A high-activity transition metal-based alkaline electrolysis water oxygen evolution reaction catalyst, a preparation method and application thereof

Abstract

The application discloses a high-activity alkaline electrolytic water oxygen evolution reaction catalyst based on transition metals and a preparation method and application thereof, and belongs to the fields of new energy technologies and electrocatalytic material applications.The electrocatalyst is expressed by a chemical formula of Ni m Fe n LDH / CeO 2‑x / NF.The preparation method comprises the following steps: dissolving a nitrate precursor containing a Ce element in deionized water, then performing electrodeposition on a foam nickel which has been treated in advance, placing the foam nickel in a corresponding transition state metal nitrate solution containing Ni and Fe after high-temperature annealing treatment, and finally performing a hydrothermal reaction to obtain the electrocatalyst. m Fe n LDH / CeO 2‑x / NF.The oxygen evolution performance of the electrocatalyst is obviously superior to that of single-metal-based Ni LDH / CeO 2‑x / NF, single-layer Ni m Fe n LDH / NF and Ni m Fe n LDH / CeO2.The main reasons for improving the oxygen evolution activity of the catalyst are that the catalyst introduces low-spin Fe doping, formation of a heterojunction interface and creation of multi-oxygen vacancies.Meanwhile, the material exhibits sustained high stability, and the design of the catalyst provides technical feasibility for large-scale electrolytic water hydrogen production.

Description

Technical Field

[0001] This invention belongs to the field of new energy technology and electrocatalytic material application, specifically relating to a heterostructure alkaline oxygen evolution catalyst for water electrolysis composed of cerium dioxide nanoparticles and nickel-iron-based double hydroxide nanosheets; particularly relating to the preparation method of the catalyst and its electrocatalytic application in the water electrolysis reaction. Background Technology

[0002] Hydrogen energy, as a new generation of clean energy carrier, has a high gravimetric energy density (14.3 kJ / kg) and is a carbon-free fuel. Electrochemical water splitting is a promising and effective technology for the industrial production of high-purity hydrogen. Developing hydrogen energy production and storage as a major direction is of great significance in alleviating the energy crisis and environmental problems. The water splitting reaction consists of the oxygen evolution reaction (OER) at the anode and the hydrogen evolution reaction (HER) at the cathode. Compared with HER, OER has slow kinetics and a larger reaction barrier. In particular, the multi-step proton-coupled electron transfer involved usually leads to a large potential, limiting the efficiency and widespread deployment of hydrogen production through water electrolysis. Noble metal-based Pt and IrO2 / RuO2 electrocatalysts are water splitting catalysts with high catalytic activity, but their large-scale application is limited by their scarcity, high cost, and poor stability. To address these issues, the rational design of efficient, stable, abundant, and low-cost transition metal-based oxygen evolution electrocatalysts is crucial for water splitting.

[0003] Considering these characteristics, transition metal layered double hydroxides (LDHs) with a unique layered structure, consisting of a positively charged layer and an intermediate balanced charge anion, grown directly on conductive substrates such as nickel foam (NF), are considered among the most promising Earth-abundant catalysts. The weak exchangeable intermediate anions and interlayer interactions facilitate high compositional tunability, making them highly active OER electrocatalysts. NiFe LDHs with two-dimensional ultrathin nanosheet arrays are a widely studied structure, possessing a low energy barrier promoting electron transport, a stable structure, high diffusion efficiency, and suitable precursors. Cerium (Ce) has unfilled 4f orbitals; under oxidizing or reducing conditions, Ce... 3+ and Ce 4+ There is a rapid conversion between them, thus acting as an electronic "storage" device. This unique valence-changing capability enables CeO2 to... 2-x The surface is rich in oxygen vacancies, thus endowing CeO with... 2-x CeO-based catalytic materials possess the ability to activate oxygen-containing small molecules, accelerating interfacial electron transfer. Furthermore, CeO... 2-x The strong interaction between CeO and metals allows the metals to be highly dispersed on their surfaces, thereby improving metal utilization. 2-xThe formation of heterostructures through coupling with transition metal-based catalysts can modulate the adsorption of oxygen-containing intermediates (-OH and -OOH), thereby regulating surface active sites, accelerating electron transport, increasing oxygen vacancies, and enhancing structural stability in the OER reaction. Furthermore, three-dimensional heterostructure catalysts composed of ultrathin nanosheets possess a large surface area, providing abundant active sites, and their larger pores facilitate the escape of evolved gases, accelerating the kinetic reaction. Based on this, developing heterostructured oxygen evolution electrocatalysts with high oxygen vacancies, high activity, and stability under alkaline conditions is a favorable condition for advancing the industrial application of water electrolysis.

