A nickel-molybdenum hydrogen evolution electrode based on surfactant compounding, and a preparation method and application thereof

Abstract

This invention discloses a nickel-molybdenum hydrogen evolution electrode based on a surfactant complex, its preparation method, and its application, belonging to the field of water electrolysis for hydrogen production technology. The preparation method includes: pretreating a nickel mesh substrate and using it as the cathode for electrodeposition in an electroplating solution containing nickel salt, molybdate, complexing agent, and a complexed surfactant; the complexed surfactant consists of at least one anionic surfactant and at least one cationic surfactant. This invention, by introducing a complex system of anionic and cationic surfactants into the electrodeposition solution, synergistically regulates the electrocrystallization process, effectively refining the grains of the nickel-molybdenum alloy catalyst layer, increasing the number of active sites, and significantly reducing the hydrogen evolution overpotential. The electrode prepared by this method achieves a hydrogen evolution overpotential of 100 mA / cm². 2 At the specified current density, the overpotential can be as low as 92.8 mV, and it exhibits excellent stability. This method is simple, low-cost, and reproducible, making it suitable for large-scale preparation of high-performance water electrolysis hydrogen production cathodes.

Description

Technical Field

[0001] This invention relates to the field of water electrolysis for hydrogen production technology, specifically to a nickel-molybdenum hydrogen evolution electrode based on surfactant compounding, its preparation method, and its application. Background Technology

[0002] With the deepening of the global energy structure transformation, developing clean and renewable energy alternatives to fossil fuels has become a consensus. Hydrogen energy, due to its high energy density and pollution-free combustion products, is considered an ideal secondary energy carrier. Water electrolysis for hydrogen production can achieve "zero-carbon emission" hydrogen production and is a key link connecting renewable energy and hydrogen energy. However, the large-scale application of this technology is constrained by high energy costs, with the slow kinetics of the cathode hydrogen evolution reaction and high overpotential being one of the main reasons for increased energy consumption.

[0003] To reduce the hydrogen evolution overpotential, developing highly active non-precious metal catalysts is crucial. Among them, nickel-molybdenum alloys are considered promising candidate materials due to their excellent hydrogen evolution activity, good stability, and cost advantages in alkaline media.

[0004] Among electrode fabrication methods, electrodeposition is simple, inexpensive, and easy to scale up, making it particularly suitable for large-scale preparation of catalytic electrodes. However, nickel-molybdenum alloy catalyst layers prepared by conventional electrodeposition methods often suffer from problems such as coarse grains, uneven morphology, high internal stress, and weak adhesion to the substrate. These structural defects not only limit the full exposure and utilization of catalytic active sites but also easily lead to cracking or peeling of the catalyst layer under long-term operating conditions, seriously affecting the stability and service life of the electrode.

[0005] To address the aforementioned issues, existing technologies typically introduce additives into the electroplating solution to regulate the deposition process. Surfactants, as commonly used additives, can alter the double-layer structure through interfacial adsorption, thereby optimizing the coating morphology. However, practice shows that while using a single type of surfactant can improve coating quality to some extent, it still has limitations in synergistically regulating the microstructure of the catalytic layer, releasing internal stress, and further enhancing intrinsic catalytic activity. For those skilled in the art, although it is theoretically possible to synergistically regulate the effect by combining multiple types of surfactants, in practice, multiple surfactant combinations are prone to mutual interference, competitive adsorption, and even precipitation, leading to decreased solution stability and uncontrollable deposition processes. Furthermore, existing literature and technical practices lack verifiable and reliable solutions, making it difficult to achieve the desired microstructure optimization through simple combinations. Therefore, how to rationally construct a compound surfactant system to synergistically optimize the catalytic performance of nickel-molybdenum alloys while ensuring the stability of the electroplating solution and the controllability of deposition has become a pressing technical challenge in this field.

[0006] Patent application CN120625085A discloses a high-performance nickel-molybdenum hydrogen evolution electrode and its electrodeposition preparation method. It provides an effective solution for the preparation of nickel-molybdenum alloy electrodes through optimized pretreatment processes (including sandblasting, electrochemical degreasing, strong acid deoxidation, and weak acid etching) and a basic electroplating solution system composed of nickel sulfate hexahydrate, sodium molybdate dihydrate, sodium citrate dihydrate, boric acid, sodium chloride, and thiourea. However, with increasingly stringent energy efficiency requirements for industrial water electrolysis hydrogen production, further reducing the hydrogen evolution overpotential to achieve energy saving and consumption reduction has become a persistent challenge in this field. Existing technologies still face bottlenecks in electrode grain refinement, active site control, and hydrogen evolution kinetics regulation, making it difficult to further optimize the grain size and microstructure of the obtained nickel-molybdenum alloy catalyst layer, and leaving considerable room for improvement in the density of active sites.

