Preparation of anode catalyst for hydrogen production by high current density electrolysis of water and electrolysis device

Abstract

Preparation of anode catalyst for hydrogen production by high current density electrolysis of water and electrolysis device. The catalyst preparation method comprises: dissolving nickel nitrate in anhydrous ethanol to form a first solution; dropwise adding an aqueous ferrous sulfate solution to the first solution to form a second solution, wherein the concentration of nickel nitrate is 0.1-0.2 mol / L, the concentration of ferrous sulfate is 0.02-0.04 mol / L, and the volume ratio of ethanol to water is (2-4):1; placing a foamed nickel support substrate into the second solution, taking out the loaded intermediate after standing; dissolving ferric nitrate in a mixed solution of anhydrous ethanol and water to form a third solution, wherein the concentration of ferric nitrate is 2-4 mmol / L, and the volume ratio of ethanol to water is (2-4):1; taking the loaded intermediate as a working electrode, taking the third solution as an electrolyte, and performing constant-voltage electrodeposition to form a supported anode catalyst on the loaded intermediate. Thus, a self-supporting electrocatalyst is obtained, which can be efficiently and stably used for industrial high current density alkaline water electrolysis for hydrogen production.

Description

Technical Field

[0001] This application relates to a catalyst for hydrogen production by water electrolysis, particularly the preparation and application of an anode catalyst. Background Technology

[0002] Developing water electrolysis for hydrogen production technology is of vital strategic value for promoting the green transformation of the energy structure, achieving efficient storage and utilization of clean energy, and contributing to the achievement of global carbon neutrality goals. Electrocatalysts play a crucial role in the entire water electrolysis hydrogen production system, significantly and directly impacting the efficiency and cost of the process.

[0003] However, most current research on catalysts for hydrogen production through water electrolysis is still focused on low current densities (less than 200 mA cm⁻¹). -2 The laboratory conditions are not suitable for industrialization; for example, the preparation methods disclosed in CN121781196A, CN122466507A, CN117779079A, CN118422258A, etc.

[0004] With the continuous acceleration and in-depth advancement of the industrialization process of hydrogen production through water electrolysis, there is an urgent need for catalysts, especially anolyte catalysts (OER), capable of operating at high current densities (1000 mA cm⁻¹). -2 Under the condition of high current density, long-term stable operation is achieved. In this special operating environment, many phenomena that are almost imperceptible or even negligible under low current density are significantly amplified, leading to a marked decline in catalyst performance and posing a severe challenge to the catalyst's catalytic activity and long-term stability. Specifically: First, the reaction rate accelerates at high current density, generating a large number of bubbles, causing blockage of active sites and hindering mass transfer. Second, at high current density, the rate of multi-electron electrochemical reactions is increased, leading to rapid charge depletion and making charge transfer the rate-limiting step in water electrolysis. Furthermore, the harsh conditions encountered in industrial water electrolysis, such as high pressure, high temperature, and corrosive electrolytes, severely damage the original structure and composition of the electrocatalyst, leading to irreversible deactivation.

[0005] Therefore, achieving high activity and long-term stability of water electrolysis catalysts, especially anode catalysts, under high current density is a key bottleneck restricting the industrialization of water electrolysis hydrogen production technology. Summary of the Invention

[0006] The purpose of this invention is to provide at least one anode catalyst suitable for high current density water electrolysis to produce hydrogen.

[0007] According to a first aspect of the present invention, a method for preparing a supported anode catalyst for hydrogen production by water electrolysis is provided, comprising: Provide clean nickel foam as a load substrate; Nickel nitrate is dissolved in anhydrous ethanol to form the first solution; A second solution is formed by adding an aqueous solution of ferrous sulfate dropwise to the first solution, wherein the concentration of nickel nitrate is 0.1~0.2 mol / L, the concentration of ferrous sulfate is 0.02~0.04 mol / L, and the volume ratio of ethanol to water is (2~4):1; The loaded substrate was placed in the second solution, allowed to stand, and then removed to obtain the loaded intermediate. Ferric nitrate is dissolved in a mixture of anhydrous ethanol and water to form a third solution, wherein the concentration of ferric nitrate is 2~4 mmol / L and the volume ratio of ethanol to water is (2~4):1; Using the supported intermediate as the working electrode and the third solution as the electrolyte, a supported anode catalyst is formed on the supported intermediate by constant voltage electrodeposition.

