A cobalt diselenide electrocatalyst and its preparation method and application

Abstract

The present invention discloses a cobalt diselenide electrocatalyst and a preparation method and application thereof, and relates to the field of catalysts, wherein the catalyst molecular formula is CoSe2, the structure is a rhombic dodecahedron, and the length is 1‑2 μm. The preparation method comprises the following steps: (1) preparation of a ZIF‑67 precursor; (2) preparation of CoSe; (3) preparation of a CoSe2 electrocatalyst. The present invention also discloses the application of the cobalt diselenide composite electrocatalyst in electrocatalytic hydrogen production. The CoSe2 electrocatalyst provided by the present invention has uniform size, regular morphology, large specific surface area, and high activity and stability. In addition, the present invention has mild preparation conditions, simple operation, strong repeatability, and low requirements for instruments and equipment, providing a good technical basis and material guarantee for large-scale applications.

Description

Technical Field

[0001] The invention relates to the technical field of catalysts, and in particular to a cobalt diselenide electrocatalyst and a preparation method and application thereof. Background Art

[0002] Problems such as high price, difficult synthesis and scarce reserves have affected the development of electrocatalytic water splitting catalysts for hydrogen production. In recent years, hydrogen energy has received widespread attention, and electrocatalytic seawater splitting provides an effective means to solve the energy crisis and develop new energy. However, electrocatalyst materials are affected by their high price and scarce reserves, resulting in their lack of rapid development.

[0003] Among traditional transition metal materials, transition metal selenides, such as nickel selenide and cobalt selenide, have received extensive attention in the field of electrocatalytic hydrogen production due to their abundant reserves and low prices. However, their poor electrical conductivity and high adsorption energy currently limit their performance in electrocatalytic water splitting to produce hydrogen. At the same time, in the prior art, there are few reports on the synthesis of cobalt selenide electrocatalysts by crystal phase transformation, and there is still much room for improvement in terms of synthesis methods and design strategies.

[0004] Therefore, how to provide an economical and efficient electrocatalyst to promote the rapid development of selenide-based materials in the field of electrocatalytic water splitting and ultimately realize their industrialization is a technical problem that technical personnel in this field urgently need to solve. Summary of the invention

[0005] The purpose of the present invention is to provide a cobalt diselenide electrocatalyst and a preparation method and application thereof, so as to solve the problems existing in the above-mentioned prior art, so that the catalyst has excellent performance and efficiently promotes the cracking of water to produce hydrogen.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] The invention provides an electrocatalyst, the chemical composition of the electrocatalyst is CoSe2, and the structure is a rhombic dodecahedron.

[0008] The prepared CoSe2 electrocatalyst has a nanostructure of rhombic dodecahedron structure, which can provide abundant specific surface area and thus improve its catalytic activity.

[0009] Furthermore, the length of the electrocatalyst is 1-2 μm.

[0010] The present invention also provides a method for preparing the electrocatalyst, comprising the following steps:

[0011] (1) Preparation of ZIF-67 precursor: dimethyl imidazole solution and cobalt nitrate hexahydrate solution were mixed and continuously stirred (at a rate of 300 to 500 r / min), and then reacted at 0 to 100° C. for 15 to 35 hours, cooled to room temperature, and the obtained solid product was washed and vacuum dried in sequence to obtain the ZIF-67 precursor;

[0012] The concentration of the dimethylimidazole solution is 0.01-0.1 mol / L, and the concentration of the cobalt nitrate hexahydrate solution is 0.01-0.1 mol / L.

[0013] Furthermore, the added mass ratio of the dimethylimidazole to the cobalt nitrate hexahydrate is 1:0.1-5.0.

[0014] (2) Preparation of CoSe: The ZIF-67 precursor is dispersed in water (the concentration of the dispersion is 0.01 to 0.10 mol / L), selenium powder and sodium borohydride are added for mixed reaction, and the obtained solid product is filtered, washed, vacuum dried, and ground to obtain CoSe;

[0015] Furthermore, the mass ratio of the ZIF-67 precursor to selenium powder and sodium borohydride is 1:0.1-5.0:0.1-5.0.

