Preparation method, product and application of a hydrogen evolution cathode catalyst

Abstract

This invention relates to the field of hydrogen evolution electrode material preparation technology, and in particular to a method for preparing a hydrogen evolution cathode catalyst, its product, and its application. The method for preparing the hydrogen evolution cathode catalyst includes the following steps: dissolving a nickel source, a molybdenum source, citric acid, a high-valence metal salt, sodium bicarbonate, and urea in a solvent to prepare a mixed solution; subjecting the mixed solution to a isothermal heating reaction at a first temperature, followed by the addition of an organic solute and a isothermal heating reaction at a second temperature to obtain a precursor; and heat-treating the precursor to obtain the hydrogen evolution cathode catalyst; the high-valence metal salt is at least one selected from Co, Zr, Cr, Ce, Ti, Nb, and La metal salts. The high-valence metal-doped NiMo-based hydrogen evolution cathode catalyst prepared by the segmented nucleation and growth method provided by this invention is an ultrafine powder that is not easily agglomerated, has a large specific surface area, high yield, good hydrogen evolution activity, and good oxidation stability.

Description

Technical Field

[0001] This invention relates to the field of hydrogen evolution electrode material preparation technology, and in particular to a method for preparing a hydrogen evolution cathode catalyst, a product thereof, and its application. Background Technology

[0002] Against the backdrop of the global energy transition towards green and sustainable development, hydrogen energy has become one of the core energy sources. The hydrogen evolution reaction (HER) is a crucial step in the acquisition and utilization of hydrogen energy, and its efficiency directly determines the cost of hydrogen production and the feasibility of industrialization. As the core carrier of the reaction, the catalytic activity, stability, preparation cost, and scalability potential of HER cathode materials are key factors restricting the implementation of hydrogen energy technologies. Therefore, the development of efficient, low-cost, and easily scalable HER cathode materials has become a research hotspot.

[0003] Existing hydrogen evolution cathode materials are mainly divided into two categories: noble metal-based and non-noble metal-based. Platinum (Pt)-based materials have excellent catalytic activity, but their reserves are small and their prices are high, which is not conducive to large-scale application. Non-noble metal-based materials (transition metal nitrides, phosphides, etc.) have abundant reserves and low costs, making them the preferred alternatives.

[0004] Chinese invention patent 201810915648.X describes the preparation of a metallic carbon precursor under a 65-75℃ water bath condition, followed by high-temperature phosphating to obtain a cobalt phosphide@three-dimensional nitrogen-doped porous carbon composite hydrogen evolution electrocatalyst material, achieving a hydrogen evolution electrocatalyst of 10 mA / cm² in 1 M KOH. 2 The voltage drop was 93 mV, and the Tafel slope was 102 mV / dec. Chinese invention patent 202311652654.8 discloses a method for preparing bimetallic phosphide nanoparticle hydrogen evolution catalysts under water bath conditions of 80-90℃. The prepared NiCoP catalyst exhibits good hydrogen evolution activity, 10 mA / cm². 2 The voltage was 93mV and the Tafel slope was 102mV / dec. In the existing water bath method for synthesizing HER precursors, the following common problems are faced: (1) A single isothermal coprecipitation mode is often used (e.g., 70~100℃, pH value is adjusted by directly adding alkaline solution (e.g., NaOH, ammonia). This type of method is difficult to balance the temperature requirements of nucleation and grain growth. The single isothermal mode cannot take into account both rapid nucleation and stable growth; (2) pH control is rough and local over-alkali can easily cause agglomeration; (3) Carbon coating is mostly introduced after synthesis, resulting in uneven distribution of organic matter and discontinuous coating layer; (4) Continuous high temperature operation consumes a lot of energy and is prone to Ostwald ripening, resulting in wide particle size distribution and poor uniformity of the product, which affects the exposure efficiency of hydrogen evolution active sites.

