A bifunctional catalyst electrode material, a preparation method and application thereof

Abstract

The application discloses a kind of bifunctional catalyst electrode materials and preparation method and application thereof, the method comprises: nickel source, molybdenum source and sulfur source are sequentially dissolved in glycol aqueous solution, then with foam nickel base together sealed and carried out hydrothermal reaction, again the reaction product is washed with pure water and dried, obtains bifunctional catalyst electrode material.The method selects abundant reserves, relatively lower price transition metal as main active component, avoids using expensive noble metal, so that bifunctional catalyst electrode material can be obtained at lower cost.The bifunctional catalyst electrode material has unique structure design and good chemical stability, has high activity for glycerol electrooxidation and hydrogen evolution reaction after being applied to the electrode of the preparation of double-function electrolytic cell, and can maintain the stability of catalytic performance in long-time electrolysis process, thereby effectively promoting glycerol oxidation coupled hydrogen evolution, which is conducive to reducing hydrogen production cost and promoting large-scale application of hydrogen energy.

Description

Technical Field

[0001] This invention belongs to the field of catalytic hydrogen production technology, and particularly relates to a bifunctional catalyst electrode material, its preparation method, and its application. Background Technology

[0002] With the increasing global demand for clean energy and growing emphasis on environmental protection, the development of efficient and sustainable energy technologies has become an urgent priority. Hydrogen energy, due to its cleanliness, efficiency, and high energy density, is considered one of the ideal energy choices for the future. Currently, water electrolysis for hydrogen production is a highly promising green method. However, in traditional water electrolysis, the oxygen evolution reaction (OER) at the anode suffers from a high thermodynamic energy barrier and slow reaction kinetics. This not only leads to high energy consumption for hydrogen production but also limits the large-scale application of water electrolysis technology. Glycerol, a major byproduct in biodiesel production, is abundant, inexpensive, and has a lower thermodynamic energy barrier than water splitting. Therefore, utilizing the glycerol electro-oxidation reaction (GOR) to replace the oxygen evolution reaction (OER) in coupling with the hydrogen evolution reaction (HER) has become a highly attractive strategy. Glycerol electro-oxidation not only reduces the overpotential of the anolyte reaction and decreases hydrogen production energy consumption, but also converts glycerol into high-value-added chemicals such as formate and glyceric acid, achieving efficient utilization of biomass resources. Therefore, by developing efficient, stable, and low-cost bifunctional catalysts, it is possible to simultaneously promote glycerol electro-oxidation and the HER.

[0003] However, most existing bifunctional catalysts used for the electro-oxidation of glycerol and hydrogen evolution reaction suffer from problems such as low activity, poor stability, or high cost. For example, while some noble metal-based catalysts possess high catalytic activity, their scarcity and high cost make large-scale application difficult; while some non-noble metal-based catalysts fail to meet practical requirements in terms of activity and selectivity. Furthermore, the structural stability and electronic conductivity of catalysts also affect their catalytic performance. Therefore, improving the overall electrolysis performance of catalysts through rational material design and preparation methods is a pressing issue that needs to be addressed. Summary of the Invention

[0004] Therefore, the purpose of this invention is to provide a bifunctional catalyst electrode material, its preparation method, and its application, so as to solve the problems of low activity, poor stability, and high cost of existing bifunctional catalyst electrode materials.

[0005] The first aspect of this invention discloses a method for preparing a bifunctional catalyst electrode material, the bifunctional catalyst electrode material being used to simultaneously catalyze the electro-oxidation reaction of glycerol and the hydrogen evolution reaction, wherein the method includes: Preparation of nickel foam substrate; According to the molar ratio of nickel, molybdenum and sulfur of 1:1:3-5, the nickel source, molybdenum source and sulfur source are dissolved in ethylene glycol aqueous solution in sequence to obtain the precursor solution. The precursor solution and the nickel foam substrate were placed in a reaction vessel, sealed, and subjected to a hydrothermal reaction to obtain an intermediate. The intermediate was washed with pure water and then dried in a vacuum drying oven to obtain the bifunctional catalyst electrode material.

[0006] In one embodiment, the preparation of a nickel foam substrate specifically includes: Cut the nickel foam to match the size of the electrolytic cell; The cut nickel foam was ultrasonicated for 15 minutes each with hydrochloric acid solution and acetone solution. The ultrasonically treated nickel foam was washed with pure water and then freeze-dried to obtain the nickel foam substrate.

[0007] In one embodiment, the density of the nickel foam is 350 g / m³. 3 It has a pore size of 0.1 mm and a porosity of 97.2%.

[0008] In one embodiment, obtaining the precursor solution specifically includes: The nickel source, the molybdenum source, and the sulfur source are weighed according to an element molar ratio of 1:1:3-5; The nickel source, the molybdenum source, and the sulfur source were sequentially added to a 20% ethylene glycol aqueous solution to obtain a mixed solution; The mixture is stirred and urea and ammonium fluoride are added simultaneously. The mixture is then sonicated to fully dissolve the solute, thus obtaining the precursor solution.

[0009] In one embodiment, the nickel source includes nickel acetate, nickel chloride, nickel nitrate, or nickel sulfate, the molybdenum source includes ammonium molybdate, sodium molybdate, molybdenum chloride, or molybdenum sulfide, and the sulfur source is thiourea.

[0010] In one embodiment, the precursor solution and the nickel foam substrate are placed in a reaction vessel and sealed for a hydrothermal reaction, specifically including: The precursor solution and the nickel foam substrate were transferred together into a polytetrafluoroethylene-lined stainless steel reactor. The stainless steel reactor was sealed and subjected to hydrothermal reaction at 120-180°C for 10-14 hours to obtain the intermediate.

