A her electrochemical cathode material based on ni-mo-al composite coating

Abstract

The present application relates to the technical field of electrochemical hydrogen evolution reaction, in particular to a HER electrochemical cathode material based on Ni-Mo-Al composite coating. The conventional coating preparation technology has high cost, low powder utilization rate and poor bonding force between the coating and the current collector substrate. In view of the above problems, the present application provides a HER electrochemical cathode material based on Ni-Mo-Al composite coating, which is a metal composite coating formed by loading Ni, Mo and Al three kinds of metal powder on the surface of porous nickel current collector, the metal composite coating and the surface of porous nickel current collector form metallurgical bonding, and the metal composite coating is a coating obtained by coating Mo powder in the Ni-Al binary eutectic phase formed by Ni element and Al element. In the electrode material of the present application, no noble metal is used, the cost is low, the bonding force between the coating and the current collector substrate forms metallurgical bonding, the bonding force is strong, no toxic Cl2 gas is produced, and it is more environmentally friendly.

Description

Technical Field

[0001] This invention relates to the field of electrochemical hydrogen evolution reaction technology, specifically to an electrochemical cathode material for hydrogen evolution reaction (HER) based on a Ni-Mo-Al composite coating. Background Technology

[0002] Hydrogen energy, as a clean, efficient, and renewable energy source, has shown enormous application potential in various fields such as energy storage, transportation, and industry. Electrolysis of water to produce hydrogen, as one of the key methods for obtaining hydrogen energy, operates on the core principle of using electricity to decompose water into hydrogen and oxygen, achieving the efficient conversion of electrical energy into chemical energy.

[0003] In water electrolysis hydrogen production systems, the hydrogen evolution electrode is the core component of this conversion process. Its performance directly determines the efficiency, energy consumption, and operational stability of the entire hydrogen production system. Therefore, developing high-performance hydrogen evolution electrodes is of paramount importance for promoting the large-scale application and commercial development of water electrolysis hydrogen production technology.

[0004] Currently, nickel (Ni) mesh has become the mainstream electrode substrate in the field of hydrogen production through water electrolysis due to its series of outstanding advantages. Ni mesh has excellent conductivity, with a resistivity of approximately 6.99 × 10⁻⁶. -8 With a Ω·m ratio, Ni effectively reduces energy loss during current transmission, improving energy utilization efficiency. Simultaneously, Ni mesh exhibits excellent alkali resistance, maintaining stable chemical properties in alkaline water electrolysis hydrogen production environments and resisting corrosion, thus extending electrode lifespan. Furthermore, compared to some other metallic materials, Ni has a relatively low cost, contributing to reduced overall hydrogen production system costs and enhanced market competitiveness.

[0005] However, pure Ni mesh also has significant drawbacks, exhibiting low hydrogen evolution catalytic activity. At a current density of 100 mA / cm², the hydrogen evolution overpotential of pure Ni mesh is approximately between 250 and 300 mV. This excessively high overpotential means that more electrical energy is required to overcome the energy barrier during hydrogen production, leading to increased energy consumption and reduced efficiency. Therefore, to improve the catalytic performance and structural stability of Ni mesh electrodes, surface coating modification is typically necessary.

[0006] Traditional physical coating techniques, such as plasma spraying and arc spraying, face serious powder utilization problems when preparing coatings for Ni mesh. Because Ni mesh has a woven mesh structure with a mesh size of approximately 30% to 50%, a large amount of powder is lost through the mesh during the spraying process, resulting in a powder utilization rate that is generally less than 30%.

[0007] The coating formed by physical spraying is primarily mechanically bonded to the Ni mesh substrate. This bonding method has relatively low strength, with interfacial bonding strength typically below 15 MPa. During actual operation, the electrolyzer faces harsh conditions including high temperature, high potential, and strong convective alkaline scouring. Alkaline electrolyzers operate at temperatures of 60-90℃, while PEM electrolyzers operate at 80-100℃; the hydrogen evolution electrode potential is approximately -0.8 to -1.2 V vs SHE; simultaneously, the alkaline solution continuously circulates within the electrolyzer, exerting a strong scouring effect on the electrodes. Under the combined influence of these complex conditions, the coating is highly susceptible to peeling and detachment. Once the coating detaches, the catalytic performance of the electrode decreases significantly, severely impacting the stable operation and long-term service life of the hydrogen production system.

[0008] To improve the hydrogen evolution catalytic activity of Ni mesh electrodes, researchers have attempted to use noble metal coatings, such as platinum (Pt) and palladium (Pd). These noble metal coatings do indeed exhibit excellent hydrogen evolution activity. However, noble metals are extremely expensive, costing thousands of yuan per gram, which significantly increases the cost of electrodes with noble metal coatings, making large-scale application impossible and limiting them to small-scale, high-end applications where cost is not a major concern.

[0009] Some existing coating preparation processes present serious environmental problems and complex challenges. Taking the electrodeposition method for preparing Ni-based noble metal oxide coatings as an example, this process requires the use of noble metal chloride solutions, such as H₂PtCl₆ and PdCl₂. During heat treatment, these noble metal chlorides decompose to produce Cl₂ gas. Cl₂ is a toxic gas with a toxicity threshold TLV-TWA of 0.5 ppm, posing a serious threat to the health of operators and polluting the surrounding environment, which is inconsistent with current green and environmentally friendly development requirements.

[0010] In summary, conventional coating preparation technologies suffer from numerous insurmountable shortcomings in terms of powder utilization, adhesion, and environmental friendliness, making it difficult to meet the comprehensive requirements of "high efficiency, low cost, and environmental friendliness" for large-scale hydrogen production. Therefore, developing a novel coating preparation technology has become crucial for overcoming the bottlenecks in the electrolytic water hydrogen production industry and promoting the large-scale commercial application of hydrogen energy. Summary of the Invention

[0011] The problems with existing technologies are: high cost, low powder utilization, and poor adhesion between the coating and the current collector substrate. To address these issues, this invention provides a HER electrochemical cathode material based on a Ni-Mo-Al composite coating. This material is a metal composite coating formed by loading Ni, Mo, and Al metal powders onto the surface of a porous nickel current collector. The metal composite coating forms a metallurgical bond with the porous nickel current collector surface. The metal composite coating is obtained by encapsulating Mo powder within a Ni-Al binary eutectic phase formed by Ni and Al elements.

[0012] Preferably, the metal raw materials used to form the metal composite coating consist of 60%-65% Ni powder, 15%-20% Mo powder, and 15%-20% Al powder by mass percentage.

[0013] Preferably, the Ni powder is spherical, the Mo powder is irregularly shaped, and the Al powder is in the form of flakes.

[0014] Preferably, the particle size of Ni powder, Mo powder and Al powder is ≤10μm.

[0015] Preferably, the particle size range of Ni powder is 1-5 μm, the particle size range of Mo powder is 0.5-2 μm, and the particle size of Al powder is 5-10 μm.

[0016] Preferably, the purity of the porous nickel current collector is ≥99.5%.

[0017] Preferably, the porous nickel current collector is a Ni mesh with a pore size of 1-2 mm and a wire diameter of 0.2-0.3 mm.

[0018] An electrolyzer for hydrogen production uses the aforementioned HER electrochemical cathode material as its working electrode. The preparation method of the HER electrochemical cathode material includes the following steps:

[0019] (1) Grind the three metal raw materials used in the metal composite coating evenly according to the formula, and after sieving, obtain the metal mixture.

[0020] (2) The metal mixture is uniformly dispersed in the photocurable adhesive to obtain the photocurable coating. The photocurable coating is uniformly loaded onto the surface of the pretreated (sequentially acid-washed, alcohol-washed, and dried) porous nickel current collector. After photocuring, a precured coating is obtained. The precured coating is placed in a degreasing furnace at a temperature ≤450℃ under nitrogen or inert gas protection for degreasing reaction. When the residual carbon content in the precured coating is ≤0.5%, the degreasing reaction ends and a degreased electrode is obtained.

