Ni-based nanocluster supported silicon carbide catalyst for electrolysis of water to produce hydrogen and preparation method thereof

Abstract

The application belongs to the technical field of hydrogen production catalysts for water electrolysis, and particularly relates to a Ni-based nanocluster loaded silicon carbide hydrogen production catalyst for water electrolysis and a preparation method thereof. The preparation method comprises the following steps: dissolving NiCl2.6H2O and TOAB) in THF, adding PhCH2SH, fully stirring to ensure that all metal atoms are fully positioned, and dropping NaBH4 solution to prepare a cyclic Ni6 nanocluster by a wet chemical method; and after the nanocluster is loaded on silicon carbide and treated by NaBH4, a SiC electrocatalytic material with uniform Ni cluster loading is obtained. The material has high catalytic activity and good stability for hydrogen evolution reaction (HER) catalyst. The application provides a new strategy for preparing more Ni-based nanocluster-based electrocatalytic hydrogen production catalysts. Compared with existing synthesis methods of electrocatalytic hydrogen production catalysts, the preparation method has simple conditions, high safety, low cost, high stability, high yield and environmental friendliness.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen production catalyst technology through water electrolysis, specifically relating to a Ni-based nanocluster supported silicon carbide hydrogen production catalyst for water electrolysis and its preparation method. Background Technology

[0002] Electrocatalysis is considered an effective route for hydrogen production, offering high energy conversion efficiency and zero greenhouse gas emissions. The performance of electrocatalytic hydrogen production catalysts significantly impacts the cost, yield, and stability of hydrogen production. Platinum (Pt) is one of the most commonly used catalysts in electrocatalytic hydrogen evolution due to its excellent electrochemical performance and catalytic activity; however, its high cost and scarcity limit its industrial application.

[0003] Some non-precious metals, such as nickel (Ni) and iron (Fe), have been used to replace the precious metal phosphorus (Pt) as catalysts for the electrocatalytic hydrogen evolution reaction. Carbon-based materials, such as carbon nanotubes and graphene, have also been studied as supports for Pt alternatives to further reduce costs and improve electrocatalytic performance. Nickel is abundant in the Earth's crust, has a lower cost compared to precious metals, and exhibits good catalytic activity in water electrolysis. However, its activity and selectivity are affected by factors such as crystal structure, surface characteristics, hydrogen adsorption capacity, and alloying, resulting in variability, complexity, and poor durability in catalysis, which limits its application. Studies have shown that controlling the morphology, size, and surface modification of nickel nanoparticles can regulate the distribution and density of active sites on the nickel surface, thereby improving its catalytic activity and selectivity. Furthermore, loading nickel onto inert or active supports, such as oxides or carbon materials, can increase its dispersion and stability. Current non-precious metal catalysts generally suffer from problems such as low catalytic conversion efficiency, complex synthesis process, and low stability. There is an urgent need to develop a simple and efficient synthesis method for non-precious metal catalysts to achieve a stable and high-conversion-efficiency catalytic electrolysis of water to produce hydrogen. Summary of the Invention

[0004] One of the objectives of this invention is to provide a method for preparing a Ni-based nanocluster supported silicon carbide electrolysis hydrogen production catalyst. This method is simple, safe, low-cost, stable, high-yield, and environmentally friendly. The resulting catalyst exhibits high HER catalytic activity and good stability.

[0005] To achieve the above objectives, the present invention employs the following technical solution: a method for preparing a Ni-based nanocluster supported silicon carbide electrolysis catalyst for hydrogen production, comprising the following steps:

[0006] S1. Dissolve Ni salt and tetraoctylammonium bromide (TOAB) in tetrahydrofuran (THF) at a mass ratio of 1:2 to 2:1 to form a deep blue solution; wherein the concentration of Ni salt in tetrahydrofuran is 0.004-0.01 g / ml.

[0007] S2. Take 300 ml of the dark blue solution, add 4-6 ml of toluene mercaptan (PhCH2SH), stir thoroughly until all metal atoms are fully coordinated, slowly add borohydride or hydroxide solution dropwise until the solution turns gray, then stop adding. Maintain the reaction at 10±2℃ for 48-72 h to obtain Ni6(SCH2Ph). 12 A dark brown solution containing nanoclusters;

[0008] S3. Filter the dark brown solution, and wash the filter residue to obtain a crude product. Dissolve the crude product in a mixed solvent of methanol and THF in a volume ratio of 1:1 to form a cluster-saturated solution. Let it stand in air until the solvent evaporates completely to obtain a regular black hexagonal single crystal Ni6 (SCH2Ph). 12 ;

[0009] S4. Apply black hexagonal single-crystal Ni6(SCH2Ph) 12 Dissolved in dichloromethane solution, then SiC is added and ultrasonically dispersed to obtain a mixed solution, resulting in black hexagonal single crystal Ni6(SCH2Ph). 12 The mass ratio of Ni6 to SiC is 1:(4-6); then the dichloromethane in the mixed solution is completely evaporated, the resulting solid is collected and ground to obtain Ni6 / SiC;

[0010] S5. Ni6 / SiC was added to a NaBH4 solution with a concentration of 0.35-0.45 mol / L, at a concentration of 2.5-4 mg / ml. The mixture was then sonicated, separated, washed, and dried to obtain a Ni-based nanocluster supported silicon carbide electrolysis catalyst for hydrogen production, denoted as Ni6 / SiC-H catalyst.

