Novel acidic electrolytic water oxygen evolution reaction electrocatalyst and preparation method thereof

Abstract

The invention discloses a novel acidic electrolytic water oxygen evolution reaction electrocatalyst and a preparation method thereof.The electrocatalyst is a novel material with foamed nickel as a substrate, and the preparation method of the material comprises the steps that pretreated foamed nickel is soaked in a RuCl3 aqueous solution; taking out after a certain period of time, dipping in an ammonia water solution of potassium permanganate and dopamine hydrochloride for reaction, and finally roasting in an inert atmosphere. According to the method for preparing the electrocatalyst for the acidic water electrolysis oxygen evolution reaction, Ru is uniformly dispersed in the foamed nickel substrate and is low in loading capacity, in the 0.5 M H2SO4 acidic water electrolysis oxygen evolution reaction, under the current density of 10 mA cm <-2 >, the overpotential is only 174 mv, and the stability exceeds 44 h. According to the invention, the problems of poor activity, poor stability and high cost of the OER catalyst in the process of hydrogen production by electrolyzing water with an acidic electrolyte are solved.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalytic materials application, specifically relating to a novel electrocatalytic material and its preparation method, particularly to a novel acidic water electrolysis oxygen evolution reaction electrocatalyst material and its preparation method for a highly efficient acidic oxygen evolution reaction. Background Technology

[0002] With the depletion of fossil fuels and increasingly severe environmental problems, developing new energy sources to replace traditional fossil fuels has become a focus. Hydrogen energy, as a green energy source that is abundant, efficient, environmentally friendly, storable, and renewable, has attracted much attention. Depending on the preparation method, hydrogen is mainly divided into gray hydrogen and green hydrogen. Currently, over 95% of hydrogen comes from gray hydrogen produced by fossil fuel reforming, but this method also generates various pollutants. Green hydrogen, produced by electrolyzing water using renewable energy, does not produce air pollutants, does not require fossil fuels, and produces no carbon emissions, making it a green and environmentally friendly hydrogen production method.

[0003] Depending on the properties of the water electrolyzed, the preparation of green hydrogen can be divided into acidic water electrolysis, alkaline water electrolysis, and neutral water electrolysis. Among these, acidic water electrolysis is more promising due to its high proton conductivity, fast response speed, low ohmic loss, high current density, and high purity of the produced hydrogen. However, acidic water electrolysis has a low pH, and the OER reaction involves water molecule adsorption and desorption, as well as the breaking of H2O bonds. The reaction involves multiple intermediates and requires a significant external potential to overcome the energy barrier, thus posing a greater challenge to improving the stability and activity of OER electrocatalysts.

[0004] Precious metal electrocatalysts such as iridium, ruthenium, and platinum exhibit high reactivity but are expensive. Composite electrocatalysts prepared by doping precious metals with non-precious metals such as Fe, Ni, Co, and Mn are one of the key technologies for achieving large-scale industrial production of green hydrogen, as they improve electrocatalyst activity while reducing catalyst costs.

[0005] Nickel foam is a three-dimensional porous network-structured metal material composed of elemental nickel. Its good electrical conductivity and uniform porous structure make it one of the preferred materials for preparing electrocatalysts. Patent No. CN117966193A proposed a method for preparing a ruthenium-loaded molybdenum nitride / nickel foam composite material. Patent No. CN117966173A proposed a method for preparing a ruthenium-loaded molybdenum carbide / nickel foam electrocatalyst. Patent No. CN114016050B proposed a method for preparing an iron-molybdenum-doped nickel sulfide / nickel foam electrocatalyst. These electrocatalysts prepared with nickel foam as the carrier all showed good activity and stability in the hydrogen evolution reaction in an alkaline water electrolysis system. However, under acidic conditions, due to the easy acidolysis of nickel foam to form high-valent substances, its stability is poor. Therefore, there is little research on using electrocatalysts prepared with nickel foam as the carrier for the preparation of green hydrogen by acidic water electrolysis.

[0006] Developing low-precious-metal / non-precious-metal OER electrocatalysts with high activity and stability in acidic media is of great significance for improving the efficiency and product quality of green hydrogen production. Patent No. CN117699870A prepared a Se-RuO2AS catalyst using carbon black as the carrier. In the electrochemical test under acidic conditions, the overpotential was 166 mV at a current density of 10 mA cm -2 and the stability reached 48 h, where the atomic ratio of Ru / Se was about 88.1:11.9 and the Ru content was relatively high. Patent No. CN117468033A proposed a synthesis method for Ru 1-x Zr x O2(0 < x < 1) acidic oxygen evolution catalyst. The reported example of Ru 0 .90 Zr 0 .10 O2 had an overpotential of 170 mV at a current density of 10 mA cm -2 and lacked stability and had a relatively high Ru content. Patent No. CN117684183A disclosed a Ru-containing metal-organic catalyst. In the acidic oxygen evolution reaction, the optimal overpotential example at a current density of 10 mA cm -2 was 225 mV and the stability reached 100 h, and the Ru loading was 1.6 mg cm -2 , with a relatively high content. The catalysts prepared in the above patents showed good reaction activity in the acidic OER reaction, but the preparation process was relatively complex, the cost was high, and the prepared catalysts were all in powder form and still needed to be further processed into electrode integrated materials.