[0021] (3) The degreasing electrode is subjected to high-temperature vacuum through a two-stage stepped heating method (preferably with a vacuum degree ≤10). -3The high-temperature vacuum sintering process is as follows: the heating rate of the first stage is ≤10℃ / min, the heating rate of the second stage is ≤5℃ / min, the temperature of the first stage is 850℃, and the holding temperature is at least 10min; the temperature of the second stage is 1050℃, and the holding temperature is at least 2h. After the high-temperature vacuum sintering is completed, the sample is cooled to room temperature (cooling rate ≤5℃ / min). A metal composite coating of Mo powder coated in the Ni-Al binary eutectic phase formed by Ni and Al elements is obtained by loading Mo powder onto the surface of the porous nickel current collector. The metal composite coating and the porous nickel current collector form a metallurgical bond at the interface to obtain the modified electrode.

[0022] (4) The modified electrode was successively subjected to alkaline etching (sodium hydroxide aqueous solution, mass concentration 20-25%, etching temperature 80℃, 2-3h) to remove NaAlO2 from the metal composite coating, washed with water until neutral, and dried (temperature ≤150℃, dried to constant weight) to obtain HER electrochemical cathode material.

[0023] Preferably, the grinding in step (1) is ball milling, and the ball milling process is as follows:

[0024] Equipment selection: A planetary ball mill (model QM-3SP4, agate jar volume 500 mL, agate ball diameter 5-10 mm) is used. The reason for choosing agate material is that agate has a Mohs hardness of 7, which is higher than Al (2.75), Ni (4), and Mo (5.5), and it has strong chemical inertness (does not react with metal powder), which can avoid the introduction of metal impurities during the ball milling process (for example, if a stainless steel ball mill jar is used, Fe impurities will be introduced, which will reduce the hydrogen evolution activity of the coating by 10%-15%).

[0025] Process parameter design basis:

[0026] The optimal ball-to-powder ratio is 8:1-10:1: If the ball-to-powder ratio is too low (<8:1), the impact force will be insufficient, and the Al powder will not be able to fully plastically deform and coat the Ni and Mo powders; if it is too high (>10:1), the powder will be excessively broken, generating ultrafine powder (<0.1μm), increasing the risk of agglomeration. A ball-to-powder ratio of 8:1-10:1 can achieve the best coating effect.

[0027] Rotation speed 200-250 r / min: According to the linear velocity formula of a planetary ball mill (v=πdn / 60, where d is the diameter of the ball mill and n is the rotation speed), the linear velocity corresponding to 200-250 r / min is 1.5-2 m / s. At this speed, Al powder can undergo sufficient plastic deformation (strain rate of about 103 s⁻¹), while avoiding the oxidation of Mo powder (Mo powder is easily oxidized to MoO₂ in air when the rotation speed exceeds 300 r / min due to frictional heat (temperature rises above 150 ℃)).

[0028] Ball milling time: Dynamic observation by SEM (sampling every 30 min) revealed that after 2 h of ball milling, more than 90% of the Ni and Mo particles were covered with an Al layer of 50-100 nm thickness. After more than 3 h of ball milling, the coating thickness did not increase significantly, but the powder breakage rate increased (the proportion of ultrafine powder increased from 5% to 15%). Therefore, 2-3 h is the optimal time.

[0029] Atmosphere control: During ball milling, it is preferred to use Ar gas with a purity of 99.999% for protection, and the Ar gas flow rate is preferably not less than 50 mL / min. The purpose is to remove air (O2 volume fraction ≤0.1%) from the ball milling jar and inhibit the oxidation of Al powder (Al powder is prone to forming a 5-10 nm thick Al2O3 film in the air, which will hinder the subsequent Ni-Al melt diffusion reaction and cause the bonding strength to decrease by more than 20%).

[0030] Screening and purification:

[0031] Screen selection: After ball milling, a 200-mesh standard sieve (80 μm aperture, wear-resistant and non-reactive to powder, material can be stainless steel 316L) is preferred. The reason for choosing an 80 μm aperture is that the particle size of the composite powder after ball milling is mainly distributed in 1-10 μm. An 80 μm aperture can effectively remove uncoated large particle agglomerates (particle size > 80 μm, mainly Ni and Mo agglomerates that have not been fully ball-milled) while retaining the target particle size powder.

[0032] Screening method: Negative pressure screening is preferred (negative pressure value is preferably -0.05 MPa). The principle is that the airflow generated by negative pressure draws the powder that meets the particle size requirements into the collection device, avoiding the accumulation of powder on the screen and thus reducing screening efficiency. Experiments show that the yield of negative pressure screening (≥95%) is 5%-10% higher than that of normal pressure screening (85%-90%).

[0033] The photocurable adhesive used in step (2) is preferably an acrylic photocurable resin containing a photoinitiator, with a viscosity of 500-800 mPa·s at 25 ℃. The reason for choosing this viscosity range is that a viscosity below 500 mPa·s will cause the slurry to be too fluid and prone to sagging during application; a viscosity above 800 mPa·s will cause the slurry to have poor fluidity, making it difficult to apply evenly with a scraper and prone to generating bubbles; at the same time, acrylic resins have the advantages of fast photocuring speed (curing after 30-60 s of UV irradiation, with a degree of curing ≥90%) and low residual carbon content (residual carbon content ≤0.5% after degreasing), which avoids affecting the conductivity of the coating.

[0034] Powder-to-adhesive ratio design: The preferred mass ratio of metal mixture to UV-curable adhesive is 7:3-8:2. If the powder-to-adhesive ratio is too low (<7:3), the powder content in the slurry will be insufficient, resulting in low density (porosity >50%) and poor structural strength after sintering. If the ratio is too high (>8:2), the viscosity of the slurry will increase sharply (exceeding 1500 mPa·s), making it impossible to coat evenly. A powder-to-adhesive ratio of 7:3-8:2 can achieve a balance between "coating properties and density".

[0035] The method for uniformly dispersing the metal mixture in the UV-curable adhesive employs a mixing and degassing process: preferably, a planetary mixer is used for mixing for at least 30 minutes. This mixing method generates strong shear force through the combined motion of revolution and rotation, which makes the powder uniformly dispersed in the adhesive (dispersion uniformity is tested by a colorimeter, ΔE≤1.0); subsequently, preferably, degassing is performed in a vacuum degassing machine with a vacuum degree ≤-0.095MPa for at least 10 minutes. The principle is to allow the air bubbles in the slurry to expand and escape through the vacuum environment, thus avoiding the formation of pores after the coating is sintered.

[0036] The method for obtaining a pretreated porous nickel current collector includes the following steps:

[0037] During storage and handling, porous nickel current collectors (preferably Ni mesh, made of Ni200 with a purity ≥99.5%) easily form an oxide layer on their surface (mainly composed of NiO and Ni(OH)2, with a thickness of approximately 10-20 nm). This oxide layer has a resistivity as high as 1×10⁻⁶. 3 A value exceeding Ω·m will significantly increase the interfacial resistance between the coating and the substrate, reducing electrode conductivity. Pretreatment is required before use. Taking a Ni mesh as an example, the pretreatment steps are as follows:

[0038] Pickling: The preferred method is immersion in hydrochloric acid (analytical grade) to remove the Ni oxide layer from the Ni mesh surface. The reaction principle is NiO + 2HCl = NiCl2 + H2O, Ni(OH)2 + 2HCl = NiCl2 + 2H2O. After pickling, Ni is detected by X-ray photoelectron spectroscopy. 2+ The characteristic peak (binding energy 855 eV) intensity decreased by more than 90%, indicating that the oxide layer removal rate was ≥90%, exposing a fresh Ni surface (Ni). 0 The characteristic peak (binding energy 852.6 eV) has an 80% increase in strength, laying the foundation for subsequent coating bonding.

