alkaline or acidic solutionThe reaction path difference of hydrogen evolution is related. More precisely, the electrolytic water evolution of hydrogen reaction shows slow kinetics in alkaline solutions, probably due to the fact that the H intermediate is derived from water rather than hydronium ion (H)₃O⁺) Caused by medium release. This problem can be solved by creating a synergistic catalyst by combining metal hydroxides, which promote the dissociation of water, with metal atoms, which promote the hydrogen intermediate to H₂Adsorption and binding of molecules.

The potential of molybdenum-based materials as electrocatalysts for hydrogen evolution by water electrolysis catalysis is receiving more and more attention. To date, a great deal of effort has been devoted to lowering the energy barrier (Δ G (H)₂O)) water separation step. Research reports that doping of heteroatoms and adjusting the valence state of molybdenum are effective strategies to accelerate the kinetics of alkaline HER reactions, particularly transition metal molybdates (mmoos)₄) And hydrates thereof are ideal precursors for the preparation of active rare earth electrocatalysts, because the molybdenum-based materials are highly active and the electronic structure between molybdenum and the heteroatom (M) is adjustable. It was also found that in a 1.0M KOH solution, the oxide contained Mo of a lower valence state (surface Mo)⁵⁺And Mo⁴⁺) The activity of the precursor is obviously enhanced compared with that of the bimetallic oxide precursor containing Mo with the valence of + 6.

The invention provides copper/cuprous oxide/molybdenum dioxide (Cu/Cu)₂O/MoO₂) The electro-catalytic hydrogen evolution catalyst takes three-dimensional porous foamed nickel with a net structure as a carrier, so that on one hand, the contact surface area of the catalyst and water is increased, and a good channel is provided for electron transfer; on the other hand, the conductivity of the hybrid catalyst is improved, the dispersibility of the electroactive phase is enhanced, and the electroactive phase has more active sites. Cu/Cu grown in situ on foamed nickel surface₂O/MoO₂The two-dimensional active nano-sheet has an open framework and is in close contact with a three-dimensional conductive substrate. Due to the synergistic effects of strong interaction, electron transfer and the like at the interface of the metal/oxide, the material shows excellent activity in the aspect of hydrogen evolution; the oxide carrier strongly influences the physical and chemical properties of the metal nanoparticles by providing dual active sites at the metal/oxide interfacePlays a key role in the catalysis process, and finally improves the catalytic activity, selectivity and durability of the catalytic material. Experiments show that the low-valence copper-molybdenum bimetal oxide prepared by the thermal reduction method has better catalytic activity and stability under the alkaline condition. In addition, the invention also has the advantages of cheap and easily obtained raw materials, simple preparation process, lower cost and the like.

Drawings

FIG. 1 shows Cu/Cu obtained in example 1 of the present invention₂O/MoO₂XRD pattern of (a);

FIG. 2 shows Cu/Cu obtained in example 1 of the present invention₂O/MoO₂SEM picture of (1);

FIG. 3 shows Cu/Cu obtained in example 1 of the present invention₂O/MoO₂Working electrode polarization curves and Tafel comparison graphs of the nickel foam of comparative example 1 and the copper-molybdenum bimetal oxide precursor of comparative example 2;

FIG. 4 shows Cu/Cu obtained in example 1 of the present invention₂O/MoO₂Chronopotentiometry at constant current density in alkaline solution.

Detailed Description

In order to make those skilled in the art fully understand the technical solutions and advantages of the present invention, the following embodiments are further described.

Example 1

(1) And putting the three-dimensional foam nickel into absolute ethyl alcohol, and carrying out ultrasonic treatment for 30min so as to remove oil stains on the surface. Taking out and putting into an autoclave filled with 1mol/L dilute hydrochloric acid aqueous solution, heating to 100 ℃, and carrying out hydrothermal reaction for 6h so as to remove the oxide on the surface. And taking out the foamed nickel after the reaction is finished, and washing the foamed nickel with deionized water for later use.

(2) Deionized water is used as a solvent to prepare a mixed solution of copper nitrate and sodium molybdate, wherein the concentration of the copper nitrate is 0.02mol/L, and the concentration of the sodium molybdate is 0.01 mol/L. And (3) adjusting the pH value of the mixed solution to 3-4 by using 1mol/L dilute hydrochloric acid aqueous solution to obtain a clear and transparent mixed solution. And (3) placing the cleaned foam nickel into an autoclave filled with an acidic mixed solution, and heating to 180 ℃ for hydrothermal reaction for 6 hours. And taking out the foamed nickel after the reaction is finished, washing the foamed nickel by deionized water, and drying to obtain the copper-molybdenum bimetal oxide precursor.