[0004] Achieving higher current densities with smaller overpotentials under alkaline conditions yields greater hydrogen production. The heterojunction catalyst with high oxygen vacancies prepared in this invention possesses a unique three-dimensional structure. In-situ mediated synergistic effects between the multi-defect heterojunction interfaces promote strong charge transfer, enhancing the oxygen evolution reaction (OER) activity. The presence of high oxygen vacancies in the system improves the adsorption and activation of OER reaction intermediates, accelerating reaction kinetics and exhibiting better stability. Therefore, this invention's highly efficient and stable novel catalyst and simple preparation method provide technical support for the practical application of non-precious metal-based alkaline water desorption oxygen reaction electrocatalysts in large-scale water electrolysis. Summary of the Invention

[0005] This invention proposes a new research approach to address the shortcomings of existing technologies, aiming to provide a non-noble metal-based high-activity and high-stability electrocatalyst for alkaline water desorption oxygen reaction. This catalyst is a heterostructure catalyst formed by transition metal double hydroxides and rare earth oxides. This invention also provides a method for preparing this heterostructure electrocatalyst.

[0006] The technical solution of the present invention:

[0007] The first objective of this invention is to provide a novel transition metal-based heterostructure alkaline water desorption oxygen reaction electrocatalyst, wherein the electrocatalyst is a transition metal-based hydroxide Ni5Fe1 LDH and a rare earth oxide CeO 2-x The resulting heterojunction catalyst exhibits a disordered amorphous two-dimensional nanosheet structure and a three-dimensional "flower cluster" structure composed of two-dimensional nanosheets. The transition metal-based heterostructure catalyst is prepared by in-situ electrochemical deposition followed by annealing, and then directly hydrothermally grown in-situ on nickel foam, described as Ni... m Fe n LDH / CeO 2-x / NF, in which the content ratio of Ce, Ni and Fe elements is 2:1:0.2.

[0008] The electrocatalytic activity of the transition metal-based heterojunction catalytic material reaches 10 mA / cm² in an alkaline medium at pH 13.8.2 The overpotential range required for the catalytic current density is 160–200 mV; at 50 mA / cm 2 Stable operation time exceeds 200 hours under current density conditions.

[0009] The second objective of this invention is to provide a method for preparing the above-mentioned transition metal-based heterojunction basic water desorption oxygen reaction electrocatalyst, comprising the following steps:

[0010] 1) CeO 2-x / NF preparation method

[0011] Pre-treated nickel foam (1*2cm) 2 The working electrode is a platinum sheet, the counter electrode is a saturated Ag / AgCl electrode, and the electrolyte is a NaCl:Ce(NO3)3·6H2O mixed solution with a molar ratio of 5:1. The current density is -0.25 mA / cm². -2 Under constant conditions, electrodeposition was performed within a deposition time range of 300–1200 s to grow CeO2 nanoparticles on the surface. After drying, CeO2 nanoparticles were obtained by high-temperature annealing at 500 °C under 10% H2 / Ar conditions. 2-x / NF;

[0012] 2) Ni m Fe n LDH / CeO 2-x / NF

[0013] Keeping the total molar amounts of the two nitrates corresponding to Ni and Fe constant, dissolve them in 30 mL of deionized water at molar ratios of 1:0, 9:1, 7:1, 5:1, 4:1, 3:1, 1:1, 7:3, 3:7, or 1:9 respectively. Add a pre-prepared solution of urea and ammonium fluoride with a molar ratio of 2.4:1 to the above solution and stir to mix them evenly.

[0014] After the solution is thoroughly mixed, transfer it to a 50ml polytetrafluoroethylene hydrothermal reactor, and quickly add the CeO2 prepared in step 1). 2-x / NF was heated at 120°C for 6–12 hours. After cooling, the obtained product was ultrasonically treated and washed several times with deionized water. Then, it was freeze-dried to obtain a catalyst-supported nickel foam electrode.

[0015] The electrolyte in step 1) is a mixture of cerium nitrate hexahydrate and sodium chloride; the nitrates corresponding to Ni and Fe in step 2) are nickel nitrate hexahydrate and ferric nitrate nonahydrate, respectively.

[0016] The nickel foam is 2*1cm in size. 2 ;

[0017] The pretreatment method for the nickel foam is as follows: the nickel foam is sequentially immersed in hydrochloric acid, water, and anhydrous ethanol and ultrasonicated for 15 minutes each.

[0018] The electrochemical activation method of the three-electrode system is as follows: a nickel foam electrode loaded with 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 0-0.8V, and CV activation is performed with a scan rate of 50mV / s and a number of cycles of 50.

[0019] In one embodiment, the electrodeposition time in step 1) is set to 300s, 600s, 900s, and 1200s, respectively, with 900s being the optimal deposition time.

[0020] The electrochemical activation and electrochemical performance testing steps of the transition metal-based heterojunction alkaline water electrolysis oxygen evolution reaction catalyst 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 foam electrode as the working electrode.

[0022] 2) Potential Reference Reversible Hydrogen Electrode (RHE): E RHE =E Ag / AgCl +0.197 +0.059 × pH (1M KOH solution). Calculate the overpotential (η) according to the following equation: η = E RHE -1.23V. Polarization curves were obtained by linear sweep voltammetry (LSV) in a saturated 1M KOH solution at a scan rate of 1mV / s. All electrode potential data were compensated for with 85% voltage drop.