[0039] Alcohol washing: Anhydrous ethanol (analytical grade) is preferred as the cleaning solution, and cleaning is preferably performed in a 300 W, 40 kHz ultrasonic cleaner for 15 min. The cavitation effect of ultrasound generates strong shock waves, which strip the residual hydrochloric acid and NiCl2 impurities from the Ni mesh surface. After cleaning, inductively coupled plasma atomic emission spectrometry (ICP-AES) is used to detect the presence of Cl2 on the Ni mesh surface. - The residue level is <10 ppm, ensuring no corrosive impurities remain.

[0040] Drying: The ethanol-washed Ni mesh is subjected to forced-air drying until constant weight. The preferred forced-air drying temperature is 80 °C, which allows the ethanol evaporation rate to reach 0.5 g / (cm³). 2 •h), completely dry within 30 min;

[0041] The UV-curable coating is uniformly applied to the pretreated porous nickel current collector surface using a doctor blade coating method. The preferred equipment is a TBJ-X1 manual doctor blade coating machine. The doctor blade is made of tungsten carbide with a hardness of HRC65 and a blade edge flatness ≤0.005 mm to avoid uneven coating thickness due to doctor blade wear during coating. The UV-curable slurry is uniformly applied to the porous nickel current collector surface. If the porous nickel current collector is a Ni mesh, the coating direction should be at a 45° angle to the Ni mesh weave pattern. A coating speed of 50-80 mm / s is preferred. A speed that is too low (<50 mm / s) will cause the slurry to accumulate at the mesh openings, resulting in localized thickening (thickness deviation >±10 μm); a speed that is too high (>80 mm / s) will result in insufficient slurry flowability (viscosity 500-800 mPa・s).

[0042] In step (2), UV curing is preferred. A UV lamp with a wavelength of 365 nm and a power of 50 W is used for 30-60 seconds to initially cure and set the adhesive. The 365 nm wavelength belongs to the UV-A band and can be effectively absorbed (absorption peak at 331 nm) by photoinitiators in acrylate photocurable resins (such as 1173 photoinitiator), initiating a polymerization reaction of the C=C double bonds in the resin to form a cross-linked structure. After photocuring, Fourier transform infrared spectroscopy is used to detect the characteristic peak of the C=C double bonds in the coating (1630 cm⁻¹). -1 The strength of the coating is reduced by ≥95%, and the degree of curing is ≥95%, ensuring that the coating morphology is stable before subsequent degreasing and is not prone to deformation or peeling.

[0043] The core purpose and principle of the defatting reaction in step (2) are as follows:

[0044] The core of degreasing is to remove acrylate resins from the UV-cured adhesive, preventing blistering and cracking of the coating caused by gases generated during the combustion or carbonization of organic matter during sintering. Simultaneously, the residual carbon content must be controlled to ≤0.5% (residual carbon increases the coating's internal resistance and reduces conductivity). The degreasing reaction is preferably performed in a protective atmosphere degreasing furnace (model SK-G06123K), preferably with 99.999% pure N2. N2 isolates the Ni mesh and coating from air, preventing oxidation at high temperatures (Ni readily forms NiO in air above 300 ℃, and Mo readily forms MoO3 above 400 ℃).

[0045] The design principle of the temperature rise curve for the defatting reaction is as follows:

[0046] The heating curve was divided into three stages: room temperature → 200 ℃ (heating rate ≤ 5 ℃ / min), 200 ℃ → 400 ℃ (heating rate ≤ 2 ℃ / min), and holding at 400 ℃ for 1 h. Thermogravimetric analysis (TGA) curves showed that in the 100-200 ℃ temperature range, the acrylic resin mainly underwent the volatilization of low-boiling-point monomers (such as methyl methacrylate, boiling point 100.3 ℃), with a mass loss of about 30%. The low-boiling-point components were removed in this stage, preventing their accumulation inside the coating. The 200-400 ℃ temperature range was the thermal decomposition stage of the resin backbone (mainly C-C bond breakage), with a mass loss of about 60%. Holding at 400 ℃ for at least 1 h allowed the remaining small amount of difficult-to-decompose organic matter (such as carbon chains in the cross-linked structure) to completely decompose, and the mass loss tended to stabilize. The residual carbon content was verified by TGA, and the residual carbon content was ultimately guaranteed to be ≤ 0.5%. If the residual carbon content is >0.5%, the holding time at 400℃ needs to be extended to 1.5 h, or the holding temperature should be appropriately increased to 420℃ (but the temperature should not exceed 450℃, otherwise Ni will begin to oxidize). A residual carbon content ≤0.5% ensures that the coating resistivity is ≤5×10⁻⁷ Ω・m, avoiding an increase in ohmic losses due to residual carbon (when the residual carbon content is 1%, the coating resistivity will increase to 1×10⁻⁶ Ω・m, and the ohmic loss will increase by about 50%). The test method for residual carbon content is as follows:

[0047] The pre-cured coating sample after degreasing reaction was heated from room temperature to 800 ℃ in air atmosphere at a heating rate ≤10℃ / min. The residual carbon content at 800℃ was the percentage of the remaining mass of the pre-cured coating sample to the initial mass of the pre-cured coating sample.

[0048] The high-temperature vacuum sintering in step (3) is as follows:

[0049] Basis for selecting vacuum environment:

[0050] The degreased electrode obtained in step (2) is transferred to a vacuum sintering furnace (preferably model ZT-40-20Y). The main functions of the vacuum environment are: firstly, to prevent Ni, Mo, and Al from oxidizing at high temperatures; and secondly, to promote the discharge of small amounts of gas (such as adsorbed H2O and N2) generated during the Ni-Al melting and diffusion process, thus avoiding the formation of pores inside the coating.

[0051] The thermodynamic design of the high-temperature vacuum sintering heating curve is as follows:

[0052] The heating curve is divided into three stages, and the parameters for each stage are designed based on the phase diagram and thermodynamic properties of the Ni-Al-Mo system: The first stage is the high-temperature vacuum sintering stage: 400℃ to 850℃ (heating rate ≤10℃ / min), based on the Ni-Al binary phase diagram (as shown in the instruction manual). Figure 1As shown, Ni and Al form a eutectic phase (Ni3Al-NiAl eutectic) at 596 °C. The reaction rate is slow below the eutectic temperature. Starting at 400 °C, Ni and Al gradually undergo solid-state diffusion to form Ni3Al (enthalpy of formation -118 kJ / mol). In the range of 400-850 °C, Mo remains in the solid state (melting point of Mo is 2623 °C) and does not react with Ni or Al.

[0053] At 1050 K (Ni-Al-Mo system):

[0054] ΔG(Mo-Ni) = +42.3 kJ / mol;

[0055] ΔG(Mo-Al) = +38.5 kJ / mol.

[0056] All of the above reactions are non-spontaneous reactions, to avoid Mo participating in the reaction too early and affecting its dispersibility.

[0057] The second stage, high-temperature vacuum sintering, ranges from 850℃ to 1050℃ (heating rate ≤ 5℃ / min). At 850℃, the Ni-Al system is completely melted (Ni melting point 1455℃, Al melting point 660℃, Ni-Al eutectic point 596℃, molten state ratio > 90% at 850℃). This stage requires slow heating (≤ 5℃ / min) to allow sufficient time for the molten Ni-Al matrix to uniformly coat Mo particles (particle size 0.5-2 μm). From an interfacial chemistry perspective, the wetting angle between molten Ni-Al and Mo is approximately 60° (measured by the seated drop method), indicating good wetting. Slow heating promotes interfacial atomic diffusion and enhances the bonding force between Mo and the matrix. If the heating is too rapid (> 10℃ / min), the molten matrix lacks fluidity and cannot fully coat the Mo particles, leading to Mo exposure and affecting catalytic activity.

