A non-metallic two-phase doped alkaline overall water-splitting bifunctional heterojunction electrocatalyst based on nickel foil, and a preparation method and application thereof

Abstract

The application discloses a non-metallic two-phase doped alkaline overall water-splitting bifunctional heterojunction electrocatalyst based on a nickel foil as well as a preparation method and application thereof, and belongs to the field of new energy technology and electrocatalytic material application. x The chemical formula of the electrocatalyst is NiS x / S-NiFeOOH. The preparation method comprises the following steps: dissolving transition state metal nitrate corresponding to Ni and Fe in deionized water, mixing the solution with a water solution in which sodium sulfide is dissolved to serve as an electrolyte, performing electrodeposition on a nickel foil which is pretreated as an anode, and then performing electrodeposition on the nickel foil in a solution containing a sulfur source and a nickel precursor. The application solves the problem of competitive adsorption of two electrode reactions on active sites in the process of electrolysis of water, and greatly improves the catalytic efficiency. Meanwhile, the material has the advantages of low cost and excellent alkaline oxygen evolution / hydrogen evolution electrocatalytic activity, and is expected to be applied to industrial large-scale electrolysis of water to produce hydrogen, and has certain practical significance.

Description

Technical Field

[0001] This invention relates to a novel electrocatalyst material and its preparation method, belonging to the fields of new energy technology and electrocatalytic material application. It relates to a low-cost electrocatalyst material and its preparation method for alkaline total water splitting reaction with a heterostructure composed of non-metallic two-phase co-doped material. In particular, it relates to a low-cost electrocatalyst material and its preparation method for alkaline total water splitting reaction with a heterostructure composed of non-metallic two-phase co-doped material. Background Technology

[0002] Electrocatalytic hydrogen production utilizes a catalyst to promote the cracking of water through an electrochemical reaction, yielding hydrogen as a green and sustainable method. Compared to traditional fossil fuel-based hydrogen production methods, such as coal gasification or steam reforming, electrocatalytic hydrogen production features lower carbon emissions and is more environmentally friendly. Furthermore, electrocatalytic hydrogen production can leverage renewable energy sources, such as wind and solar power, to achieve sustainable hydrogen production, and is expected to become an important component of future clean energy systems.

[0003] In electrocatalytic hydrogen production, catalysts should possess high activity and stability to promote reaction rates and increase hydrogen yield. Electrocatalytic water splitting mainly includes two reactions: hydrogen evolution at the cathode and oxygen evolution at the anode. For the hydrogen evolution reaction, the evolution of hydrogen ions requires overcoming the polarity and redox potential limitations of water molecules, and high-energy active sites are needed to catalyze hydrogen evolution. The oxygen evolution reaction, due to its four-electron transfer process, exhibits slow kinetics, limiting its reaction rate. Therefore, catalysts capable of overcoming reaction energy barriers need to be designed. In recent years, much research has focused on developing highly efficient electrocatalysts, involving various materials, including noble metals, transition metals, and carbon materials. By controlling the structure, composition, and surface properties of the catalyst, precise control and optimization of the electrocatalytic hydrogen production process can be achieved.

[0004] In traditional water electrolysis, the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) compete for the same catalytic site, limiting catalyst activity. However, the design of a bifunctional catalyst can solve the competitive adsorption problem in water electrolysis and possesses active centers that promote both OER and HER reactions. This integrated design simplifies the structure of the electrolysis unit, reduces system complexity and cost, and also helps improve energy conversion efficiency.

[0005] In metal-based electrocatalytic reactions, the active sites are typically atoms or lattice defects on the metal surface. These sites possess specific surface properties and activities, enabling them to adsorb reactants and promote the reaction. The formation and properties of catalytic active sites can be effectively controlled by adjusting the structure and composition of the metal surface. Doping with non-metallic elements can introduce additional active sites into metal catalysts to promote the reaction. This doping typically alters the catalyst's electronic structure, surface chemistry, and crystal structure, thereby affecting the interaction between the catalyst and reactants and the reaction pathway. Furthermore, it may change the catalyst's adsorption capacity, surface active site density, and charge transport characteristics, thus influencing the interaction strength and reaction rate between the catalyst and reactants. Therefore, by rationally designing and controlling the doping methods of non-metallic elements, the performance and efficiency of the catalyst can be effectively improved. Moreover, electrocatalysts based on low-cost nickel foil can be directly combined with photovoltaic cells, enabling efficient energy conversion and utilization. This has significant implications for the practical application of low-cost alkaline water electrolysis catalysts in large-scale water electrolysis, promoting the development of clean energy. Summary of the Invention

[0006] The purpose of this invention is to address the activity defects of single-reaction catalysts in total water splitting, as well as the corrosion problem of the electrolyte on the solar cell in the integrated hydrogen production system of electrocatalyst and solar cell. This invention proposes a low-cost alkaline bifunctional electrocatalyst for total water splitting based on nickel foil, which is a heterostructure material composed of transition metal-based sulfides and sulfur-hydroxides. This invention also provides a method for preparing the transition metal-based sulfur-hydroxide.

[0007] The technical solution of the present invention:

[0008] The first objective of this invention is to provide a non-metallic two-phase doped alkaline water-splitting bifunctional heterojunction electrocatalyst based on nickel foil, wherein the electrocatalyst is a NiS heterostructure composed of transition metal-based sulfides and sulfur-hydroxides. x / S-NiFeOOH is a three-dimensional porous nanosphere branched structure; the non-metallic two-phase doped transition metal-based heterostructure catalyst is grown on nickel foil by in-situ electrochemical deposition during the preparation process, wherein the Ni:Fe element content ratio is 1.25:1.

[0009] The electrocatalytic performance of the non-metallic two-phase doped transition metal-based heterostructure material based on nickel foil exhibits an oxygen evolution activity of 10 mA / cm² in an alkaline medium at pH 13.8. 2 The overpotential range required for the catalytic current density is 180–230 mV; its hydrogen evolution activity is 10 mA / cm². 2 The required overpotential range under current density conditions is 70–120 mV; the total water splitting activity is 10 mA / cm². 2The required voltage range for the catalytic current density is 1.50–1.57V, and the stable operating time exceeds 50 hours.

