Preparation Method and Application of a Cobalt Phosphide-Supported Noble Metal Nanosheet Catalyst

Abstract

The present invention provides a preparation method and application of a cobalt phosphide supported noble metal nanosheet catalyst, belonging to the technical field of electrolytic water catalysts. The preparation method comprises the following steps: dissolving divalent cobalt salt and polyvinylpyrrolidone in deionized water to obtain a metal cobalt salt solution; then dropping an L-ascorbic acid aqueous solution to carry out a reduction reaction to obtain a cobalt nanosheet precursor; ultrasonically dispersing the cobalt nanosheet precursor and the Group VIII noble metal salt in ethanol, and reacting to obtain a noble metal supported cobalt nanosheet intermediate; mixing and grinding the noble metal supported cobalt nanosheet intermediate with red phosphorus, and carrying out a microwave reaction to obtain a cobalt phosphide supported noble metal nanosheet catalyst. The above catalyst has an ultrathin nanosheet structure, which increases the contact area between the active sites and the electrolyte, and exhibits excellent catalytic activity in the field of electrolytic water hydrogen production in the whole pH range.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrolyzed water catalysts, and particularly relates to a preparation method and application of a highly active cobalt phosphide supported noble metal nanosheet catalyst. Background Art

[0002] Developing clean electrolyzed water hydrogen production technology will be crucial. Currently, the mainstream electrolyzed water hydrogen production technologies mainly include alkaline electrolyzed water and proton exchange membrane electrolyzed water technology in an acidic environment. However, the hydrogen production technologies in two different pH environments are both restricted by the kinetics of the hydrogen evolution reaction (HER), and catalysts are often used industrially to accelerate the reaction.

[0003] Currently, noble metal catalysts are still recognized as the most effective and stable electrolyzed water catalysts, but the high cost hinders the possibility of large-scale industrial applications. Cobalt phosphide (CoP), as a transition metal compound, is inexpensive and easy to regulate the electronic structure by atomic modification to enhance the electrocatalytic activity. Therefore, using CoP as a carrier for noble metal atom modification, utilizing the metal-carrier interaction, regulating the electronic structure between the noble metal atoms and the CoP carrier, and improving the intrinsic activity of the noble metal are the keys to improving the catalytic performance. However, there are still many defects in the preparation of CoP materials at present. The preparation process is complex, contains toxic gases, and is prone to agglomeration during the preparation process, which restricts its application in electrolyzed water.

[0004] The Chinese patent document with the publication number CN118047369A discloses a preparation method and application of a cobalt phosphide-phosphorus doped carbon (CoP-PC) cubic metal-organic framework phosphide derivative material. Using cubic Co-MOF as a precursor, a metal-organic framework phosphide derivative CoP-PC with small particle size and single shape is prepared by a one-step calcination method.

[0005] The Chinese patent document with the publication number CN104393312A discloses a preparation method of a Pt-CoP / C anode electrocatalyst with ultra-low platinum loading for high-activity and high-stability direct methanol fuel cells. Dispersing a carrier and cobalt chloride hexahydrate in water, and evaporating to dryness to obtain a first composite carrier; mixing the first composite carrier with sodium hypophosphite monohydrate and grinding and reacting for one hour, washing and drying to obtain a second composite carrier; dispersing the second composite carrier in ethylene glycol, adding chloroplatinic acid, and ultrasonically dispersing and stirring to obtain a first suspension; adjusting the pH value of the first suspension with sodium hydroxide under room temperature stirring to obtain a second suspension; subjecting the second suspension to microwave radiation, washing and drying to obtain a supported Pt-CoP / C catalyst.

[0006] There are mainly two problems in the preparation methods of the above two CoP catalysts. First, in the process of preparing the CoP catalyst, the synthesis steps are complex, involving conditions such as high temperature, and flammable and toxic PH3 gas is generated. Second, for the prepared CoP catalyst, atoms are prone to agglomeration, reducing the number of active sites, resulting in a low specific surface area of the support, which is not conducive to the loading of noble metal atoms. Summary of the Invention

[0007] The object of the present invention is to provide a preparation method of a cobalt phosphide supported noble metal nanosheet catalyst, and the catalyst prepared by this method can efficiently electrocatalyze hydrogen evolution from water in the whole pH range.

[0008] To achieve the above object, the present invention adopts the following technical solutions, which specifically include the steps:

[0009] (1) Dissolve divalent cobalt salt and polyvinylpyrrolidone in deionized water to obtain a metal cobalt salt solution; dropwise add an aqueous solution of L-ascorbic acid to the metal cobalt salt solution until the solution completely turns black to obtain a suspension; centrifuge, wash and dry the suspension to obtain a cobalt nanosheet precursor.

