Difunctional sulfide self-supporting electrode and preparation method thereof

Abstract

The invention provides a difunctional sulfide self-supporting electrode and a preparation method thereof, and relates to the technical field of electrocatalysts.The self-supporting electrode comprises foamed nickel and molybdenum / nickel sulfide materials evenly distributed on the foamed nickel, and the foamed nickel serves as a substrate and a nickel source of the electrode at the same time; a nanostructured precursor scaffold is provided and formation of a molybdenum / nickel sulfide is facilitated, the molybdenum / nickel sulfide having a nanocluster structure. The preparation method comprises the following steps: uniformly dispersing molybdate, soluble nickel salt and an organic sulfur compound in deionized water, transferring to a polytetrafluoroethylene hydrothermal kettle lining, immersing pretreated foamed nickel into the mixed solution, and carrying out hydrothermal synthesis to obtain the sulfide self-supporting electrode. The method is simple and easy to operate, the hydrothermal reaction condition is mild, no special requirement is needed for equipment, and the prepared sulfide self-supporting electrode can efficiently catalyze electrochemical sulfur oxidation reaction and electrochemical hydrogen evolution reaction.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrocatalysts, and more specifically, relates to a bifunctional sulfide self-supporting electrode and a preparation method thereof. Background Art

[0002] Hydrogen production by water electrolysis is a clean, efficient, and sustainable method for hydrogen production. It consists of two half-reactions: the hydrogen evolution reaction (HER) at the cathode and the oxygen evolution reaction (OER) at the anode. The high overpotential driving the OER half-reaction results in high energy consumption. Furthermore, currently commercially available HER and OER catalysts are based on the precious metals Pt and Ir or Ru, respectively, which present challenges such as high cost and susceptibility to deactivation that require urgent attention.

[0003] To address the high energy consumption of this system, replacing the OER half-reaction with other electrochemical oxidation reactions is an effective way to reduce the anode overpotential and achieve low-energy hydrogen production. Compared to the electrocatalytic oxidation of organic alcohols, aldehydes, and biomass, the electrocatalytic sulfur oxidation reaction (SOR) offers advantages over the OER. This is because hydrogen sulfide (HS) is highly reducible and easily oxidized. Using it as the anolyte for SOR coupled with the HER can reduce the theoretical hydrogen production voltage from 1.23 V to 0.17 V. Furthermore, HS is a ubiquitous toxic byproduct in the traditional chemical industry and has a wide range of sources. SOR desulfurizes sulfur-containing waste gas while simultaneously recovering elemental sulfur and producing hydrogen, addressing environmental pollution issues and providing a high-quality hydrogen source. However, many metal-based electrodes are easily poisoned and deactivated by sulfur species. Developing efficient, low-cost catalytic electrodes for both SOR and HER is key to advancing the field of electrochemical hydrogen production.

[0004] Transition metal sulfides offer unique advantages in resisting sulfur poisoning. They possess excellent intrinsic conductivity and are amenable to micro- and nanostructure construction, fully exposing the active sites of the catalyst and enhancing mass transfer, resulting in higher electrocatalytic activity and durability. Furthermore, transition metal sulfides can be synthesized via low-cost hydrothermal methods. Currently, research has focused on the preparation and optimization of transition metal sulfide catalysts for single HER reactions, while significant gaps remain in the development of transition metal sulfide catalysts for SOR reactions. Therefore, the development of efficient SOR electrodes, particularly bifunctional catalytic electrodes with both HER and SOR activity, holds great research value and industrial promise. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a bifunctional sulfide self-supporting electrode and a preparation method thereof to solve the above problems.

[0006] A bifunctional sulfide self-supporting electrode uses nickel foam as a substrate and nickel source. Molybdate, a soluble nickel salt, and an organic sulfur compound are reacted by a hydrothermal method to form a molybdenum / nickel sulfide material in situ grown on the nickel foam. The molybdenum / nickel sulfide presents a nanocluster structure, wherein the nanorod-like structures constituting the nanoclusters have a diameter within the range of 80-550nm and a length of 0.8-3.5μm. The nickel foam provides a precursor support for the formation of the nanostructure and sulfide, thereby promoting the generation and uniform distribution of the molybdenum / nickel sulfide.