[0010] The second objective of this invention is to provide a method for preparing the above-mentioned non-metallic two-phase doped alkaline water-splitting bifunctional heterojunction electrocatalyst based on nickel foil, the steps of which are as follows:

[0011] 1) Dissolve the corresponding nitrates of Ni and Fe in deionized water at a molar ratio of 1.25:1, with a total molar amount of 0.05M or 0.1M. Then add the prepared sulfur source to the above solution, mix, and sonicate.

[0012] 2) After the solution is fully mixed, the precursor solution is used as the electrolyte. Pre-treated nickel foils of 0.05 nm, 0.15 nm, and 0.25 nm are used as working electrodes, platinum sheets are used as counter electrodes, and saturated Ag / AgCl is used as reference electrodes. Electrochemical deposition reactions are carried out using the three-electrode system at 40 °C and 50 °C for 180 s, 300 s, and 600 s, respectively. The obtained products are washed with deionized water and anhydrous ethanol, and then dried to obtain S-NiFe(oxy)hydroxide / Ni foil electrodes.

[0013] 3) Dissolve Ni-based nitrate and sulfur source in deionized water. Use the nickel foil electrode obtained in 1) as the working electrode, the platinum sheet as the counter electrode, and the saturated Ag / AgCl as the reference electrode. Perform electrochemical deposition reaction using the three-electrode system for 5-60 min. Clean the obtained product with deionized water and anhydrous ethanol, and then vacuum dry it to obtain the electrode with precursor loaded on the nickel foil substrate.

[0014] 4) The nickel foil electrode loaded with the precursor was fixed with a platinum electrode clamp and electrochemically activated with a three-electrode system with 1M KOH electrolyte to obtain the final three-dimensional nanosphere branched electrocatalyst.

[0015] The nitrates corresponding to Ni and Fe are nickel nitrate hexahydrate and ferric nitrate nonahydrate, respectively; the sulfur sources are sodium sulfide and thiourea.

[0016] The nickel foil is 2cm x 1cm in size;

[0017] The method for pre-treating the nickel foil is as follows: the nickel foil is soaked in hydrochloric acid, anhydrous ethanol, and water and ultrasonicated for 10 minutes each.

[0018] The electrochemical activation method for the three-electrode system is as follows: a nickel foam electrode loaded with a precursor catalyst is used as the working electrode, Ag / AgCl is used as the reference electrode, and a platinum sheet is used as the working electrode. The voltage is set to -0.3-0.8V, and CV activation is performed at a scan rate of 50mV / s. The number of cycles is set to 50.

[0019] In one embodiment, the total molar amount in step 1) is 0.05M; the thickness of the nickel foil in step 2) is 0.25nm, and the deposition temperature and time are 40℃ and 300s, respectively; the electrochemical reaction deposition time in step 3) is set to 5min, 10min, 20min, 30min and 60min, respectively, where 30min is the optimal temperature setting.

[0020] The electrochemical activation and electrochemical performance testing steps of the nickel foil-based non-metallic two-phase doped alkaline water-splitting bifunctional heterojunction electrocatalyst provided by this invention are as follows:

[0021] 1) Evaluate electrochemical measurements in a three-electrode setup with an Ag / AgCl electrode as the reference electrode and a platinum sheet electrode as the counter electrode, with a catalyst-supported nickel foil electrode as the working electrode.

[0022] 3) Potential-referenced reversible hydrogen electrode (RHE): E RHE =E Ag / AgCl +0.098 +0.059 × pH (1M KOH solution). Calculate the overpotential (η) according to the following equation: η = E RHE -1.23V. Cyclic voltammetry (CV) was performed in a saturated 1M KOH solution at a scan rate of 50 mV / s to obtain the electrochemically activated target catalyst. Linear sweep voltammetry (LSV) was recorded in a saturated 1M KOH solution at a scan rate of 5 mV / s to obtain polarization curves. All electrode potential data were compensated for with 85% voltage drop.

[0023] The advantages and effects of this invention are as follows:

[0024] The non-metallic two-phase doped alkaline water-splitting bifunctional heterojunction electrocatalyst based on nickel foil of this invention is a low-cost composite material. It uses transition metal-based compounds, which are abundant, inexpensive, and readily available, as the source of catalytic active centers. The water-splitting bifunctional electrocatalyst with multiple active sites and high stability is synthesized by electrochemical deposition and electrochemical in-situ activation. The operation process of the electrocatalyst material is simple and suitable for large-scale production.

[0025] The electrocatalyst, when applied to the oxygen evolution reaction under alkaline conditions, requires only an overpotential of 181 mV to achieve a current of 10 mA cm⁻¹. -2 The current density. Its hydrogen evolution reaction occurs at -10 mA cm⁻¹. -2 The overpotential at the given current density is only 75 mV, indicating that this non-noble metal electrocatalyst exhibits excellent oxygen evolution and hydrogen evolution kinetics in an alkaline environment. Simultaneously, the prepared electrocatalyst demonstrates excellent stability in alkaline electrolytes, maintaining a stable overpotential at 20 mA cm⁻¹. -2It remains stable for more than 50 hours at the specified current density.

[0026] The high performance is attributed to the interfacial effects of the non-metallic doped two-phase composite structure and the optimization of overall structural performance by non-metallic bonding interactions. Surface reconstruction also creates more sulfur vacancies and active high-valence metal compounds, enhancing the catalyst's oxygen evolution and hydrogen evolution performance. This novel material solves the problem of competitive adsorption at active sites during water electrolysis, significantly improving catalytic efficiency. Furthermore, the nickel foil-based design will drive the development of integration with solar cells, providing strategic guidance for the design of the overall structure and catalyst. This has significant practical implications for the research and application of low-cost materials in the whole-phase water electrolysis hydrogen production process. Attached Figure Description

[0027] Figure 1 Example 1 of the present invention (NiS) x Comparative Example 1 (NiFeOOH), Comparative Example 2 (S-NiFeOOH), and Comparative Example 3 (NiS-NiFeOOH) x The prepared electrocatalyst was recorded in 1M KOH solution at a scan rate of 1 mV / s to obtain the anodic reaction polarization curve.