[0005] Therefore, there is an urgent need to provide a method for preparing hydrogen evolution cathode catalysts that is simple in process conditions, controllable in regulation, and capable of producing ultrafine, non-agglomerated, high specific surface area, high activity, and strong oxidation resistance after transition metal doping. This is of great significance for promoting the economic and industrial development of hydrogen energy. Summary of the Invention

[0006] Based on the above, this invention provides a method for preparing a hydrogen evolution cathode catalyst, a product thereof, and its application. The hydrogen evolution cathode catalyst prepared using the method of this invention exhibits good hydrogen evolution activity and oxidation resistance, and the process conditions are simple and the raw materials are readily available.

[0007] To achieve the above objectives, the present invention provides the following solution: One of the technical solutions of this invention is a method for preparing a hydrogen evolution cathode catalyst, comprising the following steps: A mixed solution is prepared by dissolving nickel source, molybdenum source, citric acid, high-valence metal salt, sodium bicarbonate and urea in a solvent. The mixed solution is subjected to a isothermal heating reaction at a first temperature, followed by the addition of an organic solute and a isothermal heating reaction at a second temperature to obtain the precursor. The precursor is subjected to heat treatment to obtain the hydrogen evolution cathode catalyst; The high-valence metal salt is at least one of the following metal salts: Co, Zr, Cr, Ce, Ti, Nb, and La.

[0008] The second technical solution of the present invention is a hydrogen evolution cathode catalyst, which is prepared by the above-mentioned preparation method.

[0009] The third technical solution of this invention is the application of the above-mentioned hydrogen evolution cathode catalyst in alkaline water electrolysis for hydrogen production.

[0010] The fourth technical solution of the present invention is a hydrogen evolution cathode, comprising the above-mentioned hydrogen evolution cathode catalyst.

[0011] Compared with the prior art, the present invention has the following beneficial effects: The high-valence metal-doped NiMo-based hydrogen evolution cathode catalyst prepared by the segmented nucleation and growth method provided by this invention is an ultrafine powder that is not prone to agglomeration, has a large specific surface area, high yield, good hydrogen evolution activity, and good oxidation stability. Furthermore, the catalyst preparation does not require high-temperature and high-pressure reactor equipment, and has the potential for large-scale production. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 SEM image of the hydrogen evolution cathode catalyst prepared in Example 1; Figure 2 SEM image of the hydrogen evolution cathode catalyst prepared in Comparative Example 1; Figure 3 The XRD pattern of the hydrogen evolution cathode catalyst prepared in Example 1; Figure 4 LSV test results for the hydrogen evolution cathode catalysts prepared in Examples 1-3 and Comparative Example 1, as well as the commercial Pt / C material, in 1 mol / L KOH; Figure 5 The performance of the hydrogen evolution cathode catalyst prepared in Example 1 was tested in an anion exchange membrane electrolyzer (AEM). Detailed Implementation

[0014] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0015] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0016] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0017] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0018] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0019] The first aspect of this invention provides a method for preparing a hydrogen evolution cathode catalyst, comprising the following steps: A mixed solution is prepared by dissolving nickel source, molybdenum source, citric acid, high-valence metal salt, sodium bicarbonate and urea in a solvent. The mixed solution is subjected to a isothermal heating reaction at a first temperature, followed by the addition of an organic solute and a isothermal heating reaction at a second temperature to obtain the precursor. The precursor is subjected to heat treatment to obtain the hydrogen evolution cathode catalyst; The high-valence metal salt is at least one of the following metal salts: Co, Zr, Cr, Ce, Ti, Nb, and La.

[0020] The high-valence metal salt may be one or more of chloride, sulfate, acetate, or nitrate. When the high-valence metal salt is any two of Co, Zr, Cr, Ce, Ti, Nb, or La metal salts, the cation molar ratio is controlled at 1:1.