[0058] Holding at 850℃ for at least 10 minutes is intended to effectively release sintering internal stress, inhibit coating cracking and high-temperature deformation of the nickel mesh, promote uniform diffusion of alloying elements within the coating, optimize microstructure and performance, and fully thermally decompose and release the binder in the powder, remove surface oxide film and residual impurities, further improving coating purity and density. Moreover, 850℃ is far below the phase transformation softening temperature of the nickel mesh, which can balance the coating film formation effect with the integrity of the nickel mesh substrate structure, avoiding problems such as coating sagging, insufficient adhesion, and nickel mesh oxidation deformation caused by improper temperature or duration.

[0059] Hold at 1050 ℃ for at least 2 h: 1050 ℃ is the optimal sintering temperature for the Ni-Al-Mo system. At this temperature, the Ni-Al molten matrix exhibits optimal fluidity, allowing it to fully fill the internal pores of the coating. Simultaneously, the formation reactions of the Ni3Al and NiAl phases reach equilibrium.

[0060] 3Ni + Al = Ni3Al.

[0061] Its reaction rate constant is 0.01 s⁻¹ at 1050 K. -1 Within 2 hours, the reaction conversion rate is ≥99%. When the holding time is less than 1 hour, the reaction conversion rate is <90%, and unreacted Ni and Al are present in the coating, affecting the structural stability. If the holding time exceeds 3 hours, it will lead to grain growth (Ni3Al grain size increases from 1μm to 3μm), a decrease in specific surface area, a reduction in active sites, and a decrease in catalytic activity.

[0062] After high-temperature vacuum sintering is completed, the temperature is cooled to room temperature. The specific operation includes the following steps:

[0063] After high-temperature vacuum sintering, the coating is cooled to room temperature in the furnace at a rate ≤5 ℃ / min. Rapid cooling (>20 ℃ / min) will cause thermal stress to be generated inside the coating (coefficient of thermal expansion: Ni3Al approximately 13 × 10⁻⁶). -6 / ℃, Mo about 5×10 -6 / ℃), which varies greatly, and is prone to cracking; furnace cooling can slowly reduce the coating temperature and gradually release thermal stress. After cooling to room temperature, the residual stress of the coating is <50 MPa, which is lower than the fracture strength of Ni3Al (about 300 MPa), ensuring the integrity of the coating structure.

[0064] The method for modifying electrodes by alkaline etching includes the following steps:

[0065] The modified electrode was completely immersed in a 20%-25% NaOH aqueous solution at 80°C for 2-3 hours for etching. After that, it was washed with deionized water until pH=7, and then dried at 120°C to constant weight.

[0066] After alkaline etching, the modified electrode must be removed from the NaOH aqueous solution and immediately rinsed with deionized water (resistivity ≥18.2 MΩ・cm) until the filtrate pH=7. The rinsing process should adopt a three-step method of "immersion-ultrasound-rinse": first, immerse in deionized water for at least 10 minutes to initially dissolve residual alkaline solution on the surface; then, clean with a 40 kHz, 300 W ultrasonic cleaner for at least 5 minutes to remove residual NaAlO2 in the pores using the cavitation effect; finally, rinse with deionized water under high pressure to ensure that there are no impurities remaining on the electrode surface.

[0067] After cleaning, the electrodes need to be dried to constant weight in a forced-air drying oven at a temperature ≤150 ℃. If the drying temperature is too high (>150 ℃), it may cause slight oxidation of the coating surface (forming a thin NiO layer with a thickness <2 nm), which has little impact on catalytic activity but will increase the interfacial resistance.

[0068] The metal powder formulation design of the metal composite coating of this invention is based on the synergistic mechanism of "catalytic activity-structural stability-pore-forming efficiency". Experimental verification determined the optimal mass percentage to be: Ni powder 60%-65%, Mo powder 15%-20%, and Al powder 15%-20%. The selection criteria for the three metal powders are as follows:

[0069] Ni powder: Spherical powder with a particle size of 1-5 μm (purity ≥99.9%) is selected. Its core function is:

[0070] (1) Provides basic hydrogen evolution activity (the 3d orbital electrons of Ni are easy to combine with the 1s orbital electrons of H to form Ni-H adsorption bonds, providing active sites for hydrogen evolution reaction).

[0071] (2) As a molten matrix element, it reacts with Al at the sintering temperature to generate Ni-Al intermetallic compounds, thereby constructing a composite metal coating framework structure;

[0072] (3) Reasons for choosing a particle size of 1-5 μm: If the particle size is too small (<1 μm), it is easy to agglomerate, resulting in poor coating density; if the particle size is too large (>5 μm), it will reduce the specific surface area of ​​the coating and reduce the number of active sites. A particle size of 1-5 μm can achieve a balance between the number of active sites and the density of the coating.

[0073] Mo powder: Irregular powder with a particle size of 0.5-2μm (purity ≥99.5%) is selected. Its mechanism of action is as follows:

[0074] (1) Electronic regulation effect: Mo has an atomic number of 42 and an outer electron configuration of [Kr]4d 55 s 1 d orbital electrons can be transferred to the 3d orbitals of Ni, adjusting the electron density of Ni and optimizing the H adsorption energy from -0.5 eV of pure Ni to about -0.3 eV (close to the ideal hydrogen evolution adsorption energy, taking into account both adsorption and desorption efficiency).

[0075] (2) Enhanced conductivity: The resistivity of Mo is approximately 5.7 × 10⁻⁶. -8 Ω・m, lower than Ni's 6.99×10 -8 Ω・m can reduce the internal resistance of the coating and reduce ohmic losses;

[0076] (3) Suppressing agglomeration: The irregular morphology of Mo powder can form a "spatial barrier" effect in the Ni-Al matrix, which can prevent Ni particles from agglomerating during sintering (experiments show that adding 15%-20% Mo powder can reduce the agglomeration rate of Ni particles from 30% to below 5%).

[0077] (4) Reasons for choosing a particle size of 0.5-2μm: If the particle size is too small (<0.5μm), it is easy to be oxidized to form MoO3 (which is oxidized in air above 300℃), reducing conductivity; if the particle size is too large (>2μm), it is difficult to disperse evenly, resulting in uneven electron conduction. Therefore, 0.5-2 μm is the optimal range.

[0078] Al powder: Selected is flaky powder with a particle size of 5-10μm (thin flakes, purity ≥99.7%), and its core working mechanism is as follows:

[0079] (1) Ball milling coating carrier: Flake Al powder has a large specific surface area (approximately 0.5-1m²). 2 Al has good plastic deformation ability (the yield strength of Al is about 70 MPa, and it is easy to undergo plastic deformation under the action of ball milling impact force, and it is easy to be coated on the surface of Ni and Mo powder), forming a core-shell structured composite powder, avoiding the agglomeration of Ni and Mo powder;

[0080] (2) Sintering bonding promoter: Al has a strong affinity for Ni (the mixing enthalpy of the Ni-Al system is -42 kJ / mol, which is a strong exothermic reaction), and it is easy to form Ni3Al and NiAl intermetallic compounds with Ni during sintering, so as to achieve metallurgical bonding between the coating and the substrate;

[0081] (3) Pore-forming agent: Unreacted Al powder can be completely removed by alkaline etching (Al reacts with NaOH) to form a porous structure of 1-5 μm, increasing the specific surface area;

[0082] (4) Reasons for choosing 5-10μm flake powder: If the particle size is too small (<5μm), it is easy to be over-broken during ball milling and lose its coating ability; if the particle size is too large (>10μm), the pores formed after etching will be too large (>5μm), resulting in a reduction in the strength of the coating structure. Therefore, 5-10μm flake powder can take into account both coating effect and pore quality.

[0083] The following are the verification data for the thermodynamic controllability during high-temperature vacuum sintering:

[0084] (1) Thermodynamic calculation basis for the spontaneous reaction in the sintering process:

[0085] The Gibbs free energy (ΔG) of Ni-Al, Mo-Ni, and Mo-Al systems in the range of 298-1200 K was calculated using HSC Chemistry 6.0 software, with 1050 K (corresponding to the sintering holding temperature) as the key node for analysis.