[0016] Furthermore, the mixing reaction process of step (2) is: after reacting at 0-100° C. for 0-0.5 hours, heating to 100-200° C. and reacting for 10-24 hours, and the reaction time is not 0.

[0017] In step (2), the vacuum drying temperature is 5 to 100° C., the drying time is 8 to 72 hours, and the vacuum degree is 133 to 267 Pa.

[0018] Under the above process parameter conditions, the selenization reaction can be guaranteed to provide a precursor for the synthesis of CoSe2.

[0019] The above raw materials provide a selenium source and a reducing agent (sodium borohydride).

[0020] (3) Preparing a catalyst: heat-treating the CoSe under a protective atmosphere to obtain the electrocatalyst.

[0021] Furthermore, the temperature of the heat treatment in step (3) is 200 to 600° C., and the reaction time is 1 h to 3 h.

[0022] Furthermore, the protective atmosphere is an argon atmosphere.

[0023] Under the above process parameter conditions, the crystal phase transformation can be guaranteed.

[0024] The reagents used in the washing treatment of the present invention are deionized water and ethanol solution (mass concentration is 99.5%), and the washing times are 3 to 5 times.

[0025] The present invention further provides the use of the above electrocatalyst in producing hydrogen by electrolysis of water.

[0026] The application conditions of the catalyst electrolysis hydrogen production are: CoSe2 catalyst is used as the working electrode; calomel electrode is used as the reference electrode; graphite electrode is used as the counter electrode; the electrolyte is alkaline seawater; and the pH of the electrolyte is 10-14.

[0027] In the present invention, the crystal phase regulation can transform cobalt monoselenide into cobalt diselenide, optimize the electronic structure of the cobalt diselenide material, accelerate the transfer speed of electrons, and the water molecules in the electrolyte are adsorbed on the surface of the catalyst. The water molecules obtain electrons to generate hydrogen protons, and then the two hydrogen protons combine to generate hydrogen.

[0028] The present invention discloses the following technical effects:

[0029] The present invention prepares a cobalt diselenide (CoSe2) catalyst, which has the characteristics of large specific surface area, high activity and high stability, and has excellent performance in hydrogen production by water electrolysis. In addition, the preparation of the CoSe2 catalyst in the present invention is short in time, simple in operation and highly repeatable, providing a good technical basis and material guarantee for the application of large-area catalytic hydrogen production. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0031] Figure 1 is a scanning electron micrograph of the CoSe2 electrocatalyst prepared in Example 1;

[0032] Figure 2 is the X-ray diffraction spectrum of the CoSe2 electrocatalyst prepared in Example 1;

[0033] Figure 3 The polarization curve of water splitting of CoSe2 electrocatalyst prepared in Example 1-3;

[0034] Figure 4 This is the stability performance diagram of the CoSe2 electrocatalyst prepared in Example 1. DETAILED DESCRIPTION

[0035] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0036] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0037] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0038] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present application description and examples are exemplary only.

[0039] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0040] Example 1

[0041] A method for preparing a CoSe2 electrocatalyst comprises the following steps:

[0042] (1) dispersing cobalt nitrate hexahydrate in deionized water at room temperature to obtain a red transparent cobalt nitrate hexahydrate solution, wherein the concentration of cobalt nitrate hexahydrate is 0.015 mol / L;

[0043] (2) dissolving dimethylimidazole in deionized water at room temperature so that the concentration of dimethylimidazole is 0.02 mol / L to obtain a colorless and transparent dimethylimidazole solution;

[0044] (3) adding the dimethylimidazole solution of step (2) dropwise into the cobalt nitrate hexahydrate solution of step (1), and continuously stirring to obtain a purple transparent solution; wherein the mass ratio of dimethylimidazole to the cobalt nitrate hexahydrate in the above step (1) is 1:1;

[0045] (4) reacting the obtained purple solution at 25° C. for 24 h to obtain ZIF-67, washing it thoroughly with deionized water and ethanol, and vacuum drying it to obtain a ZIF-67 precursor;

[0046] (5) dispersing the ZIF-67 precursor obtained in step (4) in deionized water to obtain a suspension with a concentration of 0.05 mol / L;