[0023] The main advantages and better effects of this invention compared with the prior art are as follows:

[0024] 1) The transition metal-based Ni described in this invention m Fe n LDH / CeO 2-x The / NF electrocatalyst is a non-precious metal composite material. It utilizes transition metal-based nitrates, which are abundant, inexpensive, and readily available as catalytic precursors, and synthesizes a highly active and stable non-precious metal catalyst for water electrolysis via electrodeposition and hydrothermal methods. The preparation of this electrocatalytic material is simple and easy to mass-produce.

[0025] 2) The electrocatalyst described in this invention, when applied to the oxygen evolution reaction under alkaline conditions, requires only an overpotential of 164 mV to achieve a 10 mA cm⁻¹. -2 The current density. The Tafel slope of this catalyst is 32 mV dec. -1This indicates that the non-noble metal electrocatalyst exhibits excellent oxygen evolution kinetics. Simultaneously, the prepared electrocatalyst demonstrates excellent stability at 50 mA cm⁻¹. -2 It remained stable for over 200 hours at the specified current density.

[0026] 3) The heterojunction catalyst described in this invention, a novel material, still exhibits good OER catalytic activity and stability when applied to alkaline solutions, and can provide strategic guidance for the design of practical catalysts for alkaline water electrolysis. Attached Figure Description

[0027] Figure 1 Example 1 of the present invention (Ni5Fe1 LDH / CeO) 2-x Comparative Example 1 (Ni5Fe1LDH / NF), Comparative Example 2 (Ni5Fe1LDH / CeO2 / NF), and Comparative Example 3 (NiLDH / CeO2 / NF) 2-x The electrocatalyst prepared by / NF-1) was polarized by linear sweep voltammetry (LSV) in 1M KOH solution at a scan rate of 1 mV / s, where all electrode potential data were compensated for 85% iR.

[0028] Figure 2 Example 1 of the present invention (Ni5Fe1 LDH / CeO) 2-x Comparative Example 1 (Ni5Fe1LDH / NF), Comparative Example 2 (Ni5Fe1LDH / CeO2 / NF), and Comparative Example 3 (NiLDH / CeO2 / NF) 2-x OER AC impedance spectrum of the electrocatalyst prepared by / NF-1) in 1M KOH solution;

[0029] Figure 3 Example 1 of the present invention (Ni5Fe1 LDH / CeO) 2-x / NF-1) electrocatalyst at 50 mA cm -2 Stability test curves maintained at constant current density for 200 hours;

[0030] Figure 4 The SEM morphology test results of the electrocatalyst prepared in Comparative Example 1 (Ni5Fe1 LDH / NF) of this invention;

[0031] Figure 5 Example 1 of the present invention (Ni5Fe1 LDH / CeO) 2-x SEM morphology test results of the electrocatalyst prepared by / NF-1);

[0032] Figure 6 Example 1 of the present invention (Ni5Fe1 LDH / CeO) 2-xThe UV-Vis absorption spectra of the electrocatalysts prepared in Example 1 (Ni5Fe1LDH / NF-1) and Comparative Example 1 (Ni5Fe1LDH / NF);

[0033] Figure 7 Example 1 of the present invention (Ni5Fe1 LDH / CeO) 2-x Summary photoelectron spectra of the electrocatalysts prepared in Example 1 (Ni5Fe1LDH / NF-1) and Comparative Example 1 (Ni5Fe1LDH / NF);

[0034] Figure 8 Example 1 of the present invention (Ni5Fe1 LDH / CeO) 2-x Comparative Example 1 (Ni5Fe1LDH / NF-1), Comparative Example 2 (Ni5Fe1LDH / CeO2 / NF-2), Comparative Example 3 (NiLDH / CeO2 / NF-2), and Comparative Example 3 (Ni5Fe1LDH / CeO2 / NF-1). 2-x XRD pattern of the electrocatalyst prepared by / NF-1). Detailed Implementation

[0035] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] Example 1:

[0037] 1) CeO 2-x Preparation of / NF-1

[0038] The nickel foam was sequentially immersed in hydrochloric acid, water, and anhydrous ethanol, and ultrasonicated for 15 minutes each, to prepare 2*1cm preforms. 2 Electrodeposition was performed using a three-electrode system: nickel foam as the working electrode, a platinum sheet as the counter electrode, and saturated Ag / AgCl as the reference electrode. The electrolyte was a NaCl:Ce(NO3)3·6H2O mixed solution with a molar ratio of 5:1, at a current density of -0.25 mA cm⁻¹. -2 Under constant conditions, electrodeposition was performed for 900 s, followed by drying and high-temperature annealing at 500 °C under 10% H2 / Ar conditions to obtain CeO. 2-x / NF-1.

[0039] 2) Ni5Fe1 LDH / CeO 2-x Preparation of / NF-1

[0040] Dissolve 0.291 g nickel nitrate hexahydrate, 0.081 g ferric nitrate nonahydrate, 360 mg uric acid, and 89 mg ammonium fluoride in 30 mL of deionized water and stir mechanically for 20 min to ensure complete dissolution. Transfer the mixed solution to a 50 mL polytetrafluoroethylene hydrothermal reactor, and simultaneously and rapidly add the CeO2 prepared in step 1). 2-x / NF-1(2*1cm 2The sample was added to the reactor. After sealing, it was heated continuously at 120°C for 12 hours. After heating, it was allowed to cool to room temperature. The nickel foam substrate sample was then removed from the reactor, sonicated three times with deionized water, and subsequently freeze-dried to obtain the target catalyst Ni5Fe1 LDH / CeO. 2-x / NF-1.