[0010] (2) Ultrasonically disperse the cobalt nanosheet precursor in ethanol, then add a Group VIII noble metal salt, stir to obtain a suspension, centrifuge and wash the suspension, and vacuum dry it to obtain a noble metal-loaded cobalt nanosheet intermediate.

[0011] (3) Mix and grind the noble metal-loaded cobalt nanosheet intermediate and red phosphorus, carry out a microwave reaction under an inert atmosphere, and after the reaction, wash and dry the reaction mixture with hot alkaline solution and deionized water respectively to obtain a cobalt phosphide supported noble metal nanosheet catalyst.

[0012] Further, in the step (1), the divalent cobalt salt is one of cobalt nitrate, cobalt chloride or cobalt acetate; the mass ratio of the cobalt salt to polyvinylpyrrolidone in the divalent cobalt salt is 1:1 to 1.5.

[0013] Further, in the step (2), the Group VIII noble metal salt is any one of metal salts containing Ru 3+ or Pt 4+ or Ir 3+ or Pd 2+ ; the mass ratio of the cobalt nanosheet precursor to the noble metal salt is 1:0.05 to 0.2; the stirring time is 12 to 24 h.

[0014] Further, in the step (3), the mass ratio of the noble metal-loaded cobalt nanosheet intermediate to red phosphorus is 1:1.5-2; the microwave power is 500-800 w; the microwave reaction time is 180-300 s. The thickness of the prepared noble metal-loaded cobalt phosphide nanosheet catalyst is 5-20 nm, and the equivalent diameter is 300-500 nm.

[0015] The present invention also provides an application of the noble metal-loaded cobalt phosphide nanosheet catalyst prepared by the above method in hydrogen production by electrolyzing water in the whole pH range.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] (1) The technical solution of the present invention successfully prepares a noble metal-loaded cobalt phosphide nanosheet catalyst with an ultrathin nanosheet structure by using polyvinylpyrrolidone assistance, an L-ascorbic acid aqueous solution as a reducing agent, and microwave reaction. The macromolecular chain structure of polyvinylpyrrolidone has a steric effect, enabling divalent cobalt salts to self-assemble into an ordered aggregate and construct a flaky structure; by using an L-ascorbic acid aqueous solution as a reducing agent to reduce divalent cobalt salts into metallic cobalt, compared with traditional reducing agents, L-ascorbic acid has moderate reducibility and mild reaction conditions, avoiding the agglomeration of metallic cobalt nanosheets and maintaining the nanosheet morphology characteristics to obtain a metallic cobalt nanosheet precursor; after mixing the noble metal-loaded cobalt nanosheet intermediate with red phosphorus, a noble metal-loaded cobalt phosphide nanosheet catalyst is prepared by microwave radiation reaction. Compared with the traditional high-temperature heating method for phosphidation, microwave radiation can achieve uniform heating of the sample, reduce the reaction temperature, shorten the reaction time, avoid the temperature gradient and thermal agglomeration phenomenon of the noble metal-loaded cobalt phosphide nanosheet catalyst that may occur in the traditional high-temperature heating method for phosphidation, and improve the catalytic activity and stability of the product.

[0018] (2) The noble metal-loaded cobalt phosphide nanosheet catalyst prepared by the technical solution of the present invention using polyvinylpyrrolidone assistance, an L-ascorbic acid aqueous solution as a reducing agent, and microwave reaction has an ultrathin nanosheet structure, with a nanosheet thickness of 5-20 nm and an equivalent diameter of 300-500 nm; the ultrathin structure endows it with a large specific surface area, increasing the contact area between the active sites and the electrolyte, which is conducive to fully loading and exposing the noble metal active sites, thus significantly improving the rate and efficiency of the catalytic reaction; the ultrathin structure also has good electrical conductivity, which helps the rapid transfer of electrons and further improves the catalytic activity; by adjusting the mass ratio of divalent cobalt salts to polyvinylpyrrolidone, the thickness and size of the divalent cobalt flaky structure can be adjusted, and then the thickness and size of the catalyst can be changed. The thickness and size of the catalyst affect the catalytic activity of the catalyst. When the mass ratio of divalent cobalt salts to polyvinylpyrrolidone is 1:1-1.5, the catalyst has the most ideal catalytic activity.

[0019] (3) The phosphating process of the technical solution of the present invention uses microwave reaction. Compared with traditional high-temperature phosphating, the reaction time is only 180 - 300 s, greatly shortening the reaction time. At the same time, microwave radiation can avoid the generation of toxic substances such as phosphine in traditional high-temperature phosphating, reducing environmental pollution, and being more environmentally friendly and economical. Moreover, the technical solution of the present invention greatly simplifies the reaction steps while controlling the mass ratio of the cobalt nanosheet intermediate loaded with noble metal to red phosphorus to 1:1.5 - 2, greatly enhancing the reaction activity of the cobalt phosphide loaded with noble metal nanosheets catalyst.