[0007] Preferably, the molybdate is sodium molybdate or ammonium molybdate, and its amount is between 0.15-1.2 mmol. After being dissolved in the reaction system, it participates in the reaction as a molybdenum source, synergistically acts with the nickel source and the sulfur source, affects the composition and structure of the final molybdenum / nickel sulfide, and thus regulates the catalytic performance of the electrode. The soluble nickel salt is nickel nitrate, nickel sulfate or nickel chloride, and its amount is 0.01-0.12 mmol. It provides nickel elements in the reaction and reacts with the molybdate and the organic sulfur compound to generate molybdenum / nickel sulfide with specific structure and properties. The change in its concentration will change the crystallinity and number of active sites of the product. The organic sulfur compound is thioacetamide or thiourea, and its amount is in the range of 0.8-12 mmol. It is combined with the molybdenum source and the nickel source in the hydrothermal reaction as a sulfur source. The change in its amount will affect the sulfur content and distribution in the molybdenum / nickel sulfide, which has an important effect on the catalytic activity and stability of the electrode.

[0008] A method for preparing a bifunctional sulfide self-supporting electrode comprises the following steps: a) dissolving molybdate, soluble nickel salt, and organic sulfide in 25-80 mL of deionized water in a specific ratio, and ultrasonically dispersing for 8-35 minutes to ensure a uniform solution to obtain a mixed solution. Variations in ultrasonic time and solution volume in this step may affect the dispersion of the raw materials, thereby affecting the uniformity of the reaction and the consistency of the product; b) transferring the mixed solution obtained in step a) into a polytetrafluoroethylene hydrothermal autoclave lining, and completely immersing the pretreated nickel foam into the mixed solution, wherein the nickel foam has a size of (0.4-2.5) (0.4-4.5) cm² and a thickness of 0.1-2.5 mm. The selection of the size and thickness will affect the electrode loading and mass transfer efficiency; c) The hydrothermal reactor is sealed and placed in a forced air drying oven, and the temperature is maintained at 140-220° C. for 6-30 hours to carry out a sulfurization reaction, so that the metal precursor is converted into a sulfide and in situ grown on the nickel foam substrate. Changes in reaction temperature and time will significantly affect the crystallinity, morphology and catalytic performance of the product; d) repeatedly washing the product obtained in step c) with deionized water and ethanol until the pH value reaches 6.5-7.5, and then vacuum drying at 50-70° C. for 8-16 hours to obtain a bifunctional sulfide self-supporting electrode. Optimizing the washing and drying conditions helps remove impurities and improve the purity and stability of the electrode.

[0009] Preferably, in step a), when sodium molybdate is used as the molybdate, in a specific reaction system, 0.03 mmol nickel nitrate and 3 mmol thioacetamide are dissolved in 40 mL deionized water, and the mixed solution obtained by ultrasonication for 20 min can make the generated electrode in the subsequent reaction be subjected to an electrochemical SOR test in a 1.0 M NaOH (containing 1.0 M Na2S) electrolyte. When the current density is 120 mA / cm², the overpotential is 330 mV. When the electrochemical HER test is carried out in a 1.0 M NaOH electrolyte, when the current density is 120 mA / cm², the overpotential is 150 mV. In step a), if ammonium molybdate is selected as the molybdate, 0.05 mmol nickel sulfate and 4 mmol thiourea are dissolved in 50 mL deionized water, and the mixed solution obtained by ultrasonication for 25 min is obtained, and the electrode prepared in the subsequent step is subjected to an electrochemical SOR test in a 1.0 M NaOH (containing 1.0 M Na2S) electrolyte. When the current density is 120 mA / cm², the overpotential is 150 mV. The electrochemical SOR test was carried out in a 1.0 M NaOH electrolyte. When the current density was 110 mA / cm², the overpotential was 340 mV. When the electrochemical HER test was carried out in a 1.0 M NaOH electrolyte, when the current density was 110 mA / cm², the overpotential was 145 mV. In step b), when the nickel foam size was 1.5 × 3 cm² and the thickness was 1.5 mm, under the same reaction conditions, the prepared electrode was compared with the electrode prepared by the nickel foam with a size of 0.5 × 1 cm² and a thickness of 0.5 mm. When the electrochemical SOR test was carried out in a 1.0 M NaOH (containing 1.0 M Na2S) electrolyte, the current density was increased by 15%-25% in the range of 100-150 mA / cm². When the electrochemical HER test was carried out in a 1.0 M NaOH electrolyte, the current density was increased by 10%-20% in the range of 100-150 mA / cm².

