A cobalt-based catalyst doped with carbon in situ, and a preparation method and application thereof
Patent Information
- Application Number
- CN202411916934.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-24
- Publication Date
- 2026-09-25
- Estimated Expiration
- 2044-12-24
AI Technical Summary
[0006]为了解决上述现有技术中的金属有机框架的低导电性等问题，本发明提供一种原位掺碳的钴基催化剂及其制备方法和应用
[0024]根据本发明的原位掺碳的钴基催化剂的制备方法简单，可以实现大规模生产；通过水热法制备有机金属框架前驱体，制备温度低，反应时间短，节能降耗，得到的有机金属框架前驱体具有很高的碳含量，为后续一步热解法制备原位掺碳的钴基催化剂提供丰富碳源；提供有机金属框架前驱体的热解，有机配体引入的有机物煅烧为碳并原位掺杂到钴基材料中以解决导电性差的问题，同时也解决其他非原位掺杂方法会破坏材料的原有结构，导致掺杂元素分布不均匀的问题，且掺杂引起的缺陷会产生大量活性位点；通过整合各种金属元素组分的特征，不仅在一定程度上扩大了金属有机框架的应用范围，而且还扩大了其衍生物的多样性。
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Figure CN119592996B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to electrochemical catalysts, and more specifically to an in-situ carbon-doped cobalt-based catalyst, its preparation method, and its application. Background Technology
[0002] Hydrogen production through water electrolysis is a clean energy conversion technology crucial for meeting modern society's demand for renewable energy. Especially against the backdrop of global energy structure transformation and the reduction of greenhouse gas emissions, the demand for hydrogen energy, as a clean and efficient energy carrier, is increasing daily. The oxygen evolution reaction (OER) occurring at the anode involves the transfer of four electrons, resulting in a high reaction barrier that requires a highly active catalyst to reduce the overpotential.
[0003] Although noble metal-based materials such as platinum and iridium exhibit highly efficient catalytic activity in the oxygen evolution reaction (OER), their high cost and scarcity limit their large-scale application. Therefore, the development of non-noble metal catalysts with high activity, low cost, and durability has become particularly urgent.
[0004] Cobalt-based catalysts have been widely used in the field of hydrogen production through water electrolysis due to their high activity and low cost. However, their performance still falls short of the requirements of industrial applications due to drawbacks such as a limited number of active sites, poor conductivity, and low intrinsic catalytic activity.
[0005] Metal-organic frameworks (MOFs) and their derivatives have shown great potential in the field of novel electrocatalysts due to their advantages such as large specific surface area, abundant pore structure, diverse composition, and well-defined metal centers. However, the low conductivity of MOF materials has become a key technical bottleneck restricting their further application in electrocatalysis. Summary of the Invention
[0006] To address the issues of low conductivity in metal-organic frameworks in the prior art, this invention provides an in-situ carbon-doped cobalt-based catalyst, its preparation method, and its application.
[0007] According to one aspect of the present invention, a method for preparing an in-situ carbon-doped cobalt-based catalyst is provided, comprising the following steps: S1, mixing a metal source and an organic ligand to obtain a solid mixture, dissolving the solid mixture in a mixed solvent to obtain a mixed solution, wherein the metal source includes a cobalt salt, the organic ligand is 5-aminoisophthalic acid, and the mixed solvent is composed of deionized water, ethanol, and N-dimethylformamide; S2, preparing an organometallic framework precursor from the mixed solution at 70°C-90°C via a hydrothermal method (solvothermal method); S3, calcining the organometallic framework precursor at 800°C-1000°C, and obtaining the in-situ carbon-doped cobalt-based catalyst after natural cooling.
[0008] In a preferred embodiment, the metal source further includes manganese, nickel, chromium, and / or iron salts. In a preferred embodiment, the cobalt salt is cobalt nitrate. In a preferred embodiment, the manganese salt is manganese chloride. In a preferred embodiment, the nickel salt is nickel nitrate. In a preferred embodiment, the chromium salt is chromium nitrate. In a preferred embodiment, the iron salt is ferric nitrate.