[0007] Therefore, precisely controlling the nucleation and growth process of alloys by regulating the microstructure of the electroplating solution to overcome the performance bottleneck of existing technologies has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0008] To address the problems of high hydrogen evolution overpotential, inhomogeneous catalyst layer structure, and poor adhesion to the substrate in existing nickel-molybdenum electrodes, this invention proposes a method for preparing a nickel-molybdenum hydrogen evolution electrode based on a composite system of anionic and cationic surfactants. Through the synergistic effect of the anionic and cationic surfactants, precise control over nucleus formation and growth, as well as the microstructure of the catalyst surface, is achieved during the electrodeposition process, thereby obtaining a highly active, highly stable, and firmly bonded nickel-molybdenum alloy catalyst layer in one step. This method is simple, low-cost, and easily scaled up, providing a practical new solution for the industrial preparation of high-performance, long-life water electrolysis cathodes.

[0009] To achieve the above objectives, in a first aspect, the present invention provides a method for preparing a nickel-molybdenum hydrogen evolution electrode based on a surfactant complex, comprising the following steps: S1. Pre-treat the nickel mesh substrate to obtain a pre-treated nickel mesh; S2. Using the pretreated nickel mesh as the cathode, electrodeposition is performed in the electroplating solution; The electroplating solution comprises nickel salt, molybdate, complexing agent, pH buffer, conductive salt, thiourea, and a compound surfactant; the compound surfactant is composed of anionic surfactant and cationic surfactant in a molar ratio of 1:1 to 4:1, wherein the anionic surfactant is selected from at least one of alkyl sulfate, alkyl sulfonate, alkylbenzene sulfonate, succinate sulfonate, and fatty acid ester sulfonate, and the cationic surfactant is selected from at least one of quaternary ammonium salt surfactants; S3. Remove the electrode after electrodeposition, clean and dry it to obtain the nickel-molybdenum hydrogen evolution electrode.

[0010] As a further preferred embodiment of the present invention, the anionic surfactant is at least one of sodium dodecyl sulfate, sodium 2-ethylhexyl sulfate, sodium dodecylbenzene sulfonate, sodium fatty acid methyl ester sulfonate, and sodium diisooctyl succinate sulfonate; and / or, the cationic surfactant is at least one of benzalkonium chloride, hexadecyltrimethylammonium bromide, and hexadecyltrimethylammonium chloride.

[0011] As a further preferred embodiment of the present invention, in the electroplating solution, the nickel salt is nickel sulfate hexahydrate with a concentration of 40-160 g / L; the molybdate is sodium molybdate dihydrate with a concentration of 5-40 g / L; the complexing agent is sodium citrate dihydrate with a concentration of 20-50 g / L; the pH buffer is boric acid with a concentration of 5-15 g / L; and the conductive salt is sodium chloride with a concentration of 5-20 g / L.

[0012] As a further preferred embodiment of the present invention, the electrodeposition conditions are: solution pH value of 3.0-6.0, temperature of 25-50℃, and cathode current density of 20-140 mA / cm². 2 The deposition time is 26-180 minutes. Specifically, the pH of the solution is adjusted using hydrochloric acid.

[0013] As a further preferred technical solution of the present invention, the pretreatment includes sandblasting, electrochemical degreasing, strong acid deoxidation, and weak acid etching in sequence.

[0014] According to a second aspect of the present invention, the present invention also provides a nickel-molybdenum hydrogen evolution electrode prepared by the above-described preparation method.

[0015] According to a second aspect of the present invention, the present invention also provides an application of the above-described nickel-molybdenum hydrogen evolution electrode in the electrolysis of water to produce hydrogen. Specifically, the nickel-molybdenum hydrogen evolution electrode is used to produce hydrogen gas by electrolyzing an aqueous solution of potassium hydroxide, preferably with a potassium hydroxide aqueous solution concentration of 1~3 mol / L.

[0016] This invention introduces a compound of cationic and anionic surfactants, which produce a significant synergistic effect with additives such as thiourea in the electroplating solution system. This compound system can more effectively control the electrocrystallization process, resulting in a nickel-molybdenum alloy catalyst layer with a superior microstructure, higher intrinsic activity, and stronger substrate adhesion. Compared with existing technologies, it has the following advantages: 1. Significantly enhanced catalytic activity. The prepared electrode was used for the electrolysis of a 1 mol / L potassium hydroxide aqueous solution, and it exhibited significantly improved catalytic activity at a current density of 100 mA / cm². 2 At this time, the lowest overpotential can reach 92.8 mV, which is about 25.7 mV lower than the control electrode without added compound surfactant (overpotential 118.5 mV), and the catalytic activity is significantly improved.