[0028] Figure 2 Example 1 of the present invention (NiS) x Comparative Example 1 (NiFeOOH), Comparative Example 2 (S-NiFeOOH), and Comparative Example 3 (NiS-NiFeOOH) x The prepared electrocatalyst was recorded in 1M KOH solution at a scan rate of 1 mV / s using linear sweep voltammetry (LSV) to obtain the cathode reaction polarization curve;

[0029] Figure 3 Example 1 of the present invention (NiS) x Comparative Example 1 (NiFeOOH), Comparative Example 2 (S-NiFeOOH), and Comparative Example 3 (NiS-NiFeOOH) x The OER AC impedance spectrum of the prepared electrocatalyst obtained in 1M KOH solution;

[0030] Figure 4 Example 1 of the present invention (NiS) x Comparative Example 1 (NiFeOOH), Comparative Example 2 (S-NiFeOOH), and Comparative Example 3 (NiS-NiFeOOH) x The Tafel slope diagram of the electrocatalyst prepared in 1M KOH solution;

[0031] Figure 5 Example 1 of the present invention (NiS)x The electrocatalyst prepared by / S-NiFeOOH) was tested in 1M KOH solution using a two-electrode method to obtain the total water splitting polarization curve.

[0032] Figure 6 Example 1 of the present invention (NiS) x The two-electrode test of the / S-NiFeOOH) electrocatalyst at 20 mA cm⁻¹ -2 The stability test curves under constant current density for 50 hours were obtained, and all electrode potential data were compensated with 85% iR.

[0033] Figure 7 Example 1 of the present invention (NiS) x The total water splitting polarization curves were obtained by linear sweep voltammetry (LSV) before and after the stability test of the / S-NiFeOOH electrocatalyst under two-electrode testing.

[0034] Figure 8 Comparative Example 1 (NiFeOOH), Comparative Example 2 (S-NiFeOOH), and Comparative Example 3 (NiS) are examples of the present invention. x ) and Example 1 (NiS x SEM morphology test results of the electrocatalyst prepared by (S-NiFeOOH);

[0035] Figure 9 Example 1 of the present invention (NiS) x SEM morphology test results of the electrocatalyst prepared by (S-NiFeOOH);

[0036] Figure 10 Comparative Example 2 (S-NiFeOOH) and Comparative Example 3 (NiS) of the present invention x ) and Example 1 (NiS x XRD pattern of the electrocatalyst prepared by (S-NiFeOOH). Detailed Implementation

[0037] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] Example 1:

[0039] Nickel foil was sequentially immersed in hydrochloric acid, anhydrous ethanol, and deionized water, and ultrasonically treated for 10 minutes each. A three-electrode system was formed, using a pre-fabricated 2cm x 1cm nickel foil with a thickness of 0.25nm as the working electrode, a platinum sheet as the counter electrode, and saturated Ag / AgCl as the reference electrode, for electrodeposition. The electrolyte consisted of 0.03M nickel nitrate hexahydrate, 0.02M ferric nitrate nonahydrate, and 0.05g sodium sulfide, which were ultrasonically dissolved in 30 mL of deionized water, followed by the addition of 200 μL of hydrogen peroxide solution. Electrodeposition was performed at 40℃ under a constant voltage of -1.1V vs. Ag / AgCl for 300 s. After deposition, the sample was rinsed sequentially with deionized water and anhydrous ethanol, and then dried in an oven at 60℃ for 12 hours to obtain the target precursor. Electrodeposition was performed using a three-electrode system: a nickel foil-supported precursor as the working electrode, a platinum sheet as the counter electrode, and saturated Ag / AgCl as the reference electrode. The electrolyte consisted of 0.05 M nickel nitrate hexahydrate, 0.05 M sodium citrate, and 0.75 M thiourea. Electrodeposition was carried out at a constant voltage of -1.0 V vs. Ag / AgCl for 30 min. After deposition, the sample was rinsed sequentially with deionized water and anhydrous ethanol, and then freeze-dried for 12 hours to obtain the electrocatalyst described in this invention.

[0040] Example 2:

[0041] Nickel foil was sequentially immersed in hydrochloric acid, anhydrous ethanol, and deionized water, and ultrasonically treated for 10 minutes each. A three-electrode system was formed, consisting of a pre-fabricated 2cm x 1cm nickel foil with a thickness of 0.25nm as the working electrode, a platinum sheet as the counter electrode, and saturated Ag / AgCl as the reference electrode, for electrodeposition. The electrolyte consisted of 0.06M nickel nitrate hexahydrate, 0.04M ferric nitrate nonahydrate, and 0.05g sodium sulfide, which were ultrasonically dissolved in 30 mL of deionized water, followed by the addition of 200 μL of hydrogen peroxide solution. Electrodeposition was performed at 40℃ under a constant voltage of -1.1V vs. Ag / AgCl for 300 s. After deposition, the sample was rinsed sequentially with deionized water and anhydrous ethanol, and then dried in an oven at 60℃ for 12 hours to obtain the target precursor. Electrodeposition was performed using a three-electrode system: a nickel foil-supported precursor as the working electrode, a platinum sheet as the counter electrode, and saturated Ag / AgCl as the reference electrode. The electrolyte consisted of 0.05 M nickel nitrate hexahydrate, 0.05 M sodium citrate, and 0.75 M thiourea. Electrodeposition was carried out at a constant voltage of -1.0 V vs. Ag / AgCl for 30 min. After deposition, the sample was rinsed sequentially with deionized water and anhydrous ethanol, and then freeze-dried for 12 hours to obtain the target electrocatalyst.