[0008] According to the preparation method of the present invention, the supported substrate is preferably subjected to ultrasonic treatment in the second solution and then allowed to stand. The ultrasonic treatment time is preferably not less than 5 min, and the standing time is preferably not less than 10 h.

[0009] According to the preparation method of the present invention, the preferred voltage range for electrodeposition is -1.2 to -0.8 V vs. Ag / AgCl, for example -1.0 V vs. Ag / AgCl.

[0010] According to a preferred embodiment of the preparation method of the present invention, the concentration of nickel nitrate in the second solution can be 0.3 mol / L, the concentration of ferrous sulfate can be 0.03 mol / L, and the volume ratio of ethanol to water can be 3:1; the concentration of ferrous nitrate in the third solution can be 3 mmol / L, and the volume ratio of ethanol to water can be 3:1.

[0011] According to another aspect of the present invention, an anion exchange membrane water electrolysis apparatus is also provided, which uses a supported anode catalyst prepared by the above method as the anode to electrolyze alkaline water to produce hydrogen, wherein the current density used is not less than 900 mA cm⁻¹. -2 For example, 1000 mA cm -2 .

[0012] Electrolysis can be carried out at temperatures above 55°C, such as 60°C. Additionally, the alkaline water can contain a strong base, such as 6 mol / L KOH.

[0013] This invention forms a specific form of nickel-iron catalyst in situ on a supported substrate of nickel foam by impregnation, and then further introduces iron elements on the catalyst surface by electrodeposition to enhance the overall bonding (the bond strength of Fe-O and Ni-O bonds is enhanced).

[0014] The preparation method of this invention successfully obtained a self-supporting NiFe-LDH electrocatalyst: a nickel-iron layered bimetallic hydroxide is grown in situ on the surface of nickel foam, which can be used efficiently and stably for industrial-grade high-current-density alkaline water electrolysis to produce hydrogen.

[0015] The catalyst preparation method of the present invention is simple to operate and has mild reaction conditions, making it particularly suitable for industrial-scale preparation.

[0016] In summary, the catalyst prepared in this invention exhibits excellent electrochemical performance: the NiFe-LDH(SE) of this invention has an OER overpotential of only 208 mV (without ohmic drop compensation) at 60 °C and 6 mol / L KOH, and shows no significant voltage decay in a 168 h galvanostatic stability test. Compared to other types of catalysts, the NiFe-LDH(SE) of this invention has the largest electrochemical active surface area, allowing for the loading of more active sites. Furthermore, the NiFe-LDH(SE) of this invention has the lowest charge transfer resistance and faster charge transfer kinetics. Attached Figure Description

[0017] Figure 1 The X-ray diffraction pattern of the catalyst prepared according to the present invention is shown below. Figure 2 A scanning electron microscope image of the catalyst prepared according to the present invention; Figure 3 X-ray energy dispersive spectroscopy (EDS) of the catalyst prepared according to the present invention; Figure 4a The corresponding linear sweep voltammetry curves for the oxygen evolution reaction of each catalyst are shown. Figure 4b The corresponding Tafel slope is shown; Figure 4c The corresponding electrochemical impedance spectroscopy is shown; Figure 4d The corresponding double-layer capacitance is shown; Figure 4e The corresponding constant current stability test curve is shown. Figure 5 Linear sweep voltammetry curves of a water electrolyzer assembled according to the present invention are shown; Figure 6 The constant current stability test curve of the water electrolyzer assembled according to the present invention is shown. Detailed Implementation

[0018] The present invention will be further explained and described below through specific embodiments and in conjunction with the accompanying drawings.