[0009] In a preferred embodiment, the Co from the metal source 2+ The molar ratio is 70%-100%, and the Ni metal source is... 2+ Fe 3+ Cr 3+ and / or Mn 2+ The molar ratio is 0%-30%. In Example 1, Co 2+ The molar ratio is 100%; in Example 2, the molar ratio of Co to Mn is 7:3, that is, Co... 2+ The molar ratio is 70%; in Example 3, the molar ratio of Co to Ni is 7:3, that is, Co... 2+ The molar ratio was 70%; in Example 4, the molar ratio of Co to Cr was 9:1, i.e., Co... 2+ The molar ratio of Co, Ni, and Mn is between 90%; in Example 5, the molar ratio of Co, Ni, and Mn is 7:2:1, that is, Co... 2+ The molar ratio was 70%; in Example 6, the molar ratio of Co, Ni, and Fe was 7:2:1, i.e., Co... 2+ The molar ratio is 70%.
[0010] In a preferred embodiment, the total amount of metal ions from the metal source (Co) 2+ Ni 2+ Fe 3+ Cr 3+ and / or Mn 2+ The molar ratio of the metal source to the organic ligand is 0.0235:0.0703. In a preferred embodiment, the total amount of metal ions in the metal source is 23.5 mol.
[0011] In a preferred embodiment, the volume ratio of deionized water, ethanol, and N-dimethylformamide in the mixed solvent is 1:1:1. In one preferred embodiment, 756 ml of the mixed solvent consists of 252 ml of deionized water, 252 ml of ethanol, and 252 ml of N-dimethylformamide.
[0012] In a preferred embodiment, the solid mixture is sonicated until it is completely dissolved in the mixed solvent.
[0013] In a preferred embodiment, in step S2, the mixed solution is transferred to the reactor, the reactor is sealed and placed in an oven, the oven is heated to 70°C-90°C and kept at that temperature, the oven and reactor are cooled to room temperature, the reactor is opened, and centrifugation is performed to obtain the organometallic framework precursor.
[0014] In a preferred embodiment, step S2 further includes washing three times with deionized water and ethanol respectively, drying naturally at room temperature, and then grinding into a solid powder using a mortar and pestle.
[0015] In a preferred embodiment, the reactor has a polytetrafluoroethylene liner.
[0016] In a preferred embodiment, the oven is gradually heated to 80°C at a rate of 5°C / min and operated at 80°C for 48 hours.
[0017] In a preferred embodiment, in step S3, the organometallic framework precursor is placed in a ceramic boat and calcined in an inert atmosphere using a tube furnace. The tube furnace is heated to 800°C-1000°C and then held at that temperature.
[0018] In a preferred embodiment, the tube furnace heats the temperature to 800°C-1000°C at a rate of 8°C / min-10°C / min. In another preferred embodiment, the tube furnace heats the temperature to 800°C at a rate of 9°C / min.
[0019] In a preferred embodiment, each gram of organometallic framework precursor is incubated for 10-30 minutes.
[0020] In a preferred embodiment, the inert gas is nitrogen or argon.
[0021] According to another aspect of the present invention, an in-situ carbon-doped cobalt-based catalyst obtained by the above-described preparation method is provided.
[0022] According to another aspect of the present invention, the application of the above-described in-situ carbon-doped cobalt-based catalyst in alkaline water electrolysis for hydrogen production is provided.
[0023] In a preferred embodiment, the electrolyte is 1 mol / L KOH and the current density is 10 mA / cm². 2 Under these conditions, the overpotential is 340mV-355mV.