[0041] Example 2:

[0042] 1) CeO 2-x Preparation of / NF-2

[0043] The nickel foam was sequentially immersed in hydrochloric acid, water, and anhydrous ethanol, and ultrasonicated for 15 minutes each, to prepare 2*1cm preforms. 2 Electrodeposition was performed using a three-electrode system: nickel foam as the working electrode, a platinum sheet as the counter electrode, and saturated Ag / AgCl as the reference electrode. The electrolyte was a NaCl:Ce(NO3)3·6H2O mixed solution with a molar ratio of 5:1, at a current density of -0.25 mA cm⁻¹. -2 Under constant conditions, the deposition time was 300 s, and after drying, CeO was obtained by high-temperature annealing at 500 °C under 10% H2 / Ar conditions. 2-x / NF-2.

[0044] 2) Ni5Fe1 LDH / CeO 2-x Preparation of / NF-2

[0045] Dissolve 0.291 g nickel nitrate hexahydrate, 0.081 g ferric nitrate nonahydrate, 360 mg uric acid, and 89 mg ammonium fluoride in 30 mL of deionized water and stir mechanically for 20 min to ensure complete dissolution. Transfer the mixed solution to a 50 mL polytetrafluoroethylene hydrothermal reactor, and simultaneously and rapidly add the CeO2 prepared in step 1). 2-x / NF-2(2*1cm 2 The sample was added to the reactor. After sealing, it was heated continuously at 120°C for 12 hours. After heating, it was allowed to cool to room temperature. The nickel foam substrate sample was then removed from the reactor, sonicated three times with deionized water, and subsequently freeze-dried to obtain the target catalyst Ni5Fe1 LDH / CeO. 2-x / NF-2.

[0046] Example 3:

[0047] 1) CeO 2-x Preparation of / NF-3

[0048] The nickel foam was sequentially immersed in hydrochloric acid, water, and anhydrous ethanol, and ultrasonically treated for 15 minutes each to prepare 2*1cm preforms. 2Electrodeposition was performed using a three-electrode system: nickel foam as the working electrode, a platinum sheet as the counter electrode, and saturated Ag / AgCl as the reference electrode. The electrolyte was a NaCl:Ce(NO3)3·6H2O mixed solution with a molar ratio of 5:1, at a current density of -0.25 mA cm⁻¹. -2 Under constant conditions, electrodeposition was performed for 600 s, followed by drying and high-temperature annealing at 500 °C under 10% H2 / Ar conditions to obtain CeO. 2-x / NF-3.

[0049] 2) Ni5Fe1 LDH / CeO 2-x Preparation of / NF-3

[0050] Dissolve 0.291 g nickel nitrate hexahydrate, 0.081 g ferric nitrate nonahydrate, 360 mg uric acid, and 89 mg ammonium fluoride in 30 mL of deionized water and stir mechanically for 20 min to ensure complete dissolution. Transfer the mixed solution to a 50 mL polytetrafluoroethylene hydrothermal reactor, and simultaneously and rapidly add the CeO2 prepared in step 1). 2-x / NF-3(2*1cm 2 The sample was added to the reactor. After sealing, it was heated continuously at 120°C for 12 hours. After heating, it was allowed to cool to room temperature. The nickel foam substrate sample was then removed from the reactor, sonicated three times with deionized water, and subsequently freeze-dried to obtain the target catalyst Ni5Fe1 LDH / CeO. 2-x / NF-3.

[0051] Example 4:

[0052] 1) CeO 2-x Preparation of / NF-4

[0053] The nickel foam was sequentially immersed in hydrochloric acid, water, and anhydrous ethanol, and ultrasonically treated for 15 minutes each to prepare 2*1cm preforms. 2 Electrodeposition was performed using a three-electrode system: nickel foam as the working electrode, a platinum sheet as the counter electrode, and saturated Ag / AgCl as the reference electrode. The electrolyte was a NaCl:Ce(NO3)3·6H2O mixed solution with a molar ratio of 5:1, at a current density of -0.25 mA cm⁻¹. -2 Under constant conditions, electrodeposition was performed for 1200 s, followed by drying and high-temperature annealing at 500 °C under 10% H2 / Ar conditions to obtain CeO. 2-x / NF-4.

[0054] 2) Ni5Fe1 LDH / CeO 2-x Preparation of / NF-4

[0055] Dissolve 0.291 g nickel nitrate hexahydrate, 0.081 g ferric nitrate nonahydrate, 360 mg uric acid, and 89 mg ammonium fluoride in 30 mL of deionized water and stir mechanically for 20 min to ensure complete dissolution. Transfer the mixed solution to a 50 mL polytetrafluoroethylene hydrothermal reactor, and simultaneously and rapidly add the CeO2 prepared in step 1). 2-x / NF-4(2*1cm 2 The sample was added to the reactor. After sealing, it was heated continuously at 120°C for 12 hours. After heating, it was allowed to cool to room temperature. The nickel foam substrate sample was then removed from the reactor, sonicated three times with deionized water, and subsequently freeze-dried to obtain the target catalyst Ni5Fe1 LDH / CeO. 2-x / NF-4.