[0019] Example

[0020] Nickel foam (area: 1.0 × 2.0 cm) 2(Thickness: 1.0 mm) was ultrasonically cleaned sequentially with acetone, 3 mol / L hydrochloric acid, deionized water, and anhydrous ethanol for 30 min, and then set aside for use. Weigh 2.541 g of nickel nitrate hexahydrate and dissolve it in 45 mL of anhydrous ethanol. Weigh 0.486 g of ferrous sulfate heptahydrate and dissolve it in 15 mL of water. Under vigorous stirring (800 rpm), slowly add the ferrous sulfate heptahydrate aqueous solution to the ethanol solution of nickel nitrate hexahydrate and mix evenly to obtain a mixed solution. Nickel foam was placed in the above mixed solution and sonicated for 10 min. After standing at room temperature for 24 h, it was taken out and washed with anhydrous ethanol to obtain the electrocatalyst NiFe-LDH(S). Weigh 0.0848 g of ferric nitrate nonahydrate and dissolve it in 70 mL of a mixed solution of ethanol and water (the volume ratio of anhydrous ethanol to deionized water is 3:1). Mix well to obtain the electrolyte. Using NiFe-LDH(S) as the working electrode, a platinum sheet as the counter electrode, and an Ag / AgCl electrode as the reference electrode, a constant potential electrodeposition was performed in the above electrolyte at a potential of -1.0 V vs. Ag / AgCl for 200 s. After removal, the electrode was washed with deionized water and dried naturally at room temperature to obtain the electrocatalyst NiFe-LDH(SE).

[0021] Figure 1 The X-ray diffraction pattern of the obtained electrocatalyst NiFe-LDH(SE) is shown below. Figure 2 Its scanning electron microscope image; Figure 3 Its X-ray energy dispersive spectrum (EDS) is shown.

[0022] Comparative Example 1 The electrocatalyst NiFe-LDH(S) was obtained only according to the examples.

[0023] Comparative Example 2 Weigh out 0.3053 g of nickel nitrate hexahydrate and 0.0584 g of ferrous sulfate heptahydrate, respectively, and dissolve them in 70 ml of a mixed solution of ethanol and water (the volume ratio of anhydrous ethanol to deionized water is 3:1). Mix them evenly to obtain the electrolyte. Nickel foam (area: 1.0 × 2.0 cm) 2 A platinum sheet (thickness: 1.0 mm) was used as the working electrode, an Ag / AgCl electrode as the reference electrode, and a constant potential electrodeposition was performed in the above electrolyte at a potential of -1.0 V vs. Ag / AgCl for 700 s. The electrode was then removed, washed with deionized water, and naturally dried at room temperature to obtain the electrocatalyst NiFe-LDH(E).

[0024] Comparative Example 3 12 μL of Nafion, 0.15 mL of anhydrous ethanol, and 0.15 mL of isopropanol were transferred to a container, and 3 mg of RuO2 was added. After mixing thoroughly, the mixture was ultrasonically dispersed for 30 min to obtain a catalyst slurry. The slurry was then uniformly drop-coated onto a cleaned nickel foam substrate (area: 1.0 × 2.0 cm). 2 The RuO2 electrode sheet was obtained by drying the RuO2 electrode sheet in a vacuum oven at 60℃ (thickness: 1.0 mm).

[0025] Test Example 1: Electrocatalytic Oxygen Evolution Reaction All electrochemical tests were performed at 60 °C, with 6 mol / L KOH, using a three-electrode system. A platinum mesh was used as the counter electrode, and Hg / HgO was used as the reference electrode. The catalysts prepared in the examples and the samples prepared in the comparative examples were used as working electrodes, respectively. Before the electrochemical tests, the working electrodes were electrochemically activated by cyclic voltammetry for 30 cycles at a scan rate of 100 mV / s. -1 .

[0026] Figure 4a The corresponding linear sweep voltammetric curves of the oxygen evolution reaction of the electrocatalyst NiFe-LDH(SE) and each comparative sample are shown. Figure 4b The corresponding Tafel slope is shown; Figure 4c The corresponding electrochemical impedance spectroscopy is shown; Figure 4d The corresponding double-layer capacitance is shown; Figure 4e The corresponding constant current stability test curve is shown.

[0027] Test Example 2: Complete water electrolysis reaction in an anion exchange membrane water electrolyzer Using NiFe-LDH(SE) as the anode, Pt / C as the cathode, and KMem AM01 anion exchange membrane as the intermediate separator, an anion exchange membrane water electrolyzer was assembled and a complete water electrolysis test was conducted at 60℃ and 6 mol / L KOH. Figure 5 Its linear sweep voltammetry curve is shown. Figure 6 The constant current stability test curve is shown.