[0020] (4) The highly active cobalt phosphide loaded with noble metal nanosheets catalyst prepared by the technical solution of the present invention realizes the electron transfer between the cobalt phosphide carrier and the noble metal by loading noble metal atoms on the cobalt phosphide, optimizing the adsorption and desorption of reaction intermediates on the active sites, thus accelerating the hydrogen evolution activity of the catalyst in the full pH range. Moreover, the noble metal loaded on the ultrathin cobalt phosphide nanosheets can achieve better dispersion of noble metal atoms, improving the atomic utilization rate. Compared with traditional catalysts loaded with noble metals, on the basis of enhancing the catalytic activity, it can reduce the noble metal loading, thereby reducing the overall cost of the catalyst.

[0021] (5) The technical solution of the present invention provides a highly active cobalt phosphide loaded with noble metal nanosheets catalyst applicable to the field of electrolytic water hydrogen production. In 1 M KOH aqueous solution, 0.5 M H2SO4 aqueous solution, and 1 M PBS neutral solution (alkaline, acidic, and neutral solutions), when achieving a current density of 10 mA cm -2 , its overpotentials are 75 - 90 mV, 33 - 56 mV, and 102 - 126 mV respectively. Therefore, the technical solution of the present invention can effectively evolve hydrogen in different acidic, alkaline, and neutral environments and exhibits excellent electrocatalytic hydrogen production activity in the full pH range. The hydrogen evolution reaction in the full pH range can be applied to various industrial processes such as water electrolysis, hydrogen production, and wastewater treatment, etc., and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is the transmission electron microscopy (TEM) image of the catalyst prepared in Example 1;

[0023] Figure 2 is the X-ray powder diffraction (XRD) pattern of the catalyst prepared in Example 1;

[0024] Figure 3 is the X-ray photoelectron spectroscopy (XPS) of the catalyst prepared in Example 1 and the catalyst prepared in Comparative Example 4;

[0025] Figure 4 is the transmission electron microscopy (TEM) image of the catalyst prepared in Comparative Example 1;

[0026] Figure 5 It is the transmission electron microscopy (TEM) image of the catalyst prepared in Comparative Example 2;

[0027] Figure 6 It is the transmission electron microscopy (TEM) image of the catalyst prepared in Comparative Example 3;

[0028] Figure 7 It is the transmission electron microscopy (TEM) image of the catalyst prepared in Comparative Example 5;

[0029] Figure 8 It is the linear sweep voltammetry (LSV) curve of the catalyst in Example 1;

[0030] Figure 9 It is the current-time (I-t) curve of the catalyst in Example 1. Detailed implementation manners

[0031] The present invention will be further described below through examples and accompanying drawings, but the protection scope of the present invention is not limited thereto. Example 1

[0032] (1) 0.177 g of cobalt chloride and 0.266 g of polyvinylpyrrolidone were dissolved in 100 mL of deionized water to obtain a metal cobalt salt solution; an aqueous solution of L-ascorbic acid with a concentration of 1 mol / L was added dropwise to the metal cobalt salt solution until the solution completely turned black to obtain a suspension, which was then centrifuged, washed, and dried to obtain a cobalt nanosheet precursor;

[0033] (2) 0.1 g of the cobalt nanosheet precursor was ultrasonically dispersed in 20 mL of ethanol, and then 10 mg of ruthenium trichloride was added. After stirring for 12 h, a suspension was obtained. The suspension was centrifuged, washed, and vacuum dried at 60 °C to obtain a cobalt nanosheet intermediate loaded with noble metal;

[0034] (3) 0.2 g of red phosphorus and 0.1 g of the cobalt nanosheet intermediate loaded with noble metal were fully mixed and ground, and then placed in a microwave reactor under an argon atmosphere with a power of 700 w for 180 s. After the reaction, it was stirred with a 1 mol / L hot NaOH aqueous solution at 60 °C for 1 h, and then washed clean with water. Finally, a cobalt phosphide nanosheet loaded with noble metal Ru catalyst was obtained, named 2D-Ru-CoP. Example 2

[0035] (1) 0.177 g of cobalt nitrate and 0.177 g of polyvinylpyrrolidone were dissolved in 100 mL of deionized water to obtain a metal cobalt salt solution; an aqueous solution of L-ascorbic acid with a concentration of 1 mol / L was added dropwise to the metal cobalt salt solution until the solution completely turned black to obtain a suspension, which was then centrifuged, washed, and dried to obtain a cobalt nanosheet precursor;

[0036] (2) Ultrasonically disperse 0.1 g of cobalt nanosheet precursor in 20 mL of ethanol, then add 5 mg of ruthenium trichloride, stir for 24 h to obtain a suspension, centrifuge and wash the suspension, and dry it under vacuum at 60 °C to obtain an intermediate, which is cobalt nanosheets loaded with noble metals;