[0011] Further improvements to the preparation method of Ni-based nanocluster supported silicon carbide electrolysis catalyst for hydrogen production:

[0012] Preferably, the Ni salt is NiCl2·6H2O.

[0013] Preferably, the borohydride solution is a sodium, potassium, or lithium borohydride solution, and the hydroxide solution is a sodium, potassium, or lithium hydroxide solution.

[0014] Preferably, the concentration of the borohydride solution or hydroxide solution is 0.9-1.1 g / ml.

[0015] Preferably, in step S3, the dark brown solution is filtered using degreased cotton.

[0016] Preferably, in step S3, CH2Cl2 and water are added to wash the filter media to obtain a crude product.

[0017] Preferably, in step S4, the black hexagonal single-crystal Ni6(SCH2Ph) 12 The solubility concentration in dichloromethane solution is 0.8-1.2 mg / ml.

[0018] Preferably, in step S4, the mixed solution is sealed in a rotary evaporator at 30-40°C to allow the dichloromethane to evaporate completely.

[0019] Preferably, in step S5, the product is separated by sonication for 2-3 hours, centrifugation at 8000-10000 rpm for 3-5 minutes, washed four times with deionized water, and dried at 60-80℃ for 12-15 hours.

[0020] The second objective of this invention is to provide a Ni-based nanocluster supported silicon carbide electrolysis catalyst for hydrogen production prepared by any one of the above-mentioned methods.

[0021] The advantages of this invention compared to the prior art are as follows:

[0022] 1) This invention pioneers a novel, highly efficient, and stable electrocatalytic hydrogen evolution Ni-based catalyst and its preparation method. A cyclic Ni6 nanocluster is prepared by a wet chemical method, and then the inexpensive Ni-based nanocluster is loaded onto the surface of SiC. After reduction treatment with inexpensive raw material NaBH4, without the need for complex operations such as high temperature and hydrothermal treatment, SiC electrocatalytic material with uniformly loaded Ni clusters can be obtained quickly and efficiently, exhibiting highly efficient and stable electrocatalytic water splitting hydrogen production performance.

[0023] Nanoclusters Ni6(SCH2PH) 12 In the preparation process, NiCl₂·6H₂O and tetraoctylammonium bromide (TOAB) were dissolved in tetrahydrofuran (THF) to form a deep blue solution. Toluene mercaptan (PhCH₂SH) was then added, and the solution was stirred for more than 2 hours to ensure complete coordination of all metal atoms. Then, 2 mL of a 1 g / mL NaBH₄ solution was slowly added dropwise, and the solution quickly turned gray. After maintaining the reaction at 10±2 °C for 48 hours, a deep brown solution was obtained, indicating Ni₆(SCH₂Ph) 12 Synthesis of nanoclusters. The resulting solution was further filtered with defatted cotton and washed 3-5 times with CH2Cl2 and water to remove soluble byproducts and unreacted water-soluble precursors. The crude product of isolated nanoclusters was obtained by removing the solvent from the obtained organic phase. This was then used for the growth of Ni6(SCH2Ph). 12 Single crystals of nanoclusters were obtained by dissolving the crude product in a 1:1 methanol and THF mixture to form a cluster-saturated solution. The solvent in the saturated solution was then slowly evaporated in air, yielding regular black hexagonal single crystals of Ni6 (SCH2Ph) in five days. 12 .

[0024] Preparation of Ni6 / SiC catalyst: The Ni6 / SiC sample was prepared using a simple rotary evaporation method. Specifically, 20 mg of Ni6 nanocluster crystals were dissolved in 20 mL of dichloromethane solution, and 100 mg of SiC was added. After sonication for 10 minutes, the solution was sealed in a rotary evaporator at 30 °C to allow complete evaporation of the dichloromethane. The resulting solid was then collected and ground to obtain Ni6 / SiC.