[0021] In a preferred embodiment of the present invention, the nickel source is at least one of nickel chloride, nickel acetate, and nickel nitrate; the molybdenum source is at least one of sodium molybdate and ammonium molybdate; and the solvent is water.

[0022] In a preferred embodiment of the present invention, the concentration of the nickel source in the mixed solution is 50–200 mmol / L (preferably 80–120 mmol / L), the concentration of the molybdenum source is 5–50 mmol / L (preferably 5–30 mmol / L), the concentration of citric acid is 5–50 mmol / L (preferably 5–30 mmol / L), the concentration of the high-valence metal salt is 3–50 mmol / L (preferably 3–20 mmol / L), the concentration of sodium bicarbonate is 20–150 mmol / L, and the concentration of urea is 20–150 mmol / L.

[0023] In a preferred embodiment of the present invention, the first temperature is 85℃~95℃, and the isothermal heating reaction time at the first temperature is 4~6 hours; the second temperature is 60℃~85℃, and the isothermal heating reaction time at the second temperature is 6~10 hours.

[0024] After the isothermal heating reaction at the second temperature is completed, the process also includes ultrasonication, filtration, and drying.

[0025] In this invention, the first temperature is a high-temperature range, and the second temperature is a medium-temperature range. The organic solute in the high-temperature range is urea, and the organic solute in the medium-temperature range is one of glucose, dicyandiamide, or ethylene glycol. This invention utilizes segmented isothermal heating to induce different nucleation and growth processes in the catalyst precursor under varying temperatures and solute conditions, ultimately forming a composite morphology of nanosheets and nanoparticles.

[0026] In a preferred embodiment of the present invention, the organic solute is at least one of ethylene glycol, glucose, and dicyandiamide; the concentration of the organic solute in the mixed solution is 150–900 mmol / L.

[0027] In a preferred embodiment of the present invention, the heat treatment is carried out in a hydrogen-argon mixed atmosphere, wherein the volume fraction of hydrogen in the hydrogen-argon mixed atmosphere is 5% to 15%; the temperature of the heat treatment is 450 to 650°C, and the heat treatment time is 0.5 to 5 hours.

[0028] In a preferred embodiment of the present invention, the heating rate of the heat treatment is 3–10 °C / min. In the present invention, the heat treatment serves the functions of reduction and carbonization.

[0029] The heat treatment process also includes a step of natural cooling to room temperature.

[0030] A second aspect of the present invention provides a hydrogen evolution cathode catalyst, characterized in that it is prepared by the above-described preparation method.

[0031] The third aspect of this invention provides the application of the above-mentioned hydrogen evolution cathode catalyst in alkaline water electrolysis for hydrogen production.

[0032] A fourth aspect of the present invention provides a hydrogen evolution cathode comprising the above-described hydrogen evolution cathode catalyst.

[0033] This invention employs a segmented isothermal water bath method to synthesize precursors. Its core innovation lies in the precise, staged control of the reaction temperature and modulation of the solute environment within a liquid phase, synergistically achieving targeted regulation of the material nucleation and growth process, thereby constructing precursors with specific structures. High-temperature rapid nucleation stage: High temperature accelerates the metal ion nucleation-precipitation reaction rate, prompting the system to rapidly generate a large number of uniform crystal nuclei. Simultaneously, the thermal decomposition of urea releases CO2 and NH3, and the slow release of precipitated groups by NaHCO3 ensures a stable pH rise, effectively avoiding agglomeration caused by localized over-alkaliness and ensuring uniform and stable product synthesis. Medium-temperature slow growth and surface modification stage: After the reaction system is cooled to a medium temperature, energy consumption is significantly reduced, and the crystal growth rate is slowed, allowing unreacted metal ion monomers to grow stably on the surface of existing crystal nuclei. Furthermore, Ostwald ripening is effectively suppressed, preventing abnormal grain growth and achieving precise control over grain size. More importantly, this stage introduces water-soluble nonionic organic solutes with abundant hydroxyl or amino groups to form a controllable organic adsorption layer on the surface of the nucleated precursor. This layer can not only change the growth orientation of Ni-based hydroxides through the directional adsorption of interfacial functional groups, thereby forming a nanosheet coating structure doped with high-valence metal elements, but can also be transformed into a carbon coating structure during the subsequent catalyst thermal treatment reduction process, further significantly improving the catalyst's antioxidant capacity.