[0086] The reaction of Ni with Al:

[0087] ΔG for 3Ni + Al = Ni3Al:

[0088] ΔG = -95600 + 21.5T (J / mol), substituting into T = 1050 K;

[0089] ΔG=-95600+21.5×1050=-95600+22575=-73025 J / mol≈-73.0 kJ / mol.

[0090] The fact that the data was in a strongly negative range earlier indicates that the reaction was spontaneous;

[0091] ΔG for Ni + Al = NiAl:

[0092] ΔG = -68200 + 18.2T (J / mol), substituting into T = 1050 K;

[0093] ΔG=-68200+18.2×1050=-68200+19110=-49090J / mol≈-49.1 kJ / mol.

[0094] Both are spontaneous reactions. In terms of reaction priority, Ni3Al has a more negative ΔG, so Ni3Al is preferentially formed during sintering, followed by NiAl. Both intermetallic compounds have excellent mechanical properties (Ni3Al has a tensile strength of about 600 MPa, and NiAl has a hardness of about 400 HV), which can enhance the structural stability of the coating.

[0095] The reaction of Mo with Ni / Al:

[0096] The formula for calculating ΔG in the reaction of Mo and Ni to form MoNi3 is:

[0097] ΔG = 42300 - 15.8T (J / mol), substituting into T = 1050 K:

[0098] ΔG=42300-15.8×1050=42300-16590=25710J / mol≈+25.7 kJ / mol

[0099] The formula for calculating ΔG in the reaction of Mo and Al to form MoAl3 is:

[0100] ΔG = 38500 - 14.3T (J / mol), substituting into T = 1050 K:

[0101] ΔG=38500-14.3×1050=38500-14915=23585J / mol≈+23.6 kJ / mol

[0102] According to thermodynamic principles, the reaction is non-spontaneous when ΔG>0. Therefore, Mo does not chemically react with Ni or Al during sintering, but is uniformly dispersed in the Ni-Al matrix in elemental form. The elemental form of Mo can fully utilize its electronic regulation effect. Through density functional theory (DFT) calculations, after the transfer of d orbital electrons of Mo to Ni, the d band center of Ni is adjusted from -1.5 eV to -1.2 eV, which is closer to the ideal d band center (-1.0 to -1.3 eV) for the hydrogen evolution reaction. This optimizes the H adsorption energy from -0.5 eV to -0.3 eV, significantly reducing the activation energy of the hydrogen evolution reaction.

[0103] (2) Thermodynamic analysis of melting and solid retention of Mo in the Ni-Al system:

[0104] According to the Ni-Al binary phase diagram (as shown in the instruction manual) Figure 1 As shown in the figure, in the eutectic system formed by Ni and Al, the eutectic point temperature is 596 ℃, and the eutectic composition contains about 31% Al (atomic fraction). At a sintering temperature of 1050 ℃, regardless of the initial Ni-Al ratio, it is in the liquid phase region of the Ni-Al phase diagram, that is, the Ni-Al system is completely melted, forming a molten matrix with good fluidity.

[0105] Mo has a melting point of 2623 °C, and at 1050 °C, it is far below its melting point and exists in a solid state. Measured by a thermal dilatometer, the coefficient of thermal expansion of Mo at 1050 °C is approximately 5.5 × 10⁻⁶. -6 / ℃, while the coefficient of thermal expansion of the Ni-Al molten matrix after cooling is approximately 12×10. -6 The difference between the two temperatures (°C and °C) is compensated by an interfacial diffusion layer, preventing cracking due to mismatched thermal expansion coefficients during cooling. Simultaneously, the presence of solid-state Mo inhibits grain growth in the Ni-Al matrix during cooling.

[0106] (3) In-depth verification of the thermodynamic feasibility of alkaline etching reaction:

[0107] The reaction of Al with NaOH:

[0108] 2Al+2NaOH+2H2O=2NaAlO2+3H2↑.

[0109] The calculation of ΔG at 353 K (80 °C) needs to consider the influence of the activity of the reaction system. The Debye-Hückel limiting equation is used to calculate the ionic activity coefficient in NaOH aqueous solution. The ionic strength of a 20%-25% NaOH aqueous solution at 80 °C is approximately 10 mol / kg. + The activity coefficient is approximately 0.7, OH - The activity coefficient is approximately 0.6. Substituting this into the ΔG calculation formula:

[0110] ΔG = ΔG° + RTlnQ

[0111] Where ΔG° is the standard Gibbs free energy (-823 kJ / mol), and Q is the reaction quotient. The calculation yields:

[0112] Q=[a(NaAlO2) 2 ×p(H2) 3 ] / [a(NaOH) 2 ×a(H2O) 2 ]

[0113] Since NaAlO2 is completely dissolved and H2 is an ideal gas, after substituting the activity value:

[0114] Q≈10 -5 .

[0115] RTlnQ≈8.314×353×ln(10 -5 )≈-33 kJ / mol;

[0116] ΔG = -823 - 33 = -856 kJ / mol.

[0117] The value remains strongly negative, indicating that the reaction exhibits extremely strong spontaneity in an aqueous solution of NaOH at 80 °C and a mass concentration of 20%-25%.

[0118] From a kinetic perspective, the rate equation for this reaction is:

[0119] v=k[c(Al)×c(OH - ) 2 ].

[0120] The rate constant k is approximately 0.1 L at 80℃. 2 / (mol 2 •h). OH in a 20%-25% NaOH aqueous solution. - The concentration is approximately 5-6 mol / L, and the initial Al concentration (based on the unreacted Al content in the coating) is approximately 0.1 mol / L. Substituting these values, we get:

[0121] v≈0.1×0.1×(5) 2 =0.25 mol / (L・h).

[0122] This indicates that unreacted Al can be completely consumed within 2-3 hours (the amount of unreacted Al in the coating is approximately 0.005 mol / cm³). 2 At this rate, over 95% can be consumed in 2 hours.

[0123] Beneficial effects:

[0124] (1) Existing physical spraying techniques (such as plasma spraying) form a coating that is primarily mechanically bonded to the nickel mesh substrate, resulting in low bonding strength (typically <15 MPa). Under the harsh conditions of high temperature, high potential, and strong alkaline scouring in the electrolytic cell, the coating is easily peeled off, leading to rapid degradation of electrode performance. The core breakthrough of this invention lies in the formation of a strong "metallurgical bond" between the coating and the substrate through precise material design and process control. The technical path of this invention is original:

[0125] a: Al powder was selected as a "bonding accelerator". Al and Ni have a strong chemical affinity (the mixing enthalpy of the Ni-Al system is -42 kJ / mol), and a violent exothermic reaction can occur during high-temperature sintering.

[0126] b: The reaction process was precisely controlled through a combination of "ball milling pre-coating - degreasing - stepped heating vacuum sintering". Under the vacuum sintering environment of 1050℃, Ni and Al fully melted and diffused, generating intermetallic compounds such as Ni3Al and NiAl in situ. These compounds grew and interlocked at the interface between the coating and the nickel mesh substrate, forming an atomic-scale metallurgical bonding interface.

[0127] c: This bonding method is far stronger than mechanical bonding, allowing the coating to fuse seamlessly with the substrate. Therefore, the electrode can withstand alkaline erosion and bubble peeling forces during long-term operation, laying a solid physical foundation for a service life exceeding 5000 hours.

[0128] (2) Existing technologies often rely on coatings of noble metals such as platinum (Pt) and palladium (Pd) to improve catalytic activity. Although the hydrogen evolution overpotential can be reduced to ≤100 mV, the cost of several thousand yuan per gram is completely unacceptable for large-scale applications. This invention takes a different approach by constructing a unique composite structure of "Ni-Al metal framework encapsulating elemental Mo", achieving excellent activity close to that of noble metals in a completely non-noble metal system.