[0025] Reduction treatment of Ni6 / SiC catalyst. A certain amount of Ni6 / SiC catalyst was weighed and added to a 0.4 mol / L NaBH4 solution. The mixture was sonicated for 2 h, centrifuged at 8000 rpm for 3 min, washed with deionized water, and the process was repeated four times. The catalyst was then dried at 60 °C for 12 h. The resulting catalyst was labeled Ni6 / SiC-H. Other metal borohydrides can be used to replace NaBH4 to prepare Ni-based nanocluster-supported SiC catalysts with different reduction effects.

[0026] 2) The Ni-cluster uniformly supported SiC electrocatalytic material prepared in this invention exhibits high catalytic activity and good stability as a hydrogen evolution reaction (HER) catalyst. This provides a new strategy for preparing more Ni-based nanocluster-based electrocatalytic hydrogen production catalysts. Nanoclusters, as HER catalysts, possess unique advantages in terms of activity, size effect, selectivity, and synthesis. For example, their high specific surface area and abundant active sites help improve the activity of the HER; due to their small size, the electronic structure and surface activity of nanoclusters may differ from those of large nanoparticles or bulk materials, leading to a size effect that improves catalytic performance; nanocluster synthesis technology allows for precise control of the cluster composition and structure, which helps optimize catalytic performance; and nanoclusters can selectively regulate the reaction by modulating the chemical environment of surface active sites, helping to reduce or avoid side reactions. Therefore, Ni-based nanoclusters with well-defined structures can be synthesized through solvothermal methods, cluster ion chemistry, etc., and used as models for HER to adjust catalytic performance, thus preparing novel catalysts. Combined with further theoretical and experimental research, their wide application in the field of hydrogen evolution reaction can be realized. Attached Figure Description

[0027] Figure 1 The Ni6(SCH2Ph) cluster prepared in Example 1 of this invention is shown. 12 The skeleton structure diagram and single crystal structure diagram (a), UV-Vis spectrum and cluster crystal photograph (b).

[0028] Figure 2XRD patterns of SiC, Ni6 / SiC and Ni6 / SiC-H prepared in Example 1 (a), and UV-Vis absorption spectra of Ni6 and Ni6 supported on Ni6 / SiC and Ni6 / SiC-H dissolved in dichloromethane (b).

[0029] Figure 3 In the middle, (a) and (b) are TEM images of the Ni6 / SiC sample before and after treatment with NaBH4 obtained in Example 1, respectively; (c), (d), and (e) are high-resolution images, respectively; and (f) and (g) are the corresponding EDS mapping images.

[0030] Figure 4 XPS full spectra of Ni6 / SiC before reduction and Ni6 / SiC-H after reduction obtained in Example 1 are shown in (a), (b), (c), (d), (e) and (f), which are fine spectra of Ni 2p, O 1s, Si 2p, S2p and C 1s, respectively.

[0031] Figure 5 Polarization curves (a) and 10 mA cm⁻¹ of SiC, Ni6 / SiC, and Ni6 / SiC-H obtained in Example 1 are shown. -2 Overpotential at current density (b), Tafel slope (c), and EIS plot at 140mV overpotential (d); electrolyte is 1.0M KOH.

[0032] Figure 6 The image shows a comparison of the 10-hour constant voltage stability curve (a) and the polarization curve before and after 1000 scans of Ni6 / SiC-H prepared in Example 1 (b). The electrolyte was 1.0M KOH.

[0033] Figure 7 (a) is the optimized structure diagram of Ni6 obtained in Example 1, (b) is the optimized structure diagram of SiC surface part of C replaced by O, and (c) is the optimized structure diagram of Ni6 / SiC-H.

[0034] Figure 8 The calculated Gibbs free energies for H adsorption in SiC, Ni6 / SiC, and Ni6 / SiC-H are given. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0036] Example 1

[0037] This embodiment provides a method for preparing a Ni-based nanocluster supported silicon carbide electrolysis catalyst for hydrogen production, comprising the following steps:

[0038] (1) Nanoclusters Ni6(SCH2PH) 12

[0039] The preparation process is as follows: First, 2.0 g of NiCl2·6H2O and 2.0 g of tetraoctylammonium bromide (TOAB) are dissolved in 300 mL of tetrahydrofuran (THF) to form a deep blue solution; wherein, the mass ratio of NiCl2·6H2O to tetraoctylammonium bromide is 1:1, and the concentration of NiCl2·6H2O in tetrahydrofuran is 2 g / 300 mL;

[0040] Add 5.0 mL of toluene mercaptan (PhCH2SH) to the above 300 mL dark blue solution, and stir the resulting solution for more than 2 hours to ensure that all metal atoms are fully coordinated; then slowly add 2 mL of NaBH4 solution with a concentration of 1 g / mL. The solution quickly turns gray, and after maintaining the reaction at 10±2 °C for 48 hours, a dark brown solution is obtained, indicating Ni6(SCH2Ph). 12 Synthesis of nanoclusters.