[0017] 2. The process is stable and reproducible. The combined use of cationic and anionic surfactants makes the electrodeposition process more stable, and the performance of electrodes prepared in different batches is highly consistent, which is beneficial for industrial production and quality control.

[0018] 3. Improved electrode structure and enhanced stability. The synergistic effect of the compound surfactant not only refines the grain size but also further enhances the bonding strength between the catalyst layer and the conductive substrate, providing structural assurance for the long-term stable operation of the electrode.

[0019] 4. The method is simple and easy to implement. The catalyst is obtained through a single-step electrodeposition process, without the need for complex equipment or harsh conditions. The process is simple, the cost is controllable, and it has great potential for large-scale application. Attached Figure Description

[0020] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0021] Figure 1 Linear sweep voltammetric curves of nickel-molybdenum alloy electrodes prepared in 1 mol / L potassium hydroxide aqueous solution are shown for comparison of Comparative Examples 1-3 (thiourea only, thiourea and a single anionic surfactant, and thiourea and a single cationic surfactant added to the electroplating solution, respectively). Figure 2 The linear sweep voltammetry curves of the nickel-molybdenum alloy electrodes prepared in Comparative Example 1 and the series of compound examples (Examples 1-5) using benzalkonium chloride as a cationic surfactant are compared in 1 mol / L potassium hydroxide aqueous solution. Figure 3 Comparative Example 1 and the nickel-molybdenum alloy electrodes prepared in the series of compound examples (Examples 1-5) using benzalkonium chloride as a cationic surfactant are shown in high-magnification scanning electron microscope images. Figure 4 This is a low-magnification scanning electron microscope image of the nickel-molybdenum alloy electrode prepared in Example 5; Figure 5 The linear sweep voltammetric curves of the nickel-molybdenum alloy electrodes prepared in Comparative Example 1 and other anionic and cationic surfactant complex systems (Examples 6-8) in 1 mol / L potassium hydroxide aqueous solution are compared. Figure 6 This is a high-magnification scanning electron microscope comparison image of the nickel-molybdenum alloy electrodes prepared in Comparative Example 1 and Examples 6-8.

[0022] Figure 7 High-magnification scanning electron microscope image of the nickel-molybdenum alloy electrode prepared using a complex system of hexadecylpyridine chloride (CPC) and sodium diisooctyl succinate sulfonate (AOT) for Comparative Example 7.

[0023] Figure 8 High-magnification scanning electron microscope image of the nickel-molybdenum alloy electrode prepared using a complex system of sodium allyl sulfonate (SAS) and hexadecyltrimethylammonium bromide (CTAB) for Comparative Example 10.

[0024] Figure 9 For Example 1, 9-15, under the conditions of fixed benzalkonium chloride (BC) concentration of 0.040 g / L and sodium dodecyl sulfate (SDS) concentration of 0.016~0.196 g / L respectively, the hydrogen evolution overpotential of the prepared nickel-molybdenum alloy electrode is shown as the relationship between the molar ratio of anionic and cationic surfactants (1:1~6:1).

[0025] The objectives, features, and advantages of this invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0026] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0027] Unless otherwise defined, the technical terms used in the following embodiments have the same meanings as commonly understood by those skilled in the art to which this invention pertains. Unless otherwise specified, the experimental reagents used in the following embodiments are conventional biochemical reagents; and the experimental methods described are conventional methods.

[0028] The general preparation and testing conditions for nickel-molybdenum hydrogen evolution electrodes are as follows: (1) Substrate pretreatment: After sandblasting the 60-mesh commercial nickel mesh, cut it into 1 cm x 1 cm pieces, and perform electrochemical degreasing, strong acid deoxidation, weak acid etching in sequence, and then wash it with deionized water and dry it.

[0029] (2) Basic preparation of electroplating solution: 100 g / L nickel sulfate hexahydrate, 20 g / L sodium molybdate dihydrate, 30 g / L sodium citrate dihydrate, 15 g / L boric acid, 10 g / L sodium chloride, 0.2 g / L thiourea, and adjust the pH to 4.0 with hydrochloric acid.

[0030] (3) Electrodeposition: Using a pretreated commercial nickel mesh as the cathode, electrodeposition was performed at 40°C and a current density of 45 mA / cm². 2 Electrodeposition was performed under the specified conditions for 80 min. The surface was then cleaned with deionized water and dried to obtain a nickel-molybdenum hydrogen evolution electrode.

[0031] (4) Performance testing: A three-electrode system was formed using the prepared nickel-molybdenum hydrogen evolution electrode as the working electrode, a carbon rod as the counter electrode, and Hg / HgO as the reference electrode. The linear sweep voltammetry curve of the electrode was tested at a scan rate of 5 mV / s in a 1 mol / L potassium hydroxide aqueous solution at room temperature, and the voltammetry curve was calculated at a current density of 100 mA / cm². 2 The hydrogen evolution overpotential at that time.