[0129] The synergistic catalytic mechanism of the Ni-Mo-Al system formed by Ni-Al binary eutectic encapsulating elemental Mo is as follows:

[0130] Ni-Al framework: provides a stable conductive network and structural support.

[0131] Mo active sites: The d-orbital electrons of Mo can modulate the electron density of neighboring Ni atoms, optimizing its adsorption energy for hydrogen intermediates (H*), bringing it closer to the ideal -0.3 eV from -0.5 eV for pure Ni, thereby significantly improving intrinsic catalytic activity. Furthermore, Mo can inhibit Ni3Al grain growth, maintaining the long-term stability of the coating's microstructure.

[0132] Structural advantages: By removing some of the Al through alkaline etching to generate NaAlO2, a porous structure of 1-5 μm is created in situ within the coating. This significantly increases the electrochemically active area and exposes more Mo active sites.

[0133] Performance data: Under alkaline conditions and at a high current density of 100 mA / cm², the hydrogen evolution overpotential of this composite coating can be stably controlled, significantly better than that of pure nickel mesh (250-300 mV), and it completely avoids the use of precious metals, resulting in a cost reduction of several orders of magnitude. It is fully adapted to the operating conditions required for long-term stable operation of electrolytic cells.

[0134] (3) Existing technologies have two major process defects: first, powder is lost through the nickel mesh during spraying, with a utilization rate of less than 30%; second, methods such as electrodeposition use precious metal chlorides, and heat treatment generates highly toxic Cl2 gas, posing a high environmental risk. This invention solves the above problems through an innovative process combination of "slurry coating + photocuring and setting":

[0135] Nearly 100% powder utilization: Metal powder is mixed with UV-curable resin to form a slurry, which is then coated onto a nickel mesh. The slurry completely fills and covers the mesh structure, and is then rapidly cured and set by UV light. During this process, there is no powder splashing or loss, resulting in near 100% raw material utilization, significantly reducing material costs and production waste.

[0136] The entire process is clean and environmentally friendly: the entire process (ball milling, degreasing, sintering) is carried out under inert gas or vacuum protection to avoid metal oxidation; the coating preparation does not involve any toxic halide precursors, the degreasing products are carbon dioxide and water, and there are no toxic waste gas emissions throughout the process, which meets the requirements of green manufacturing.

[0137] (4) This invention not only pursues high initial performance, but also ensures the durability of the electrode under harsh working conditions and the consistency of quality in large-scale production through a series of detailed designs. The metallurgical interface formed between the current collector surface and the metal composite coating ensures extremely low contact resistance. The Ni-Al intermetallic compound framework itself has good conductivity and chemical stability in alkaline solutions. Mo powder is encapsulated in the framework, avoiding the possible shedding or dissolution that may occur when it is used alone as a catalyst.

[0138] (5) The present invention uses inexpensive Ni, Mo and Al as raw materials and a high-efficiency, low-loss preparation process, so that the overall manufacturing cost of the high-performance electrode is only slightly higher than that of the nickel mesh substrate itself, which has the economic premise for large-scale commercial application. Attached Figure Description

[0139] Figure 1 Ni-Al binary phase diagram.

[0140] Figure 2Stability test results of conventional commercially available BSL-5.0 electrode mesh samples and electrodes 1, 2, and 3 obtained in Examples 1-3 of this invention. Detailed Implementation

[0141] The present invention will be described in detail below with reference to embodiments. However, it should be understood that the following embodiments are merely illustrative examples of implementation of the present invention and are not intended to limit the scope of the present invention.

[0142] The light-curing adhesive used in the following embodiments of the present invention comprises, by weight percentage, the following components:

[0143] Matrix resin 85%;

[0144] Photoinitiator (photoinitiator 1173) 15%;

[0145] The matrix resin is composed of trimethylolpropane triacrylate and hydroxy acrylic resin (Guangzhou Bangtai New Material Technology Co., Ltd., model: Steba AW 2F5064) in a mass ratio of 7:3.

[0146] The Ni mesh used in the following examples has a mesh size of 2mm, is made of Ni 200 with a purity of ≥99.5%, has a mesh size of 1-2mm, and a wire diameter of 0.2-0.3mm.

[0147] The Ni powder used in the following examples is spherical powder with a particle size of 1-5 μm (prepared by gas atomization method, with a purity of ≥99.9%).

[0148] The Mo powder used in the following examples is an irregular powder with a particle size of 0.5-2 μm (prepared by reduction method, with a purity ≥99.5%).

[0149] The Al powder used in the following examples is: thin flake powder with a particle size of 5-10 μm (prepared by mechanical grinding, with a purity ≥99.7%).

[0150] The spherical Mo powder and Al powder used in this invention have a purity of ≥99.5% and particle sizes of 0.5-2 μm and 5-10 μm, respectively.

[0151] Example 1

[0152] The preparation method of HER electrochemical cathode material is as follows:

[0153] (1) According to the formula, grind the three metal raw materials used for the metal composite coating evenly in a mass ratio of 60:20:20, and pass them through a 200-mesh sieve to obtain the metal mixture;

[0154] (2) The metal mixture is uniformly dispersed in the photocurable adhesive to obtain the photocurable coating. The photocurable coating is uniformly loaded on the surface of the pretreated Ni mesh. After photocuring, a precurable coating is obtained. The precurable coating is placed in a degreasing furnace at a temperature of 450°C under nitrogen protection for degreasing reaction. When the residual carbon content in the precurable coating is 0.5%, the degreasing reaction ends and a degreased electrode is obtained.

[0155] (3) The degreasing electrode is subjected to high-temperature vacuum (vacuum degree 10) through a two-stage stepped heating method. -3 The high-temperature vacuum sintering process was carried out at a heating rate of 10℃ / min for the first stage and 5℃ / min for the second stage. The temperature of the first stage was 850℃, and the temperature was held at 850℃ for 10 min. The temperature of the second stage was 1050℃, and the temperature was held at 1050℃ for 2 h. After the high-temperature vacuum sintering was completed, the electrode was cooled to room temperature (cooling rate 5℃ / min) to obtain the modified electrode.

[0156] (4) The modified electrode was successively subjected to alkaline etching to remove NaAlO2 from the metal composite coating, washed with water until neutral, and dried at 120°C to constant weight to obtain the HER electrochemical cathode material, which is referred to as electrode 1.

[0157] The grinding in step (1) is ball milling: a planetary ball mill (equipment model: QM-3SP4, agate ball diameter 5mm, agate purity ≥99.9%) is used. During the ball milling process, Ar gas with purity ≥99.999% is used for protection (to ensure that the oxygen content in the ball milling jar is ≤0.1%), and the ball milling is carried out for 3 hours at a ball-to-material ratio of 8:1 and a rotation speed of 200 r / min.

[0158] The sieving in step (1) is also known as sieving and purification: a 200-mesh standard sieve (the sieve material is stainless steel 316L, the sieve hole size is 80 μm, and the sieve accuracy is ±5 μm) is used for negative pressure sieving with a negative pressure value of -0.05MPa.

[0159] In step (2), the metal mixture is uniformly dispersed in the photocurable adhesive by planetary mixing. The planetary mixer model is XJB-5, with a revolution speed of 500 r / min and a rotation speed of 1000 r / min. The mixing paddle is a blade type made of polytetrafluoroethylene. The mixture is stirred for 30 min and then degassed for 10 min in a vacuum degassing machine (model: DZ-2BC, degassing temperature 25℃) with a vacuum degree of -0.095 MPa to obtain the photocurable coating.

[0160] The steps for obtaining the preprocessed Ni mesh in step (2) are as follows:

[0161] Pickling: The Ni mesh (20mm × 20mm × 0.3mm) was immersed in 10% hydrochloric acid for 30 minutes to remove the Ni oxide layer on the surface of the Ni mesh. After pickling, Ni was analyzed by X-ray photoelectron spectroscopy. 2+ The intensity of the characteristic peak (binding energy 855 eV) decreased by 92%.