[0028] Performance test results analysis (1) Structural characterization of NiFe-LDH(SE) from Figure 1 The X-ray diffraction patterns show that the synthesized NiFe-LDH(S) and NiFe-LDH(SE) highly match the standard card PDF#00-036-0382, both belonging to nickel-iron layered bimetallic hydroxides. The X-ray diffraction pattern of NiFe-LDH(SE) does not show any new diffraction peaks compared to NiFe-LDH(S), because the iron species electrodeposited on the surface are in an amorphous state. Figure 2Scanning electron microscopy (SEM) images of NiFe-LDH(SE) show that its morphology consists of interwoven, stacked nanosheets, which is highly beneficial for mass transfer. Furthermore, Figure 3 X-ray energy dispersive spectroscopy showed that Ni, Fe, and O elements were uniformly distributed on the surface of the NiFe-LDH(SE) electrocatalyst, without agglomeration or segregation.

[0029] (2) Electrochemical testing of NiFe-LDH(SE) In the oxygen evolution reaction, Figure 4a The results show that NiFe-LDH(SE) at 1 A cm⁻¹ -2 The OER overpotential under high current density is only 208 mV (without ohmic drop compensation), which is significantly better than the comparative samples (NiFe-LDH(S), NiFe-LDH(E), RuO2 and NF (simple nickel foam substrate). Figure 4b NiFe-LDH(SE) has 87 mV dec -1 This indicates that the OER reaction kinetics are good. Figure 4c NiFe-LDH(SE) exhibits the lowest charge transfer resistance, indicating superior charge transfer kinetics. Figure 4d NiFe-LDH (SE) has a smaller electrochemical active surface area, which allows it to load more active sites. Figure 4e The results showed that at 60 °C, 6 mol / L KOH, and 1000 mA cm⁻¹ -2 After a 168-hour constant current stability test under the specified conditions, the voltage of the NiFe-LDH(SE) electrocatalyst showed no significant decrease, with a voltage decay rate of only 0.365 mV / h. -1 This indicates excellent stability.

[0030] (3) Test of complete water electrolysis in anion exchange membrane water electrolyzer like Figure 5 As shown, the electrolytic cell using NiFe-LDH(SE) as the anode in this embodiment achieves a current density as high as 4.5 A cm⁻¹ at a cell voltage of 1.8 V. -2 (Electrode area: 2×2 cm) -2 ) or 4.3 A cm -2 (Electrode area: 1×1 cm) -2 This already far exceeds the performance target for anion exchange membrane water electrolyzers set by the U.S. Department of Energy (DOE) for 2035 (1.8 V cell current density reaching 3 A cm⁻¹). -2 ). Figure 6 The results were displayed at 60℃, 6 mol / L KOH, and 1000 mA cm⁻¹ -2Under these conditions, a constant current stability test was conducted for 1100 hours. The cell voltage of the anion exchange membrane water electrolyzer remained relatively stable, with a voltage decay rate of only 0.016 mVh. -1 This indicates that NiFe-LDH(SE) has excellent stability.

[0031] In summary, the catalyst prepared by this invention exhibits excellent electrochemical performance and long-term stability under high current density.

Claims

1. A method for preparing a supported anode catalyst for hydrogen production by water electrolysis, comprising: Provide clean nickel foam as a load substrate; Nickel nitrate is dissolved in anhydrous ethanol to form the first solution; A second solution is formed by adding an aqueous solution of ferrous sulfate dropwise to the first solution, wherein the concentration of nickel nitrate is 0.1~0.2 mol / L, the concentration of ferrous sulfate is 0.02~0.04 mol / L, and the volume ratio of ethanol to water is (2~4):1; The loaded substrate was placed in the second solution, allowed to stand, and then removed to obtain the loaded intermediate. Ferric nitrate is dissolved in a mixture of anhydrous ethanol and water to form a third solution, wherein the concentration of ferric nitrate is 2-4 mmol / L and the volume ratio of ethanol to water is (2-4):

1. Using the supported intermediate as the working electrode and the third solution as the electrolyte, a supported anode catalyst is formed on the supported intermediate by constant voltage electrodeposition.

2. The preparation method according to claim 1, wherein the loaded substrate is subjected to ultrasonic treatment in the second solution and then allowed to stand.

3. The preparation method according to claim 1, wherein the voltage range used for electrodeposition is -1.2 to -0.8 V vs. Ag / AgCl.

4. An anion exchange membrane water electrolysis device, using a supported anode catalyst prepared according to any one of claims 1-3 as the anode for electrolyzing alkaline water to produce hydrogen, wherein the current density used is not less than 900 mA cm⁻¹ -2 .

5. The anion exchange membrane water electrolysis device according to claim 4, wherein electrolysis is carried out at a temperature above 55°C.

Images