[0032] Unless otherwise specified, all the following embodiments and comparative examples are performed using the same general steps described above.

[0033] Comparative Example 1 No surfactants were added to the electroplating solution other than the general components. The linear sweep voltammetry curves of the resulting electrode are shown below. Figure 1 (Curve a), which is also shown as a performance comparison benchmark. Figure 2 (Curve a) and Figure 5 (Curve a); its high-magnification scanning electron microscope images, which serve as a benchmark for morphological comparison, are shown in... Figure 3 (a) and Figure 6 (a) of the electrode. The hydrogen evolution overpotential of this electrode is 118.5 mV.

[0034] Comparative Example 2 In addition to the general components, sodium dodecyl sulfate (SDS) 0.04 g / L was added to the electroplating solution; no cationic surfactants were added. The linear sweep voltammetry curve of the resulting electrode is shown below. Figure 1 (Curve b). The hydrogen evolution overpotential of this electrode is 121.8 mV.

[0035] Comparative Example 3 In addition to the general components, benzalkonium chloride (BC) 0.04 g / L was added to the electroplating solution; no anionic surfactants were added. The linear sweep voltammetry curve of the resulting electrode is shown in [Figure / Formula would be inserted here]. Figure 1 (Curve c). The hydrogen evolution overpotential of this electrode is 121.7 mV.

[0036] Comparative Example 4 In addition to the general components, the electroplating solution contained 0.04 g / L hexadecylpyridine chloride (CPC) and 0.04 g / L sodium dodecyl sulfate (SDS). The hydrogen evolution overpotential of this electrode was 119.7 mV.

[0037] Comparative Example 5 In addition to the general components, the electroplating solution contains 0.04 g / L hexadecylpyridine chloride (CPC) and 0.04 g / L sodium 2-ethylhexyl sulfate (EHS). The hydrogen evolution overpotential of this electrode is 121.6 mV.

[0038] Comparative Example 6 In addition to the general components, the electroplating solution contains 0.04 g / L hexadecylpyridine chloride (CPC) and 0.04 g / L sodium dodecylbenzenesulfonate (SDBS). The hydrogen evolution overpotential of this electrode is 124.3 mV.

[0039] Comparative Example 7 In addition to the general components, the electroplating solution contained 0.04 g / L hexadecylpyridine chloride (CPC) and 0.04 g / L sodium diisooctyl succinate sulfonate (AOT). The hydrogen evolution overpotential of this electrode was 128.1 mV. Its high-magnification scanning electron microscope image is shown below. Figure 7 .

[0040] Comparative Example 8 In addition to the general components, the electroplating solution contains 0.04 g / L hexadecylpyridine chloride (CPC) and 0.04 g / L sodium methyl ester sulfonate (MES). The hydrogen evolution overpotential of this electrode is 118.5 mV.

[0041] Comparative Example 9 In addition to the general components, sodium allyl sulfonate (SAS) 0.04 g / L and benzalkonium chloride (BC) 0.04 g / L were added to the electroplating solution. The hydrogen evolution overpotential of this electrode was 133.2 mV.

[0042] Comparative Example 10 In addition to the general components, the electroplating solution contained 0.04 g / L sodium allyl sulfonate (SAS) and 0.04 g / L hexadecyltrimethylammonium bromide (CTAB). The hydrogen evolution overpotential of this electrode was 142.8 mV. Its high-magnification scanning electron microscope image is shown below. Figure 8 .

[0043] Comparative Example 11 In addition to the general components, sodium allyl sulfonate (SAS) 0.04 g / L and hexadecyltrimethylammonium chloride (CTAC) 0.04 g / L were added to the electroplating solution. The hydrogen evolution overpotential of this electrode was 140.5 mV.

[0044] Example 1 In addition to the general components, the electroplating solution was formulated with sodium dodecyl sulfate (SDS) 0.04 g / L and benzalkonium chloride (BC) 0.04 g / L. The linear sweep voltammetry curves of the resulting electrode are shown below. Figure 2 (Curve b), its high-magnification scanning electron microscope image is shown in Figure 3 (b) shows that the hydrogen evolution overpotential of this electrode decreased significantly to 92.8 mV.

[0045] Example 2 In addition to the general components, the electroplating solution contained a compound of sodium 2-ethylhexyl sulfate (EHS) 0.08 g / L and benzalkonium chloride (BC) 0.04 g / L. The linear sweep voltammetry curves of the resulting electrode are shown below. Figure 2 (Curve c), its high-magnification scanning electron microscope image is shown in Figure 3 (c). The hydrogen evolution overpotential of this electrode is 97.7 mV.