[0011] In one embodiment, the intermediate is washed with pure water and then dried in a vacuum drying oven, specifically including: The intermediate was washed five times with pure water and then placed in the vacuum drying oven. The bifunctional catalyst electrode material was dried at 120°C and under a vacuum of less than 0.1 MPa for 6 hours to obtain the material, cooled to room temperature, and then sealed for storage.

[0012] A second aspect of the present invention discloses a bifunctional catalyst electrode material, which is prepared by the preparation method of the bifunctional catalyst electrode material as described in any of the preceding claims.

[0013] A third aspect of the present invention discloses a bifunctional electrolyzer for simultaneously achieving glycerol uplift conversion and energy-saving hydrogen production, wherein the bifunctional catalyst electrode material described above is used to fabricate the electrode, and a solution containing glycerol is used as the electrolyte.

[0014] In one embodiment, the concentration of glycerol in the electrolyte is 0.01 mol / L to 1 mol / L.

[0015] This invention discloses a bifunctional catalyst electrode material, its preparation method, and its application. The method includes: sequentially dissolving a nickel source, a molybdenum source, and a sulfur source in an ethylene glycol aqueous solution, then sealing them together with a nickel foam substrate for a hydrothermal reaction; washing the reaction product with pure water and drying it to obtain the bifunctional catalyst electrode material. This method uses abundant and relatively inexpensive transition metals as the main active components, avoiding the use of expensive precious metals, thus enabling the acquisition of the bifunctional catalyst electrode material at a lower cost. The bifunctional catalyst electrode material possesses a unique structural design and good chemical stability. When applied to the electrode of a bifunctional electrolyzer, it exhibits high activity for both glycerol electrooxidation and hydrogen evolution reactions, and maintains stable catalytic performance during long-term electrolysis, effectively promoting the coupling of glycerol oxidation and hydrogen evolution. This is beneficial for reducing hydrogen production costs and promoting the large-scale application of hydrogen energy. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art 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.

[0017] Figure 1 This is a schematic flowchart of a method for preparing a bifunctional catalyst electrode material according to an embodiment of the present invention.

[0018] Figure 2 This is a SEM image of the bifunctional catalyst electrode material prepared according to Example 1 of the present invention.

[0019] Figure 3 This is a TEM image of the bifunctional catalyst electrode material prepared according to Example 1 of the present invention.

[0020] Figure 4 The image shows the XRD pattern of the bifunctional catalyst electrode material prepared according to Example 1 of the present invention.

[0021] Figure 5 This is a schematic diagram of the catalytic performance of the bifunctional catalyst electrode material prepared according to Example 1 of the present invention in the electro-oxidation reaction of glycerol and the oxygen evolution reaction.

[0022] Figure 6 This is a schematic diagram showing the potential values ​​of the bifunctional catalyst electrode material prepared according to Example 1 of the present invention at different current densities in the electro-oxidation reaction of glycerol and the oxygen evolution reaction.

[0023] Figure 7 This is a schematic diagram of the Tafel slope for the electro-oxidation reaction of glycerol and the oxygen evolution reaction of the bifunctional catalyst electrode material prepared according to Example 1 of the present invention.

[0024] Figure 8 This is a schematic diagram comparing the performance of the bifunctional catalyst electrode material prepared according to Example 1 of the present invention with that of other materials in the hydrogen evolution reaction.

[0025] Figure 9 This is a schematic diagram of the electrochemical impedance spectroscopy of the bifunctional catalyst electrode material prepared according to Example 1 of the present invention and other materials.

[0026] Figure 10 This is a schematic diagram of the voltage-time curve of the bifunctional catalyst electrode material prepared according to Example 1 of the present invention during the catalytic electrolysis process.

[0027] Figure 11 A schematic diagram of a bifunctional electrolyzer using the bifunctional catalyst electrode material described in this invention.

[0028] Figure 12 This is a schematic diagram illustrating the performance of a bifunctional electrolyzer using the bifunctional catalyst electrode material described in this invention, with and without glycerol in the electrolyte.

[0029] Figure 13 This diagram illustrates the performance changes of a bifunctional electrolyzer using the bifunctional catalyst electrode material described in this invention during multiple cycles.

[0030] Figure 14 This diagram illustrates the comparison between experimental and theoretical values ​​of hydrogen evolution in a bifunctional electrolyzer using the bifunctional catalyst electrode material described in this invention. Detailed Implementation

[0031] This invention provides a bifunctional catalyst electrode material, its preparation method, and its application, to solve the problems of low activity, poor stability, and high cost in existing bifunctional catalyst electrode materials. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0032] This invention first provides a method for preparing a bifunctional catalyst electrode material. A transition metal, which is abundant and relatively inexpensive, is selected as the raw material. Elements and their compounds with special electronic structures and chemical properties are then introduced for doping modification. A bifunctional catalyst electrode material with optimized surface properties and electronic structure is prepared using a hydrothermal method. This bifunctional catalyst electrode material is then applied to the electrodes of an electrolyzer, along with an electrolyte containing glycerol, to obtain a bifunctional electrolyzer that simultaneously performs the hydrogen evolution reaction and the glycerol electrooxidation reaction. In this bifunctional electrolyzer, the bifunctional catalyst electrode material, serving as the electrode, can effectively catalyze both the hydrogen evolution reaction and the glycerol electrooxidation reaction, requiring a low potential and exhibiting good stability. By coupling the hydrogen evolution reaction and the glycerol electrooxidation reaction, the entire electrolysis process can significantly reduce energy consumption, achieving a more economical, stable, and efficient hydrogen production process.

[0033] Specifically, the preparation method of the bifunctional catalyst electrode material of the present invention first selects nickel foam as the base material and uses transition metals and their compounds as the main active components, such as nickel (Ni) and molybdenum (Mo) and their compounds. These metals and corresponding compounds have abundant reserves and relatively low costs, which is conducive to the market promotion of the preparation method. At the same time, some elements and their compounds with special electronic structures and chemical properties, such as sulfur (S), are introduced into the bifunctional catalyst electrode material for doping modification to optimize the electronic structure and surface properties of the catalyst.