[0047] (6) adding selenium powder and sodium borohydride to the suspension in step (6), and continuously stirring at 0° C. for 0.1 hour to obtain a black suspension, wherein the mass ratio of selenium powder, sodium borohydride and ZIF-67 in the above step (5) is 2:2:1;

[0048] (7) transferring the solution in step (6) into a reactor, reacting at 30° C. for 0.5 hours, and then reacting at 180° C. for 20 hours to obtain a black solid, filtering and collecting the solid, washing it with deionized water and ethanol, and vacuum drying it, and grinding it to obtain a black powdered CoSe electrocatalyst;

[0049] (8) The CoSe in step (7) was transferred to a tube furnace and reacted for 2 h at 350 °C in an argon atmosphere to obtain a black CoSe2 electrocatalyst.

[0050] Figure 1 This is the scanning electron microscope image of the prepared CoSe2 electrocatalyst, which shows that its morphology is a rhombic dodecahedron;

[0051] Figure 2 This is the powder X-ray diffraction spectrum of the prepared CoSe2 electrocatalyst. It can be seen that the chemical composition of the product is CoSe2.

[0052] Example 2

[0053] A method for preparing a CoSe2 electrocatalyst comprises the following steps:

[0054] (1) dispersing cobalt nitrate hexahydrate in deionized water at room temperature to obtain a red transparent cobalt nitrate hexahydrate solution, wherein the concentration of cobalt nitrate hexahydrate is 0.015 mol / L;

[0055] (2) dissolving dimethylimidazole in deionized water at room temperature so that the concentration of dimethylimidazole is 0.02 mol / L to obtain a colorless and transparent dimethylimidazole solution;

[0056] (3) adding the dimethylimidazole solution of step (2) dropwise into the cobalt nitrate hexahydrate solution of step (1), and continuously stirring to obtain a purple transparent solution; wherein the mass ratio of dimethylimidazole to the cobalt nitrate hexahydrate in the above step (1) is 1:1;

[0057] (4) reacting the obtained purple solution at 25° C. for 24 h to obtain ZIF-67, washing it thoroughly with deionized water and ethanol, and vacuum drying it to obtain a ZIF-67 precursor;

[0058] (5) dispersing the ZIF-67 precursor obtained in step (4) in deionized water to obtain a suspension with a concentration of 0.05 mol / L;

[0059] (6) adding selenium powder and sodium borohydride to the suspension in step (6), and continuously stirring at 0° C. for 0.1 hour to obtain a black suspension, wherein the mass ratio of selenium powder, sodium borohydride and ZIF-67 in the above step (5) is 2:2:1;

[0060] (7) transferring the solution in step (6) into a reactor, reacting at 30° C. for 0.5 hours, and then reacting at 180° C. for 20 hours to obtain a black solid, filtering and collecting the solid, washing it with deionized water and ethanol, and vacuum drying it, and grinding it to obtain a black powdered CoSe electrocatalyst;

[0061] (8) The CoSe in step (7) was transferred to a tube furnace and reacted at 250 °C for 1 h in an argon atmosphere to obtain a black CoSe2 electrocatalyst.

[0062] Example 3

[0063] A method for preparing a CoSe2 electrocatalyst comprises the following steps:

[0064] (1) dispersing cobalt nitrate hexahydrate in deionized water at room temperature to obtain a red transparent cobalt nitrate hexahydrate solution, wherein the concentration of cobalt nitrate hexahydrate is 0.015 mol / L;

[0065] (2) dissolving dimethylimidazole in deionized water at room temperature so that the concentration of dimethylimidazole is 0.02 mol / L to obtain a colorless and transparent dimethylimidazole solution;

[0066] (3) adding the dimethylimidazole solution of step (2) dropwise into the cobalt nitrate hexahydrate solution of step (1), and continuously stirring to obtain a purple transparent solution; wherein the mass ratio of dimethylimidazole to the cobalt nitrate hexahydrate in the above step (1) is 1:1;

[0067] (5) dispersing the ZIF-67 precursor obtained in step (4) in deionized water to obtain a suspension with a concentration of 0.05 mol / L;