[0046] Example 3 In addition to the general components, the electroplating solution contained a compound of sodium methyl ester sulfonate (MES) 0.08 g / L and benzalkonium chloride (BC) 0.04 g / L. The linear sweep voltammetry curves of the resulting electrode are shown below. Figure 2 (Curve d), its high-magnification scanning electron microscope image is shown in Figure 3 (d) of the electrode. The hydrogen evolution overpotential of this electrode is 95.7 mV.

[0047] Example 4 In addition to the general components, the electroplating solution contained a compound of sodium diisooctyl succinate sulfonate (AOT) 0.04 g / L and benzalkonium chloride (BC) 0.04 g / L. The linear sweep voltammetric curve of the resulting electrode is shown in [Figure / Formula would be inserted here]. Figure 2 (Curve e), its high-magnification scanning electron microscope image is shown in Figure 3 (e) of the electrode. The hydrogen evolution overpotential of this electrode is 100.2 mV.

[0048] Example 5 In addition to the general components, the electroplating solution contained a compound of sodium dodecylbenzenesulfonate (SDBS) 0.08 g / L and benzalkonium chloride (BC) 0.04 g / L. The linear sweep voltammetry curves of the resulting electrode are shown below. Figure 2 (Curve f), its high-magnification scanning electron microscope image is shown in Figure 3 (f) is a low-magnification scanning electron microscope image shown in Figure 4 The hydrogen evolution overpotential of this electrode is 98.2 mV.

[0049] Example 6 In addition to the general components, the electroplating solution was formulated with 0.08 g / L sodium 2-ethylhexyl sulfate (EHS) and 0.04 g / L hexadecyltrimethylammonium bromide (CTAB). The linear sweep voltammetric curve of the resulting electrode is shown in [Figure / Formula would be inserted here]. Figure 5 (Curve b), its high-magnification scanning electron microscope image is shown in Figure 6 (b) of the figure. The hydrogen evolution overpotential of this electrode is 94.2 mV.

[0050] Example 7 In addition to the general components, the electroplating solution was formulated with sodium dodecylbenzenesulfonate (SDBS) 0.08 g / L and hexadecyltrimethylammonium bromide (CTAB) 0.04 g / L. The linear sweep voltammetry curve of the resulting electrode is shown below. Figure 5 (Curve c), its high-magnification scanning electron microscope image is shown in Figure 6 (c) of the figure. The hydrogen evolution overpotential of this electrode is 98.2 mV.

[0051] Example 8 In addition to the general components, the electroplating solution contained a compound of sodium diisooctyl succinate sulfonate (AOT) 0.04 g / L and hexadecyltrimethylammonium chloride (CTAC) 0.04 g / L. The linear sweep voltammetric curve of the resulting electrode is shown below. Figure 5 (Curve d), its high-magnification scanning electron microscope image is shown in Figure 6 (d) of the electrode. The hydrogen evolution overpotential of this electrode is 102.2 mV.

[0052] Example 9 In addition to the general components, the electroplating solution contains a compound of benzalkonium chloride (BC) 0.04 g / L and sodium dodecyl sulfate (SDS) 0.016 g / L, with a molar ratio of anionic and cationic surfactants of 1:2. The hydrogen evolution overpotential of this electrode is 118.0 mV. A comparison of the molar ratios and hydrogen evolution overpotential is shown in the figure below. Figure 9 .

[0053] Example 10 In addition to the general components, the electroplating solution contains a compound of benzalkonium chloride (BC) 0.040 g / L and sodium dodecyl sulfate (SDS) 0.033 g / L, with a molar ratio of anionic and cationic surfactants of 1:1. The hydrogen evolution overpotential of this electrode is 110.6 mV. A comparison of the molar ratio and hydrogen evolution overpotential is shown in the figure below. Figure 9 .

[0054] Example 11 In addition to the general components, the electroplating solution contains a compound of benzalkonium chloride (BC) 0.040 g / L and sodium dodecyl sulfate (SDS) 0.065 g / L, with a molar ratio of anionic to cationic surfactants of 2:1. The hydrogen evolution overpotential of this electrode is 93.9 mV. A comparison of the molar ratios and hydrogen evolution overpotential is shown in the figure below. Figure 9 .

[0055] Example 12 In addition to the general components, the electroplating solution contains a compound of benzalkonium chloride (BC) 0.040 g / L and sodium dodecyl sulfate (SDS) 0.098 g / L, with a molar ratio of anionic to cationic surfactants of 3:1. The hydrogen evolution overpotential of this electrode is 96.5 mV. A comparison of the molar ratios and hydrogen evolution overpotential is shown in the figure below. Figure 9 .