[0042] Example 3:

[0043] Nickel foil was sequentially immersed in hydrochloric acid, anhydrous ethanol, and deionized water, and ultrasonically treated for 10 minutes each. A three-electrode system was formed, consisting of a pre-fabricated 2cm x 1cm nickel foil with a thickness of 0.05nm as the working electrode, a platinum sheet as the counter electrode, and saturated Ag / AgCl as the reference electrode, for electrodeposition. The electrolyte consisted of 0.03M nickel nitrate hexahydrate, 0.02M ferric nitrate nonahydrate, and 0.05g sodium sulfide, which were ultrasonically dissolved in 30 mL of deionized water, followed by the addition of 200 μL of hydrogen peroxide solution. Electrodeposition was performed at 40℃ under a constant voltage of -1.1V vs. Ag / AgCl for 300 s. After deposition, the sample was rinsed sequentially with deionized water and anhydrous ethanol, and then dried in an oven at 60℃ for 12 hours to obtain the target precursor. Electrodeposition was performed using a three-electrode system: a nickel foil-supported precursor as the working electrode, a platinum sheet as the counter electrode, and saturated Ag / AgCl as the reference electrode. The electrolyte consisted of 0.05 M nickel nitrate hexahydrate, 0.05 M sodium citrate, and 0.75 M thiourea. Electrodeposition was carried out at a constant voltage of -1.0 V vs. Ag / AgCl for 30 min. After deposition, the sample was rinsed sequentially with deionized water and anhydrous ethanol, and then freeze-dried for 12 hours to obtain the target electrocatalyst.

[0044] Example 4:

[0045] Nickel foil was sequentially immersed in hydrochloric acid, anhydrous ethanol, and deionized water, and ultrasonically treated for 10 minutes each. A three-electrode system was formed, consisting of a pre-fabricated 2cm x 1cm nickel foil with a thickness of 0.15nm as the working electrode, a platinum sheet as the counter electrode, and saturated Ag / AgCl as the reference electrode, for electrodeposition. The electrolyte consisted of 0.03M nickel nitrate hexahydrate, 0.02M ferric nitrate nonahydrate, and 0.05g sodium sulfide, which were ultrasonically dissolved in 30 mL of deionized water, followed by the addition of 200 μL of hydrogen peroxide solution. Electrodeposition was performed at 40℃ under a constant voltage of -1.1V vs. Ag / AgCl for 300 s. After deposition, the sample was rinsed sequentially with deionized water and anhydrous ethanol, and then dried in an oven at 60℃ for 12 hours to obtain the target precursor. Electrodeposition was performed using a three-electrode system: a nickel foil-supported precursor as the working electrode, a platinum sheet as the counter electrode, and saturated Ag / AgCl as the reference electrode. The electrolyte consisted of 0.05 M nickel nitrate hexahydrate, 0.05 M sodium citrate, and 0.75 M thiourea. Electrodeposition was carried out at a constant voltage of -1.0 V vs. Ag / AgCl for 30 min. After deposition, the sample was rinsed sequentially with deionized water and anhydrous ethanol, and then freeze-dried for 12 hours to obtain the target electrocatalyst.

[0046] Example 5:

[0047] Nickel foil was sequentially immersed in hydrochloric acid, anhydrous ethanol, and deionized water, and ultrasonically treated for 10 minutes each. A three-electrode system was formed, consisting of a pre-fabricated 2cm x 1cm nickel foil with a thickness of 0.25nm as the working electrode, a platinum sheet as the counter electrode, and saturated Ag / AgCl as the reference electrode, for electrodeposition. The electrolyte consisted of 0.03M nickel nitrate hexahydrate, 0.02M ferric nitrate nonahydrate, and 0.05g sodium sulfide, which were ultrasonically dissolved in 30 mL of deionized water, followed by the addition of 200 μL of hydrogen peroxide solution. Electrodeposition was performed at 50°C under a constant voltage of -1.1V vs. Ag / AgCl for 300 s. After deposition, the sample was rinsed sequentially with deionized water and anhydrous ethanol, and then dried in an oven at 60°C for 12 hours to obtain the target precursor. Electrodeposition was performed using a three-electrode system: a nickel foil-supported precursor as the working electrode, a platinum sheet as the counter electrode, and saturated Ag / AgCl as the reference electrode. The electrolyte consisted of 0.05 M nickel nitrate hexahydrate, 0.05 M sodium citrate, and 0.75 M thiourea. Electrodeposition was carried out at a constant voltage of -1.0 V vs. Ag / AgCl for 30 min. After deposition, the sample was rinsed sequentially with deionized water and anhydrous ethanol, and then freeze-dried for 12 hours to obtain the electrocatalyst described in this invention.

[0048] Example 6:

[0049] Nickel foil was sequentially immersed in hydrochloric acid, anhydrous ethanol, and deionized water, and ultrasonically treated for 10 minutes each. A three-electrode system was formed, consisting of a pre-fabricated 2cm x 1cm nickel foil with a thickness of 0.25nm as the working electrode, a platinum sheet as the counter electrode, and saturated Ag / AgCl as the reference electrode, for electrodeposition. The electrolyte consisted of 0.03M nickel nitrate hexahydrate, 0.02M ferric nitrate nonahydrate, and 0.05g sodium sulfide, which were ultrasonically dissolved in 30 mL of deionized water, followed by the addition of 200 μL of hydrogen peroxide solution. Electrodeposition was performed at 40℃ under a constant voltage of -1.1V vs. Ag / AgCl for 180 s. After deposition, the sample was rinsed sequentially with deionized water and anhydrous ethanol, and then dried in an oven at 60℃ for 12 hours to obtain the target precursor. Electrodeposition was performed using a three-electrode system: a nickel foil-supported precursor as the working electrode, a platinum sheet as the counter electrode, and saturated Ag / AgCl as the reference electrode. The electrolyte consisted of 0.05 M nickel nitrate hexahydrate, 0.05 M sodium citrate, and 0.75 M thiourea. Electrodeposition was carried out at a constant voltage of -1.0 V vs. Ag / AgCl for 30 min. After deposition, the sample was rinsed sequentially with deionized water and anhydrous ethanol, and then freeze-dried for 12 hours to obtain the electrocatalyst described in this invention.