[0034] The segmented approach proposed in this invention, characterized by "rapid nucleation at high temperature followed by slow growth at medium temperature," offers significant advantages such as uniform and regular size, full exposure of active sites, and high hydrogen evolution activity, while avoiding the high energy consumption associated with continuous high-temperature reactions. Different temperature stages, coupled with varying solute environments, achieve multiple functions including rapid and uniform nucleation, stable epitaxial growth, and surface carbon layer construction, thereby guiding the precise construction of multi-level structures on the precursor surface.

[0035] In this hydrogen evolution cathode, nickel is the main source of hydrogen evolution activity, while molybdenum regulates the electronic structure and optimizes the hydrogen adsorption-desorption kinetics, thus promoting the activity of the hydrogen evolution cathode. Simultaneously, the high-valence metal doping can accelerate the charge transfer effect between the active sites of NiMo and the active Ni through electron donation, preventing the active Ni from being affected. 0 and low price Mo 3+ It is oxidized and thus deactivated, improving the stability of the hydrogen evolution cathode.

[0036] The results of the examples show that the high-valence metal-doped NiMo-based catalyst (i.e., the hydrogen evolution cathode catalyst of the present invention) prepared by the method provided by the present invention achieves a current of 100 mA·cm⁻¹ in a 1 mol / L KOH solution during room temperature three-electrode performance testing. -2At that time, the overpotential was only 98~138 mV, and after accelerated aging test at an oxidation potential of 1.06 V (vs. RHE), the overpotential increased by no more than 15 mV, demonstrating excellent electrocatalytic hydrogen evolution activity and oxidation resistance.

[0037] Unless otherwise specified, the technical solutions described in this invention are all conventional solutions in the field, and the reagents or raw materials used are all purchased from commercial channels or are publicly available unless otherwise specified.

[0038] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0039] Example 1 A method for preparing a hydrogen evolution cathode catalyst (Cr-doped NiMo hydrogen evolution cathode catalyst) comprises the following steps: (1) Prepare a homogeneous mixed solution (solvent: water) by mixing 120 mmol / L nickel nitrate, 20 mmol / L ammonium molybdate, 20 mmol / L citric acid, 3 mmol / L chromium chloride, 100 mmol / L sodium bicarbonate, and 150 mmol / L urea. Place the solution in a constant temperature water bath preheated to 90°C and react for 6 h. Then add 500 mmol / L dicyandiamide and mix thoroughly. Transfer the solution to a constant temperature water bath at 65°C and continue the reaction for 6 h. After sonicating the resulting suspension for 5 min, filter the solution to obtain a moist NiMoCr oxide precursor. Dry the precursor in a vacuum drying oven at 70°C for later use.

[0040] (2) The precursor obtained in step (1) was placed in a tube furnace and a 5% / 95% hydrogen-argon mixture was introduced for 30 min (i.e., the volume fraction of hydrogen in the mixture was 5%). Then, the 5% / 95% hydrogen-argon mixture was continuously introduced and the temperature was increased to 650℃ at 5℃ / min and held at that temperature for 2 h. After that, it was naturally cooled to room temperature, and the sample was taken out to obtain the Cr-doped NiMo hydrogen evolution cathode catalyst.

[0041] Figure 1 The image shows a SEM image of the Cr-doped NiMo hydrogen evolution cathode catalyst prepared in Example 1. The material consists of spherical particles with a cluster size of 400-600 nm. The particle surface exhibits a lamellar structure, which can greatly increase the surface area.