[0056] Example 13 In addition to the general components, the electroplating solution contains a compound of benzalkonium chloride (BC) 0.040 g / L and sodium dodecyl sulfate (SDS) 0.130 g / L, with a molar ratio of anionic to cationic surfactants of 4:1. The hydrogen evolution overpotential of this electrode is 101.4 mV. A comparison of the molar ratios and hydrogen evolution overpotential is shown in the figure below. Figure 9 .

[0057] Example 14 In addition to the general components, the electroplating solution contains a compound of benzalkonium chloride (BC) 0.040 g / L and sodium dodecyl sulfate (SDS) 0.163 g / L, with a molar ratio of anionic to cationic surfactants of 5:1. The hydrogen evolution overpotential of this electrode is 108.5 mV. A comparison of the molar ratios and hydrogen evolution overpotential is shown in the figure below. Figure 9 .

[0058] Example 15 In addition to the general components, the electroplating solution contains a compound of benzalkonium chloride (BC) 0.040 g / L and sodium dodecyl sulfate (SDS) 0.196 g / L, with a molar ratio of anionic to cationic surfactants of 6:1. The hydrogen evolution overpotential of this electrode is 117.1 mV. A comparison of the molar ratios and hydrogen evolution overpotential is shown in the figure below. Figure 9 .

[0059] The above examples and comparative examples show that in electrodeposition systems containing thiourea, adding anionic or cationic surfactants alone (Comparative Examples 2 and 3) has no significant effect on reducing the hydrogen evolution overpotential, and may even slightly degrade it. However, as described in this invention, when specific anionic and cationic surfactants are combined (Examples 1-14), the hydrogen evolution overpotential of the prepared electrodes is significantly reduced, with the most effective example showing a reduction of approximately 25 mV (Comparative Example 1 compared to Example 1). Simultaneously, SEM images show that the catalyst layer obtained from the combined system has finer crystallites and a richer pore structure, which corroborates the improved electrode performance, demonstrating the synergistic effect of anionic / cationic surfactant combination in regulating microstructure and enhancing catalytic activity.

[0060] To systematically verify the specificity of the cationic and anionic surfactant complex system described in this invention and to elucidate the influence of surfactant molecular structure on the synergistic effect, this section selects cationic surfactant cetylpyridine chloride (CPC) and anionic surfactant sodium allyl sulfonate (SAS), which have typical structural differences, as representative counterexample components. They are respectively complexed with various corresponding ionic surfactants with different structures to investigate the influence of different molecular structure combinations on the hydrogen evolution performance of the electrode.

[0061] CPC was chosen as a representative cationic surfactant counterexample because its molecular structure contains a pyridine ring, exhibiting a large rigid framework and significant steric hindrance, which is fundamentally different in molecular configuration from quaternary ammonium salt surfactants such as benzalkonium chloride (BC) preferred in this invention. By compounding CPC with different types of anionic surfactants, the influence of changes in the molecular structure of cationic surfactants on the synergistic effect of the compounded system can be effectively reflected.

[0062] The reason for choosing SAS as a representative counterexample of anionic surfactant is that its molecular chain is relatively short and its hydrophobic group structure is simple, which is significantly different from the long-chain alkyl sulfates such as sodium dodecyl sulfate (SDS) preferred in this invention in terms of carbon chain length and hydrophobic interaction strength. By compounding SAS with different types of cationic surfactants, the influence of the hydrophobic chain length of anionic surfactants on interfacial adsorption behavior and synergistic regulation ability can be investigated.

[0063] Based on the above design, this section constructs two comparative systems using CPC and SAS as "anchors": The first uses CPC as the fixed cationic component, compounded with anionic surfactants of varying structures, including sodium dodecyl sulfate (SDS), sodium 2-ethylhexyl sulfate (EHS), sodium dodecylbenzenesulfonate (SDBS), sodium diisooctyl succinate sulfonate (AOT), and sodium methyl fatty acid ester sulfonate (MES) (Comparative Examples 4-8); the second uses SAS as the fixed anionic component, compounded with different cationic surfactants, including benzalkonium chloride (BC), hexadecyltrimethylammonium bromide (CTAB), and hexadecyltrimethylammonium chloride (CTAC) (Comparative Examples 9-11). These two comparative systems comprehensively reveal the differences in interfacial adsorption behavior of cationic and anionic surfactants with different molecular structures during electrodeposition and their influence on the electrocrystallization process of nickel-molybdenum alloys.

[0064] This embodiment includes a series of comparative experiments, using the same basic electroplating solution composition and electrodeposition process as the previous embodiment, only changing the type of compound surfactant. The specific combination and the resulting electrode are compared at 100 mA·cm⁻¹. - The hydrogen evolution overpotentials at the given current density are shown in Table 1.

[0065] Table 1

[0066] As shown in Table 1, although the anionic / cationic surfactant combinations used in the comparative examples all constituted complex systems, the overpotentials of the resulting nickel-molybdenum hydrogen evolution electrodes were generally higher than 118 mV, significantly inferior to the preferred combination of this invention. This indicates that not all combinations of anionic and cationic surfactants can produce a synergistic effect.