[0037] (3) Thoroughly mix and grind 0.15 g of red phosphorus and the collected 0.1 g of cobalt nanosheets intermediate loaded with noble metals, place them in a microwave reactor under an argon atmosphere, with a power of 700 w, react for 300 s, after the reaction, use a 1 mol / L hot NaOH aqueous solution at 60 °C, stir for 1 h, wash it clean with water, and finally obtain a cobalt phosphide loaded with noble metal Ru nanosheet catalyst. Example 3

[0038] (1) Dissolve 0.177 g of cobalt acetate and 0.195 g of polyvinylpyrrolidone in 100 mL of deionized water to obtain a metal cobalt salt solution; gradually add a 1 mol / L aqueous solution of L-ascorbic acid dropwise to the metal cobalt salt solution until the solution completely turns black to obtain a suspension, then perform centrifugation, washing and drying to obtain a cobalt nanosheet precursor;

[0039] (2) Ultrasonically disperse 0.1 g of cobalt nanosheet precursor in 20 mL of ethanol, then add 15 mg of ruthenium trichloride, stir for 12 h to obtain a suspension, centrifuge and wash the suspension, and dry it under vacuum at 60 °C to obtain an intermediate, which is cobalt nanosheets loaded with noble metals;

[0040] (3) Thoroughly mix and grind 0.2 g of red phosphorus and the collected 0.1 g of cobalt nanosheets intermediate loaded with noble metals, place them in a microwave reactor under an argon atmosphere, with a power of 700 w, react for 180 s, after the reaction, use a 1 mol / L hot NaOH aqueous solution at 60 °C, stir for 1 h, wash it clean with water, and finally obtain a cobalt phosphide loaded with noble metal Ru nanosheet catalyst. Example 4

[0041] (1) Dissolve 0.177 g of cobalt acetate and 0.212 g of polyvinylpyrrolidone in 100 mL of deionized water to obtain a metal cobalt salt solution; gradually add a 1 mol / L aqueous solution of L-ascorbic acid dropwise to the above-mentioned metal cobalt salt solution until the solution completely turns black to obtain a suspension, then perform centrifugation, washing and drying to obtain a cobalt nanosheet precursor;

[0042] (2) Ultrasonically disperse 0.1 g of cobalt nanosheet precursor in 20 mL of ethanol, then add 20 mg of ruthenium trichloride, stir for 18 h to obtain a suspension, centrifuge and wash the suspension, and dry it under vacuum at 60 °C to obtain an intermediate, which is cobalt nanosheets loaded with noble metals;

[0043] (3) After fully mixing and grinding 0.16 g of red phosphorus and the collected 0.1 g of the intermediate of cobalt nanosheets loaded with noble metals, place them in a microwave reactor under an argon atmosphere with a power of 700 w and react for 270 s. After the reaction, use a 1 mol / L hot NaOH aqueous solution at 60 °C, stir for 1 h, then wash it clean with water to finally obtain a cobalt phosphide-loaded noble metal Ru nanosheet catalyst. Example 5

[0044] (1) Dissolve 0.177 g of cobalt acetate and 0.23 g of polyvinylpyrrolidone in 100 mL of deionized water to obtain a metal cobalt salt solution; gradually add a 1 mol / L aqueous solution of L-ascorbic acid dropwise to the above metal cobalt salt solution until the solution completely turns black to obtain a suspension. Then, perform centrifugal washing and drying to obtain a cobalt nanosheet precursor.

[0045] (2) Ultrasonically disperse 0.1 g of the cobalt nanosheet precursor in 20 mL of ethanol, then add 10 mg of ruthenium trichloride, stir for 24 h to obtain a suspension, perform centrifugal washing on the suspension, and vacuum dry it at 60 °C to obtain an intermediate of cobalt nanosheets loaded with noble metals.

[0046] (3) After fully mixing and grinding 0.17 g of red phosphorus and the collected 0.1 g of the intermediate of cobalt nanosheets loaded with noble metals, place them in a microwave reactor under an argon atmosphere with a power of 700 w and react for 240 s. After the reaction, use a 1 mol / L hot NaOH aqueous solution at 60 °C, stir for 1 h, then wash it clean with water to finally obtain a cobalt phosphide-loaded noble metal Ru nanosheet catalyst. Example 6

[0047] (1) Dissolve 0.177 g of cobalt acetate and 0.248 g of polyvinylpyrrolidone in 100 mL of deionized water to obtain a metal cobalt salt solution; gradually add a 1 mol / L aqueous solution of L-ascorbic acid dropwise to the above metal cobalt salt solution until the solution completely turns black to obtain a suspension. Then, perform centrifugal washing and drying to obtain a cobalt nanosheet precursor.