(3) In the hydrogen atmosphere, heating the copper-molybdenum bimetal oxide precursor from room temperature to 450 ℃ at the heating rate of 5 ℃/min, and keeping the temperature for 2h to obtain Cu/Cu₂O/MoO₂An electrocatalytic material.

Example 2

(1) Putting the three-dimensional foamed nickel into 1mol/L dilute hydrochloric acid aqueous solution, and performing ultrasonic treatment for 20min to remove oxides on the surface; taking out, washing with deionized water, soaking in anhydrous ethanol for about 20min to remove oil, and ultrasonic treating in deionized water for about 10 min.

(2) Deionized water is used as a solvent to prepare a mixed solution of copper nitrate and sodium molybdate, wherein the concentration of the copper nitrate is 0.02mol/L, and the concentration of the sodium molybdate is 0.01 mol/L. And (3) adjusting the pH value of the mixed solution to 3-4 by using 1mol/L dilute hydrochloric acid aqueous solution to obtain a clear and transparent mixed solution. And (3) placing the cleaned foam nickel into an autoclave filled with an acidic mixed solution, and heating to 160 ℃ for hydrothermal reaction for 6 hours. And taking out the foamed nickel after the reaction is finished, washing the foamed nickel by deionized water, and drying to obtain the copper-molybdenum bimetal oxide precursor.

Comparative example 1

Putting the three-dimensional foamed nickel into absolute ethyl alcohol, performing ultrasonic treatment for 30min, taking out the three-dimensional foamed nickel, putting the three-dimensional foamed nickel into a high-pressure kettle filled with 1mol/L dilute hydrochloric acid aqueous solution, heating the three-dimensional foamed nickel to 100 ℃, performing hydrothermal reaction for 6h, taking out the foamed nickel after the reaction is finished, and washing the foamed nickel with deionized water for later use.

Comparative example 2

(1) Putting the three-dimensional foamed nickel into absolute ethyl alcohol, performing ultrasonic treatment for 30min, taking out the three-dimensional foamed nickel, putting the three-dimensional foamed nickel into a high-pressure kettle filled with 1mol/L dilute hydrochloric acid aqueous solution, heating the three-dimensional foamed nickel to 100 ℃, performing hydrothermal reaction for 6h, taking out the foamed nickel after the reaction is finished, and washing the foamed nickel with deionized water for later use.

(2) Deionized water is used as a solvent to prepare a mixed solution of copper nitrate and sodium molybdate, wherein the concentration of the copper nitrate is 0.02mol/L, and the concentration of the sodium molybdate is 0.01 mol/L. And (3) adjusting the pH value of the mixed solution to 3 by using 1mol/L dilute hydrochloric acid aqueous solution, putting the cleaned foam nickel into an autoclave filled with the mixed solution, and heating to 180 ℃ for hydrothermal reaction for 6 hours. And taking out the foamed nickel after the reaction is finished, washing the foamed nickel by deionized water, and drying to obtain the copper-molybdenum bimetal oxide precursor.

To fully understand the Cu/Cu obtained in example 1₂O/MoO₂The performance of the electrocatalytic material, which was subjected to XRD and SEM tests, is shown in fig. 1-2. As can be seen from fig. 1, the characteristic peaks of the nickel foam at 44.5 °, 51.8 ° and 76.4 ° of 2 θ, the characteristic peaks of the metal copper at 43.3 °, 50.4 ° and 74.1 ° of 2 θ, the characteristic peaks of the molybdenum dioxide at 26.3 ° and 37 ° of 2 θ, and the characteristic peak of the cuprous oxide at 36.4 ° of 2 θ. FIG. 2 shows Cu/Cu₂O/MoO₂The SEM photograph of the electrocatalytic material shows that molybdenum dioxide and cuprous oxide are deposited on the surface of the nickel foam in a lamellar structure with non-uniform size.