[0010] Preferably, in step c), when the hydrothermal reaction temperature is 160 ° C and the temperature is maintained for 24 hours, the prepared electrode is subjected to an electrochemical SOR test in a 1.0 M NaOH (containing 1.0 M Na2S) electrolyte. The catalytic activity is increased by 10%-18% at a current density of 80-120 mA / cm² compared to the reaction conditions of 180 ° C for 12 hours. The electrochemical HER test is carried out in a 1.0 M NaOH electrolyte and the current density is increased by 8%-15% in the range of 80-120 mA / cm². In step d), if the washed product is vacuum dried at 65 ° C for 12 hours, the stability of the obtained electrode is compared to the electrode vacuum dried at 55 ° C for 10 hours. After 50 electrochemical cycle tests, the activity retention rate is increased by 8%-12% when the electrochemical SOR test is carried out in a 1.0 M NaOH (containing 1.0 M Na2S) electrolyte, and the activity retention rate is increased by 6%-10% when the electrochemical HER test is carried out in a 1.0 M NaOH electrolyte.

[0011] Compared with the prior art, the present invention has the following beneficial effects: Raw materials and cost advantages: Various raw materials are widely available, such as molybdates (sodium molybdate, ammonium molybdate), soluble nickel salts (nickel nitrate, nickel sulfate, nickel chloride), organic sulfur compounds (thioacetamide, thiourea), etc., which are easy to obtain and inexpensive on the market. They do not rely on expensive and scarce precious metal precursors, greatly reducing production costs and facilitating large-scale industrial production.

[0012] Preparation process advantages: The operation is simple and easy. It only requires dissolving the raw materials, ultrasonically dispersing them, conducting a hydrothermal reaction, and then going through conventional steps such as washing and drying to complete the preparation. The professional skills of the operator are not high.

[0013] The hydrothermal conditions are mild, and the reaction temperature is between 140-220°C. Compared with some high-temperature, high-pressure or complex synthesis processes, it has low energy consumption and no special requirements for equipment. Ordinary laboratory or industrial production equipment can meet the requirements, reducing equipment investment costs and production difficulty.

[0014] Electrode performance advantages: The prepared sulfide self-supporting electrode has a unique micro-nanostructure, in which molybdenum / nickel sulfide presents a nanocluster structure, the nanorod-like diameter is between 80-550nm, and the length is 0.8-3.5μm. This structure fully exposes the active sites of the catalyst, enhances the mass transfer effect, and thus has a higher electrocatalytic activity.

[0015] In terms of catalytic electrochemical sulfur oxidation reaction (SOR), for example, in a 1.0MNaOH (containing 1.0MNa2S) electrolyte, the electrodes prepared under different conditions can be controlled to have an overpotential between 330-380mV at a higher current density (e.g., 100-120mA / cm²), showing good catalytic performance and can effectively achieve desulfurization of sulfur-containing exhaust gas and recovery of elemental sulfur.

[0016] In terms of catalyzing the electrochemical hydrogen evolution reaction (HER), in a 1.0M NaOH electrolyte, when the current density reaches 100-120mA / cm², the overpotential can be as low as 145-175mV, with a high hydrogen evolution efficiency, which helps to reduce the energy consumption of electrochemical hydrogen production and promote the development and utilization of hydrogen energy.

[0017] The electrode has good stability and its activity retention rate is high after multiple electrochemical cycle tests. For example, after 50 cycle tests, the activity retention rate of the electrode prepared under specific conditions in the SOR and HER reactions can be increased by 8%-12% and 6%-10%, respectively, which can meet the needs of long-term use. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a SEM image of the bifunctional sulfide self-supporting electrode prepared in Example 1; Figure 2 is the polarization curve of the self-supporting electrode prepared in Example 1 for SOR; Figure 3 This is the polarization curve of the self-supporting electrode prepared in Example 1 for HER. DETAILED DESCRIPTION

[0019] The following embodiments of the present invention are described in further detail with reference to the accompanying drawings and examples. The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0020] See also Figure 1-Figure 3 The present invention provides a bifunctional sulfide self-supporting electrode, which uses nickel foam as a substrate and nickel source, and uses a hydrothermal method to react molybdate, a soluble nickel salt and an organic sulfur compound to in situ grow a molybdenum / nickel sulfide material on the nickel foam. The molybdenum / nickel sulfide has a nanocluster structure, wherein the nanorod-like diameters constituting the nanoclusters are in the range of 80-550nm and the lengths are 0.8-3.5μm. The nickel foam provides a precursor support for the formation of the nanostructure and sulfide, thereby promoting the generation and uniform distribution of the molybdenum / nickel sulfide.