[0048] (2) Ultrasonically disperse 0.1 g of the cobalt nanosheet precursor in 20 mL of ethanol, then add 10 mg of chloroplatinic acid, stir for 12 h to obtain a suspension, perform centrifugal washing on the suspension, and vacuum dry it at 60 °C to obtain an intermediate of cobalt nanosheets loaded with noble metals.

[0049] (3) 0.18 g of red phosphorus and the collected 0.1 g of the intermediate of noble metal-loaded cobalt nanosheets were thoroughly mixed and ground, and then placed in a microwave reactor under an argon atmosphere with a power of 700 W for 210 s. After the reaction, it was treated with a 1 mol / L hot NaOH aqueous solution at 60 °C, stirred for 1 h, washed thoroughly with water, and finally a noble metal Pt-loaded cobalt phosphide nanosheet catalyst, named 2D-Pt-CoP, was obtained. Example 7

[0050] (1) 0.177 g of cobalt acetate and 0.266 g of polyvinylpyrrolidone were dissolved in 100 mL of deionized water to obtain a metal cobalt salt solution; an aqueous solution of L-ascorbic acid with a concentration of 1 mol / L was added dropwise to the above metal cobalt salt solution until the solution completely turned black, obtaining a suspension. Subsequently, it was centrifuged, washed, and dried to obtain a cobalt nanosheet precursor.

[0051] (2) 0.1 g of the cobalt nanosheet precursor was ultrasonically dispersed in 20 mL of ethanol, then 10 mg of iridium trichloride was added, and after stirring for 12 h, a suspension was obtained. The suspension was centrifuged, washed, and vacuum dried at 60 °C to obtain an intermediate of noble metal-loaded cobalt nanosheets.

[0052] (3) 0.19 g of red phosphorus and the collected 0.1 g of the intermediate of noble metal-loaded cobalt nanosheets were thoroughly mixed and ground, and then placed in a microwave reactor under an argon atmosphere with a power of 700 W for 180 s. After the reaction, it was treated with a 1 mol / L hot NaOH aqueous solution at 60 °C, stirred for 1 h, washed thoroughly with water, and finally a noble metal Ir-loaded cobalt phosphide nanosheet catalyst, named 2D-Ir-CoP, was obtained. Example 8

[0053] (1) 0.177 g of cobalt acetate and 0.266 g of polyvinylpyrrolidone were dissolved in 100 mL of deionized water to obtain a metal cobalt salt solution; an aqueous solution of L-ascorbic acid with a concentration of 1 mol / L was added dropwise to the metal cobalt salt solution until the solution completely turned black, obtaining a suspension. Subsequently, it was centrifuged, washed, and dried to obtain a cobalt nanosheet precursor.

[0054] (2) 0.1 g of the cobalt nanosheet precursor was ultrasonically dispersed in 20 mL of ethanol, then 10 mg of palladium dichloride (a noble metal) was added, and after stirring for 12 h, a suspension was obtained. The suspension was centrifuged, washed, and vacuum dried at 60 °C to obtain an intermediate of noble metal-loaded cobalt nanosheets.

[0055] (3) Mix 0.2 g of red phosphorus and the collected 0.1 g of the intermediate of noble metal-loaded cobalt nanosheets thoroughly, grind them, place them in a microwave reactor under an argon atmosphere with a power of 700 W, react for 180 s. After the reaction, use 1 mol / L hot NaOH aqueous solution at 60 °C, stir for 1 h, then wash it clean with water. Finally, obtain a cobalt phosphide-supported noble metal Pd nanosheet catalyst, named 2D-Pd-CoP. Example 9

[0056] (1) Dissolve 0.177 g of cobalt acetate and 0.215 g of polyvinylpyrrolidone in 100 mL of deionized water to obtain a metal cobalt salt solution; gradually add a 1 mol / L aqueous solution of L-ascorbic acid dropwise to the metal cobalt salt solution until the solution completely turns black to obtain a suspension. Then, perform centrifugation, washing, and drying to obtain a cobalt nanosheet precursor.

[0057] (2) Ultrasonically disperse 0.1 g of the cobalt nanosheet precursor in 20 mL of ethanol, then add 10 mg of noble metal ruthenium trichloride, stir for 12 h to obtain a suspension. Centrifuge and wash the suspension, and dry it under vacuum at 60 °C to obtain an intermediate of noble metal-loaded cobalt nanosheets.