[0067] The synergistic effect of surfactants depends on their adsorption behavior at the solid-liquid interface and intermolecular interactions. Taking Comparative Examples 4-8 as an example, hexadecylpyridine chloride (CPC) is a cationic surfactant, and the anionic surfactants it is compounded with differ in molecular structure. For example, sodium dodecyl sulfate (SDS) is a straight-chain alkyl sulfate, sodium dodecylbenzene sulfonate (SDBS) has increased steric hindrance due to the presence of a benzene ring, while sodium diisooctyl succinate sulfonate (AOT) has a double-chain structure. Figure 7 As can be seen, the catalyst layer exhibits a highly anisotropic needle-like / fibrous crystal structure, with dense, sharp protrusions and dendritic growths covering its surface. The grain size is significantly increased and the arrangement is loose and disordered, accompanied by obvious cracks and voids, resulting in a hydrogen evolution overpotential as high as 128.1 mV. These structural differences lead to an imbalance in its adsorption competition with CPC at the electrode interface, making it difficult to form an ordered mixed adsorption layer. It may even cause an increase in internal stress in the coating due to disordered intermolecular stacking, thus limiting the grain refinement effect.

[0068] Similarly, in Comparative Examples 9-11, when sodium allyl sulfonate (SAS) was used as the anionic component in combination with different cationic surfactants, its molecular chain was relatively short, resulting in insufficient density of the adsorption film formed at the interface and weak control over the metal electrocrystallization nucleation process. As can be observed in the figures, the catalyst layer exhibits large-sized blocky aggregates and layered stacking morphologies, with coarse grains and severe agglomeration. The surface pores are sparse and poorly connected, with microcracks visible in some areas. This undesirable microstructure directly limits the density and utilization rate of intrinsic active sites, causing the electrode hydrogen evolution overpotential to deteriorate to 142.8 mV, far exceeding the 92.8 mV of the preferred compound system of this invention.

[0069] Therefore, the synergistic effect of anionic and cationic surfactants is highly structure-specific and cannot be achieved by arbitrary combination. Only the benzalkonium chloride (BC) and sodium dodecyl sulfate (SDS) compound system preferred in this invention has specific synergistic compatibility in terms of molecular configuration, chain length matching degree and interfacial adsorption behavior, so as to obtain a catalytic layer with fine grains, rich pores and strong bonding under the premise of ensuring the stability of electroplating solution. This cannot be expected by simple arbitrary combination.

[0070] As mentioned above, through systematic screening of different combinations of anionic and cationic surfactants, this invention has found that not all combinations can produce a synergistic effect. Among them, the combination of benzalkonium chloride (BC) and sodium dodecyl sulfate (SDS) exhibits the best hydrogen evolution catalytic performance at the same addition amount, indicating that the two have good compatibility in terms of molecular structure, carbon chain length and interfacial adsorption behavior, and can form a stable mixed adsorption layer, thereby synergistically regulating the electrocrystallization process of nickel-molybdenum alloy.

[0071] Based on this, to further explore the influence of the ratio of cationic and anionic surfactants on electrode performance in this optimized compound system and to determine the optimal ratio range, this embodiment uses benzalkonium chloride (BC) and sodium dodecyl sulfate (SDS) as a representative compound system. Under the condition of a fixed amount of cationic surfactant, the amount of anionic surfactant was adjusted systematically to investigate the effect of different molar ratios on the hydrogen evolution overpotential. It should be noted that since the synergistic mechanism of surfactants mainly depends on their intermolecular interactions and interfacial adsorption equilibrium, once a specific combination with a synergistic effect is determined, the rules exhibited by its ratio optimization have guiding significance for similar surfactant compound systems. Therefore, using the representative combination of benzalkonium chloride (BC) and sodium dodecyl sulfate (SDS) for ratio optimization is sufficient to reflect the common rules of ratio control in the cationic and anionic surfactant compound systems described in this invention.

[0072] Examples 9-15: Under the condition that the amount of cationic surfactant benzalkonium chloride (BC) added is fixed at 0.040 g / L, the amount of anionic surfactant sodium dodecyl sulfate (SDS) added is adjusted to change the molar ratio of cationic and anionic surfactants. The composition of the remaining electroplating solution and process conditions are the same as in Example 1. The resulting electrode is tested at 100 mA·cm⁻¹. - The results of the hydrogen evolution overpotential test at the current density are shown in Table 2.