[0021] The molybdate is sodium molybdate or ammonium molybdate, and its dosage is between 0.15-1.2 mmol. After being dissolved in the reaction system, it participates in the reaction as a molybdenum source, and synergistically acts with the nickel source and the sulfur source to affect the composition and structure of the final molybdenum / nickel sulfide, thereby regulating the catalytic performance of the electrode. The soluble nickel salt is nickel nitrate, nickel sulfate or nickel chloride, and its dosage is 0.01-0.12 mmol. It provides nickel elements in the reaction and reacts with the molybdate and the organic sulfur compound to generate a molybdenum / nickel sulfide with a specific structure and performance. The change in its concentration will change the crystallinity and the number of active sites of the product. The organic sulfur compound is thioacetamide or thiourea, and its dosage is within the range of 0.8-12 mmol. It acts as a sulfur source and combines with the molybdenum source and the nickel source in the hydrothermal reaction. The change in its dosage will affect the content and distribution of sulfur in the molybdenum / nickel sulfide, and play an important role in the catalytic activity and stability of the electrode.

[0022] A method for preparing a bifunctional sulfide self-supporting electrode comprises the following steps: a) dissolving molybdate, soluble nickel salt, and organic sulfide in 25-80 mL of deionized water in a specific ratio, and ultrasonically dispersing for 8-35 minutes to ensure a uniform solution to obtain a mixed solution. Variations in ultrasonic time and solution volume in this step may affect the dispersion of the raw materials, thereby affecting the uniformity of the reaction and the consistency of the product; b) transferring the mixed solution obtained in step a) into a polytetrafluoroethylene hydrothermal autoclave lining, and completely immersing the pretreated nickel foam into the mixed solution, wherein the nickel foam has a size of (0.4-2.5) (0.4-4.5) cm² and a thickness of 0.1-2.5 mm. The selection of the size and thickness will affect the electrode loading and mass transfer efficiency; c) The hydrothermal reactor is sealed and placed in a forced air drying oven, and the temperature is maintained at 140-220° C. for 6-30 hours to carry out a sulfurization reaction, so that the metal precursor is converted into a sulfide and in situ grown on the nickel foam substrate. Changes in reaction temperature and time will significantly affect the crystallinity, morphology and catalytic performance of the product; d) repeatedly washing the product obtained in step c) with deionized water and ethanol until the pH value reaches 6.5-7.5, and then vacuum drying at 50-70° C. for 8-16 hours to obtain a bifunctional sulfide self-supporting electrode. Optimizing the washing and drying conditions helps remove impurities and improve the purity and stability of the electrode.

[0023] In step a), when sodium molybdate is used as the molybdate, in a specific reaction system, 0.03 mmol nickel nitrate and 3 mmol thioacetamide are dissolved in 40 mL deionized water, and the mixed solution obtained by ultrasonication for 20 min can make the generated electrode in the subsequent reaction be able to perform an electrochemical SOR test in 1.0 M NaOH (containing 1.0 M Na2S) electrolyte. When the current density is 120 mA / cm², the overpotential is 330 mV. When the electrochemical HER test is performed in 1.0 M NaOH electrolyte, when the current density is 120 mA / cm², the overpotential is 150 mV. In step a), if ammonium molybdate is selected as the molybdate, 0.05 mmol nickel sulfate and 4 mmol thiourea are dissolved in 50 mL deionized water, and the mixed solution obtained by ultrasonication for 25 min is used, and the electrode prepared in the subsequent steps is tested in 1.0 M NaOH (containing 1.0 M Na2S) electrolyte. 2S) electrolyte, the overpotential was 340 mV when the current density was 110 mA / cm², and the overpotential was 145 mV when the current density was 110 mA / cm². In step b), when the nickel foam size was 1.5×3 cm² and the thickness was 1.5 mm, under the same reaction conditions, the prepared electrode was compared with the electrode prepared by nickel foam with a size of 0.5×1 cm² and a thickness of 0.5 mm. When the electrochemical SOR test was carried out in 1.0 M NaOH (containing 1.0 M Na2S) electrolyte, the current density was increased by 15%-25% in the range of 100-150 mA / cm², and when the electrochemical HER test was carried out in 1.0 M NaOH electrolyte, the current density was increased by 10%-20% in the range of 100-150 mA / cm².