[0041] The dark brown solution was filtered, and the filter residue was washed 3-5 times with CH2Cl2 and water to obtain the crude product. The crude product was dissolved in a mixed solvent of methanol and THF in a volume ratio of 1:1 to form a cluster-saturated solution. The solution was left to stand in air until the solvent was completely evaporated to obtain regular black hexagonal single crystal Ni6 (SCH2Ph). 12 ;

[0042] (2) Preparation of Ni6 / SiC catalyst

[0043] 20 mg of black hexagonal single crystal Ni6 (SCH2Ph) was used. 12 Dissolve 100 mg of SiC in 20 mL of dichloromethane solution. After sonication for 10 minutes, seal the solution in a rotary evaporator at 30 °C to allow the dichloromethane to evaporate completely. Then collect the solid and grind it to obtain Ni6 / SiC.

[0044] (3) Reduction treatment of Ni6 / SiC catalyst

[0045] 50 mg of Ni6 / SiC catalyst was weighed and added to 20 ml of 0.4 mol / L NaBH4 solution. The mixture was sonicated for 2 h, centrifuged at 8000 rpm for 3 min, washed with deionized water, and the process was repeated four times. The mixture was then dried at 60 °C for 12 h to obtain Ni-based nanocluster supported silicon carbide electrolysis hydrogen production catalyst, namely Ni6 / SiC catalyst, labeled as Ni6 / SiC-H.

[0046] Example 2

[0047] This embodiment provides a method for preparing a Ni-based nanocluster supported silicon carbide electrolysis hydrogen production catalyst. The specific steps are the same as in Example 1, except that in step (1), "2 mL of 1 g / mL NaBH4 solution" is replaced with "2 mL of 1 g / mL NaOH solution". The final catalyst is labeled Ni6 / SiC-H1.

[0048] Example 3

[0049] This embodiment provides a method for preparing a Ni-based nanocluster supported silicon carbide electrolysis hydrogen production catalyst. The specific steps are the same as in Example 1, except that "20 mL of dichloromethane solution" in step (2) is replaced with "50 mL of dichloromethane solution". The catalyst is finally prepared and labeled as Ni6 / SiC-H2.

[0050] Example 4

[0051] This embodiment provides a method for preparing a Ni-based nanocluster-supported silicon carbide electrolysis hydrogen production catalyst. The specific steps are the same as in Example 1, except that step (3) "centrifuge at 8000 rpm for 3 minutes, wash with deionized water, repeat four times, and dry at 60°C for 12 hours" is replaced with "centrifuge at 10000 rpm for 3 minutes, wash with deionized water, repeat four times, and dry at 80°C for 15 hours". The catalyst is finally prepared and labeled as Ni6 / SiC-H3.

[0052] The intermediate and final products of the embodiments were subjected to the following performance tests:

[0053] 1) Characterization of Ni6 cluster

[0054] The obtained cluster crystals were selected, and their structure was first confirmed by single-crystal X-ray diffraction. Figure 1 The Ni6(SCH2Ph) cluster prepared in Example 1 of this invention is shown. 12 The skeletal structure diagram and single crystal structure diagram (a), UV-Vis spectrum, and cluster crystal photograph (b) are shown. The results indicate that four identical Ni6(SCH2Ph) crystals... 12 The molecule (abbreviated as Ni6) (Z=4) crystallizes in a tetragonal lattice with space group P-421c, and the lattice parameters are a=b=19.02 and . Ni6(SCH2Ph) 12 Molecular structure such as Figure 1 (a) Its core structure consists of 6 nickel atoms arranged in a hexagonal pattern. Sulfur atoms are symmetrically distributed above and below the nickel ring plane, with each sulfur atom coordinated to two nickel atoms. Figure 1(b) shows the UV-Vis spectrum of the obtained crystal dissolved in dichloromethane. The figure shows that the characteristic absorption of the Ni6 clusters is located at 339, 409, and 540 nm. All results indicate that the double-crown Ni6(SCH2Ph) is indeed compliant. 12 Nanoclusters were successfully synthesized.