[0007] Developing low-precious-metal / non-precious-metal OER electrocatalysts with simple processes, high activity, high stability, and low cost in acidic media is of great significance for improving the efficiency and product quality of green hydrogen production. Summary of the Invention

[0008] This invention relates to a method for preparing a highly active, highly stable, and low-cost acidic OER catalyst by using low-cost porous nickel foam as a carrier, loading trace amounts of precious metals, and then modifying the surface.

[0009] The technical solution of this invention:

[0010] A novel acidic electrocatalyst for oxygen evolution reaction in water electrolysis is disclosed. The catalyst mainly contains Ru, Ni, O, and C elements, which can prevent Ni from being corroded from the outside in and inherit the original porous framework of nickel foam.

[0011] This invention also provides a novel method for preparing a ruthenium-based acidic electrocatalyst for oxygen evolution reaction in water electrolysis based on nickel foam. The preparation steps are as follows:

[0012] (1) Pretreatment of nickel foam substrate. The substrate was ultrasonically cleaned with acetone and 1M HCl for 10-30 min, then rinsed several times with deionized water and anhydrous ethanol, and finally dried at 40℃~60℃.

[0013] (2) Prepare a 0.1~1% RuCl3 aqueous solution, then immerse the nickel foam in it, and then seal both and place them in an environment of 40-100℃ for 5~15h.

[0014] (3) Remove the nickel foam, rinse it, and dry it at 80~100℃. At the same time, prepare an ammonia solution containing potassium permanganate and dopamine hydrochloride. Put the nickel foam into it and react for 10~30h.

[0015] (4) Take out the nickel foam, rinse and dry it, and then calcine it at 300~700℃ for 3~6h in an inert gas environment.

[0016] In step (1), the size of the nickel foam is 0.5cm×0.5cm-10cm×10cm.

[0017] In step (2), the Ru-containing salt used is RuCl3 or RuCl3•xH2O or RuCl3•3H2O.

[0018] In step (3), the molar ratio of potassium permanganate to dopamine hydrochloride is 1:5 to 5:5.

[0019] In one embodiment, the nickel foam used for impregnation is 1cm × 2cm, the RuCl3 solution used is 50mmol / 5mL, and the solvent is deionized water; the molar ratio of potassium permanganate to dopamine hydrochloride is 2:5.

[0020] The electrochemical performance of the electrocatalyst for the acidic water electrolysis oxygen evolution reaction is tested using the following steps:

[0021] (1) By cutting the catalyst to a certain area, the part holding the electrode and the part of a specific area are prevented from contacting water; before the reaction, argon gas is introduced until the solution is saturated;

[0022] (2) The electrochemical performance was evaluated in a three-electrode setup with an Ag / AgCl electrode as the reference electrode and a platinum sheet electrode as the counter electrode. The platinum sheet electrode clamp was used as the working electrode. The three-electrode setup was kept in a drying oven at 25°C throughout the process.

[0023] (3) Potential reference reversible hydrogen electrode (RHE): E RHE =E Ag / AgCl +0.1971 +0.059 × pH (0.5 M H₂SO₄ 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 0.5M H₂SO₄ solution at a scan rate of 5mV / s. All electrode potential data were 90% voltage drop compensated.

[0024] The present invention has the following advantages and effects:

[0025] The acidic water electrolysis oxygen evolution reaction electrocatalyst of this invention uses inexpensive nickel foam as a carrier, with the Ni source of the nickel foam itself as one of the active materials. After loading Ru and surface modification, it is finally synthesized by high-temperature calcination in an inert gas environment to produce a high-performance acidic OER catalyst. The catalyst is a self-supporting catalyst, avoiding subsequent processing steps similar to those for powdered catalysts. The catalyst inherits the original pore structure of nickel foam, facilitating the escape of bubbles during oxygen evolution and effectively preventing the formation of a gas film. Attached Figure Description

[0026] Figure 1 This is a flowchart illustrating the experimental process of the present invention;

[0027] Figure 2 This shows the LSV test results corresponding to Example 1 of the present invention (Ru@NF-KPDA-550);

[0028] Figure 3 This shows the constant current test results corresponding to Example 1 of the present invention (Ru@NF-KPDA-550);

[0029] Figure 4 The XRD diffraction pattern of the electrocatalyst prepared in Example 1 of this invention is shown.