[0058] (3) Mix 0.2 g of red phosphorus and the collected 0.1 g of the intermediate of noble metal-loaded cobalt nanosheets thoroughly, grind them, place them in a microwave reactor under an argon atmosphere with a power of 700 W, react for 180 s. After the reaction, use 1 mol / L hot NaOH aqueous solution at 60 °C, stir for 1 h, then wash it clean with water. Finally, obtain a cobalt phosphide-supported noble metal Ru nanosheet catalyst. Comparative Example 1

[0059] The difference between Comparative Example 1 and Example 1 is that polyvinylpyrrolidone is not used in step 1, and the other steps remain unchanged. Comparative Example 2

[0060] The difference between Comparative Example 2 and Experimental Example 1 is that the ratio of divalent cobalt salt to polyvinylpyrrolidone in step 1 is changed to 1:2, and the other steps remain unchanged. Comparative Example 3

[0061] The difference between Comparative Example 3 and Experimental Example 1 is that sodium borohydride is used as a reducing agent in step 1, and the other steps remain unchanged. Comparative Example 4

[0062] The difference between Comparative Example 4 and Experimental Example 1 is that there is no noble metal Ru modification (i.e., no step 2), and the other steps remain unchanged. Comparative Example 5

[0063] The difference between Comparative Example 5 and Experimental Example 1 is that microwave was not used in Step 3, and the other steps remained unchanged. The specific implementation is as follows:

[0064] 0.2 g of sodium hypophosphite and 0.1 g of the intermediate of cobalt nanosheets loaded with noble metals collected in Step 2 were respectively placed in the upstream and downstream of a tubular furnace under an argon atmosphere, heated to 350 °C, and reacted for 2 h. After completion, a noble metal Ru-modified CoP catalyst was obtained. Comparative Example 6

[0065] The difference between Comparative Example 6 and Experimental Example 1 is that the ratio of the precursor obtained in Step 2 to red phosphorus was changed to 1:1, and the other steps remained unchanged. Comparative Example 7

[0066] The difference between Comparative Example 7 and Experimental Example 1 is that in Step 3, the microwave reaction time of the precursor and red phosphorus was changed to 120 s, and the other steps remained unchanged.

[0067] Test Example 1

[0068] The 2D-Ru-CoP prepared in Example 1 was subjected to TEM testing. The results are as Figure 1 shown. The prepared cobalt phosphide-supported noble metal nanosheet catalyst has an ultrathin nanosheet structure, with a nanosheet thickness of 5 - 20 nm and an equivalent diameter of 300 - 500 nm. The 2D-Ru-CoP prepared in Example 1 was subjected to XRD testing. The results are as Figure 2 shown. In Comparative Example 1, polyvinylpyrrolidone was not used, and the prepared Ru-CoP was subjected to TEM testing. The results are as Figure 4 shown. In Comparative Example 2, the ratio of metal cobalt salt to polyvinylpyrrolidone was changed to 1:2, and the prepared catalyst was subjected to TEM testing. The results are as Figure 5 shown. In Comparative Example 3, sodium borohydride was used as a reducing agent, and the prepared catalyst was subjected to TEM testing. The results are as Figure 6 shown. In Comparative Example 5, microwave reaction was not used, and the prepared catalyst was subjected to TEM testing. The results are as Figure 7 shown.

[0069] Figure 1 The results in show that in Example 1 of the present technical solution, polyvinylpyrrolidone was used to prepare a highly active cobalt phosphide-supported noble metal nanosheet catalyst (2D-Ru-CoP) with an ultrathin nanosheet structure. Through the steric effect of the macromolecular chain structure of polyvinylpyrrolidone and its self-assembled ordered aggregates, the agglomeration of nanoparticles during the preparation process was avoided. And by controlling the mass ratio of cobalt salt to polyvinylpyrrolidone to be 1:1 - 1.5, the prepared catalyst has an ultrathin nanosheet structure, with a nanosheet thickness of about 5 - 20 nm and a diameter of 300 - 500 nm. Figure 2XRD pattern of the 2D-Ru-CoP catalyst prepared in Example 1. The results show that the 2D-Ru-CoP catalyst corresponds to the standard card CoP (PDF#29-0497), demonstrating the successful implementation of the microwave phosphating method and the feasibility of this technical solution.

[0070] For the catalyst prepared in Comparative Example 1, since polyvinylpyrrolidone was not used, it is composed of stacked nanoparticles ( Figure 4 as shown), making it difficult to load noble metal atoms.

[0071] In Comparative Example 2, the ratio of polyvinylpyrrolidone to metal cobalt salt was changed, and the prepared catalyst is composed of some nanosheets, and its thickness is significantly greater than that of the 2D-Ru-CoP catalyst prepared in Example 1.

[0072] In Comparative Example 3, sodium borohydride was used as the reducing agent. However, due to its strong reducibility, the reaction is relatively fast, and as a result, as Figure 6 shown, there is a phenomenon of nanoparticle aggregation in the prepared catalyst, and an ultrathin nanosheet structure cannot be obtained.