[0050] Example 7:

[0051] Nickel foil was sequentially immersed in hydrochloric acid, anhydrous ethanol, and deionized water, and ultrasonically treated for 10 minutes each. A three-electrode system was formed, consisting of a pre-fabricated 2cm x 1cm nickel foil with a thickness of 0.25nm as the working electrode, a platinum sheet as the counter electrode, and saturated Ag / AgCl as the reference electrode, for electrodeposition. The electrolyte consisted of 0.03M nickel nitrate hexahydrate, 0.02M ferric nitrate nonahydrate, and 0.05g sodium sulfide, which were ultrasonically dissolved in 30 mL of deionized water, followed by the addition of 200 μL of hydrogen peroxide solution. Electrodeposition was performed at 40℃ under a constant voltage of -1.1V vs. Ag / AgCl for 600 s. After deposition, the sample was rinsed sequentially with deionized water and anhydrous ethanol, and then dried in an oven at 60℃ for 12 hours to obtain the target precursor. Electrodeposition was performed using a three-electrode system: a nickel foil-supported precursor as the working electrode, a platinum sheet as the counter electrode, and saturated Ag / AgCl as the reference electrode. The electrolyte consisted of 0.05 M nickel nitrate hexahydrate, 0.05 M sodium citrate, and 0.75 M thiourea. Electrodeposition was carried out at a constant voltage of -1.0 V vs. Ag / AgCl for 30 min. After deposition, the sample was rinsed sequentially with deionized water and anhydrous ethanol, and then freeze-dried for 12 hours to obtain the electrocatalyst described in this invention.

[0052] Example 8:

[0053] Nickel foil was sequentially immersed in hydrochloric acid, anhydrous ethanol, and deionized water, and ultrasonically treated for 10 minutes each. A three-electrode system was formed, using a pre-fabricated 2cm x 1cm nickel foil with a thickness of 0.25nm as the working electrode, a platinum sheet as the counter electrode, and saturated Ag / AgCl as the reference electrode, for electrodeposition. The electrolyte consisted of 0.03M nickel nitrate hexahydrate, 0.02M ferric nitrate nonahydrate, and 0.05g sodium sulfide, which were ultrasonically dissolved in 30 mL of deionized water, followed by the addition of 200 μL of hydrogen peroxide solution. Electrodeposition was performed at 40℃ under a constant voltage of -1.1V vs. Ag / AgCl for 300 s. After deposition, the sample was rinsed sequentially with deionized water and anhydrous ethanol, and then dried in an oven at 60℃ for 12 hours to obtain the target precursor. Electrodeposition was performed using a three-electrode system: a nickel foil-supported precursor as the working electrode, a platinum sheet as the counter electrode, and saturated Ag / AgCl as the reference electrode. The electrolyte consisted of 0.05 M nickel nitrate hexahydrate, 0.05 M sodium citrate, and 0.75 M thiourea. Electrodeposition was carried out at a constant voltage of -1.0 V vs. Ag / AgCl for 5 minutes. After deposition, the sample was rinsed sequentially with deionized water and anhydrous ethanol, and then freeze-dried for 12 hours to obtain the electrocatalyst described in this invention.

[0054] Example 9:

[0055] Nickel foil was sequentially immersed in hydrochloric acid, anhydrous ethanol, and deionized water, and ultrasonically treated for 10 minutes each. A three-electrode system was formed, using a pre-fabricated 2cm x 1cm nickel foil with a thickness of 0.25nm as the working electrode, a platinum sheet as the counter electrode, and saturated Ag / AgCl as the reference electrode, for electrodeposition. The electrolyte consisted of 0.03M nickel nitrate hexahydrate, 0.02M ferric nitrate nonahydrate, and 0.05g sodium sulfide, which were ultrasonically dissolved in 30 mL of deionized water, followed by the addition of 200 μL of hydrogen peroxide solution. Electrodeposition was performed at 40℃ under a constant voltage of -1.1V vs. Ag / AgCl for 300 s. After deposition, the sample was rinsed sequentially with deionized water and anhydrous ethanol, and then dried in an oven at 60℃ for 12 hours to obtain the target precursor. Electrodeposition was performed using a three-electrode system: a nickel foil-supported precursor as the working electrode, a platinum sheet as the counter electrode, and saturated Ag / AgCl as the reference electrode. The electrolyte consisted of 0.05 M nickel nitrate hexahydrate, 0.05 M sodium citrate, and 0.75 M thiourea. Electrodeposition was carried out at a constant voltage of -1.0 V vs. Ag / AgCl for 10 min. After deposition, the sample was rinsed sequentially with deionized water and anhydrous ethanol, and then freeze-dried for 12 hours to obtain the electrocatalyst described in this invention.

[0056] Example 10:

[0057] Nickel foil was sequentially immersed in hydrochloric acid, anhydrous ethanol, and deionized water, and ultrasonically treated for 10 minutes each. A three-electrode system was formed, using a pre-fabricated 2cm x 1cm nickel foil with a thickness of 0.25nm as the working electrode, a platinum sheet as the counter electrode, and saturated Ag / AgCl as the reference electrode, for electrodeposition. The electrolyte consisted of 0.03M nickel nitrate hexahydrate, 0.02M ferric nitrate nonahydrate, and 0.05g sodium sulfide, which were ultrasonically dissolved in 30 mL of deionized water, followed by the addition of 200 μL of hydrogen peroxide solution. Electrodeposition was performed at 40℃ under a constant voltage of -1.1V vs. Ag / AgCl for 300 s. After deposition, the sample was rinsed sequentially with deionized water and anhydrous ethanol, and then dried in an oven at 60℃ for 12 hours to obtain the target precursor. Electrodeposition was performed using a three-electrode system: a nickel foil-supported precursor as the working electrode, a platinum sheet as the counter electrode, and saturated Ag / AgCl as the reference electrode. The electrolyte consisted of 0.05 M nickel nitrate hexahydrate, 0.05 M sodium citrate, and 0.75 M thiourea. Electrodeposition was carried out at a constant voltage of -1.0 V vs. Ag / AgCl for 20 min. After deposition, the sample was rinsed sequentially with deionized water and anhydrous ethanol, and then freeze-dried for 12 hours to obtain the electrocatalyst described in this invention.