[0055] 2) Phase characterization of Ni6 / SiC before and after reduction

[0056] Ni6 cluster molecules were dissolved in dichloromethane and loaded onto SiC via a simple rotary evaporation method to prepare the Ni6 / SiC catalyst. It was found that in the presence of sodium borohydride, the cluster molecules in the cluster-loaded SiC sample would leave the thiol ligand and undergo in-situ transformation. Therefore, Ni6 / SiC was further treated with sodium borohydride, and the effect of the cluster structure change on the activity was analyzed by comparing the structural changes and electrocatalytic hydrogen evolution performance of the samples before and after treatment. The obtained samples were characterized by X-ray diffraction and UV-Vis spectroscopy. The XRD patterns of the SiC, Ni6 / SiC, and Ni6 / SiC-H sample powders prepared in Example 1 are shown below. Figure 2 As shown in (a), the diffraction peaks of all samples are consistent with those of the synthesized SiC, and no other impurity diffraction peaks were observed. This indicates that the loading of Ni6 clusters and the subsequent sodium borohydride treatment have negligible effects on the crystal structure of SiC. Furthermore, the clusters in the loaded samples exist in an amorphous form on the surface of SiC before and after sodium borohydride treatment. To determine whether the structure of Ni6 is stable on the SiC surface, Ni6 / SiC samples were dispersed in dichloromethane solution for cluster extraction. Since Ni6 clusters are soluble in dichloromethane solution, the supernatant obtained by centrifugation to remove the undissolved SiC support showed the same color as the solution formed by dissolving pure Ni6 clusters in dichloromethane solution. UV-Vis absorption spectroscopy analysis was performed on solutions of Ni6, Ni6 / SiC, and Ni6 / SiC-H-loaded Ni6 in dichloromethane, and the results were compared with the UV spectra of cluster solutions with theoretical loading concentrations. The results are shown in the figure. Figure 2 As shown in (b), the peak positions in the spectrum of the resulting solution are consistent with those of the Ni6 cluster, indicating that the cluster structure did not change after loading. The UV absorption of the sample treated with sodium borohydride was significantly lower than that before treatment, suggesting that the cluster structure may have changed as expected.

[0057] To clarify the cluster structure transformation process in Ni6 / SiC samples before and after sodium borohydride reduction treatment, transmission electron microscopy (TEM) analysis was performed on the samples before and after the catalytic reaction. The results are as follows: Figure 3As shown, (a) and (b) are TEM images of the Ni6 / SiC sample before and after NaBH4 treatment obtained in Example 1, respectively; (c), (d), and (e) are high-resolution images, respectively; and (f) and (g) are the corresponding EDS-mapped images. Figure 3 It can be seen that the morphology of SiC loaded with clusters is basically the same as that of pure SiC, still mainly existing in the form of nanoparticles and nanowires. This is because the Ni6 clusters are in an amorphous state, and transmission electron microscopy cannot effectively image them. Combined with the TEM-mapping image, it can be seen that the nanoclusters exhibit local aggregation because the SiC nanoparticles are more likely to deposit clusters than the nanowires. Figure 3 (a)). TEM images of the catalyzed Ni6 / SiC-H sample show nanoparticles on the support surface, while corresponding dark-field TEM images show sub-nano particles and single atoms on the support surface. Figure 3 (e)), combined with TEM-mapping images, shows that Ni elements are uniformly distributed on the surface of SiC. Figure 3 (f) This indicates that the cluster structure has changed and Ni has appeared in a new form.

[0058] To further understand the effect of sodium borohydride treatment on cluster structure, XPS tests were performed on Ni6-supported SiC samples before and after sodium borohydride treatment. Figure 4 The XPS full spectra of Ni6 / SiC before and after reduction obtained in Example 1 are shown. (a), (b), (c), (d), (e), and (f) are the fine spectra of Ni 2p, O 1s, S 2p, C 1s, and Si 2p, respectively. Figure 4As shown in (a), characteristic signals of Si, Ni, S, C, and O can be observed in the XPS full spectra of both samples, indicating that these five elements coexist on the sample surface. In the sample treated with NaBH4 (Ni6 / SiC-H), the peak intensity of Ni 2p is significantly lower than before treatment, and the S 2p signal almost disappears, indicating that the cluster structure is somewhat lost after sodium borohydride treatment. The fine 2p spectrum of Ni shows that without sodium borohydride treatment, its corresponding characteristic signals are located at 870.51 eV (2p 1 / 2) and 853.24 eV (2p 3 / 2), corresponding to +2 valence Ni coordinated with S in the cluster structure. After treatment with NaBH4, the Ni signal in the resulting sample became complex. Peak fitting results showed that, in addition to a set of signals at 870.51 eV (2p 1 / 2) and 853.24 eV (2p 3 / 2) which could be attributed to +2 Ni atoms coordinated with S atoms, there was another set of characteristic signals at 872.76 eV (2p 1 / 2) and 855.49 eV (2p 3 / 2). This second set of signals exhibited an overall blue shift of approximately 2.2 eV compared to the first set, and was attributed to Ni atoms bonded to O in an amorphous state. This attribution was further confirmed by peak fitting results of the O 2p spectrum. Figure 4 As shown in (c), the 2p signal of O after sodium borohydride treatment exhibits significant broadening and can be fitted into two sets of characteristic signals: one at 532.7 eV, attributed to O elements coordinated with Ni; and the other at 532.7 eV, attributed to O elements coordinated with Si atoms. The latter shows a redshift of approximately 0.3 eV compared to the untreated sample, possibly due to the local reduction of the SiC surface by sodium borohydride. This redshift is also confirmed in the peak fitting results of the Si 2p spectrum, as shown in... Figure 4 As shown in (d), the Si signal at 101.41 eV, attributed to O coordination, before treatment shifted to 100.75 eV after sodium borohydride treatment, exhibiting a 0.6 eV redshift. This further illustrates the local reduction of the SiC surface by sodium borohydride. Simultaneously, the S 2p signal did not show a significant shift before and after sodium borohydride treatment, but the S 2p signal weakened after treatment, indicating partial cluster deconstruction. This point, combined with the C signal in the sample, such as... Figure 4As shown in (e), the signal at 283.86 eV, belonging to C coordinated with H, weakened after sodium borohydride treatment, further indicating that some of the organic ligands on the cluster surface were removed by sodium borohydride. Another group of C element signals at 282.48 eV, belonging to Si coordinated with H, became stronger after treatment and showed a 0.5 eV blue shift, indicating that the clusters loaded on the SiC surface were removed, exposing the SiC support. Based on the above characterization, the following conclusions can be drawn: After treatment with sodium borohydride, the organic ligands on the surface of the Ni6 clusters in the Ni6 / SiC sample were partially removed, and Ni atoms combined with O on the SiC surface to form NiO. x It was deposited on a SiC support. A series of characterization results confirmed that after Ni6 / SiC was treated with NaBH4, the cluster structure changed, some clusters decomposed, and a new substance, NiO, was formed. x .