[0073] The catalyst prepared in Comparative Example 5 ( Figure 7 as shown) is composed of large nanoparticles, and its size is significantly larger than that of the 2D-Ru-CoP catalyst prepared in Example 1, and there is no obvious nanosheet structure. This indicates that uniform heating of the sample can be achieved by microwave radiation, avoiding the temperature gradient and thermal aggregation phenomena that may occur in traditional high-temperature heating methods, thereby improving the uniformity of the nanomorphology of the catalyst.

[0074] Therefore, the catalyst prepared by this technical solution has an ultrathin structure. The ultrathin structure endows it with a large specific surface area, increasing the contact area between the active sites and the electrolyte, which is beneficial to fully expose the noble metal active sites, thus significantly improving the rate and efficiency of the catalytic reaction.

[0075] Test Example 2

[0076] The XPS test results of the catalysts prepared in Example 1 and Comparative Example 4 are as Figure 3 shown

[0077] Figure 3 High-resolution spectrum of Co2p of the 2D-Ru-CoP catalyst prepared in Example 1 and the 2D-CoP catalyst prepared in Comparative Example 4. In the 2D-Ru-CoP catalyst prepared in Example 1 of this technical solution, the characteristic peak with a binding energy of 778.3 eV corresponds to Co2p 3 / 2Co-P of the orbit. The Co-P in the 2D-CoP catalyst prepared in Comparative Example 4 has a binding energy of 778.1 eV. There are obvious differences in this electronic structure, indicating that there is an intermetallic interaction between the CoP catalyst and Ru. Therefore, by virtue of the characteristics that CoP is easy to adjust and improve properties through atomic modification strategies, the noble metal atom M was successfully loaded on CoP, optimizing the adsorption and desorption of reaction intermediates on the active sites, thereby accelerating the HER activity of the catalyst in the full pH range.

[0078] Application Example 1

[0079] The materials prepared in Examples 1-9 and the catalyst materials prepared in Comparative Examples 1-7 were applied to the hydrogen evolution reaction in the full pH range, including the following application steps:

[0080] (1) Electrode preparation

[0081] The electrode was prepared by coating 10 uL of a catalyst slurry with a concentration of 5 mg mL -1 (5 mg of the sample was ultrasonically dispersed in 0.95 mL of isopropanol and 0.05 mL of Nafion solution) on a glassy carbon electrode (electrode area: 0.07065 cm 2 ) as the working electrode, and the reference electrode and the counter electrode were a reversible hydrogen electrode and a graphite rod electrode, respectively; the stability electrode was prepared by coating 150 uL of the catalyst slurry on a carbon cloth with an area of 1 cm 2 and testing it as an electrode after natural drying.

[0082] (2) Catalytic activity test

[0083] The electrochemical activity evaluation method was to use a Chenhua CHI 760E electrochemical workstation to test the hydrogen evolution performance of the catalyst material in different medium solutions in a three-electrode system. The preparation methods and concentrations of the alkaline, acidic, and neutral electrolyte solutions were 1 M KOH aqueous solution, 0.5 M H2SO4 aqueous solution, and 1 M PBS neutral solution, respectively. The corresponding pH values were measured by a pH meter to be approximately 14, 0, and 7. The electrochemical performance evaluation was carried out by linear sweep voltammetry (LSV) in the voltage range of -0.5 V - 0 V (vs. RHE), and the scan rate was 5 mV s -1 , and all LSV polarization curves were obtained with iR (95 %) compensation; the stability of the catalyst was evaluated by using a current-time curve (I-t) at a current density of 10 mA cm -2 .

[0084] Figure 8Shown are the LSV curves of the 2D-Ru-CoP catalyst prepared in Example 1 in 1 M KOH aqueous solution, 0.5 M H2SO4 aqueous solution, and 1 M PBS neutral solution. The results show that in 1 M KOH, the prepared 2D-Ru-CoP catalyst only requires an overpotential of 80 mV to achieve a current density of 10 mA cm -2 −2. The prepared 2D-Ru-CoP catalyst only requires an overpotential of 42 mV to achieve the same current density in acidic 0.5 M H2SO4 aqueous solution, while in the more environmentally friendly neutral 1 M PBS solution, the catalyst also exhibits excellent catalytic activity and achieves an overpotential of only 110 mV when reaching a current density of 10 mA cm -2 −2.

[0085] Electrochemical activity tests were also carried out on Examples 2-9. The results are shown in Table 1. The prepared ultrathin cobalt phosphide nanosheets have a good carrier effect.

[0086] Compared with Example 1, the Ru-CoP catalyst prepared without adding polyvinylpyrrolidone in Comparative Example 1 has overpotentials of 171, 101, and 242 mV when achieving a current density of 10 mA cm -2 −2 in 1 M KOH aqueous solution, 0.5 M H2SO4 aqueous solution, and 1 M PBS neutral solution, which are much lower than 80, 42, and 110 mV of Example 1.