[0056] Example 5:

[0057] 1) CeO 2-x Preparation of / NF-1

[0058] Prepared according to the method and conditions of step 1) in Example 1;

[0059] 2) Ni9Fe1 LDH / CeO 2-x Preparation of / NF-1

[0060] Dissolve 0.314 g nickel nitrate hexahydrate, 0.0485 g ferric nitrate nonahydrate, 360 mg uric acid, and 89 mg ammonium fluoride in 30 mL of deionized water and stir mechanically for 20 min to ensure complete dissolution. Transfer the mixed solution to a 50 mL polytetrafluoroethylene hydrothermal reactor, and simultaneously and rapidly add the CeO2 prepared in step 1). 2-x / NF-1(2*1cm 2 The sample was added to the reactor. After sealing, it was heated continuously at 120°C for 12 hours. After heating, it was allowed to cool to room temperature. The nickel foam substrate sample was then removed from the reactor, sonicated three times with deionized water, and subsequently freeze-dried to obtain the target catalyst Ni9Fe1 LDH / CeO. 2-x / NF-1.

[0061] Example 6:

[0062] 1) CeO 2-x Preparation of / NF-1

[0063] Prepared according to the method and conditions of step 1) in Example 1;

[0064] 2) Ni7Fe3 LDH / CeO 2-x Preparation of / NF-1

[0065] Dissolve 0.244 g nickel nitrate hexahydrate, 0.1454 g ferric nitrate nonahydrate, 360 mg uric acid, and 89 mg ammonium fluoride in 30 mL of deionized water and stir mechanically for 20 min to ensure complete dissolution. Transfer the mixed solution to a 50 mL polytetrafluoroethylene hydrothermal reactor, and simultaneously and rapidly add the CeO2 prepared in step 1). 2-x / NF-1(2*1cm 2 The sample was added to the reactor. After sealing, it was heated continuously at 120°C for 12 hours. After heating, it was allowed to cool to room temperature. The nickel foam substrate sample was then removed from the reactor, sonicated three times with deionized water, and subsequently freeze-dried to obtain the target catalyst Ni7Fe3 LDH / CeO. 2-x / NF-1.

[0066] Example 7:

[0067] 1) CeO 2-x Preparation of / NF-1

[0068] Prepared according to the method and conditions of step 1) in Example 1;

[0069] 2) Ni7Fe1 LDH / CeO 2-x Preparation of / NF-1

[0070] Dissolve 0.3053 g of nickel nitrate hexahydrate, 0.0606 g of ferric nitrate nonahydrate, 360 mg of uric acid, and 89 mg of ammonium fluoride in 30 mL of deionized water and stir mechanically for 20 min to ensure complete dissolution. Transfer the mixed solution to a 50 mL polytetrafluoroethylene hydrothermal reactor, and simultaneously and rapidly add the CeO2 prepared in step 1). 2-x / NF-1(2*1cm 2 The sample was added to the reactor. After sealing, it was heated continuously at 120°C for 12 hours. After heating, it was allowed to cool to room temperature. The nickel foam substrate sample was then removed from the reactor, sonicated three times with deionized water, and subsequently freeze-dried to obtain the target catalyst Ni7Fe1 LDH / CeO. 2-x / NF-1.

[0071] Example 8:

[0072] 1) CeO 2-x Preparation of / NF-1

[0073] Prepared according to the method and conditions of step 1) in Example 1;

[0074] 2) Ni3Fe1 LDH / CeO 2-x Preparation of / NF-1

[0075] Dissolve 0.262 g nickel nitrate hexahydrate, 0.121 g ferric nitrate nonahydrate, 360 mg uric acid, and 89 mg ammonium fluoride in 30 mL of deionized water and stir mechanically for 20 min to ensure complete dissolution. Transfer the mixed solution to a 50 mL polytetrafluoroethylene hydrothermal reactor, and simultaneously and rapidly add the CeO2 prepared in step 1). 2-x / NF-1(2*1cm 2 The sample was added to the reactor. After sealing, it was heated continuously at 120°C for 12 hours. After heating, it was allowed to cool to room temperature. The nickel foam substrate sample was then removed from the reactor, sonicated three times with deionized water, and subsequently freeze-dried to obtain the target catalyst Ni3Fe1 LDH / CeO. 2-x / NF-1.