[0030] Figure 5 The scanning electron microscope (SEM) test results of the electrocatalyst prepared in Example 1 of this invention are shown. Detailed Implementation

[0031] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] Example 1:

[0033] Pretreated nickel foam was reacted in a 50 mmol / L RuCl3 aqueous solution at 50 °C for 10 hours. A separate 50 mL ammonia solution (pH 8.5) containing 0.2 g dopamine hydrochloride and 0.0695 g potassium permanganate was prepared. The nickel foam was then removed, rinsed with deionized water, and dried at 80 °C. It was then placed in the prepared ammonia solution and reacted at room temperature for 12 hours. The nickel foam was removed, rinsed with deionized water, and dried at 80 °C. The nickel foam was then calcined in a tube furnace at 550 °C under argon atmosphere for 3 hours. After calcination, the material was cooled to room temperature, rinsed with deionized water, and dried overnight at 80 °C to obtain the electrocatalyst. The Ru loading was determined to be 0.066 mg / cm³. -2 At 10mA cm -2 At the required current density, the required overpotential is 174 mV, and the stability is greater than 44 h. Example 1 obtained is the electrocatalyst described in this invention; its XRD diffraction pattern is shown in [reference needed]. Figure 4 .

[0034] Example 2:

[0035] Pretreated nickel foam was reacted in a 40 mmol / L RuCl3 aqueous solution at 50 °C for 10 hours. A separate 50 mL ammonia solution (pH 8.5) containing 0.2 g dopamine hydrochloride and 0.0695 g potassium permanganate was prepared. The nickel foam was then removed, rinsed with deionized water, and dried at 80 °C. It was then placed in the prepared ammonia solution and reacted at room temperature for 24 hours. The nickel foam was removed, rinsed with deionized water, and dried at 80 °C. The nickel foam was then calcined in a tube furnace at 550 °C for 3 hours under argon atmosphere at a heating rate of 5 °C / min. After calcination, the material was cooled to room temperature, rinsed with deionized water, and dried overnight in an oven at 80 °C to obtain the electrocatalyst. The Ru loading was determined to be 0.06 mg / cm³. -2 At 10mA cm -2 At current density, the required overpotential is 185mV, and the stability is greater than 40h.

[0036] Example 3:

[0037] Pretreated nickel foam was reacted in a 50 mmol / L RuCl3 aqueous solution at 50 °C for 10 hours. A separate 50 mL ammonia solution (pH 8.5) containing 0.2 g dopamine hydrochloride and 0.0695 g potassium permanganate was prepared. The nickel foam was then removed, rinsed with deionized water, and dried at 80 °C. It was then placed in the prepared ammonia solution and reacted at room temperature for 10 hours. The nickel foam was removed, rinsed with deionized water, and dried at 80 °C. The nickel foam was then calcined in a tube furnace at 450 °C for 3 hours under argon atmosphere at a heating rate of 5 °C / min. After calcination, the material was cooled to room temperature, rinsed with deionized water, and dried overnight in an oven at 60 °C to obtain the electrocatalyst. The Ru loading was determined to be 0.07 mg / cm³. -2 At 10mA cm -2 At current density, the required overpotential is 180mV, and the stability is greater than 35h.

[0038] Example 4:

[0039] Pretreated nickel foam was reacted in a 50 mmol / L RuCl3 aqueous solution at 50 °C for 15 hours. A separate 50 mL ammonia solution (pH 8.5) containing 0.2 g dopamine hydrochloride and 0.0695 g potassium permanganate was prepared. The nickel foam was then removed, rinsed with deionized water, and dried at 80 °C. It was then placed in the prepared ammonia solution and reacted at room temperature for 24 hours. The nickel foam was removed, rinsed with deionized water, and dried at 80 °C. The nickel foam was then calcined in a tube furnace at 550 °C for 5 hours under argon atmosphere at a heating rate of 5 °C / min. After calcination, the material was cooled to room temperature, rinsed with deionized water, and dried overnight at 80 °C to obtain the electrocatalyst. The Ru loading was determined to be 0.072 mg / cm³. -2 At 10mA cm -2 At current density, the required overpotential is 182mV, and the stability is greater than 40h.

[0040] Example 5:

[0041] Pretreated nickel foam was reacted in a 50 mmol / L RuCl3 aqueous solution at 50 °C for 10 hours. A separate 50 mL ammonia solution (pH 8.5) containing 0.2 g dopamine hydrochloride and 0.0348 g potassium permanganate was prepared. The nickel foam was then removed, rinsed with deionized water, and dried at 80 °C. It was then placed in the prepared ammonia solution and reacted at room temperature for 24 hours. The nickel foam was removed, rinsed with deionized water, and dried at 80 °C. The nickel foam was then calcined in a tube furnace at 550 °C for 3 hours under argon atmosphere. After calcination, the material was cooled to room temperature, rinsed with deionized water, and dried overnight in an oven at 80 °C to obtain the electrocatalyst. The Ru loading was determined to be 0.058 mg / cm³. -2 At 10mA cm -2 At current density, the required overpotential is 190mV, and the stability is greater than 35h.