[0058] Example 11:

[0059] Nickel foil was sequentially immersed in hydrochloric acid, anhydrous ethanol, and deionized water, and ultrasonically treated for 10 minutes each. A three-electrode system was formed, using a pre-fabricated 2cm x 1cm nickel foil with a thickness of 0.25nm as the working electrode, a platinum sheet as the counter electrode, and saturated Ag / AgCl as the reference electrode, for electrodeposition. The electrolyte consisted of 0.03M nickel nitrate hexahydrate, 0.02M ferric nitrate nonahydrate, and 0.05g sodium sulfide, which were ultrasonically dissolved in 30 mL of deionized water, followed by the addition of 200 μL of hydrogen peroxide solution. Electrodeposition was performed at 40℃ under a constant voltage of -1.1V vs. Ag / AgCl for 300 s. After deposition, the sample was rinsed sequentially with deionized water and anhydrous ethanol, and then dried in an oven at 60℃ for 12 hours to obtain the target precursor. Electrodeposition was performed using a three-electrode system: a nickel foil-supported precursor as the working electrode, a platinum sheet as the counter electrode, and saturated Ag / AgCl as the reference electrode. The electrolyte consisted of 0.05 M nickel nitrate hexahydrate, 0.05 M sodium citrate, and 0.75 M thiourea. Electrodeposition was carried out at a constant voltage of -1.0 V vs. Ag / AgCl for 60 min. After deposition, the sample was rinsed sequentially with deionized water and anhydrous ethanol, and then freeze-dried for 12 hours to obtain the electrocatalyst described in this invention.

[0060] Example 12:

[0061] Electrochemical activation and electrochemical performance testing of electrocatalysts prepared in Examples 1-11

[0062] (1) Electrochemical activation and evaluation were performed using a three-electrode setup with an Ag / AgCl electrode as the reference electrode and a platinum sheet electrode as the counter electrode; potential reference reversible hydrogen electrode (RHE): E RHE =E Ag / AgCl +0.098 +0.059 × pH (1M KOH solution). Calculate the overpotential (η) according to the following equation: η = E RHE -1.23V. The three-dimensional porous nanosphere branched electrocatalyst obtained in Example 1, after electrochemical activation, is the electrocatalyst described in this invention, with the chemical formula NiS. x / S-NiFeOOH. Linear sweep voltammetry (LSV) was used to obtain polarization curves in a saturated 1M KOH solution at a scan rate of 1 mV / s. See [link to relevant documentation]. Figure 1 To obtain electron transport properties, AC impedance testing under constant voltage is performed (see [reference]). Figure 2 Stability testing involved maintaining a constant current density of 20 for 50 hours; see the stability test curve for details. Figure 3 Furthermore, the LSV polarization curve after long-term testing was essentially unchanged from that before testing. All electrode potential data in the three-electrode test were compensated for with 85% voltage drop.

[0063] (2) The catalyst prepared after electrochemical activation in Example 1 and supported on nickel foil was tested by SEM. It has a porous network spherical structure. See [link to SEM]. Figure 9 .

[0064] (3) The XRD pattern of the catalyst prepared after electrochemical activation in Example 1 and supported on nickel foil was tested. The peaks showing only the nickel substrate indicated its amorphous structure. (See [reference]). Figure 10 .

[0065] Comparative Example 1:

[0066] (1) Preparation of NiFeOOH: Nickel foil was sequentially immersed in hydrochloric acid, anhydrous ethanol, and deionized water, and ultrasonicated for 10 minutes each. A three-electrode system was formed, consisting of a pre-prepared 2cm*1cm nickel foil with a thickness of 0.25nm as the working electrode, a platinum sheet as the counter electrode, and saturated Ag / AgCl as the reference electrode, for electrodeposition. The electrolyte consisted of 0.03M nickel nitrate hexahydrate and 0.02M ferric nitrate nonahydrate. Electrodeposition was performed at 40℃ under a constant voltage of -1.1V vs. Ag / AgCl for 300s. After deposition, the product was rinsed sequentially with deionized water and anhydrous ethanol, and dried in an oven at 60℃ for 12 hours to obtain the target precursor. Cyclic voltammetry was then performed in 1M KOH solution to obtain the electrochemically activated catalyst.

[0067] (2) Electrochemical activation and evaluation were performed using a three-electrode setup with an Ag / AgCl electrode as the reference electrode and a platinum sheet electrode as the counter electrode; potential reference reversible hydrogen electrode (RHE): E RHE =E Ag / AgCl +0.098 +0.059 × pH (1M KOH solution). Calculate the overpotential (η) according to the following equation: η = E RHE -1.23V. Linear sweep voltammetry (LSV) was recorded in a saturated 1M KOH solution at a scan rate of 1 mV / s to obtain the anodic / cathode polarization curves. See [reference needed]. Figure 1 / Figure 2 To obtain electron transport properties, AC impedance testing under constant voltage is performed (see [reference]). Figure 3 Tafel slope test to obtain reaction kinetics, see [link to Tafel slope test]. Figure 4 All electrode potential data were compensated for with 85% voltage drop.

[0068] Comparative Example 2:

[0069] (1) Preparation of S-NiFeOOH: Nickel foil was sequentially immersed in hydrochloric acid, anhydrous ethanol, and deionized water, and ultrasonically treated for 10 minutes each. A three-electrode system was formed, consisting of a pre-prepared 2cm*1cm nickel foil with a thickness of 0.25nm as the working electrode, a platinum sheet as the counter electrode, and saturated Ag / AgCl as the reference electrode, for electrodeposition. The electrolyte consisted of 0.03M nickel nitrate hexahydrate, 0.02M ferric nitrate nonahydrate, and 0.05g sodium sulfide, which were ultrasonically dissolved in 30 mL of deionized water, and then 200 μL of hydrogen peroxide solution was added. Electrodeposition was performed at 40℃ under a constant voltage of -1.1V vs. Ag / AgCl for 300 s. After deposition, the sample was rinsed sequentially with deionized water and anhydrous ethanol, and dried in an oven at 60℃ for 12 hours to obtain the target precursor. Cyclic voltammetry was then performed in 1M KOH solution to obtain the electrochemically activated catalyst.