[0034] Furthermore, the preparation method of the bifunctional catalyst electrode material includes the following steps: Substrate material pretreatment: The nickel foam was cut to a certain size and then ultrasonically immersed in hydrochloric acid and acetone solutions for a period of time to remove surface oxides, oil stains, and other impurities. Finally, it was rinsed several times with ultrapure water, freeze-dried, and sealed to obtain the substrate material for later use.

[0035] Precursor preparation: A certain proportion of nickel source, molybdenum source and sulfur source are dissolved in an aqueous solution of ethylene glycol in sequence. Then, a certain amount of urea and ammonium fluoride are added while stirring, and ultrasonic treatment is used to promote the full dissolution and mixing of the solutes to obtain the precursor.

[0036] Hydrothermal synthesis reaction: The prepared precursor and pretreated substrate material are transferred together into a reaction vessel, sealed, and subjected to a hydrothermal reaction. Under hydrothermal conditions, the precursor further crystallizes and grows on the surface of the substrate material to form nanomaterials with specific structures and morphologies.

[0037] Vacuum drying: The product obtained from the hydrothermal reaction was washed several times with pure water and then dried in a vacuum drying oven. After drying, the bifunctional catalyst electrode material was obtained and sealed for later use. Vacuum drying effectively removes impurities from the precursor and avoids oxidation of the metal active components, resulting in a more perfect crystal structure of the nanomaterial and enhancing the stability and conductivity of the catalyst.

[0038] The bifunctional catalyst electrode material prepared by the above method possesses a unique microstructure. Characterization analysis using XRD, TEM, and SEM revealed that the bifunctional catalyst electrode material exhibits a three-dimensional coral-like nanoarray structure, with the active components highly dispersed on the surface of the substrate material. Simultaneously, the dopant elements are uniformly distributed within the material's crystal lattice, causing lattice distortion and thereby altering the electronic structure of the bifunctional catalyst electrode material, enhancing its adsorption and activation capabilities for glycerol and water molecules.

[0039] The bifunctional catalyst electrode material was used as the working electrode to test its catalytic effect in the hydrogen evolution reaction and the electro-oxidation of glycerol, confirming that the bifunctional catalyst electrode material exhibited excellent catalytic activity in both the electro-oxidation and hydrogen evolution reactions. Specifically, the prepared bifunctional electrocatalytic electrode material was used as the working electrode, and electrochemical tests were performed using a three-electrode system or a two-electrode system. In the three-electrode system, the auxiliary electrode was a platinum sheet electrode, and the reference electrode was a saturated calomel electrode (SCE) or a reversible hydrogen electrode (RHE); in the two-electrode system, the same bifunctional electrocatalytic electrode material was used as the counter electrode. Furthermore, the electrolyte was an alkaline solution containing a certain concentration of glycerol, such as a solution with a KOH concentration of 1.0 M and a glycerol concentration of 0.05-0.2 M. The performance of the glycerol oxidation coupled with the hydrogen evolution reaction was further optimized by adjusting parameters such as reaction potential, glycerol concentration, and current density. For example, in the voltage range of 1.2-1.6 V, the reaction rate increased with increasing voltage, but excessively high voltage may lead to a decrease in product selectivity. Therefore, it is necessary to comprehensively consider various factors to determine the optimal reaction conditions.

[0040] Under the finalized test reaction conditions, the bifunctional catalyst electrode material can drive the electro-oxidation of glycerol at relatively low potentials. For example, a current density of 10 mA / cm² can be achieved at 1.3 V (vs RHE), and a current density of 120 mA / cm² can be reached at 1.6 V (vs RHE). Simultaneously, the bifunctional catalyst electrode material exhibits high selectivity for target products (such as formate) in the catalytic electro-oxidation of glycerol, with a Faradaic efficiency as high as 90%-98%. In the hydrogen evolution reaction, the bifunctional catalyst electrode material has a low initial overpotential, typically between 50-100 mV, and at a current density of 10 mA / cm², the overpotential is only 80 mV.

[0041] Furthermore, stability tests were conducted on the bifunctional catalyst electrode material during continuous electrolysis. The results showed that the current density and product selectivity of the bifunctional catalyst electrode material remained essentially unchanged, demonstrating good stability. This is mainly attributed to the special structural design of the product obtained by the preparation method of the bifunctional catalyst electrode material of the present invention, which enables the bifunctional catalyst electrode material to maintain structural integrity and the stability of active sites during the electrolysis reaction. This ensures that when the bifunctional catalyst electrode material is applied to a glycerol oxidation coupled hydrogen evolution system, it can significantly reduce energy consumption compared to traditional water electrolysis for hydrogen production. At the same current density, the required applied voltage can be reduced by 0.2-0.4 V, thereby achieving energy savings of 10%-20%.

[0042] Specifically, in one implementation, such as Figure 1 As shown, the preparation method of the bifunctional catalyst electrode material of the present invention includes the following steps: S100, Preparation of nickel foam substrate.

[0043] Nickel foam has a 3D mesh structure, which can provide higher specific capacity as a substrate material. After loading active components, it can be directly used as an electrode material in electrolyzers, which is beneficial to the subsequent application of the prepared bifunctional catalyst electrode material.

[0044] Specifically, step S100 includes: S110. Cut the nickel foam to match the size of the electrolytic cell; S120. The cut nickel foam is ultrasonicated for 15 minutes in sequence with hydrochloric acid solution and acetone solution. S130. Wash the ultrasonically treated nickel foam with pure water and freeze-dry to obtain the nickel foam substrate.