[0059] 3) Evaluation of electrocatalytic hydrogen evolution performance

[0060] To determine the effect of NaBH4 treatment on the catalytic activity of the materials, the obtained SiC, Ni6 / SiC and Ni6 / SiC-H materials were used to fabricate working electrodes and their electrocatalytic hydrogen evolution performance was evaluated. Figure 5 (a) shows the polarization curves of SiC, Ni6 / SiC, and Ni6 / SiC-H in 1.0M KOH solution. As can be seen from the figure, SiC, Ni6 / SiC, and Ni6 / SiC-H all exhibit certain activities, but there are still significant differences in their activities. Figure 5 (b) SiC, Ni6 / SiC, and Ni6 / SiC-H at 10 mA / cm -2 Overpotential at current density: The Ni6 / SiC-H sample treated with sodium borohydride at a current density of 10 mA cm⁻¹ -2 The required overpotential is 93 mV, while the untreated Ni6 / SiC sample requires 142 mV, and pure SiC requires 292 mV. Figure 5 The linear portion of the polarization curve in (a) is fitted using the Tafel formula (η=b log(j)+a). The fitted result is the Tafel slope, which helps to reveal the electrocatalytic activity. Figure 5 As shown in (c), Ni6 / SiC-H has the smallest Tafel slope of 340 mV dec. -1 Ni6 / SiC requires 387mV dec -1 SiC has an even higher value, reaching 602 mV dec. -1 This indicates that the hydrogen evolution reaction is more readily carried out on the Ni6 / SiC-H surface. The prepared catalysts all exhibit Tafel slopes of 300 mV dec. -1The above indicates that the hydrogen evolution reaction mainly proceeds via the Volmer-Heyrovsky process. To further investigate the mass transfer resistance at the catalyst interface, EIS tests were performed on the samples under an overpotential of 100 mV, as shown below. Figure 5 As shown in (d), in the low-frequency region, the charge transfer resistance obtained by fitting is the smallest for SiC and the largest for Ni6 / SiC. After treatment, the resistance of Ni6 / SiC-H decreases. The reason for this is that the surface of the Ni6 clusters is wrapped by organic ligands, resulting in poor conductivity. After treatment with sodium borohydride, some cluster structures are destroyed, exposing Ni and improving conductivity. However, the presence of O leads to the formation of NiO. x However, some clusters remain, which results in a less significant improvement in conductivity, which is still lower than that of SiC overall.

[0061] 4) Ni6 / SiC-H catalytic stability

[0062] Besides HER activity, stability is another important indicator for evaluating the HER performance of materials. Figure 6 The image shows a comparison of the 10-hour constant-voltage stability curve (a) and the polarization curves before and after 1000 scans (b) of the Ni6 / SiC-H prepared in Example 1, with 1.0M KOH as the electrolyte. Figure 6 As shown in (a), the potential is 93mV, and the current density is 10mA / cm². -2 When the current density decayed significantly after 10 hours of continuous operation, it can be seen that Ni6 / SiC-H exhibits good catalytic activity and stability in alkaline solution. Figure 6 (b) is the polarization curve of the Ni6 / SiC-H sample before and after 1000 scans in the potential range of -1.0 to 1.0 mV vs. RHE. The polarization curves changed before and after the test, indicating that the catalyst itself may have changed, which is related to the incomplete conversion of the clusters.