[0024] In step c), when the hydrothermal reaction temperature is 160°C and the temperature is maintained for 24 hours, the prepared electrode is subjected to an electrochemical SOR test in a 1.0 M NaOH (containing 1.0 M Na2S) electrolyte. The catalytic activity is increased by 10%-18% at a current density of 80-120 mA / cm² compared to the reaction conditions of 180°C for 12 hours. The electrochemical HER test is performed in a 1.0 M NaOH electrolyte and the current density is increased by 8%-15% within the range of 80-120 mA / cm². In step d), if the washed product is vacuum dried at 65°C for 12 hours, the stability of the obtained electrode is compared to the electrode vacuum dried at 55°C for 10 hours. After 50 electrochemical cycle tests, the activity retention rate is increased by 8%-12% when the electrochemical SOR test is performed in a 1.0 M NaOH (containing 1.0 M Na2S) electrolyte, and the activity retention rate is increased by 6%-10% when the electrochemical HER test is performed in a 1.0 M NaOH electrolyte.

[0025] Example 1: a) In a 100 mL beaker, 0.4 mmol of sodium molybdate, 0.04 mmol of nickel nitrate, 2 mmol of thioacetamide, and 30 mL of deionized water were sequentially added and ultrasonicated at room temperature for 30 minutes to completely dissolve and uniformly disperse the molybdenum salt, nickel salt, and organosulfur compound in the aqueous solution to obtain a mixed solution; b) The mixed solution was transferred to a 50 mL polytetrafluoroethylene-lined hydrothermal autoclave. Simultaneously, a 1 mm thick nickel foam was cut into pieces of 0.51 cm². The cut nickel foam was ultrasonically cleaned for 10 min each using 3 mol / L hydrochloric acid, anhydrous ethanol, and deionized water. The cleaned nickel foam was allowed to dry naturally and then completely immersed in the mixed solution. c) Seal the hydrothermal kettle and place it in a forced air drying oven, heating it to 180°C and maintaining the temperature for 12 hours; d) After natural cooling, the hydrothermal reactor was opened, and the reaction product was taken out and washed three times with deionized water and ethanol, respectively, and dried under vacuum at 60°C to obtain a bifunctional sulfide self-supporting electrode.

[0026] e) The prepared sulfide self-supporting electrode was directly used as the working electrode, the Hg / HgO electrode was used as the reference electrode, the graphite rod was used as the counter electrode, and 1.0 M NaOH (containing 1.0 M Na2S) was used as the electrolyte. Electrochemical SOR tests were carried out. When the current density was 100 mA / cm2, the overpotential was 354 mV.

[0027] f) The sulfide self-supporting electrode prepared above was directly used as the working electrode, the Hg / HgO electrode was used as the reference electrode, the graphite rod was used as the counter electrode, and 1.0 M NaOH was used as the electrolyte to carry out electrochemical HER tests. When the current density was 100 mA / cm2, the overpotential was 162 mV.

[0028] Example 2: a) In a 100 mL beaker, 0.4 mmol of sodium molybdate, 0.04 mmol of nickel chloride, 2 mmol of thioacetamide, and 30 mL of deionized water were sequentially added and ultrasonicated at room temperature for 30 minutes to completely dissolve and uniformly disperse the molybdenum salt, nickel salt, and organosulfur compound in the aqueous solution to obtain a mixed solution; b) The mixed solution was transferred to a 50 mL polytetrafluoroethylene-lined hydrothermal autoclave. Simultaneously, a 1 mm thick nickel foam was cut into pieces of 0.51 cm². The cut nickel foam was ultrasonically cleaned for 10 min each using 3 mol / L hydrochloric acid, anhydrous ethanol, and deionized water. The cleaned nickel foam was allowed to dry naturally and then completely immersed in the mixed solution. c) Seal the hydrothermal kettle and place it in a forced air drying oven, heating it to 180°C and maintaining the temperature for 12 hours; d) After natural cooling, the hydrothermal reactor was opened, and the reaction product was taken out and washed three times with deionized water and ethanol, respectively, and dried under vacuum at 60°C to obtain a bifunctional sulfide self-supporting electrode.

[0029] e) The prepared sulfide self-supporting electrode was directly used as the working electrode, the Hg / HgO electrode was used as the reference electrode, the graphite rod was used as the counter electrode, and 1.0 M NaOH (containing 1.0 M Na2S) was used as the electrolyte. Electrochemical SOR tests were carried out. When the current density was 100 mA / cm2, the overpotential was 360 mV.