[0045] Specifically, in this embodiment, the density of the nickel foam is 350 g / m³. 3The foamed nickel has a pore size of 0.1 mm and a porosity of 97.2% to ensure that the active components can be effectively loaded onto the substrate material, forming a specific nanoarray structure while ensuring high dispersion of the active components. The foamed nickel is pre-cut to a width smaller than the width of the electrolytic cell to ensure that the loaded and doped foamed nickel can be directly used as an electrode material to form the electrode of the electrolytic cell, which is beneficial for subsequent performance testing and specific applications. Furthermore, ultrasonic treatment with hydrochloric acid solution and acetone solution sequentially effectively removes impurities such as oil and oxides from the surface of the foamed nickel to enhance the adhesion between the active components and the foamed nickel substrate; subsequent washing with pure water and freeze-drying ensure the effective loading of the active components onto the foamed nickel.

[0046] Furthermore, such as Figure 1 As shown, the preparation method of the bifunctional catalyst electrode material of the present invention includes the following steps after step S100: S200. According to the molar ratio of nickel, molybdenum and sulfur elements of 1:1:3-5, the nickel source, molybdenum source and sulfur source are dissolved in ethylene glycol aqueous solution in sequence to obtain the precursor solution.

[0047] Nickel, molybdenum, and sulfur are abundant on Earth, and their compounds are relatively inexpensive, making them effective raw materials for reducing manufacturing costs. Furthermore, loading nickel and molybdenum as active components onto a treated nickel foam substrate allows for high dispersion on the substrate surface, forming the desired nanoarray structure to ensure catalytic efficacy for the hydrogen evolution reaction (HER) and glycerol electro-oxidation. In addition, sulfur doping into the material's crystal lattice induces lattice distortion, altering the surface's electronic structure and enhancing the adsorption and activation of glycerol and water molecules, thereby further improving the catalytic performance of the resulting bifunctional catalyst electrode material for HER and glycerol electro-oxidation.

[0048] Specifically, step S200 includes: S210. Weigh the nickel source, the molybdenum source, and the sulfur source according to an element molar ratio of 1:1:3-5; S220. The nickel source, the molybdenum source, and the sulfur source are sequentially added to a 20% ethylene glycol aqueous solution to obtain a mixed solution; S230. Stir the mixture and simultaneously add urea and ammonium fluoride. Sonicate the mixture to fully dissolve the solute and obtain the precursor solution.

[0049] Nickel, molybdenum, and sulfur sources are selected as raw materials in specific proportions to ensure that the nickel and molybdenum compounds can form nanostructures with specific morphologies on the nickel foam substrate during subsequent reactions, and to ensure that sulfur doping within the crystal lattice achieves the required lattice distortion. Further, after dissolving the nickel, molybdenum, and sulfur sources in an aqueous ethylene glycol solution, urea and ammonium fluoride are added during stirring to ensure that the selected nickel, molybdenum, and sulfur compounds are fully dissolved, thus maintaining a constant molar ratio of nickel, molybdenum, and sulfur during subsequent reactions. Specifically, the nickel source uses nickel acetate, nickel chloride, nickel nitrate, or nickel sulfate; the molybdenum source uses ammonium molybdate, sodium molybdate, molybdenum chloride, or molybdenum sulfide; and the sulfur source uses thiourea.

[0050] Furthermore, such as Figure 1 As shown, the preparation method of the bifunctional catalyst electrode material of the present invention includes the following steps after step S200: S300. The precursor solution and the nickel foam substrate are placed in a reaction vessel, sealed, and subjected to a hydrothermal reaction to obtain an intermediate.

[0051] Within a sealed reactor, hydrothermal reactions allow for effective control of the product's morphology and purity. Therefore, under hydrothermal conditions, the active components in the pre-prepared precursor solution can crystallize and grow on the surface of the pretreated substrate material, forming nanomaterials with specific structures and morphologies.

[0052] Specifically, step S300 includes: S310. The precursor solution and the nickel foam substrate are transferred together into a stainless steel reactor lined with polytetrafluoroethylene. S320. Seal the stainless steel reactor and perform a hydrothermal reaction at 120-180°C for 10-14 hours to obtain the intermediate.

[0053] The appropriate reactor is selected based on the volume of the precursor solution and the size of the nickel foam substrate. Optionally, the precursor solution and the nickel foam substrate are sealed together in a 100 mL stainless steel reactor lined with polytetrafluoroethylene and reacted at 160 °C for 12 hours to ensure that the precursor crystallizes and grows on the substrate material, forming a nanomaterial intermediate with a specific structure and morphology.

[0054] Furthermore, such as Figure 1 As shown, the preparation method of the bifunctional catalyst electrode material of the present invention includes the following steps after step S300: S400. The intermediate is washed with pure water and then dried in a vacuum drying oven to obtain the bifunctional catalyst electrode material.

[0055] The intermediate is washed with pure water and dried in a vacuum drying oven to remove impurities from the product and avoid oxidation of the active metal components. This makes the crystal structure of the solid product more perfect and enhances the overall stability and conductivity of the material, thereby ensuring the catalytic stability and catalytic activity of the final product.

[0056] Specifically, step S400 includes the following steps: S410. Wash the intermediate five times with pure water and place it in the vacuum drying oven; S420. Dry at 120°C and under a vacuum of less than 0.1 MPa for 6 hours to obtain the bifunctional catalyst electrode material, cool to room temperature and seal for storage.

[0057] Through the above steps, the resulting bifunctional catalyst electrode material possesses a unique microstructure. The active components are highly dispersed on the surface of the substrate material, and the doping elements are uniformly distributed in the crystal lattice, causing lattice distortion and thus altering the overall electronic structure of the material, enhancing its adsorption and activation capabilities for glycerol and water molecules. The ultimately prepared bifunctional catalyst electrode material can be applied to a glycerol electro-oxidation coupled hydrogen evolution system, exhibiting high activity for both the glycerol electro-oxidation and hydrogen evolution reactions. It can effectively promote the reaction and significantly reduce the cost of hydrogen production, contributing to the large-scale application of hydrogen energy.