[0063] To verify the experimental results and better understand the roles of Ni6 / SiC-H and Ni6 / SiC in the HER process, we simplified the Ni6 / SiC system to a plate model of Ni6 molecules on the (001) surface of the SiC sample. In the HER process, it is actually the surface clusters of Ni6 that participate in the reaction. Further simplifying, Ni6, as shown... Figure 7 (a). As we know from the calculations in Chapter 2, the optimized structure of the SiC(001) facets exposing C atoms still has a small amount of O on the surface. Therefore, we optimized the surface structure by replacing some C atoms with O atoms to construct O-terminated SiC, such as... Figure 7(b) The samples treated with NaBH4, as characterized by TEM and XPS, show that the cluster structure partially disintegrates, and Ni binds to O on the SiC surface, simplifying into a SiC-O-Ni structure, such as... Figure 7 (c). Based on this, we established a model for H adsorption ( Figure 8 The Gibbs free energy (ΔG) of hydrogen adsorption for different structures was compared. H* The magnitude of the Gibbs free energy (ΔG) of hydrogen adsorption. According to previous literature, the Gibbs free energy of hydrogen adsorption... H* ΔG is considered a key parameter describing HER activity. According to the Sabatier principle, ΔG... H* It should be close to 0 eV to become a highly efficient HER electrocatalyst. Lower ΔG H* The high bonding strength between hydrogen atoms and the catalyst slows down the rate of hydrogen atom release from the catalyst surface. Meanwhile, the higher ΔG... H* Making the proton / electron transfer step an endothermic process, coupled with poor bonding between the catalyst and hydrogen atoms, is also detrimental to the catalytic reaction. For example... Figure 8 As shown, the ΔG of SiC H* The value is 1.1 eV, while Ni6 / SiCΔG H* The value is even higher at 1.3 eV, indicating that after loading the clusters, the clusters cover the original active sites of SiC, resulting in a decrease in hydrogen adsorption-desorption capacity, which is consistent with the CV results. The ΔG of the treated Ni6 / SiC-H sample... H* The value is almost 0, indicating that the Ni6 / SiC-H catalyst has better hydrogen adsorption-desorption characteristics, and the hydrogen atom desorption ability of the Heyrovsky step is optimized, thereby improving the HER performance.

[0064] 5) Electrochemical performance testing

[0065] All electrochemical data were measured using a KOST CS350M electrochemical workstation. The electrolytic cell was a well-sealed, two-chamber H-type electrolytic cell, with a proton exchange membrane (Nafion 117) separating the cathode and anode chambers. The catalyst was dropped onto carbon paper as the working electrode, a Pt mesh electrode as the counter electrode, a calomel electrode as the reference electrode, and a 1.0 MkOH solution as the electrolyte. All applied potential values ​​were converted to a relative reversible hydrogen electrode.

[0066] E(RHE)=E(SCE)+0.241+0.0592*pH (1)

[0067] Linear sweep voltammetry (LSV) was used to obtain polarization profiles between 1.0 and -1.5 V (relative to RHE) at a scan rate of 10 mV / s. Electrochemical impedance spectroscopy (EIS) was performed in the frequency range of 100 kHz to 0.1 Hz with an AC amplitude of 10 mV. Cyclic voltammetry (CV) was performed between 0.2 and 0.4 V (relative to the reference electrode) at scan rates of 5–100 mV / s. Based on the current density difference and CV scan rate, the slope of the curve obtained by linear fitting was used to estimate the electrochemical double-layer capacitance (C0) of the sample. dl Specifically, as shown in formula (2):

[0068] C dl =Δj / 2v (2)

[0069] In addition, the LSV curves in this work have all been iR-corrected according to the formula. iR-校正 =E-iR, where E is the measured potential, R is the solution resistance, and i is the corresponding current. iR-校正 This is the final potential after iR correction.

[0070] The preparation process of the working electrode is as follows: Weigh 3.0 mg of the above-prepared sample into a test tube, add 300 μL of anhydrous ethanol and 20 μL of Nafion into the test tube respectively, and ultrasonically disperse for 30 min to form a uniform slurry. Then, use a pipette to transfer 100 μL of the slurry onto the surface of carbon paper with a diameter of 1.0 cm × 1.0 cm, and let it air dry for later use.