[0042] Figure 3 The image shows the XRD pattern of the Cr-doped NiMo hydrogen evolution cathode catalyst prepared in step 1. The XRD pattern is shown with Ni... 4.00 The composition of C, Mo, and Cr proves the presence of C, Ni, Mo, and Cr elements in the material.

[0043] Example 2 A method for preparing a hydrogen evolution cathode catalyst (Zr-doped NiMo hydrogen evolution cathode catalyst) comprises the following steps: (1) Prepare a homogeneous mixed solution (solvent: water) by mixing 80 mmol / L nickel chloride, 50 mmol / L ammonium molybdate, 30 mmol / L citric acid, 10 mmol / L zirconium nitrate, 100 mmol / L sodium bicarbonate, and 150 mmol / L urea. Place the solution in a constant temperature water bath preheated to 90°C and react for 6 h. Then add 500 mmol / L glucose and mix well. Transfer the solution to a constant temperature water bath at 75°C and continue the reaction for 8 h. After sonicating the resulting suspension for 20 min, filter the solution to obtain a moist NiMoZr oxide precursor. Dry the precursor in a vacuum drying oven at 70°C for later use.

[0044] (2) The precursor obtained in step (1) is placed in a tube furnace. First, a 5% / 95% hydrogen-argon mixture is introduced for 30 min. Then, a 5% / 95% hydrogen-argon mixture is continuously introduced and the temperature is increased to 600℃ at 5℃ / min. The temperature is held for 2 h. Then, it is naturally cooled to room temperature. The sample is then taken out to obtain the Zr-doped NiMo hydrogen evolution cathode catalyst.

[0045] Example 3 A method for preparing a hydrogen evolution cathode catalyst (Ce-doped NiMo hydrogen evolution cathode catalyst) comprises the following steps: (1) Prepare a homogeneous mixed solution (solvent: water) by mixing 100 mmol / L nickel nitrate, 100 mmol / L sodium molybdate, 20 mmol / L citric acid, 3 mmol / L cerium nitrate, 100 mmol / L sodium bicarbonate, and 50 mmol / L urea. Place the solution in a constant temperature water bath preheated to 85°C and react for 6 h. Then add 500 mmol / L ethylene glycol and mix thoroughly. Transfer the solution to a constant temperature water bath at 65°C and continue the reaction for 9 h. After sonicating the resulting suspension for 30 min, filter the solution to obtain a moist NiMoCe oxide precursor. Dry the precursor in a vacuum drying oven at 70°C for later use.

[0046] (2) The precursor obtained in step (1) is placed in a tube furnace and a 5% / 95% hydrogen-argon mixture is introduced for 30 min. Then, the 5% / 95% hydrogen-argon mixture is continuously introduced and the temperature is increased to 650℃ at 5℃ / min and held at that temperature for 2 h. After that, it is naturally cooled to room temperature and the sample is taken out to obtain the Ce-doped NiMo hydrogen evolution cathode catalyst.

[0047] Comparative Example 1 The only difference from Example 1 is that the entire NiMoCr oxide precursor preparation process was carried out in a 90°C water bath for 12 hours without segmented isothermal heating. All other steps and parameters were the same as in Example 1. The resulting product was designated as the control sample.

[0048] Figure 2 The image shows a SEM image of the comparative sample of the hydrogen evolution cathode catalyst prepared in this comparative example. The sample exhibits a severe dense agglomeration morphology, with a large number of nanoparticles sintered to form micron-sized large clusters (3~4 μm), which are dense in structure and have low porosity.