[0076] Example 9:

[0077] 1) CeO 2-x Preparation of / NF-1

[0078] Prepared according to the method and conditions of step 1) in Example 1;

[0079] 2) Ni1Fe1 LDH / CeO 2-x Preparation of / NF-1

[0080] Dissolve 0.1745 g of nickel nitrate hexahydrate, 0.2424 g of ferric nitrate nonahydrate, 360 mg of uric acid, and 89 mg of ammonium fluoride in 30 mL of deionized water and stir mechanically for 20 min to ensure complete dissolution. Transfer the mixed solution to a 50 mL polytetrafluoroethylene hydrothermal reactor, and simultaneously and rapidly add the CeO2 prepared in step 1). 2-x / NF-1(2*1cm 2 The sample was added to the reactor. After sealing, it was heated continuously at 120°C for 12 hours. After heating, it was allowed to cool to room temperature. The nickel foam substrate sample was then removed from the reactor, sonicated three times with deionized water, and subsequently freeze-dried to obtain the target catalyst Ni1Fe1 LDH / CeO. 2-x / NF-1.

[0081] Example 10:

[0082] 1) CeO 2-x Preparation of / NF-1

[0083] Prepared according to the method and conditions of step 1) in Example 1;

[0084] 2) Ni3Fe7 LDH / CeO 2-x Preparation of / NF-1

[0085] Dissolve 0.1047 g nickel nitrate hexahydrate, 0.3394 g ferric nitrate nonahydrate, 360 mg uric acid, and 89 mg ammonium fluoride in 30 mL of deionized water and stir mechanically for 20 min to ensure complete dissolution. Transfer the mixed solution to a 50 mL polytetrafluoroethylene hydrothermal reactor, and simultaneously and rapidly add the CeO2 prepared in step 1). 2-x / NF-1(2*1cm 2 The sample was added to the reactor. After sealing, it was heated continuously at 120°C for 12 hours. After heating, it was allowed to cool to room temperature. The nickel foam substrate sample was then removed from the reactor, sonicated three times with deionized water, and subsequently freeze-dried to obtain the target catalyst Ni3Fe7 LDH / CeO. 2-x / NF-1.

[0086] Example 11:

[0087] 1) CeO 2-x Preparation of / NF-1

[0088] Prepared according to the method and conditions of step 1) in Example 1;

[0089] 2) Ni1Fe9 LDH / CeO 2-x Preparation of / NF-1

[0090] Dissolve 0.035 g nickel nitrate hexahydrate, 0.4363 g ferric nitrate nonahydrate, 360 mg urea, 200 μm hydrogen peroxide, and 89 mg ammonium fluoride in 30 mL of deionized water and stir mechanically for 20 min to ensure complete dissolution. Transfer the mixed solution to a 50 mL polytetrafluoroethylene hydrothermal reactor, and simultaneously and rapidly add the CeO2 prepared in step 1). 2-x / NF-1(2*1cm 2 The sample was added to the reactor. After sealing, it was heated continuously at 120°C for 12 hours. After heating, it was allowed to cool to room temperature. The nickel foam substrate sample was then removed from the reactor, sonicated three times with deionized water, and subsequently freeze-dried to obtain the target catalyst Ni1Fe9LDH / CeO. 2-x / NF-1.

[0091] Electrochemical activation and electrochemical performance testing of electrocatalysts prepared in Examples 1-11

[0092] (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 two-dimensional nanosheet electrocatalyst obtained after electrochemical activation in Example 1 is the electrocatalyst described in this invention, with the chemical formula Ni5Fe1LDH / CeO. 2-x / NF-3. Polarization curves were obtained by linear sweep voltammetry (LSV) 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 50 for 200 hours; see the stability test curve for details. Figure 3 All electrode potential data were compensated for with 85% voltage drop.

[0093] (2) A small portion of the catalyst supported on nickel foam prepared after electrochemical activation in Example 1 was cut and tested using SEM. It has a two-dimensional nanosheet structure. See [link to SEM]. Figure 5 .

[0094] (3) A certain amount of the electrocatalyst prepared in Example 1 and supported on nickel foam was cut and its UV-Vis absorption spectrum was tested. It was observed that -OOH compounds were formed after electrochemical activation. See [link to relevant documentation]. Figure 6 .

[0095] (4) A certain amount of the catalyst prepared in Example 1 and loaded onto nickel foam was cut and its photoelectron spectroscopy was tested. The precipitation of Ni, Fe, and Ce elements on the surface of the material after chemical activation was observed. (See [reference]) Figure 7 .

[0096] (5) An XRD pattern of a certain amount of the catalyst prepared in Example 1 was tested. It can be seen that it has a similar crystal structure to that of Examples 2, 3, and 4. See [link to XRD pattern]. Figure 8 .

[0097] Comparative Example 1:

[0098] The size is 2*1cm 2 The nickel foam was sequentially ultrasonicated with hydrochloric acid (1 mol / L), ethanol, and deionized water for 15 min, then cleaned and dried with compressed nitrogen. 0.291 g of nickel nitrate hexahydrate, 0.081 g of ferric nitrate nonahydrate, 360 mg of uric acid, and 89 mg of ammonium fluoride were dissolved in 30 mL of deionized water and mechanically stirred for 20 min to ensure complete dissolution. The mixed solution was transferred to a 50 mL polytetrafluoroethylene hydrothermal reactor, and the pre-prepared nickel foam was quickly added to the reactor. After sealing, the reactor was heated at 120 °C for 12 h. After heating, the reactor was cooled to room temperature, and the nickel foam substrate sample was removed from the reactor. It was ultrasonicated three times with deionized water and then freeze-dried to obtain the target catalyst Ni5Fe1 LDH / NF.