[0058] The preparation process of the bifunctional catalyst electrode material of the present invention is described below with reference to specific embodiments.

[0059] Example 1 Depending on the size of the electrolytic cell, a density of 350 g / m³ is used. 3 Nickel foam with a pore size of 0.1 mm and a porosity of 97.2% was cut to a matching size. The cut nickel foam was then placed in 3 M hydrochloric acid and acetone solutions and sonicated for 15 minutes each. After that, it was washed several times with ultrapure water, freeze-dried, and sealed for later use.

[0060] Weigh out 2.52 g of nickel acetate (Ni(CH3COO)2·4H2O) and 1.77 g of ammonium molybdate ((NH4)6Mo7O). 243.06 g of thiourea (CH4N2S) solid was dissolved sequentially in 60 mL of an aqueous solution containing 20% ​​ethylene glycol. After complete dissolution, urea was added at a concentration of 10 mM and ammonium fluoride at a concentration of 20 mM while stirring. The mixture was then sonicated to promote complete dissolution and mixing of the solutes, forming a precursor solution. The precursor solution and the pretreated nickel foam substrate were then transferred to a 100 mL stainless steel reactor lined with polytetrafluoroethylene (PTFE). The reactor was sealed and subjected to a hydrothermal reaction. The hydrothermal reaction temperature was controlled at 160 °C, and the reaction time was 12 hours, yielding an intermediate. Finally, the intermediate was washed several times with pure water, and the washing product was dried in a vacuum drying oven at 120 °C under 0.09 MPa for 6 hours to obtain a bifunctional catalyst electrode material.

[0061] Example 2 The preparation process of the nickel foam substrate material was the same as in Example 1. Then, 2.38 g of nickel chloride (NiCl2·6H2O), 2.42 g of sodium molybdate (Na2MoO4·2H2O), and 3.04 g of thiourea (CH4N2S) solid were weighed and dissolved sequentially in 70 mL of an aqueous solution containing 20% ​​ethylene glycol. After complete dissolution, urea was added at a concentration of 10 mM and ammonium fluoride at a concentration of 20 mM while stirring. Ultrasonic treatment was used to promote the complete dissolution and mixing of the solutes, forming a precursor solution. Subsequently, the precursor solution and the pretreated nickel foam substrate material were transferred together to a 100 mL stainless steel reactor lined with polytetrafluoroethylene (PTFE). After sealing, a hydrothermal reaction was carried out. The hydrothermal reaction temperature was controlled at 120 °C, and the reaction time was 14 hours, yielding an intermediate. Finally, the intermediate was washed several times with pure water, and the washing product was placed in a vacuum drying oven at 120 °C and dried at 0.1 MPa for 6 hours to obtain the bifunctional catalyst electrode material.

[0062] Example 3 The preparation process of the nickel foam substrate material was the same as in Example 1. Then, 2.91 g of nickel nitrate (Ni(NO3)2·6H2O), 2.73 g of molybdenum chloride (MoCl5), and 3.81 g of thiourea (CH4N2S) solid were weighed and dissolved sequentially in 80 mL of an aqueous solution containing 20% ​​ethylene glycol. After complete dissolution, urea was added at a concentration of 10 mM and ammonium fluoride at a concentration of 20 mM while stirring. Ultrasonic treatment was used to promote the complete dissolution and mixing of the solutes, forming a precursor solution. Subsequently, the precursor solution and the pretreated nickel foam substrate material were transferred together to a 100 mL stainless steel reactor lined with polytetrafluoroethylene (PTFE). After sealing, a hydrothermal reaction was carried out. The hydrothermal reaction temperature was controlled at 180 °C, and the reaction time was 10 hours to obtain an intermediate. Finally, the intermediate was washed several times with pure water, and the washing product was placed in a vacuum drying oven at 120 °C and dried at 0.08 MPa for 6 hours to obtain a bifunctional catalyst electrode material.

[0063] Example 4 The preparation process of the nickel foam substrate material was the same as in Example 1. Then, 2.63 g of nickel sulfate (NiSO4·6H2O), 1.61 g of molybdenum sulfide (MoS2), and 2.28 g of thiourea (CH4N2S) solid were weighed and dissolved sequentially in 60 mL of an aqueous solution containing 20% ​​ethylene glycol. After complete dissolution, urea was added at a concentration of 10 mM and ammonium fluoride at a concentration of 20 mM while stirring. Ultrasonic treatment was used to promote the complete dissolution and mixing of the solutes, forming a precursor solution. Subsequently, the precursor solution and the pretreated nickel foam substrate material were transferred together to a 100 mL stainless steel reactor lined with polytetrafluoroethylene (PTFE). After sealing, a hydrothermal reaction was carried out. The hydrothermal reaction temperature was controlled at 150 °C, and the reaction time was 13 hours, yielding an intermediate. Finally, the intermediate was washed several times with pure water, and the washing product was placed in a vacuum drying oven at 120 °C and dried at 0.09 MPa for 6 hours to obtain the bifunctional catalyst electrode material.

[0064] Example 5 The preparation process of the nickel foam substrate material was the same as in Example 1. Then, 4.98 g of nickel acetate (Ni(CH3COO)2·4H2O) and 3.53 g of ammonium molybdate ((NH4)6Mo7O) were weighed out. 246.09 g of thiourea (CH4N2S) solid was dissolved sequentially in 150 mL of an aqueous solution containing 20% ​​ethylene glycol. After complete dissolution, urea was added at a concentration of 10 mM and ammonium fluoride at a concentration of 20 mM while stirring. The mixture was then sonicated to promote complete dissolution and mixing of the solutes, forming a precursor solution. The precursor solution and the pretreated nickel foam substrate were then transferred to a 200 mL stainless steel reactor lined with polytetrafluoroethylene (PTFE). The reactor was sealed and subjected to a hydrothermal reaction. The hydrothermal reaction temperature was controlled at 170 °C, and the reaction time was 15 hours, yielding an intermediate. Finally, the intermediate was washed several times with pure water, and the washing product was dried in a vacuum drying oven at 120 °C under 0.09 MPa for 6 hours to obtain a bifunctional catalyst electrode material.