[0071] XRD and UV spectroscopy studies were conducted on the products Ni6 / SiC-H1, Ni6 / SiC-H2, and Ni6 / SiC-H3 from Examples 2-4. The catalysts prepared in Examples 2-4 have the exact same structure as the Ni6 / SiC-H catalyst prepared in Example 1. This indicates that the changes in conditions in Examples 2-4 do not affect the preparation of Ni6 / SiC-H, and also proves that the preparation conditions of Ni6 / SiC-H catalyst are relatively simple and easy to implement.

[0072] Those skilled in the art should understand that the above descriptions are merely several specific embodiments of the present invention, and not all embodiments. It should be noted that many modifications and improvements can be made by those skilled in the art, and all modifications or improvements not exceeding the scope of the claims should be considered within the protection scope of the present invention.

Claims

1. A method for preparing a Ni-based nanocluster supported silicon carbide electrolysis catalyst for hydrogen production, characterized in that, Includes the following steps: S1. Dissolve Ni salt and tetraoctylammonium bromide (TOAB) in tetrahydrofuran (THF) at a mass ratio of 1:2 to 2:1 to form a deep blue solution; wherein the concentration of Ni salt in tetrahydrofuran is 0.004-0.01 g / ml. S2. Take 300 ml of the dark blue solution, add 4-6 ml of toluene mercaptan (PhCH2SH), stir thoroughly until all metal atoms are fully coordinated, slowly add borohydride or hydroxide solution dropwise until the solution turns gray, then stop adding. Maintain the reaction at 10±2℃ for 48-72 h to obtain Ni6(SCH2Ph). 12 A dark brown solution containing nanoclusters; S3. Filter the dark brown solution, and wash the filter residue to obtain a crude product. Dissolve the crude product in a mixed solvent of methanol and THF in a volume ratio of 1:1 to form a cluster-saturated solution. Let it stand in air until the solvent evaporates completely to obtain a regular black hexagonal single crystal Ni6 (SCH2Ph). 12 ; S4. Apply black hexagonal single-crystal Ni6(SCH2Ph) 12 Dissolved in dichloromethane solution, then SiC is added and ultrasonically dispersed to obtain a mixed solution, resulting in black hexagonal single crystal Ni6(SCH2Ph). 12 The mass ratio of Ni6 to SiC is 1:(4-6); then the dichloromethane in the mixed solution is completely evaporated, the resulting solid is collected and ground to obtain Ni6 / SiC; S5. Ni6 / SiC was added to a NaBH4 solution with a concentration of 0.35-0.45 mol / L, at a concentration of 2.5-4 mg / ml. The mixture was then sonicated, separated, washed, and dried to obtain a Ni-based nanocluster supported silicon carbide electrolysis catalyst for hydrogen production, denoted as Ni6 / SiC-H catalyst.

2. The preparation method of the Ni-based nanocluster supported silicon carbide electrolysis hydrogen production catalyst according to claim 1, characterized in that, The Ni salt is NiCl2·6H2O.

3. The preparation method of the Ni-based nanocluster supported silicon carbide electrolysis hydrogen production catalyst according to claim 1, characterized in that, The borohydride solution is a sodium, potassium, or lithium borohydride solution, and the hydroxide solution is a sodium, potassium, or lithium hydroxide solution.

4. The method for preparing the Ni-based nanocluster supported silicon carbide electrolysis hydrogen production catalyst according to claim 1 or 3, characterized in that, The concentration of the borohydride solution or hydroxide solution is 0.9-1.1 g / ml.

5. The preparation method of the Ni-based nanocluster supported silicon carbide electrolysis hydrogen production catalyst according to claim 1, characterized in that, In step S3, the dark brown solution is filtered using absorbent cotton.

6. The preparation method of the Ni-based nanocluster supported silicon carbide electrolysis hydrogen production catalyst according to claim 1, characterized in that, In step S3, CH2Cl2 and water are added to wash the filter media to obtain the crude product.

7. The preparation method of the Ni-based nanocluster supported silicon carbide electrolysis hydrogen production catalyst according to claim 1, characterized in that, In step S4, black hexagonal single-crystal Ni6(SCH2Ph) 12 The solubility concentration in dichloromethane solution is 0.8-1.2 mg / ml.

8. The method for preparing the Ni-based nanocluster supported silicon carbide electrolysis hydrogen production catalyst according to claim 1, characterized in that, In step S4, the mixed solution is sealed in a rotary evaporator at 30-40°C to allow the dichloromethane to evaporate completely.

9. The method for preparing the Ni-based nanocluster supported silicon carbide electrolysis hydrogen production catalyst according to claim 1, characterized in that, In step S5, sonicate for 2-3 hours, centrifuge at 8000-10000 rpm for 3-5 minutes to separate the product, wash four times with deionized water, and dry at 60-80℃ for 12-15 hours.

10. A Ni-based nanocluster supported silicon carbide electrolysis catalyst for hydrogen production obtained by the preparation method of any one of claims 1-9.

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