[0068] (6) adding selenium powder and sodium borohydride to the suspension in step (6), and continuously stirring at 0° C. for 0.1 hour to obtain a black suspension, wherein the mass ratio of selenium powder, sodium borohydride and ZIF-67 in the above step (5) is 2:2:1;

[0069] (7) transferring the solution in step (6) into a reactor, reacting at 30° C. for 0.5 hours, and then reacting at 180° C. for 20 hours to obtain a black solid, filtering and collecting the solid, washing it with deionized water and ethanol, and vacuum drying it, and grinding it to obtain a black powdered CoSe electrocatalyst;

[0070] (8) The CoSe in step (7) was transferred to a tube furnace and reacted at 550 °C for 3 h in an argon atmosphere to obtain a black CoSe2 electrocatalyst.

[0071] The performance test of water splitting and hydrogen production was carried out on the CoSe2 electrocatalyst prepared in Examples 1-3:

[0072] CoSe2 was directly used as the working electrode, calomel electrode as the reference electrode, graphite electrode as the counter electrode, and alkaline seawater (pH = 13.6) as the electrolyte. The test results are shown in Table 1:

[0073] Table 1 Comparison of electrocatalyst performance

[0074] Example 1 Example 2 Example 3 Overpotential <![CDATA[147mV@10mA cm -2 ]]> <![CDATA[172mV@10mA cm -2 ]]> <![CDATA[193mV@10mA cm -2 ]]>

[0075] As can be seen from Table 1 above, the CoSe2 electrocatalyst prepared in the present invention has excellent performance. -2 Only an overpotential of 147 mV is required at a current density of 1.

[0076] Figure 3 is the polarization curve of water splitting and hydrogen production by the CoSe2 electrocatalyst prepared in Examples 1-3, Figure 3 It can be seen that compared with Examples 2 and 3, Example 1 has a higher -2 Only an overpotential of 147 mV is required at a current density of 1.

[0077] Figure 4 The stability of the CoSe2 electrocatalyst prepared in Example 1 shows that after a 48-h constant voltage stability test, the current density changes very little, indicating that it has good stability.

[0078] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing an electrocatalyst, characterized in that: The following steps are involved: (1) Preparation of ZIF-67 precursor: dimethylimidazole and cobalt nitrate hexahydrate are mixed, and then reacted at 0-100° C. for 15-35 hours, cooled to room temperature, and the obtained solid product is washed and vacuum dried in sequence to obtain the ZIF-67 precursor; (2) Preparation of CoSe: The ZIF-67 precursor is mixed with selenium and sodium borohydride for reaction, and the obtained solid product is filtered, washed, vacuum dried, and ground to obtain CoSe; (3) preparing a catalyst: heat treating the CoSe under a protective atmosphere to obtain the electrocatalyst; The chemical composition of the electrocatalyst is CoSe2, and the structure is a rhombic dodecahedron.

2. The method for preparing an electrocatalyst according to claim 1, characterized in that: The length of the electrocatalyst is 1-2 μm.

3. The method for preparing an electrocatalyst according to claim 1, characterized in that: The mass ratio of the dimethylimidazole to the cobalt nitrate hexahydrate is 1:0.1-5.

0.

4. The method for preparing an electrocatalyst according to claim 1, characterized in that: Dimethylimidazole and cobalt nitrate hexahydrate are mixed in the form of a solution, wherein the concentration of the dimethylimidazole solution is 0.01-0.1 mol / L, and the concentration of the cobalt nitrate hexahydrate solution is 0.01-0.1 mol / L.

5. The method for preparing an electrocatalyst according to claim 1, characterized in that: The mass ratio of the ZIF-67 precursor to selenium and sodium borohydride is 1:0.1-5.0:0.1-5.

0.

6. The method for preparing an electrocatalyst according to claim 1, characterized in that: The mixing reaction process of step (2) is: After reacting at 0-100°C for 0-0.5 hours, the temperature is raised to 100-200°C and reacted for 10-24 hours. The reaction time is not zero.

7. The method for preparing an electrocatalyst according to claim 1, characterized in that: The heat treatment temperature in step (3) is 200-600° C., and the reaction time is 1 h-3 h.

8. The method for preparing an electrocatalyst according to claim 1, characterized in that: The protective atmosphere is an argon atmosphere.

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