[0087] Compared with Example 1, when the content of metal cobalt salt and polyvinylpyrrolidone is changed to 1:2 in Comparative Example 2, its overpotentials in alkaline, acidic, and neutral environments are 130, 108, and 201 mV respectively, which are much lower than 80, 42, and 110 mV of Example 1.

[0088] Compared with Example 1, in Comparative Example 3, the reducing agent is changed, and sodium borohydride is used as the reducing agent. Its overpotentials in alkaline, acidic, and neutral environments are 162, 120, and 221 mV respectively, which are much lower than 80, 42, and 110 mV of Example 1. It shows that by designing an ultrathin high specific surface area nanosheet structure, the structural environment around the active sites in the CoP catalyst is improved, the contact area between the active sites and the electrolyte is increased, and the mass diffusion rate is enhanced, etc.

[0089] Compared with Example 1, the prepared 2D-CoP catalyst without noble metal Ru in Comparative Example 4 has overpotentials of 171, 101, and 242 mV when achieving a current density of 10 mA cm -2When the current density is [specific value], the overpotentials are 182, 132, and 237 mV respectively, which are much lower than those in Example 1. This indicates that loading noble metal atoms can enhance the adsorption ability of reactants, increase the concentration of reactants on the catalyst surface, thereby accelerating the reaction rate and realizing the application of the prepared catalyst in the full pH range.

[0090] Compared with Example 1, in Comparative Example 5, the catalyst prepared without microwave reaction has overpotentials of 142, 102, and 179 mV in alkaline, acidic, and neutral environments respectively, which are much lower than 80, 42, and 110 mV in Example 1. Therefore, in this technical solution, the catalyst prepared by microwave reaction realizes uniform heating of the sample, avoiding the temperature gradient and agglomeration phenomena that may occur in the traditional high-temperature heating method for phosphating, and thus improving the catalytic activity.

[0091] Compared with Example 1, in Comparative Example 6, by changing the mass ratio of the microwave reaction precursor to red phosphorus, the prepared catalyst has overpotentials of 144, 101, and 162 mV in alkaline, acidic, and neutral environments respectively, which are much lower than 80, 42, and 110 mV in Example 1.

[0092] Compared with Example 1, in Comparative Example 7, the catalyst prepared by changing the microwave reaction time has overpotentials of 204, 158, and 271 mV in alkaline, acidic, and neutral environments respectively, which are much lower than those in Example 1.

[0093]

Claims

1. A preparation method of a cobalt phosphide-supported noble metal nanosheet catalyst, characterized in that It includes the following steps: (1) Dissolve divalent cobalt salt and polyvinylpyrrolidone in deionized water to obtain a metal cobalt salt solution; gradually add an aqueous solution of L-ascorbic acid dropwise to the metal cobalt salt solution until the solution completely turns black to obtain a suspension; centrifuge, wash and dry the suspension to obtain a cobalt nanosheet precursor; (2) Ultrasonically disperse the cobalt nanosheet precursor in ethanol, then add a Group VIII noble metal salt, stir to obtain a suspension, centrifuge, wash the suspension, and dry it under vacuum to obtain a noble metal-loaded cobalt nanosheet intermediate; (3) Mix and grind the noble metal-loaded cobalt nanosheet intermediate and red phosphorus, carry out a microwave reaction under an inert atmosphere, after the reaction ends, wash and dry the reaction mixture with hot alkaline solution and deionized water respectively to obtain a highly active cobalt phosphide-loaded noble metal nanosheet catalyst; In the step (1), the divalent cobalt salt is one of cobalt nitrate, cobalt chloride or cobalt acetate; the mass ratio of the divalent cobalt salt to polyvinylpyrrolidone is 1:1 - 1.5; In the step (2), the Group VIII noble metal salt is any one of metal salts containing Ru 3+ or Pt 4+ or Ir 3+ or Pd 2+ ; the mass ratio of the cobalt nanosheet precursor to the Group VIII noble metal salt is 1:0.05 - 0.2; the stirring time is 12 - 24 h; In the step (3), the mass ratio of the noble metal-loaded cobalt nanosheet intermediate to red phosphorus is 1:1.5 - 2; the microwave power is 500 - 800 W; the microwave reaction time is 180 - 300 s.

2. The preparation method of the cobalt phosphide supported noble metal nanosheet catalyst according to claim 1, wherein: The prepared cobalt phosphide-loaded noble metal nanosheet catalyst has a thickness of 5 - 20 nm and an equivalent diameter of 300 - 500 nm.

3. Use of a cobalt phosphide-supported noble metal nanosheet catalyst prepared by the preparation method according to any one of claims 1-2, characterized in that: Use the cobalt phosphide-loaded noble metal nanosheet catalyst for hydrogen production by electrolyzing water in the whole pH range.

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