[0070] (2) Electrochemical activation and evaluation were performed using a three-electrode setup with an Ag / AgCl electrode as the reference electrode and a platinum sheet electrode as the counter electrode; potential reference reversible hydrogen electrode (RHE): E RHE =E Ag / AgCl +0.098 +0.059 × pH (1M KOH solution). Calculate the overpotential (η) according to the following equation: η = E RHE -1.23V. Linear sweep voltammetry (LSV) was recorded in a saturated 1M KOH solution at a scan rate of 1 mV / s to obtain the anodic / cathode polarization curves. See [reference needed]. Figure 1 / Figure 2 To obtain electron transport properties, AC impedance testing under constant voltage is performed (see [reference]). Figure 3 Tafel slope test to obtain reaction kinetics, see [link to Tafel slope test]. Figure 4 All electrode potential data were compensated for with 85% voltage drop.

[0071] Comparative Example 3:

[0072] (1) NiS x Preparation: Nickel foil was sequentially immersed in hydrochloric acid, anhydrous ethanol, and deionized water, and ultrasonicated for 10 minutes each. A pre-prepared 2cm*1cm nickel foil-supported precursor with a thickness of 0.25nm was used as the working electrode, a platinum sheet as the counter electrode, and saturated Ag / AgCl as the reference electrode to form a three-electrode system for electrodeposition. Electrodeposition was performed using 0.05M nickel nitrate hexahydrate, 0.05M sodium citrate, and 0.75M thiourea as the electrolyte, under a constant voltage of -1.0V vs. Ag / AgCl for 20 minutes. After deposition, the product was rinsed sequentially with deionized water and anhydrous ethanol, and then freeze-dried for 12 hours to obtain the electrocatalyst.

[0073] (2) Electrochemical activation and evaluation were performed using a three-electrode setup with an Ag / AgCl electrode as the reference electrode and a platinum sheet electrode as the counter electrode; potential reference reversible hydrogen electrode (RHE): E RHE =E Ag / AgCl +0.098 +0.059 × pH (1M KOH solution). Calculate the overpotential (η) according to the following equation: η = E RHE -1.23V. Linear sweep voltammetry (LSV) was recorded in a saturated 1M KOH solution at a scan rate of 1 mV / s to obtain the anodic / cathode polarization curves. See [reference needed]. Figure 1 / Figure 2 To obtain electron transport properties, AC impedance testing under constant voltage is performed (see [reference]). Figure 3 Tafel slope test to obtain reaction kinetics, see [link to Tafel slope test]. Figure 4 All electrode potential data were compensated for with 85% voltage drop.

[0074] Figure 1 NiS obtained in Example 1 in 1M KOH x / S-NiFeOOH, NiFeOOH obtained in Comparative Example 1, NiS obtained from S-NiFeOOH in Comparative Example 2, and NiS obtained from Comparative Example 3 x The OER linear sweep voltammetry curve is shown in the figure. As can be seen from the figure, the current density reaches 10 mA / cm². 2 At that time, NiS x The / S-NiFeOOH catalyst exhibits the lowest overpotential, indicating that NiS x The synergistic effect of S-NiFeOOH enhances the oxygen evolution catalytic performance.

[0075] Figure 2 NiS obtained in Example 1 in 1M KOH x / S-NiFeOOH, NiFeOOH obtained in Comparative Example 1, NiS obtained from S-NiFeOOH in Comparative Example 2, and NiS obtained from Comparative Example 3 x The HER linear sweep voltammetry curves are shown in the figure. As can be seen from the figure, the current density reaches 10 mA / cm². 2 At that time, NiS x The / S-NiFeOOH catalyst exhibits the lowest overpotential, indicating that NiS x The synergistic effect of S-NiFeOOH enhances the hydrogen evolution catalytic performance.

[0076] Figure 3 NiS obtained in Example 1 in 1M KOH x / S-NiFeOOH, NiFeOOH obtained in Comparative Example 1, NiS obtained from S-NiFeOOH in Comparative Example 2, and NiS obtained from Comparative Example 3 xThe electrochemical impedance spectroscopy of NiS. As can be seen from the figure, NiS... x The / S-NiFeOOH catalyst exhibits the lowest interfacial resistance, indicating that NiS x The synergistic effect of S-NiFeOOH promotes the catalytic kinetics of the electrochemical reaction.

[0077] Figure 4 NiS obtained in Example 1 in 1M KOH x / S-NiFeOOH, NiFeOOH obtained in Comparative Example 1, NiS obtained from S-NiFeOOH in Comparative Example 2, and NiS obtained from Comparative Example 3 x The Tafel slope plot. As can be seen from the plot, NiS x The / S-NiFeOOH catalyst exhibits the smallest Tafel slope, indicating that NiS x The synergistic effect of S-NiFeOOH promotes electron transfer at the heterogeneous interface and improves the electronic properties of the catalyst surface.

[0078] Figure 5 NiS obtained in Example 1 in 1M KOH x Two-electrode linear sweep voltammetry curves were performed using / S-NiFeOOH as the cathode and / anode, respectively.

[0079] Figure 6 NiS obtained in Example 1 in 1M KOH x The stability of the two electrodes, S-NiFeOOH, used as the cathode and anode respectively, under constant voltage conditions for 50 hours was tested.

[0080] Figure 7 The stability test comparison chart of NiS in 1M KOH before and after is shown in Example 1. x The LSV curves of the two electrodes, S-NiFeOOH, used as the cathode and anode respectively, almost overlapped, indicating that the catalyst's performance did not significantly decline before and after the stability test, demonstrating excellent long-term stability.

[0081] Figure 8 The NiFeOOH obtained in Comparative Example 1, the NiFeOOH obtained in Comparative Example 2 (S-NiFeOOH), and the NiS obtained in Comparative Example 3 are respectively. x The NiS obtained in Example 1 x Scanning electron microscopy (AD) images of / S-NiFeOOH. Image D shows a common structural morphology to images B and C, with a porous network of nanosphere dendrites on the surface.

[0082] Figure 9 NiS obtained in Example 1 x The high-magnification scanning electron microscope image of / S-NiFeOOH shows a distinct surface porous state.