[0049] Table 1 shows the hydrogen evolution cathode catalysts and Pt / C prepared in Examples 1-3 and Comparative Example 1 after oxidation resistance testing at 100 mA cm⁻¹. -2 Overpotential data (all potentials in the table are relative to RHE values). Test method: Referring to the three-electrode test system in GB / T 45092, three cycles of cyclic voltammetry tests were performed in a room temperature three-electrode test apparatus within the potential range of -0.6 V to X V (X=0, 0.46, 0.66, 0.76, 0.86, 0.96, 1.06). The current density of the last cycle was recorded as -100 mA / cm². 2 The corresponding potential value is the overpotential data after the oxidation resistance test of the hydrogen evolution cathode catalyst.

[0050] Table 1. Overpotential data after oxidation resistance tests of Examples 1-3 and Pt / C

[0051] Figure 4 The LSV (Liquid Crystallization Value) test results are shown for the hydrogen evolution cathode catalysts prepared in Examples 1-3 and Comparative Example 1 of this invention, as well as the commercial Pt / C material, in 1 mol / L KOH solution (water as solvent). Figure 4 It can be seen that the hydrogen evolution cathode catalyst prepared by the preparation method provided by the present invention has hydrogen evolution activity comparable to that of a noble metal Pt / C electrode and far superior to that of a nickel foam (NF) substrate when the three-electrode electrochemical activity test is conducted at room temperature.

[0052] Figure 5 This is the electrolysis data (60°C, 1 M KOH solution) in an anion exchange membrane electrolyzer in Example 1 of the present invention. (From...) Figure 5 It can be seen that the anion exchange membrane electrolyzer assembled with the cathode electrode in Embodiment 1 of the present invention, at a current density of 1 A / cm², achieves good performance. 2 Under these conditions, the cell voltage can be as low as 1.734 V, demonstrating good potential for hydrogen production through water electrolysis.

[0053] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a hydrogen evolution cathode catalyst, characterized in that, Includes the following steps: A mixed solution is prepared by dissolving nickel source, molybdenum source, citric acid, high-valence metal salt, sodium bicarbonate and urea in a solvent. The mixed solution is subjected to a isothermal heating reaction at a first temperature, followed by the addition of an organic solute and a isothermal heating reaction at a second temperature to obtain the precursor. The precursor is subjected to heat treatment to obtain the hydrogen evolution cathode catalyst; The high-valence metal salt is at least one of the following metal salts: Co, Zr, Cr, Ce, Ti, Nb, and La.

2. The preparation method according to claim 1, characterized in that, The nickel source is at least one of nickel chloride, nickel acetate, and nickel nitrate; the molybdenum source is at least one of sodium molybdate and ammonium molybdate; and the solvent is water.

3. The preparation method according to claim 1, characterized in that, The mixed solution contains nickel source at a concentration of 50–200 mmol / L, molybdenum source at a concentration of 5–50 mmol / L, citric acid at a concentration of 5–50 mmol / L, high-valence metal salt at a concentration of 3–50 mmol / L, sodium bicarbonate at a concentration of 20–150 mmol / L, and urea at a concentration of 20–150 mmol / L.

4. The preparation method according to claim 1, characterized in that, The first temperature is 85℃~95℃, and the constant temperature heating reaction time is 4~6 hours; the second temperature is 60℃~85℃, and the constant temperature heating reaction time is 6~10 hours.

5. The preparation method according to claim 1, characterized in that, The organic solute is at least one of ethylene glycol, glucose, and dicyandiamide; the concentration of the organic solute in the mixed solution is 150–900 mmol / L.

6. The preparation method according to claim 1, characterized in that, The heat treatment is carried out in a hydrogen-argon mixed atmosphere, wherein the volume fraction of hydrogen in the hydrogen-argon mixture is 5% to 15%; the heat treatment temperature is 450 to 650°C, and the heat treatment time is 0.5 to 5 hours.

7. A hydrogen evolution cathode catalyst, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 6.

8. The application of the hydrogen evolution cathode catalyst as described in claim 7 in alkaline water electrolysis for hydrogen production.

9. A hydrogen evolution cathode, characterized in that, It includes the hydrogen evolution cathode catalyst as described in claim 7.

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