[0162] Alcohol washing: Anhydrous ethanol (analytical grade) was used as the cleaning solution, and the Ni mesh was cleaned for 15 min in a 300 W, 40 kHz ultrasonic cleaner. Drying: The alcohol-washed Ni mesh was dried to constant weight by forced air drying at 80 ℃.

[0163] The step (2) of uniformly loading the photocurable coating onto the pretreated Ni mesh surface is as follows:

[0164] A doctor blade coater (model: TBJ-X1, doctor blade material: tungsten carbide, hardness: HRC65) was used to evenly coat the UV-curable coating onto the surface of a pretreated Ni mesh placed horizontally on a conveyor belt. The coating was then passed through a UV lamp (model: HL-UV365-100, wavelength: 365 nm, power: 50 W, power density: 50 mW / cm²). 2 Irradiation for 30 seconds allows the adhesive to initially cure and set, resulting in a pre-cured coating. After coating, the pretreated Ni mesh showed a weight gain of 26 g / cm³. 2 ;

[0165] The defatting reaction steps in step (2) are as follows:

[0166] The electrode modified with the pre-cured coating was placed in a degreasing furnace (model: SK-G06123K, furnace chamber material: corundum) under N2 protection (purity ≥99.999%, flow rate 50 mL / min), and degreased according to a gradient heating curve: first, the temperature was raised from room temperature to 200 ℃ (heating rate 5 ℃ / min), then from 200 ℃ to 450 ℃ (heating rate 2 ℃ / min), and held at 450 ℃ for 1 h; when the residual carbon content in the pre-cured coating was 0.5%, the degreasing reaction ended, and the degreased electrode was obtained.

[0167] In step (3), the vacuum sintering furnace model is ZT-40-20Y, and the furnace chamber material is graphite.

[0168] The alkaline etching step in step (4) is as follows:

[0169] The degreased electrode was completely immersed in a 20% NaOH aqueous solution at a constant temperature of 80℃ for 2-3 h for etching. During the etching process, the stirring rate was 50 r / min. The electrode was then washed with deionized water until the filtrate was clear and the pH was 7. Finally, it was dried at 120℃ to constant weight.

[0170] Example 2

[0171] The preparation method of HER electrochemical cathode material is as follows:

[0172] (1) According to the formula, grind the three metal raw materials used for the metal composite coating evenly in a mass ratio of 65:15:20, and pass them through a 200-mesh sieve to obtain the metal mixture;

[0173] (2) The metal mixture is evenly dispersed in the photocurable adhesive to obtain the photocurable coating. The photocurable coating is evenly loaded on the surface of the pretreated Ni mesh. After photocuring, a precurable coating is obtained. The precurable coating is placed in a degreasing furnace at a temperature of 450°C under nitrogen protection for degreasing reaction. When the residual carbon content in the precurable coating is 0.5%, the degreasing reaction ends and a degreased electrode is obtained.

[0174] (3) The degreasing electrode is subjected to high-temperature vacuum (vacuum degree 10) through a two-stage stepped heating method. -3 The high-temperature vacuum sintering process was carried out at a heating rate of 10℃ / min for the first stage and 5℃ / min for the second stage. The temperature of the first stage was 850℃, and the temperature was held at 850℃ for 10 min. The temperature of the second stage was 1050℃, and the temperature was held at 1050℃ for 2 h. After the high-temperature vacuum sintering was completed, the electrode was cooled to room temperature (cooling rate 5℃ / min) to obtain the modified electrode.

[0175] (4) The modified electrode was successively subjected to alkaline etching to remove NaAlO2 from the metal composite coating, washed with water until neutral, and dried at 120°C to constant weight to obtain the HER electrochemical cathode material, which is referred to as electrode 2.

[0176] The grinding in step (1) is ball milling: a planetary ball mill (equipment model: QM-3SP4, agate ball diameter 5-10mm, agate purity ≥99.9%) is used. During the ball milling process, Ar gas with purity ≥99.999% is used for protection (to ensure that the oxygen content in the ball milling jar is ≤0.1%), and the ball milling is carried out for 3 hours at a ball-to-material ratio of 10:1 and a rotation speed of 250 r / min.

[0177] The sieving in step (1) is also known as sieving and purification: a 200-mesh standard sieve (the sieve material is stainless steel 316L, the sieve hole size is 80 μm, and the sieve accuracy is ±5 μm) is used for negative pressure sieving, and the negative pressure value is -0.08 MPa.

[0178] In step (2), the metal mixture is uniformly dispersed in the photocurable adhesive by planetary mixing. The planetary mixer model is XJB-5, with a revolution speed of 500 r / min and a rotation speed of 1000 r / min. The mixing paddle is a blade type made of polytetrafluoroethylene. The mixture is stirred for 30 min and then degassed for 10 min in a vacuum degassing machine (model: DZ-2BC, degassing temperature 25℃) with a vacuum degree of -0.090 MPa to obtain the photocurable coating.

[0179] The steps for obtaining the preprocessed Ni mesh in step (2) are as follows:

[0180] Pickling: The Ni mesh (20mm x 20mm x 0.3mm) was immersed in 10% hydrochloric acid for 30 minutes to remove the Ni oxide layer on the surface of the Ni mesh. After pickling, Ni was analyzed by X-ray photoelectron spectroscopy. 2+ The intensity of the characteristic peak (binding energy 855 eV) decreased by 91%.

[0181] Alcohol washing: Anhydrous ethanol (analytical grade) was used as the cleaning solution, and the Ni mesh was cleaned for 15 min in a 300 W, 40 kHz ultrasonic cleaner. Drying: The alcohol-washed Ni mesh was dried to constant weight by forced air drying at 80 ℃.

[0182] The step (2) of uniformly loading the photocurable coating onto the pretreated Ni mesh surface is as follows:

[0183] A doctor blade coater (model: TBJ-X1, doctor blade material: tungsten carbide, hardness: HRC65) was used to evenly coat the UV-curable coating onto the surface of a pretreated Ni mesh placed horizontally on a conveyor belt. The coating was then passed through a UV lamp (model: HL-UV365-100, wavelength: 365 nm, power: 50 W, power density: 50 mW / cm²). 2 Irradiation for 60 seconds allows the adhesive to initially cure and set, resulting in a pre-cured coating. After coating, the pretreated Ni mesh showed a weight gain of 26 g / cm³. 2 ;

[0184] The defatting reaction steps in step (2) are as follows:

[0185] The electrode modified with the pre-cured coating was placed in a degreasing furnace (model: SK-G06123K, furnace chamber material: corundum) under N2 protection (purity ≥99.999%, flow rate 50 mL / min), and degreased according to a gradient heating curve: first, the temperature was raised from room temperature to 200 ℃ (heating rate 5 ℃ / min), then from 200 ℃ to 450 ℃ (heating rate 2 ℃ / min), and held at 450 ℃ for 1 h; when the residual carbon content in the pre-cured coating was 0.5%, the degreasing reaction ended, and the degreased electrode was obtained.

[0186] In step (3), the vacuum sintering furnace model is ZT-40-20Y, and the furnace chamber material is graphite.

[0187] The alkaline etching step in step (4) is as follows:

[0188] The degreased electrode was completely immersed in a 25% NaOH aqueous solution at a constant temperature of 80℃ for 2 hours for etching. During the etching process, the stirring rate was 50 r / min. The electrode was then washed with deionized water until the filtrate was clear and the pH was 7. Finally, it was dried at 120℃ to constant weight.

[0189] Example 3 is the same as Example 1, except that the mass ratio of the three metal raw materials used in the metal composite coating in Example 3 is 62:18:20. The HER electrochemical cathode material obtained in Example 3 is designated as electrode 3.