[0024] The method for preparing the cobalt-based catalyst with in-situ carbon doping according to the present invention is simple and can be mass-produced. The preparation of the organometallic framework precursor via a hydrothermal method involves low preparation temperature, short reaction time, energy saving, and reduced consumption. The resulting organometallic framework precursor has a high carbon content, providing an abundant carbon source for the subsequent pyrolysis method to prepare the cobalt-based catalyst with in-situ carbon doping. The pyrolysis of the organometallic framework precursor allows the organic compounds introduced by the organic ligands to be calcined into carbon and in-situ doped into the cobalt-based material, thus solving the problem of poor conductivity. It also addresses the issues of other non-in-situ doping methods that damage the original structure of the material, leading to uneven distribution of doped elements, and the defects caused by doping generating a large number of active sites. By integrating the characteristics of various metal element components, the application range of metal-organic frameworks is not only expanded to a certain extent, but also the diversity of their derivatives is increased. Attached Figure Description
[0025] Figure 1 This is the X-ray diffraction pattern of the cobalt-based catalyst obtained according to Example 1 of the present invention.
[0026] Figure 2 This is the X-ray diffraction pattern of the cobalt-based catalyst obtained according to Example 2 of the present invention.
[0027] Figure 3 This is a scanning electron microscope image of the cobalt-based catalyst obtained according to Example 2 of the present invention.
[0028] Figure 4 yes Figure 3 Enlarged image.
[0029] Figure 5 This is a scanning electron microscope image of the cobalt-based catalyst obtained according to Example 3 of the present invention.
[0030] Figure 6 yes Figure 5 Enlarged image.
[0031] Figure 7 These are LSV polarization curves of the cobalt-based catalysts obtained according to Examples 1-6 of the present invention. Detailed Implementation
[0032] The preferred embodiments of the present invention are given below with reference to the accompanying drawings and described in detail.
[0033] In this article, alkaline water electrolysis refers to the process of producing hydrogen by electrolyzing water in an alkaline electrolyte environment. The electrolyte is generally a 30% KOH solution.
[0034] In this paper, the oxygen evolution reaction (OER) refers to a half-reaction in the water electrolysis reaction, which involves a multi-electron transfer process. The kinetic reaction is slow and is a key factor restricting the efficiency of the entire water electrolysis device.
[0035] In this paper, overpotential, also known as overcurrent potential or overelectromotive force, refers to the portion of the actual voltage required to reach a certain current density during an electrocatalytic reaction that exceeds the theoretical voltage. The working potential in actual reactions often needs to overcome the kinetic obstacles, thus exhibiting a value higher than the equilibrium potential. The voltage exceeding the theoretical value is called overpotential, and it is mainly used to overcome other resistances such as activation resistance and charge transfer resistance.
[0036] In this paper, an anode catalyst refers to a catalyst that can promote electrochemical reactions by accelerating the oxygen evolution reaction at the anode, thereby improving the efficiency and speed of the electrochemical reaction.
[0037] In this paper, the advantages of cobalt-based catalysts in water electrolysis for hydrogen production are attributed to the high activity and variable valence of the transition metal cobalt. Compared to noble metal-based catalysts, cobalt-based electrocatalysts have been widely studied due to their abundant reserves, low cost, and high catalytic activity.
[0038] In this paper, in-situ doping refers to the direct addition of dopant elements during the material synthesis process. The dopant elements form simultaneously with the host material during synthesis, allowing for better control over the distribution and concentration of the dopant elements and maintaining the overall structure and performance of the material. In electrochemical tests, in-situ doped materials exhibit superior performance and long-term stability.
[0039] In this paper, non-in-situ doping refers to synthesizing the material first and then introducing dopant elements into it. This method may disrupt the original structure of the material, leading to uneven distribution of dopant elements. Although it may exhibit certain electrochemical performance in electrochemical tests, it is generally less stable and efficient than in-situ doped materials.
[0040] In this paper, metal-organic frameworks (MOFs) refer to a class of crystalline porous materials with high specific surface area, high porosity and designable structure, which show great potential as novel electrocatalysts.
[0041] In this paper, the hydrothermal method refers to the method of preparing materials by dissolving and recrystallizing powder in a reaction vessel using water as a solvent. The powder obtained has the advantages of complete crystal development, small particle size and uniform distribution, and avoids possible powder agglomeration.