[0073] Table 2

[0074] From Table 2 and Figure 9 It is evident that when the molar ratio of anionic and cationic surfactants is within the range of 1:1 to 5:1, the hydrogen evolution overpotential of the electrode is below 110 mV, exhibiting superior catalytic activity compared to single surfactants and some non-preferred composite systems. In particular, when the molar ratio is in the range of 1:1 to 4:1, the overpotential can be as low as 92.8–101.4 mV, demonstrating the best synergistic effect. When the ratio deviates from this range, the overpotential shows an upward trend, indicating that the adsorption equilibrium of anionic and cationic surfactants at the electrode interface is disrupted, and the synergistic regulatory ability weakens.

[0075] During electrodeposition, the positively charged cationic surfactant (BC) readily adsorbs onto the cathode surface, forming an oriented adsorption layer that inhibits rapid metal ion deposition and promotes crystal nucleus refinement. The anionic surfactant (SDS), by forming a mixed adsorption film with the cationic surfactant, regulates the interfacial charge density and surface energy, further optimizing the matching relationship between the nucleation rate and growth rate. When the molar ratio of the two surfactants is within the range of 1:1 to 4:1, a dense and ordered mixed adsorption layer is formed at the interface, effectively inhibiting the coarse growth of the nickel-molybdenum alloy while maintaining a suitable deposition rate, thus obtaining a catalytic layer structure with fine grains, a dense structure, and abundant active sites. If the ratio is too low, the anionic component is insufficient, making it difficult to effectively control the interfacial charge; if the ratio is too high, cation adsorption is hindered, and interfacial stability decreases, both of which are detrimental to fully realizing the synergistic effect.

[0076] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and various changes or modifications can be made to these embodiments without departing from the principles and essence of the present invention. The scope of protection of the present invention is defined only by the appended claims.

Claims

1. A method for preparing a nickel-molybdenum hydrogen evolution electrode based on a surfactant compound, characterized in that, Includes the following steps: S1. Pre-treat the nickel mesh substrate to obtain a pre-treated nickel mesh; S2. Using the pretreated nickel mesh as the cathode, electrodeposition is performed in the electroplating solution; The electroplating solution comprises nickel salt, molybdate, complexing agent, pH buffer, conductive salt, thiourea, and a compound surfactant; the compound surfactant is composed of anionic surfactant and cationic surfactant in a molar ratio of 1:1 to 4:1, wherein the anionic surfactant is selected from at least one of alkyl sulfate, alkyl sulfonate, alkylbenzene sulfonate, succinate sulfonate, and fatty acid ester sulfonate, and the cationic surfactant is selected from at least one of quaternary ammonium salt surfactants; S3. Remove the electrode after electrodeposition, clean and dry it to obtain the nickel-molybdenum hydrogen evolution electrode.

2. The method for preparing a nickel-molybdenum hydrogen evolution electrode based on surfactant compounding according to claim 1, characterized in that, The anionic surfactant is at least one of sodium dodecyl sulfate, sodium 2-ethylhexyl sulfate, sodium dodecylbenzene sulfonate, sodium fatty acid methyl ester sulfonate, and sodium diisooctyl succinate sulfonate; and / or, the cationic surfactant is at least one of benzalkonium chloride, hexadecyltrimethylammonium bromide, and hexadecyltrimethylammonium chloride.

3. The method for preparing a nickel-molybdenum hydrogen evolution electrode based on surfactant compounding according to claim 1, characterized in that, In the electroplating solution, the nickel salt is nickel sulfate hexahydrate with a concentration of 40-160 g / L; the molybdate is sodium molybdate dihydrate with a concentration of 5-40 g / L; the complexing agent is sodium citrate dihydrate with a concentration of 20-50 g / L; the pH buffer is boric acid with a concentration of 5-15 g / L; the conductive salt is sodium chloride with a concentration of 5-20 g / L; the thiourea concentration is 0.1-0.5 g / L; and the total concentration of the compound surfactant is 0.04-0.2 g / L.

4. The method for preparing a nickel-molybdenum hydrogen evolution electrode based on surfactant compounding according to claim 1, characterized in that, The electrodeposition conditions are as follows: solution pH 3.0-6.0, temperature 25-50℃, and cathode current density 20-140 mA / cm². 2 The deposition time is 26-180 minutes.

5. The method for preparing a nickel-molybdenum hydrogen evolution electrode based on surfactant compounding according to claim 4, characterized in that, The pH was adjusted using hydrochloric acid.

6. The method for preparing a nickel-molybdenum hydrogen evolution electrode based on surfactant compounding according to claim 1, characterized in that, The pretreatment includes sandblasting, electrochemical degreasing, strong acid deoxidation, and weak acid etching, performed sequentially.

7. The nickel-molybdenum hydrogen evolution electrode prepared by the preparation method according to any one of claims 1-6.

8. The application of the nickel-molybdenum hydrogen evolution electrode according to claim 7 in the electrolysis of water to produce hydrogen.

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