[0190] Comparative Example 1 is the same as Example 1, except that the mass ratio of the three metal raw materials used in the metal composite coating in Comparative Example 1 is 80:10:10. The electrode material obtained in Comparative Example 1 is designated as Electrode 4.

[0191] Comparative Example 2 is the same as Example 1, except that all three metal raw materials used in the metal composite coating in Comparative Example 2 are spherical. The electrode material obtained in Comparative Example 2 is designated as electrode 5.

[0192] Comparative Example 3 is the same as Example 1, except that the particle size of the three metal raw materials used in the metal composite coating in Comparative Example 3 is 1-5 μm. The electrode material obtained in Comparative Example 3 is designated as Electrode 6.

[0193] Comparative Example 4 is the same as Example 1, except that the heating rate of the second stage of high-temperature vacuum sintering in Comparative Example 4 is 10℃ / min. The electrode material obtained in Comparative Example 4 is designated as Electrode 7.

[0194] Comparative Example 5 is the same as Example 1, except that in step (2) of Comparative Example 5, the degreasing reaction was only kept at 450 °C for 20 min before the degreasing reaction was completed, and the residual carbon content in the pre-cured coating was greater than 0.5%. The electrode material obtained in Comparative Example 5 is referred to as Electrode 8.

[0195] Performance testing

[0196] Using the electrodes obtained in the above examples and comparative examples as working electrodes, a platinum sheet electrode as the counter electrode, and a saturated calomel electrode as the reference electrode, and 6 mol / L KOH solution as the electrolyte, an H-type electrolytic cell containing a diaphragm was assembled to test the electrochemical hydrogen evolution reaction performance. To minimize the influence of capacitive current during polarization curve testing, a potential scan rate of 2 mV / s was set, with the potential ranging from 100 mV to -300 mV vs RHE. Each set of data was tested in triplicate, and the average value was taken. The test results are shown in Table 1. Stability testing was performed using a long-term chronoamperometry method, observing the change in current density under a constant electrode potential. The stability test results are shown in the appendix to the instruction manual. Figure 2 As shown. Figure 2 In this context, BSL-5 represents a commercially available BSL-5.0 hydrogen production electrode (purchased from Baoshilai New Materials Technology Co., Ltd., specification: Raney nickel-coated nickel mesh electrode), and ZS-1, ZS-2, and ZS-3 represent electrodes 1, 2, and 3 obtained in Examples 1-3 of this invention, respectively. Stability testing employed a three-electrode system, with BSL-5, ZS-1, ZS-2, and ZS-3 serving as the working electrodes, a platinum sheet electrode as the anode, and a saturated calomel electrode as the reference electrode. Testing was conducted at room temperature, using a 30% KOH aqueous solution as the test electrolyte.

[0197] Comparative experiments between the commercially available BSL-5.0 hydrogen production electrode and the electrode obtained in this invention revealed that, under the same test conditions and a given constant potential of -1.6V, the initial current density value of the BSL-5.0 hydrogen production electrode is lower, specifically 4.28e. -1 A, and the initial current densities corresponding to electrodes 1, 2, and 3 obtained in this invention are relatively high, at 4.29e respectively. -1 A, 4.52e -1 A, 4.39e -1 A. After approximately 3000 seconds of testing, the current density of the BSL-5.0 hydrogen production electrode instantly dropped to 3.49e. -1 A. The reduction in current density values ​​for electrodes 1, 2, and 3 obtained in this invention is less than that of the BSL-5.0 hydrogen production electrode. After 86,400 seconds of cycle stability testing, the final current density of the BSL-5.0 hydrogen production electrode decays to 3.542 e. -1 A continues to decline, and the final current densities corresponding to electrodes 1, 2, and 3 obtained in this invention decrease to 3.59e, respectively. -1 A, 3.59e -1 A, 3.57e -1A. Furthermore, the degradation trend of the BSL-5.0 hydrogen production electrode is more pronounced than that of electrodes 1, 2, and 3 obtained in this invention. In addition, during the experiment, it was found that a large amount of active material on the surface of the BSL-5.0 hydrogen production electrode detached during the stability cycling test, while this phenomenon did not occur with electrodes 1, 2, and 3 obtained in this invention.

[0198] Table 1 .

[0199] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A HER electrochemical cathode material based on a Ni-Mo-Al composite coating, characterized in that, It is a metal composite coating formed by loading Ni, Mo and Al metal powders onto the surface of a porous nickel current collector. The metal composite coating forms a metallurgical bond with the surface of the porous nickel current collector. The metal composite coating is obtained by coating Mo powder in the Ni-Al binary eutectic phase formed by Ni and Al elements.

2. The HER electrochemical cathode material based on a Ni-Mo-Al composite coating according to claim 1, characterized in that, The metal raw materials used to form the metal composite coating consist of 60%-65% Ni powder, 15%-20% Mo powder, and 15%-20% Al powder by mass percentage.

3. The HER electrochemical cathode material based on a Ni-Mo-Al composite coating according to claim 2, characterized in that, Ni powder is spherical, Mo powder is irregularly shaped, and Al powder is in flake form.

4. The HER electrochemical cathode material based on a Ni-Mo-Al composite coating according to claim 3, characterized in that, The particle size of Ni powder, Mo powder and Al powder is ≤10μm.

5. The HER electrochemical cathode material based on a Ni-Mo-Al composite coating according to claim 4, characterized in that, The particle size range of Ni powder is 1-5 μm, that of Mo powder is 0.5-2 μm, and that of Al powder is 5-10 μm.

6. The HER electrochemical cathode material based on a Ni-Mo-Al composite coating according to claim 1, characterized in that, The purity of the porous nickel current collector is ≥99.5%.

7. The HER electrochemical cathode material based on a Ni-Mo-Al composite coating according to claim 6, characterized in that, The porous nickel current collector is a Ni mesh.

8. An electrolyzer for hydrogen production, characterized in that, Its cathode is the HER electrochemical cathode material as described in any one of claims 1-7.

9. An electrolyzer for hydrogen production according to claim 8, characterized in that, The preparation method of HER electrochemical cathode material includes the following steps: (1) Grind the three metal raw materials used in the metal composite coating evenly according to the formula, and after sieving, obtain the metal mixture. (2) The metal mixture is uniformly dispersed in the photocurable adhesive to obtain a photocurable coating. The photocurable coating is uniformly loaded on the surface of the pretreated porous nickel current collector. After photocuring, a precurable coating is obtained. The precurable coating is placed in a degreasing furnace at a temperature ≤450℃ under nitrogen or inert gas protection for degreasing reaction. When the residual carbon content in the precurable coating is ≤0.5%, the degreasing reaction ends and a degreased electrode is obtained. (3) The degreased electrode is subjected to high-temperature vacuum sintering in a two-stage stepped heating method. The heating rate of the first stage of high-temperature vacuum sintering is ≤10℃ / min, the heating rate of the second stage of high-temperature vacuum sintering is ≤5℃ / min, and the high-temperature vacuum sintering temperature is ≤1050℃. After the high-temperature vacuum sintering is completed, it is cooled to room temperature. The porous nickel current collector is loaded with a metal composite coating of Mo powder coated in the Ni-Al binary eutectic phase formed by Ni and Al elements. The metal composite coating and the porous nickel current collector form a metallurgical bond at the interface to obtain the modified electrode. (4) The modified electrode was successively subjected to alkaline etching to remove NaAlO2 from the metal composite coating, washed with water until neutral, and dried to obtain the HER electrochemical cathode material.

10. An electrolyzer for hydrogen production according to claim 9, characterized in that, The temperature of the first stage of high-temperature vacuum sintering is 850℃, and the holding temperature is at 850℃ for at least 10 minutes. The temperature of the second stage of high-temperature vacuum sintering is 1050℃, and the holding temperature is at 1050℃ for at least 2 hours.

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