[0042] Electrochemical performance testing of electrocatalysts prepared in Examples 1-5

[0043] (1) By cutting the final catalyst to a certain area, leaving the clamping electrode portion and a specific area in contact with water; electrochemical measurements were evaluated in a three-electrode setup with an Ag / AgCl electrode as the reference electrode and a platinum sheet electrode as the counter electrode, using a platinum sheet electrode clamp as the working electrode; potential reference reversible hydrogen electrode (RHE): E RHE =E Ag / AgCl +0.1971 +0.059 × pH (0.5 M H₂SO₄ solution). Calculate the overpotential (η) according to the following equation: η = E RHE -1.23V. Linear sweep voltammetry (LSV) was used to obtain polarization curves in a saturated 0.5M H₂SO₄ solution at a scan rate of 5mV / s. Analysis showed that in Example 1, the polarization curve was at 10mA cm⁻¹. -2 The overpotential at the current density is 174mV, and at 100mA cm⁻¹ -2 The overpotential at the current density is 262 mV, see [reference]. Figure 2 Stability testing was conducted at 10 mA cm⁻¹. -2 The stability test curve for maintaining at least 44 hours under constant current density is shown in the figure. Figure 3 The LSV test included 90% voltage drop compensation.

[0044] (2) A certain amount of the catalyst prepared in Example 1 was cut and tested by XRD. It has a polycrystalline structure. By comparing with the PDF card, it was found that the material contains Ni, NiO, Ru, and RuO2. See [link to PDF card]. Figure 4 .

[0045] (3) A small portion of the catalyst prepared in Example 1 was cut and tested using SEM. See [link to SEM]. Figure 5 .

[0046] In summary, a novel electrocatalyst for the oxygen evolution reaction (OER) in acidic water electrolysis and its preparation method are presented. Ruthenium was loaded onto nickel foam, surface-modified, and then calcined to form a novel material structure suitable for catalyzing the OER under acidic conditions. Even with extremely low loading, the catalyst material exhibits activity comparable to commercially available RuO2 (10 mA cm⁻¹). -2 The overpotential (typically 300-350 mV) was significantly improved, and the catalyst stability was also well maintained.

[0047] 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 novel acidic electrocatalyst for oxygen evolution reaction in water electrolysis, characterized in that, The method includes the following steps.

2. S1 The substrate material, nickel foam, is pretreated by ultrasonic cleaning with acetone and 1M HCl for 10-30 minutes, followed by rinsing with deionized water and anhydrous ethanol several times alternately, and finally drying at 40℃~60℃. 3.S2 The pretreated nickel foam is immersed in a 0.1-1% RuCl3 aqueous solution at a temperature of 40-100℃ for 5-15 hours. The Ru-loaded nickel foam is then removed, rinsed with deionized water, and dried at 80-100℃. 4.S3 Prepare an ammonia solution of potassium permanganate and dopamine hydrochloride with a molar ratio of 1:5 to 5:

5. Place the Ru-loaded nickel foam in the above solution for 10 to 30 hours, then remove it, rinse it with deionized water, and dry it at 80°C to 100°C.

5. S4 is calcined in an inert atmosphere at a temperature of 300-700℃ for 3-6 hours.

6. The method according to claim 1, characterized in that, In step S1, the pretreatment time for the nickel foam is 20 minutes.

7. The method according to claim 1, characterized in that, In step S2, the concentration of the RuCl3 aqueous solution is 0.5%, the immersion temperature is 50°C, and the immersion time is 10 hours.

8. The method according to claim 1, characterized in that, In step S3, the molar ratio of potassium permanganate to dopamine hydrochloride is 2:5, and the soaking time is 24 hours.

9. The method according to claim 1, characterized in that, In step S4, the calcination temperature is 550℃ and the calcination time is 3h.

10. An electrocatalyst prepared by the method according to any one of claims 1-9, using active nickel foam as a substrate and by loading Ru and surface modification thereof, achieving an efficiency of 10 mA cm⁻¹ in the acidic water electrolysis reaction of 0.5 M H₂SO₄. -2 With 100mA cm -2 The required overpotential ranges for current density are 170-190mV and 240-270mV, respectively, at 10mA·cm -2 Stable operation time exceeds 44 hours under current density conditions, with Ru loading below 0.1 mg / cm³. -2 An OER catalyst with high activity, good stability, and low cost under acidic water electrolysis system was prepared.

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