[0030] f) The sulfide self-supporting electrode prepared above was directly used as the working electrode, the Hg / HgO electrode was used as the reference electrode, the graphite rod was used as the counter electrode, and 1.0 M NaOH was used as the electrolyte to carry out electrochemical HER tests. When the current density was 100 mA / cm2, the overpotential was 154 mV.

[0031] Example 3: a) In a 100 mL beaker, 0.4 mmol of ammonium molybdate, 0.04 mmol of nickel nitrate, 2 mmol of thioacetamide, and 30 mL of deionized water were sequentially added and ultrasonicated at room temperature for 30 minutes to completely dissolve and uniformly disperse the molybdenum salt, nickel salt, and organosulfur compound in the aqueous solution to obtain a mixed solution; b) The mixed solution was transferred to a 50 mL polytetrafluoroethylene-lined hydrothermal autoclave. Simultaneously, a 1 mm thick nickel foam was cut into pieces of 0.51 cm². The cut nickel foam was ultrasonically cleaned for 10 min each using 3 mol / L hydrochloric acid, anhydrous ethanol, and deionized water. The cleaned nickel foam was allowed to dry naturally and then completely immersed in the mixed solution. c) Seal the hydrothermal kettle and place it in a forced air drying oven, heating it to 180°C and maintaining the temperature for 12 hours; d) After natural cooling, the hydrothermal reactor was opened, and the reaction product was taken out and washed three times with deionized water and ethanol, respectively, and dried under vacuum at 60°C to obtain a bifunctional sulfide self-supporting electrode.

[0032] e) The prepared sulfide self-supporting electrode was directly used as the working electrode, the Hg / HgO electrode was used as the reference electrode, the graphite rod was used as the counter electrode, and 1.0 M NaOH (containing 1.0 M Na2S) was used as the electrolyte. Electrochemical SOR tests were carried out. When the current density was 100 mA / cm2, the overpotential was 381 mV.

[0033] f) The sulfide self-supporting electrode prepared above was directly used as the working electrode, the Hg / HgO electrode was used as the reference electrode, the graphite rod was used as the counter electrode, and 1.0 M NaOH was used as the electrolyte to carry out electrochemical HER tests. When the current density was 100 mA / cm2, the overpotential was 160 mV.

[0034] Example 4: a) In a 100 mL beaker, 0.4 mmol sodium molybdate, 0.04 mmol nickel nitrate, 2 mmol thiourea, and 30 mL deionized water were sequentially added and ultrasonicated at room temperature for 30 min to completely dissolve and uniformly disperse the molybdenum salt, nickel salt, and organosulfur compound in the aqueous solution to obtain a mixed solution; b) The mixed solution was transferred to a 50 mL polytetrafluoroethylene-lined hydrothermal autoclave. Simultaneously, a 1 mm thick nickel foam was cut into pieces of 0.51 cm². The cut nickel foam was ultrasonically cleaned for 10 min each using 3 mol / L hydrochloric acid, anhydrous ethanol, and deionized water. The cleaned nickel foam was allowed to dry naturally and then completely immersed in the mixed solution. c) Seal the hydrothermal kettle and place it in a forced air drying oven, heating it to 180°C and maintaining the temperature for 12 hours; d) After natural cooling, the hydrothermal reactor was opened, and the reaction product was taken out and washed three times with deionized water and ethanol, respectively, and dried under vacuum at 60°C to obtain a bifunctional sulfide self-supporting electrode.

[0035] e) The prepared sulfide self-supporting electrode was directly used as the working electrode, the Hg / HgO electrode was used as the reference electrode, the graphite rod was used as the counter electrode, and 1.0 M NaOH (containing 1.0 M Na2S) was used as the electrolyte. Electrochemical SOR tests were carried out. When the current density was 100 mA / cm2, the overpotential was 372 mV.

[0036] f) The sulfide self-supporting electrode prepared above was directly used as the working electrode, the Hg / HgO electrode was used as the reference electrode, the graphite rod was used as the counter electrode, and 1.0 M NaOH was used as the electrolyte to carry out electrochemical HER tests. When the current density was 100 mA / cm2, the overpotential was 175 mV.