Cu/Cu from example 1, respectively, using a three-electrode system₂O/MoO₂The electrocatalytic material, the nickel foam pretreated in the comparative example 1 and the copper-molybdenum bimetallic oxide precursor prepared in the comparative example 2 are used as working electrodes, the saturated calomel electrode is used as a reference electrode, the graphite rod is used as a counter electrode, and the electrolytic hydrogen evolution performance test is carried out in a potassium hydroxide aqueous solution (electrolyte solution) of 1.0mol/L at the temperature of 25 +/-0.3 ℃. Before testing, N was bubbled into KOH solution₂Saturation was achieved and the scan rate at the electrochemical workstation (Shanghai Chenghua instruments Co., Ltd., CHI760E) was 2mV/s and the scan voltage ranged from-0.9V to-1.5V (relative to a saturated calomel electrode) as measured, the results are shown in FIG. 3.

FIG. 3(a) is a graph in which curve 1 shows Cu/Cu₂O/MoO₂The polarization curve of (2) shows that, in the absence of resistance compensation, the hydrogen evolution current density reached-10 mA cm^-2The overpotential is only 52 mV; curve 1 in FIG. 3(b) is Cu/Cu₂O/MoO₂The corresponding Tafel slope has a specific value of 40mV dec^-1. FIG. 3(a) Curve 3, which is a polarization curve of the pretreated nickel foam of comparative example 1, shows that the hydrogen evolution current density reaches-10mA·cm^-2The overpotential is 299 mV; FIG. 3(b) Curve 3 is a Tafel slope for the nickel foam of comparative example 1, having a specific value of 142mV dec^-1. Curve 2 in FIG. 3(a) is a polarization curve of the precursor of comparative example 2, and it can be seen from the graph that the hydrogen evolution current density reached-10 mA cm^-2The overpotential is 266 mV; FIG. 3(b), Curve 2, is the Tafel slope of the precursor of comparative example 2, with a specific value of 155mV dec^-1. These data all show that the Cu/Cu produced in example 1₂O/MoO₂The hydrogen evolution electrocatalyst has excellent electrocatalytic hydrogen evolution performance in alkaline solution, and can be used for a faster dynamic electrolysis water hydrogen evolution process.

Cu/Cu from example 1 recorded during the electrolytic Hydrogen evolution Performance test₂O/MoO₂Constant current density timer (condition: -10 mA/cm)²Electrolysis was continued for 24h) at constant current the potential profile is shown in figure 4. As can be seen from the figure, the overpotential is not obviously attenuated in the long-time electrocatalytic hydrogen evolution process under the specific current density, which shows that the Cu/Cu provided by the invention₂O/MoO₂The catalytic material has good stability of electrocatalytic hydrogen evolution.

Claims

1. The preparation method of copper/cuprous oxide/molybdenum dioxide electrocatalytic material, which is characterized by comprising the following steps: (a) pretreatment of three-dimensional metal foam for standby; (b) adding copper salt and molybdenum salt into water Stir and dissolve, adjust the pH of the acid solution to be acidic to obtain a mixed solution, and add the treated three-dimensional foam metal to perform a hydrothermal reaction to obtain a copper-molybdenum bimetallic oxide precursor; (c) Put the copper-molybdenum bimetallic oxide precursor into the The reduction is carried out in a reducing atmosphere, the reducing atmosphere is hydrogen, the reduction reaction temperature is 200-600° C., and the reduction reaction time is within 6 hours; the three-dimensional foam metal is specifically foamed nickel.

2 . The preparation method according to claim 1 , wherein the pretreatment in step (a) comprises soaking and cleaning the three-dimensional metal foam by using at least one of deionized water, an acid solution, and an alcohol solvent, and soaking and cleaning The temperature does not exceed 200°C, and ultrasonic treatment is also applied while soaking and cleaning.

3. The preparation method of claim 1, wherein the acid solution is specifically a dilute aqueous hydrochloric acid solution, and the pH of the mixed solution is adjusted to 2-5.

4. preparation method as claimed in claim 1 is characterized in that: described copper salt is selected from a kind of in copper nitrate, copper chloride, copper sulfate, copper acetate, and described molybdenum salt is selected from sodium molybdate, molybdenum A kind of ammonium acid, the molar ratio of copper salt and molybdenum salt is 0.25-4:1.

5 . The preparation method according to claim 1 , wherein in the step (b), the hydrothermal reaction temperature is 100-200° C., and the hydrothermal reaction time is within 24 hours. 6 .

6. A copper/cuprous oxide/molybdenum dioxide electrocatalytic material, characterized in that the material is prepared according to any method described in claims 1-5.

7. the application of the described copper/cuprous oxide/molybdenum dioxide electrocatalytic material of claim 6 in the electrolysis of water to catalyze hydrogen evolution in alkaline solution.