[0099] Comparative Example 2:

[0100] 1) Preparation of CeO2 / NF

[0101] Pre-fabricate 2*1cm according to the processing method in Example 1. 2 Electrodeposition was performed using a three-electrode system: nickel foam as the working electrode, a platinum sheet as the counter electrode, and saturated Ag / AgCl as the reference electrode. The electrolyte was a NaCl:Ce(NO3)3·6H2O mixed solution with a molar ratio of 5:1, at a current density of -0.25 mA cm⁻¹. -2 Under constant conditions, electrodeposition was performed with a deposition time of 900s, and CeO2 / NF was obtained after drying.

[0102] 2) Preparation of Ni5Fe1 LDH / CeO2 / NF

[0103] Dissolve 0.291 g nickel nitrate hexahydrate, 0.081 g ferric nitrate nonahydrate, 360 mg uric acid, and 89 mg ammonium fluoride in 30 mL of deionized water and mechanically stir for 20 min to ensure complete dissolution. Transfer the mixed solution to a 50 mL polytetrafluoroethylene hydrothermal reactor, and simultaneously and rapidly add the CeO2 / NF (2*1 cm⁻¹) prepared in step 1). 2 The sample was added to the reactor. After sealing, it was heated continuously at 120°C for 12 hours. After heating, it was allowed to cool to room temperature. The foamed nickel substrate sample was then removed from the reactor, sonicated three times with deionized water, and then freeze-dried to finally obtain the target catalyst Ni5Fe1 LDH / CeO2 / NF.

[0104] Comparative Example 3:

[0105] 1) CeO 2-x Preparation of / NF-1

[0106] Pre-fabricate 2*1cm according to the processing method in Example 1. 2 Electrodeposition was performed using a three-electrode system: nickel foam as the working electrode, a platinum sheet as the counter electrode, and saturated Ag / AgCl as the reference electrode. The electrolyte was a NaCl:Ce(NO3)3·6H2O mixed solution with a molar ratio of 5:1, at a current density of -0.25 mA cm⁻¹. -2 Under constant conditions, electrodeposition was performed for 900 s, followed by drying and high-temperature annealing at 500 °C under 10% H2 / Ar conditions to obtain CeO. 2-x / NF-1.

[0107] 2) Ni LDH / CeO 2-x Preparation of / NF-1

[0108] Dissolve 0.349 g of nickel nitrate hexahydrate, 360 mg of uric acid, and 89 mg of ammonium fluoride in 30 mL of deionized water and stir mechanically for 20 min to ensure complete dissolution. Transfer the mixed solution to a 50 mL polytetrafluoroethylene hydrothermal reactor, and simultaneously and rapidly add the CeO2 prepared in step 1). 2-x / NF-1(2*1cm 2 The sample was added to the reactor. After sealing, it was heated continuously at 120°C for 12 hours. After heating, it was allowed to cool to room temperature. The nickel foam substrate sample was then removed from the reactor, sonicated three times with deionized water, and subsequently freeze-dried to obtain the target catalyst NiLDH / CeO. 2-x / NF-1.

[0109] Comparative examples show that:

[0110] Figure 1 Example 1 (Ni5Fe1 LDH / CeO) 2-x Comparative Example 1 (Ni5Fe1 LDH / NF), Comparative Example 2 (Ni5Fe1 LDH / CeO2 / NF-1), and Comparative Example 3 (Ni LDH / CeO2 / NF-1). 2-x The electrocatalyst prepared by / NF-1) was subjected to linear sweep voltammetry (LSV) in 1M KOH solution at a scan rate of 1 mV / s to obtain polarization curves. As shown in the figure, the current density reached 10 mA / cm². 2 At that time, Ni5Fe1LDH / CeO 2-x The / NF-1 catalyst exhibits the lowest overpotential, indicating that Ni5Fe1 LDH and CeO2... 2-x The synergistic effect of these factors improved the oxygen evolution catalytic performance.

[0111] Figure 2 Example 1 (Ni5Fe1 LDH / CeO) 2-x Comparative Example 1 (Ni5Fe1 LDH / NF), Comparative Example 2 (Ni5Fe1 LDH / CeO2 / NF-1), and Comparative Example 3 (Ni LDH / CeO2 / NF-1). 2-x The OER AC impedance spectrum of the electrocatalyst prepared by / NF-1) in 1M KOH solution is shown in the figure. As can be seen from the figure, Ni5Fe1LDH / CeO 2-x The / NF-1 catalyst exhibits the lowest interfacial resistance, indicating that Ni5Fe1 LDH and CeO2... 2-x The synergistic effect of these factors promotes the catalytic kinetics of the electrochemical reaction.

[0112] Figure 4 The morphology of Comparative Example 1 (Ni5Fe1 LDH / NF) is shown in the scanning electron microscope image. Figure 5Example 1 (Ni5Fe1 LDH / CeO) 2-x The scanning electron microscope (SEM) images of Ni5Fe1LDH / CeO are shown in the image comparison. 2-x The polymorphic morphology of the / NF-1 catalyst exhibits a higher exposed specific surface area.