[0037] Embodiment 5: a) In a 100 mL beaker, 0.6 mmol of sodium molybdate, 0.06 mmol of nickel nitrate, 3 mmol of thioacetamide, and 35 mL of deionized water were sequentially added and ultrasonicated at room temperature for 30 minutes to completely dissolve and uniformly disperse the molybdenum salt, nickel salt, and organosulfur compound in the aqueous solution to obtain a mixed solution; b) The mixed solution was transferred to a 50 mL polytetrafluoroethylene-lined hydrothermal autoclave. Simultaneously, the 1 mm thick nickel foam was cut into pieces of 0.5-1.5 cm². The cut pieces were ultrasonically cleaned for 10 min each using 3 mol / L hydrochloric acid, anhydrous ethanol, and deionized water. The cleaned nickel foam was allowed to dry naturally and then completely immersed in the mixed solution. c) Seal the hydrothermal kettle and place it in a forced air drying oven, heating it to 160°C and maintaining the temperature for 20 hours; d) After natural cooling, the hydrothermal reactor was opened, and the reaction product was taken out and washed three times with deionized water and ethanol, respectively, and dried under vacuum at 60°C to obtain a bifunctional sulfide self-supporting electrode.

[0038] e) The prepared sulfide self-supporting electrode was directly used as the working electrode, the Hg / HgO electrode was used as the reference electrode, the graphite rod was used as the counter electrode, and 1.0 M NaOH (containing 1.0 M Na2S) was used as the electrolyte. Electrochemical SOR tests were carried out. When the current density was 100 mA / cm2, the overpotential was 351 mV.

[0039] f) The sulfide self-supporting electrode prepared above was directly used as the working electrode, the Hg / HgO electrode was used as the reference electrode, the graphite rod was used as the counter electrode, and 1.0 M NaOH was used as the electrolyte to carry out electrochemical HER tests. When the current density was 100 mA / cm2, the overpotential was 173 mV.

[0040] The embodiments of the present invention are presented for purposes of illustration and description and are not intended to be exhaustive or to limit the invention to the disclosed forms. Many modifications and variations will be apparent to those skilled in the art. The embodiments are chosen and described in order to better illustrate the principles of the invention and its practical application and to enable those skilled in the art to understand the invention and design various embodiments with various modifications as suited for specific applications.

Claims

1. A bifunctional sulfide self-supporting electrode, characterized in that: Using nickel foam as a substrate and nickel source, molybdate, soluble nickel salt and organic sulfur compound are reacted by a hydrothermal method to form a molybdenum / nickel sulfide material in situ grown on the nickel foam. The molybdenum / nickel sulfide presents a nanocluster structure, wherein the nanorod-like structures constituting the nanoclusters have a diameter within the range of 80-550nm and a length of 0.8-3.5μm. The nickel foam provides a precursor support for the formation of the nanostructure and sulfide, thereby promoting the generation and uniform distribution of the molybdenum / nickel sulfide.

2. The bifunctional sulfide self-supporting electrode according to claim 1, characterized in that The molybdate is sodium molybdate or ammonium molybdate, and its usage is between 0.15-1.2 mmol. After being dissolved in the reaction system, it participates in the reaction as a molybdenum source, synergistically acts with the nickel source and the sulfur source, affects the composition and structure of the final molybdenum / nickel sulfide, and thus regulates the catalytic performance of the electrode.

3. The bifunctional sulfide self-supporting electrode according to claim 1, characterized in that: The soluble nickel salt is nickel nitrate, nickel sulfate or nickel chloride, and the amount used is 0.01-0.12 mmol. It provides nickel element in the reaction and reacts with molybdate and organic sulfur compound to generate molybdenum / nickel sulfide with specific structure and properties. The change of its concentration will change the crystallinity and number of active sites of the product.

4. The bifunctional sulfide self-supporting electrode according to claim 1, characterized in that: The organic sulfur compound is thioacetamide or thiourea, and its dosage is in the range of 0.8-12 mmol. It is combined with the molybdenum source and the nickel source in the hydrothermal reaction as a sulfur source. The change of its dosage will affect the content and distribution of sulfur in the molybdenum / nickel sulfide, which has an important effect on the catalytic activity and stability of the electrode.