[0065] After preparing the bifunctional catalyst electrode material, its various properties were determined through multiple methods. First, the microstructure of the material surface was characterized using XRD, TEM, and SEM. Then, tests were conducted to assess its catalytic performance in the electro-oxidation of glycerol, the electro-hydrogen evolution reaction, the electro-oxidation of glycerol coupled with hydrogen evolution, and its catalytic stability, in order to characterize the performance of the bifunctional catalyst electrode material in subsequent applications.

[0066] Specifically, the bifunctional catalyst electrode material prepared in Example 1 was selected for characterization. Figure 2 Here is a SEM image of the bifunctional catalyst electrode material. Figure 3 This is a TEM image of the bifunctional catalyst electrode material. Figure 4 XRD patterns of the bifunctional catalyst electrode material (Ni-Mo-S / NF), pure nickel foam (NF), nickel / molybdenum / sulfur composite oxide (Ni2Mo6S6O2), molybdenum sulfide (MoS2), nickel sulfide (NiS), and pure nickel (Ni). Combined with... Figure 2 , Figure 3 and Figure 4 As can be seen from the content, the surface of the bifunctional catalyst electrode material is a three-dimensional coral-like nanoarray structure, and the active components are highly dispersed on the support surface. Furthermore, the doping elements are uniformly distributed in the catalyst lattice, causing lattice distortion, thereby altering the electronic structure of the bifunctional catalyst electrode material and improving its adsorption and activation capabilities for glycerol and water molecules.

[0067] Furthermore, the catalytic performance of the catalyst for the electro-oxidation of glycerol was tested at room temperature in a 100 mL standard three-electrode closed electrolytic cell. The bifunctional catalyst electrode material prepared in Example 1 was used as the working electrode, and carbon rod and Ag / AgCl (saturated KCl) were used as the counter electrode and reference electrode, respectively. The electrolyte was 1.0 M KOH solution. The electro-oxidation performance and OER performance of the catalyst for glycerol were tested by linear sweep voltammetry (LSV) at a scan rate of 10 mV / s and a scan potential range of 0-1.6 V (vsSCE). The test results are as follows. Figure 5 As shown, at a potential of 1.4 V (vs SCE), the current density reaches 32 mA / cm², and the Faraday efficiency for formate is 96%.

[0068] In the absence of glycerol, the electrode fabricated using the bifunctional catalyst electrode material exhibits moderate oxygen evolution reaction (OER) activity, achieving an anodic current density of 10 mA / cm² at a potential of 1.57 V (vs. RHE). However, upon the introduction of 0.1 M glycerol, the current density increases significantly, and the anodic potential corresponding to 10 mA / cm² decreases markedly to 1.31 V (vs. RHE). Potential values ​​at different current densities obtained from linear sweep voltammetry (LSV) curves are shown below. Figure 6 As shown, the data at the same current density represent the results with 0.1 M glycerol (glycerol electro-oxidation reaction) on the left and the results without glycerol (oxygen evolution reaction) on the right. Compared to the oxygen evolution reaction, the addition of 0.1 M glycerol reduced the anode potential by 250-350 mV at current densities of 10 mA / cm², 20 mA / cm², 50 mA / cm², 100 mA / cm², and 150 mA / cm². This significantly reduced energy consumption, and the overpotential of the bifunctional catalyst electrode material described in this invention is lower than that of electrochemically assisted water splitting systems reported in the prior art.

[0069] Figure 7 The results, derived from LSV data, show the bifunctional catalyst electrode material prepared in Example 1. The electrode prepared from this material exhibits an extremely low Tafel slope (only 112 mV / dec) for the glycerol electro-oxidation reaction, significantly lower than the 234 mV / dec for the oxygen evolution reaction. This clearly demonstrates that the catalytic kinetics of the glycerol electro-oxidation reaction (GOR) at the anode are considerably faster. Furthermore, quantitative analysis of formic acid yield at different potentials reveals the optimal operating potential for energy efficiency. Specifically, approximately 1.35 V represents the optimal energy efficiency potential, at which formate selectivity and Faraday efficiency can reach approximately 93% and 97%, respectively.

[0070] The bifunctional catalyst electrode material prepared in Example 1 was tested for its catalytic performance in the hydrogen evolution reaction under conditions where the electrolyte contained glycerol and where it did not. Specifically, as shown... Figure 8 As shown, the bifunctional catalyst electrode material requires only a 60 mV overpotential to drive 10 mA / cm². 2 The hydrogen evolution reaction (HER) at the specified current density is significantly lower than that of pure nickel foam (NF, 80 mV), nickel-supported nickel foam (Ni / NF, 90 mV), and nickel foam supported on nickel / molybdenum composite oxides (NiMo-O / NF, 120 mV). Furthermore, the bifunctional catalyst electrode material exhibits an extremely low Tafel slope (70 mV / dec), comparable to that of platinum-supported nickel foam (Pt / NF, 58 mV / dec) and significantly lower than that of nickel foam supported on nickel / molybdenum composite oxides (Ni-Mo-O / NF, 108 mV / dec) and nickel foam supported on nickel / molybdenum alloys (Ni-Mo / NF, 91 mV / dec), demonstrating the superior kinetics of the HER. Additionally, as... Figure 9 The electrochemical impedance spectroscopy (EIS) analysis shown indicates that the bifunctional catalyst electrode material has the lowest charge transfer resistance, which is much lower than that of other electrodes, greatly promoting its catalytic activity.