[0083] Figure 10 NiS obtained in Example 1 x / S-NiFeOOH, NiFeOOH obtained in Comparative Example 1, NiS obtained from S-NiFeOOH in Comparative Example 2, and NiS obtained from Comparative Example 3 x The XRD pattern shows that only the strong diffraction peaks of Ni are visible on the (111), (200), and (220) planes, indicating that the catalyst is mainly amorphous. In addition, the active surfaces exposed in the heterojunction are mainly oriented towards the (220) plane with lower surface energy, which is more conducive to the adsorption of species and the catalytic reaction.

[0084] In summary, a novel, low-cost, non-metallic, two-phase-doped bifunctional electrocatalyst for alkaline water electrolysis on a nickel foil substrate and its preparation method were presented. The overall microstructure of the material was optimized through the interfacial effect of the two-phase composite structure and the non-metallic bonding during in-situ electrochemical activation, resulting in a novel material structure suitable for both oxygen evolution and hydrogen evolution reactions in alkaline conditions. The activity of the target catalyst material was significantly improved compared to undoped and single-phase catalysts, while the catalyst stability was also well maintained.

[0085] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A non-metallic two-phase doped alkaline water-splitting bifunctional heterojunction electrocatalyst based on nickel foil, characterized in that, The electrocatalyst is a nickel-based sulfide, NiS. x The catalyst, composed of a heterostructure of sulfur-doped nickel-iron hydroxyl oxide (S-NiFeOOH), exhibits a three-dimensional porous nanosphere dendritic structure and is described as NiS. x / S-NiFeOOH, where the molar ratio of Ni to Fe is 1.25:

1.

2. The non-metallic two-phase doped alkaline water-splitting bifunctional heterojunction electrocatalyst based on nickel foil according to claim 1, characterized in that, The catalyst exhibits an oxygen evolution activity of 10 mA / cm² in an alkaline medium at pH 13.

8. 2 The overpotential range required for the catalytic current density is 180–230 mV; the voltage range required for the catalytic current density is 1.50–1.57 V.

3. The non-metallic two-phase doped alkaline water-splitting bifunctional heterojunction electrocatalyst based on nickel foil according to claim 1, characterized in that, The hydrogen evolution activity of the catalyst reaches -10 mA / cm under the same conditions. 2 The overpotential range required for the catalytic current density is 70–120 mV.

4. The non-metallic two-phase doped alkaline water-splitting bifunctional heterojunction electrocatalyst based on nickel foil according to claim 1, characterized in that, The catalyst showed a strength of 20 mA / cm² in a two-electrode system test. 2 Stable operation time exceeds 50 hours under current density conditions.

5. The preparation method of the non-metallic two-phase doped alkaline water-splitting bifunctional heterojunction electrocatalyst based on nickel foil according to any one of claims 1-4, comprising the following steps: 1) Dissolve the corresponding nitrates of Ni and Fe in deionized water at a molar ratio of 1.25:1, with a total molar amount of 0.05 M or 0.1 M. Then add the prepared sulfur source to the above solution, mix, and sonicate. 2) After the solution is fully mixed, the precursor solution is used as the electrolyte. Pre-treated nickel foils of 0.05 nm, 0.15 nm, and 0.25 nm are used as working electrodes, platinum sheets are used as counter electrodes, and saturated Ag / AgCl is used as reference electrodes. Electrochemical deposition reaction is carried out using the three-electrode system at 25℃ ~ 50℃ for 180 ~ 600 s. The obtained product is washed with deionized water and anhydrous ethanol, and then dried to obtain a sulfur-doped nickel-iron hydroxyl oxide electrode based on nickel foil. 3) Dissolve Ni-based nitrate and sulfur source in deionized water. Use the sulfur-doped nickel-iron hydroxyl oxide electrode based on nickel foil obtained in step 2) as the working electrode, platinum sheet as the counter electrode, and saturated Ag / AgCl as the reference electrode. Perform electrochemical deposition reaction using a three-electrode system for 5 to 60 minutes. Clean the obtained product with deionized water and anhydrous ethanol, and then vacuum dry it to obtain an electrode with precursor loaded on nickel foil substrate. 4) The nickel foil electrode loaded with the precursor was fixed with a platinum electrode clamp and electrochemically activated with a three-electrode system with 1 M KOH electrolyte to obtain the final three-dimensional nanosphere branched electrocatalyst.

6. The preparation method of the non-metallic two-phase doped alkaline total water splitting bifunctional heterojunction electrocatalyst based on nickel foil according to claim 5, characterized in that, The corresponding nitrates for Ni and Fe are nickel nitrate hexahydrate and ferric nitrate nonahydrate, respectively; the sulfur source is sodium sulfide or thiourea.

7. The preparation method of the non-metallic two-phase doped alkaline water-splitting bifunctional heterojunction electrocatalyst based on nickel foil according to claim 5, characterized in that, The nickel foil pretreatment method is as follows: the nickel foil is immersed in hydrochloric acid, anhydrous ethanol and deionized water and ultrasonicated for 10 minutes each.

8. The preparation method of the non-metallic two-phase doped alkaline total water splitting bifunctional heterojunction electrocatalyst based on nickel foil according to claim 5, characterized in that, The electrochemical activation method of the three-electrode system is as follows: a nickel foil electrode loaded with the precursor is used as the working electrode, Ag / AgCl is used as the reference electrode, and a platinum sheet is used as the working electrode; the voltage is set to -0.3-0.8 V, CV activation is performed, the scan rate is 50 mV / s, and the number of cycles is set to 50.

9. The preparation method of the non-metallic two-phase doped alkaline total water splitting bifunctional heterojunction electrocatalyst based on nickel foil according to claim 5, characterized in that, In step 3), the electrochemical reaction deposition time is set to 5 min, 10 min, 20 min, 30 min, and 60 min, respectively.

10. The application of the nickel foil-based non-metallic two-phase doped alkaline water-evolving bifunctional heterojunction electrocatalyst according to any one of claims 1-4 in the oxygen evolution reaction under alkaline conditions.

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