5. A method for preparing a bifunctional sulfide self-supporting electrode, characterized in that: The following steps are involved: a) dissolving molybdate, soluble nickel salt, and organic sulfide in 25-80 mL of deionized water in a specific ratio, and ultrasonically dispersing for 8-35 minutes to ensure a uniform solution to obtain a mixed solution. Variations in ultrasonic time and solution volume in this step may affect the dispersion of the raw materials, thereby affecting the uniformity of the reaction and the consistency of the product; b) transferring the mixed solution obtained in step a) into a polytetrafluoroethylene hydrothermal autoclave lining, and completely immersing the pretreated nickel foam into the mixed solution, wherein the nickel foam has a size of (0.4-2.5) (0.4-4.5) cm² and a thickness of 0.1-2.5 mm. The selection of the size and thickness will affect the electrode loading and mass transfer efficiency; c) The hydrothermal reactor is sealed and placed in a forced air drying oven, and the temperature is maintained at 140-220° C. for 6-30 hours to carry out a sulfurization reaction, so that the metal precursor is converted into a sulfide and in situ grown on the nickel foam substrate. Changes in reaction temperature and time will significantly affect the crystallinity, morphology and catalytic performance of the product; d) repeatedly washing the product obtained in step c) with deionized water and ethanol until the pH value reaches 6.5-7.5, and then vacuum drying at 50-70° C. for 8-16 hours to obtain a bifunctional sulfide self-supporting electrode. Optimizing the washing and drying conditions helps remove impurities and improve the purity and stability of the electrode.

6. The method for preparing a bifunctional sulfide self-supporting electrode according to claim 5, characterized in that: In step a), when sodium molybdate is used as the molybdate, in a specific reaction system, 0.03 mmol nickel nitrate and 3 mmol thioacetamide are dissolved in 40 mL of deionized water, and ultrasonicated for 20 minutes to obtain a mixed solution. In the subsequent reaction, the generated electrode can be subjected to an electrochemical SOR test in a 1.0 M NaOH (containing 1.0 M Na2S) electrolyte. When the current density is 120 mA / cm², the overpotential is 330 mV. When the electrochemical HER test is carried out in a 1.0 M NaOH electrolyte, the overpotential is 150 mV when the current density is 120 mA / cm².

7. The method for preparing a bifunctional sulfide self-supporting electrode according to claim 5, characterized in that: In step a), if ammonium molybdate is selected as the molybdate, it is dissolved with 0.05 mmol nickel sulfate and 4 mmol thiourea in 50 mL deionized water and ultrasonicated for 25 minutes to obtain a mixed solution. The electrode prepared in the subsequent steps is subjected to an electrochemical SOR test in a 1.0 M NaOH (containing 1.0 M Na2S) electrolyte. When the current density is 110 mA / cm², the overpotential is 340 mV. When the electrochemical HER test is carried out in a 1.0 M NaOH electrolyte, when the current density is 110 mA / cm², the overpotential is 145 mV.

8. The method for preparing a bifunctional sulfide self-supporting electrode according to claim 5, characterized in that: In step b), when the nickel foam has a size of 1.5×3 cm² and a thickness of 1.5 mm, under the same reaction conditions, the prepared electrode is compared with the electrode prepared from nickel foam having a size of 0.5×1 cm² and a thickness of 0.5 mm. When the electrochemical SOR test is performed in 1.0 M NaOH (containing 1.0 M Na2S) electrolyte, the current density is increased by 15%-25% in the range of 100-150 mA / cm². When the electrochemical HER test is performed in 1.0 M NaOH electrolyte, the current density is increased by 10%-20% in the range of 100-150 mA / cm².

9. The method for preparing a bifunctional sulfide self-supporting electrode according to claim 5, characterized in that: In step c), when the hydrothermal reaction temperature was 160°C and the temperature was maintained for 24 hours, the prepared electrode was subjected to an electrochemical SOR test in a 1.0 M NaOH (containing 1.0 M Na2S) electrolyte. The catalytic activity was improved by 10%-18% at a current density of 80-120 mA / cm² compared to the reaction conditions of 180°C for 12 hours. The electrochemical HER test was conducted in a 1.0 M NaOH electrolyte, and the catalytic activity was improved by 8%-15% at a current density of 80-120 mA / cm².

10. The method for preparing a bifunctional sulfide self-supporting electrode according to claim 5, characterized in that: In step d), if the washed product is vacuum dried at 65°C for 12 hours, the stability of the resulting electrode is compared to that of the electrode vacuum dried at 55°C for 10 hours. After 50 electrochemical cycle tests, the activity retention rate is improved by 8%-12% when the electrochemical SOR test is performed in a 1.0M NaOH (containing 1.0M Na2S) electrolyte, and the activity retention rate is improved by 6%-10% when the electrochemical HER test is performed in a 1.0M NaOH electrolyte.

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