[0071] Optionally, by comparing the HER activity of the bifunctional catalyst electrode material in electrolytes containing and without glycerol, the potential impact of organic substances such as glycerol on the HER performance in the electrolyte can be evaluated. Specifically, based on linear sweep voltammetry (LSV) curves, the HER performance of the bifunctional catalyst electrode material is almost unaffected in electrolytes containing glycerol, and the corresponding Tafel slope does not change significantly. This indicates that the bifunctional catalyst electrode material not only possesses excellent hydrogen evolution activity and fast reaction kinetics, but also exhibits excellent tolerance in the presence of glycerol. Furthermore, as... Figure 10 The potential-time curves shown indicate that the bifunctional catalyst electrode material exhibits minimal voltage change during long-term electrolysis, demonstrating excellent long-term stability.

[0072] Finally, an electrolysis system capable of co-producing hydrogen and formate was constructed, namely a bifunctional electrolyzer capable of simultaneously realizing the hydrogen evolution reaction and the electro-oxidation reaction of glycerol, to test the catalytic performance of the bifunctional catalyst electrode material in the electro-oxidation of glycerol coupled with hydrogen evolution system. Specifically, as shown... Figure 11As shown, in the bifunctional electrolyzer, the bifunctional catalyst electrode material serves as both the anode and cathode, and the electrolyte is a mixed solution containing 0.1 mol / L glycerol and 1 mol / L KOH (denoted as Ni-Mo-S / NF || Ni-Mo-S / NF). This electrolysis system requires only a low voltage of 1.36 V to achieve a current density of 10 mA / cm², exhibiting excellent co-electrolysis performance in both the hydrogen evolution reaction (HER) and the glycerol electrooxidation reaction. In contrast, as... Figure 12 As shown, under the same conditions, a Ni-Mo-S / NF electrolyzer without glycerol electrolyte requires a higher voltage (1.62 V) to achieve the same current density.

[0073] In addition, such as Figure 13 As shown, the electrolysis system maintains excellent catalytic performance and charge selectivity even after prolonged operation. At an operating voltage of 1.4 V (where competitive water oxidation is negligible), formate ions (HCOO)... - The average Faraday efficiency generated is as high as 95.0%. Correspondingly, such as... Figure 14 As shown, the experimentally measured hydrogen evolution amount is in high agreement with the theoretical value, and the Faraday efficiency of HER reaches 99.7%. These results demonstrate that the glycerol oxidation / hydrogen evolution co-electrolysis system constructed based on the bifunctional catalyst electrode material described in this invention possesses both high activity and excellent durability.

[0074] Compared with existing electrode materials, the bifunctional catalyst electrode material of the present invention has a superior effect in the simultaneous energy-saving hydrogen production through glycerol oxidation and value enhancement.

[0075] The literature "Anodic glycerol oxidation to formate facilitating cathodic hydrogen evolution with earth-abundant metal oxide catalysts. Chemical Engineering Journal, 2023 Vol. 468" uses a two-chamber system with nickel foam-based non-noble metal compounds as the anode and nickel foam as the cathode. Electrolysis of 0.1 M glycerol under 1.0 M KOH conditions and a cell voltage of 1.35 V achieves 10 mA / cm². 2While the current density was high, after nine cycles at 1.4 V, the Faradaic efficiency and selectivity for formic acid formation decreased, from 95% to 92% and from 95% to 90%, respectively. Furthermore, the use of a proton exchange membrane in the dual-chamber system increased process complexity and economic cost. In contrast, the bifunctional catalyst electrode material prepared by the method of this invention, under the same electrolysis reaction conditions, only requires a cell voltage of 1.31 V to achieve 10 mA / cm². 2 The current density was maintained at a constant, and after ten cycles at 1.4 V, the Faradaic efficiency and selectivity for formic acid formation did not show a significant decrease, remaining above 94% and 92%, respectively. Furthermore, the method of this invention is carried out in a single-chamber system, eliminating the need for a proton exchange membrane, making the process simpler and more economical.

[0076] The paper "Organic oxidation-assisted hydrogen production: glycerole electroreforming to formate on nickel diselenide nanoparticles. Journal of Colloid and Interface Science, 2025 Vol. 700" investigated the electrochemical reforming of glycerol in an alkaline medium to simultaneously produce hydrogen at a platinum cathode and formate at a NiSe2 anode. Specifically, the NiSe2 electrode achieved 100 mA / cm² at 1.6 V in a solution containing 1 M glycerol and 1 M KOH. 2 The current density, formate production rate, and Faradaic efficiency of the glycerol electro-oxidation reaction (GOR) were approximately 93% and 94%, respectively. Under similar conditions, the present invention, using the described bifunctional catalyst electrode material, can achieve 100 mA / cm² current density with only 1.45 V. 2 The current density is high, and the formate production rate and Faraday efficiency can reach up to 94% and 97%, respectively. Furthermore, the electrode current density in this paper exhibits a decay rate exceeding 40% in a 24-hour long-term test, while the electrode of this invention exhibits a decay rate of less than 7% in a 25-hour test. Finally, the use of the noble metal platinum (Pt) as the electrode in this paper increases operating costs.

[0077] Therefore, the bifunctional catalyst electrode material prepared by this invention has significant advantages in the simultaneous energy-saving hydrogen production through glycerol oxidation and value enhancement. Through reasonable material design and preparation process, it can effectively improve the activity, selectivity and stability of the product, and realize efficient and energy-saving glycerol oxidation coupled with hydrogen evolution reaction.