[0113] Figure 6 Example 1 (Ni5Fe1 LDH / CeO) 2-x The UV-Vis absorption spectra of the electrocatalysts prepared by Example 1 (Ni5Fe1 LDH / NF-1) and Comparative Example 1 (Ni5Fe1 LDH / NF) are shown in the figures. As can be seen from the figures, under the same driving conditions, the Ni5Fe1 LDH / CeO... 2-x The / NF-1 catalyst preferentially exhibited oxygen evolution activity, and the high-valence active substance NiOOH was detected.

[0114] In summary, a novel non-precious metal-based alkaline electrocatalyst for oxygen evolution reaction in water electrolysis and its preparation method are presented. Through in-situ electrodeposition and hydrothermal reaction, activation results in a novel material structure suitable for oxygen evolution reaction in water under alkaline conditions. The catalyst material exhibits significantly improved activity compared to comparative examples of hydroxide catalysts lacking electrochemical activity, while maintaining excellent stability.

[0115] 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 method for preparing a highly active alkaline catalyst for oxygen evolution reaction in water electrolysis based on transition metals, comprising the following specific steps: 1) CeO 2-x / NF preparation Pre-treated nickel foam was used as the working electrode, a platinum sheet as the counter electrode, and saturated Ag / AgCl as the reference electrode. A 2 mM Ce(NO3)3·6H2O and 10 mM NaCl solution was used as the electrolyte. At 70 °C, the current density was -0.25 mA cm⁻¹. -2 Under constant current electrodeposition conditions with deposition times of 300–1200 s, CeO2 nanoparticles were grown on the surface of nickel foam. The CeO2 / NF was then subjected to high-temperature annealing at 500 °C under 10% H2 / Ar conditions to obtain CeO2 nanoparticles with high oxygen vacancies. 2-x / NF; 2) Ni m Fe n LDH / CeO 2-x / NF preparation Keeping the total molar amount of nitrates corresponding to Ni and Fe constant, dissolve them in deionized water at molar ratios of 1:0, 9:1, 7:1, 5:1, 4:1, 3:1, 1:1, 7:3, 3:7, or 1:9 respectively. Add the pre-prepared solution containing urea and ammonium fluoride to the above solution and stir to mix them evenly. After the solutions are thoroughly mixed, a precursor mixture solution is obtained. This solution is then transferred to a polytetrafluoroethylene hydrothermal reactor, and CeO2 prepared in step 1) is added. 2-x / NF, and heat it at 120℃ for 6~12h. After cooling to room temperature, the obtained product is ultrasonically treated, washed with deionized water, and then vacuum dried to obtain an electrode with precursor loaded on a nickel foam substrate. 3) The nickel foam electrode loaded with the precursor was fixed with a platinum sheet electrode clamp and electrochemically activated in a three-electrode system with 1 M KOH electrolyte to finally obtain a two-dimensional nanosheet electrocatalyst. The electrolyte in step 1) is a mixture of cerium nitrate hexahydrate and sodium chloride; the nitrates corresponding to Ni and Fe in step 2) are nickel nitrate hexahydrate and ferric nitrate nonahydrate, respectively. The pretreatment method for the nickel foam is as follows: the nickel foam is sequentially immersed in hydrochloric acid, water, and anhydrous ethanol and ultrasonicated for 15 minutes each. The electrochemical activation method of the three-electrode system is as follows: a nickel foam electrode loaded with 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 0-0.8 V, CV activation is performed, the scan rate is 50 mV / s, and the number of cycles is set to 50.

2. The method for preparing a highly active alkaline alkaline electrocatalyst for oxygen evolution reaction in water electrolysis based on transition metals according to claim 1, characterized in that, In step 1), the electrodeposition times are set to 300s, 600s, 900s, and 1200s, respectively.

3. A highly active alkaline water electrolysis oxygen evolution reaction catalyst based on a transition metal obtained by the preparation method of claim 1 or 2, characterized in that, The electrocatalyst is a heterogeneous structure composed of deposited cerium dioxide nanoparticles with multiple oxygen vacancies and nickel-iron-based double hydroxide nanosheets. The catalyst has a disordered, amorphous, two-dimensional nanosheet structure and is prepared using a constant current technique. The catalyst is grown in situ on nickel foam and described as Ni... m Fe n LDH / CeO 2-x / NF, in which the content ratio of Ce, Ni and Fe elements is 2:1:0.

2.

4. The highly active alkaline water electrolysis oxygen evolution reaction catalyst based on transition metals according to claim 3, characterized in that, The catalyst exhibits an electrocatalytic activity of 10 mA / cm² in an alkaline medium at pH 13.

8. 2 The overpotential range required for the catalytic current density is 160–200 mV.

5. The highly active alkaline alkaline water electrolysis oxygen evolution reaction catalyst based on transition metals according to claim 3, characterized in that, The catalyst is at 50 mA / cm 2 Stable operation time exceeds 200 hours under current density conditions.

6. The application of the highly active alkaline water electrolysis oxygen evolution reaction catalyst based on any one of claims 4-5 in the oxygen evolution reaction under alkaline conditions.

Images