[0078] Finally, this invention also discloses the application of the bifunctional catalyst electrode material prepared by the aforementioned method in a bifunctional electrolyzer. Specifically, the bifunctional electrolyzer uses the bifunctional catalyst electrode material of this invention as both the cathode and anode, and uses a solution containing glycerol as the electrolyte to simultaneously achieve glycerol uplift conversion and energy-saving hydrogen production. Specifically, the voltage of the bifunctional electrolyzer is set to 1.25 V-1.8 V, the concentration of glycerol in the electrolyte is 0.01 mol / L-1 mol / L, and the supporting electrolyte is KOH, NaOH, or Na₂SO₄. Further, the concentration of glycerol in the electrolyte is 0.1 mol / L and the concentration of KOH is 1 mol / L. The bifunctional electrolyzer requires only a low voltage of 1.36 V to achieve a current density of 10 mA / cm², and at an operating voltage of 1.4 V, the Faraday efficiencies for formate and hydrogen generation are as high as 95.0% and 99.7%, respectively.

[0079] It should be noted that unless otherwise specified in the text, "a" and "described" can refer to a single or multiple features. If the embodiments of this invention involve descriptions such as "first," "second," etc., these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include at least one of those features. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0080] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention, as well as the prior art known to those skilled in the art and the description of the invention, may be implemented using any prior art methods, devices, and materials similar to or equivalent to the methods, devices, and materials in the embodiments of the present invention.

[0081] In summary, this invention discloses a bifunctional catalyst electrode material, its preparation method, and its application. The method includes: preparing a nickel foam substrate; sequentially dissolving a nickel source, a molybdenum source, and a sulfur source in an ethylene glycol aqueous solution according to a molar ratio of nickel, molybdenum, and sulfur of 1:1:3-5 to obtain a precursor solution; placing the precursor solution and the nickel foam substrate into a reaction vessel, sealing it, and carrying out a hydrothermal reaction to obtain an intermediate; and washing the intermediate with pure water and drying it in a vacuum drying oven to obtain the bifunctional catalyst electrode material. This method uses abundant and relatively inexpensive transition metals as the main active components, avoiding the use of expensive precious metals, thus enabling the acquisition of the bifunctional catalyst electrode material at a lower cost. The bifunctional catalyst electrode material possesses a unique structural design and good chemical stability. When applied to the electrode of a bifunctional electrolyzer, it exhibits high activity for both glycerol electro-oxidation and hydrogen evolution reactions, and maintains stable catalytic performance during long-term electrolysis, effectively promoting the coupling of glycerol oxidation and hydrogen evolution, which is beneficial for reducing hydrogen production costs and promoting the large-scale application of hydrogen energy.

Claims

1. A method for preparing a bifunctional catalyst electrode material, wherein the bifunctional catalyst electrode material is used to simultaneously catalyze the electro-oxidation reaction of glycerol and the hydrogen evolution reaction, characterized in that, The method includes: Preparation of nickel foam substrate; According to the molar ratio of nickel, molybdenum and sulfur of 1:1:3-5, the nickel source, molybdenum source and sulfur source are dissolved in ethylene glycol aqueous solution in sequence to obtain the precursor solution. The precursor solution and the nickel foam substrate were placed in a reaction vessel, sealed, and subjected to a hydrothermal reaction to obtain an intermediate. The intermediate was washed with pure water and then dried in a vacuum drying oven to obtain the bifunctional catalyst electrode material.

2. The method for preparing the bifunctional catalyst electrode material according to claim 1, characterized in that, The preparation of nickel foam substrates specifically includes: Cut the nickel foam to match the size of the electrolytic cell; The cut nickel foam was ultrasonicated for 15 minutes each with hydrochloric acid solution and acetone solution. The ultrasonically treated nickel foam was washed with pure water and then freeze-dried to obtain the nickel foam substrate.

3. The method for preparing the bifunctional catalyst electrode material according to claim 2, characterized in that, The density of the nickel foam is 350 g / m³. 3 It has a pore size of 0.1 mm and a porosity of 97.2%.

4. The method for preparing the bifunctional catalyst electrode material according to claim 1, characterized in that, Obtaining the precursor solution specifically includes: The nickel source, the molybdenum source, and the sulfur source are weighed according to an element molar ratio of 1:1:3-5; The nickel source, the molybdenum source, and the sulfur source were sequentially added to a 20% ethylene glycol aqueous solution to obtain a mixed solution; The mixture is stirred and urea and ammonium fluoride are added simultaneously. The mixture is then sonicated to fully dissolve the solute, thus obtaining the precursor solution.

5. The method for preparing the bifunctional catalyst electrode material according to claim 4, characterized in that, The nickel source includes nickel acetate, nickel chloride, nickel nitrate, or nickel sulfate; the molybdenum source includes ammonium molybdate, sodium molybdate, molybdenum chloride, or molybdenum sulfide; and the sulfur source is thiourea.

6. The method for preparing the bifunctional catalyst electrode material according to claim 1, characterized in that, The precursor solution and the nickel foam substrate are placed in a reaction vessel and sealed for a hydrothermal reaction, specifically including: The precursor solution and the nickel foam substrate were transferred together into a polytetrafluoroethylene-lined stainless steel reactor. The stainless steel reactor was sealed and subjected to hydrothermal reaction at 120-180°C for 10-14 hours to obtain the intermediate.

7. The method for preparing the bifunctional catalyst electrode material according to claim 1, characterized in that, The intermediate is washed with pure water and then dried in a vacuum drying oven, specifically including: The intermediate was washed five times with pure water and then placed in the vacuum drying oven. The bifunctional catalyst electrode material was dried at 120°C and under a vacuum of less than 0.1 MPa for 6 hours to obtain the material, cooled to room temperature, and then sealed for storage.

8. A bifunctional catalyst electrode material, characterized in that, It is prepared by the preparation method of the bifunctional catalyst electrode material as described in any one of claims 1-7.

9. A bifunctional electrolyzer for simultaneously achieving glycerol enhancement and energy-saving hydrogen production, characterized in that, The electrode is fabricated using the bifunctional catalyst electrode material as described in claim 8, and a solution containing glycerol is used as the electrolyte.

10. The bifunctional electrolytic cell according to claim 9, characterized in that, The concentration of glycerol in the electrolyte is 0.01 mol / L to 1 mol / L.

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