[0042] Example 1: Preparation of a single-metal Co catalyst
[0043] Weigh 6.8472 g (0.0235 mol) of cobalt nitrate hexahydrate and add 12.7476 g (0.0703 mol) of 5-aminoisophthalic acid to obtain a solid mixture. Dissolve the solid mixture in a mixed solution consisting of 252 ml of deionized water, 252 ml of ethanol, and 252 ml of N-dimethylformamide, and sonicate until the solid is completely dissolved. Transfer the mixed solution to a high-pressure reactor lined with polytetrafluoroethylene, seal the reactor, and place it in an oven. The oven temperature is gradually increased to 80 °C at a rate of 5 °C / min and maintained at 80 °C for 48 h. After the oven heating program is completed, the oven and reactor are cooled to room temperature. Open the reactor, and centrifuge the solid obtained as a cobalt-based catalyst precursor. Wash it three times with deionized water and ethanol, and after air drying at room temperature, grind it into a solid powder using a mortar and pestle. 1g of solid powder was placed in a porcelain boat and calcined in a tube furnace under a nitrogen atmosphere. The temperature of the tube furnace was increased to 800℃ at a rate of 9℃ / min, and held at 800℃ for 20min. After the tube furnace was allowed to cool naturally, the in-situ carbon-doped cobalt-based catalyst was obtained. Its X-ray diffraction pattern is shown below. Figure 1 As shown, the cobalt-based catalyst corresponds to Co (card number 15-0806) and the diffraction peak at 2θ = 26.5° corresponds to C (card number 26-1076). This indicates that carbon is in-situ doped into the cobalt-based catalyst obtained after high-temperature calcination, thereby increasing the material's conductivity and improving its electrochemical performance.
[0044] Example 2: Preparation of bimetallic CoMn catalyst
[0045] Weigh 4.7930 g (0.01646 mol) of cobalt nitrate hexahydrate and 1.3968 g (0.00706 mol) of manganese chloride tetrahydrate, and add 12.7476 g (0.0703 mol) of 5-aminoisophthalic acid to obtain a solid mixture. Dissolve the solid mixture in a mixed solution consisting of 252 ml of deionized water, 252 ml of ethanol, and 252 ml of N-dimethylformamide, and sonicate until the solid is completely dissolved. Transfer the mixed solution to a high-pressure reactor lined with polytetrafluoroethylene, seal the reactor, and place it in an oven. The oven temperature is gradually increased to 80 °C at a rate of 5 °C / min, and the reactor is run at 80 °C for 48 h. After the oven heating program is completed, the oven and reactor are cooled to room temperature. Open the reactor, and centrifuge the solid obtained, which is the cobalt-based catalyst precursor. Wash it three times with deionized water and ethanol, and after air drying at room temperature, grind it into a solid powder using a mortar and pestle. 1g of solid powder was placed in a porcelain boat and calcined in a tube furnace under a nitrogen atmosphere. The temperature of the tube furnace was increased to 800℃ at a rate of 9℃ / min, and held at 800℃ for 20min. After the tube furnace was allowed to cool naturally, the in-situ carbon-doped cobalt-based catalyst was obtained. Its X-ray diffraction pattern is shown below. Figure 2As shown, the cobalt-based catalyst, besides corresponding to Co (card number 15-0806) and Mn3Co7 (card number 18-0407), has a diffraction peak at 2θ = 26.5° corresponding to C (card number 26-1076). This indicates that carbon is in-situ doped into the cobalt-based catalyst obtained after high-temperature calcination, thereby increasing the material's conductivity and improving its electrochemical performance. A scanning electron microscope image of this cobalt-based catalyst is shown below. Figure 3 and Figure 4 As shown, the cobalt-based catalyst has a micron-sized, near-spherical particle size and a high specific surface area. The larger the specific surface area, the more active sites are exposed on the catalyst powder surface, resulting in better catalytic performance and ultimately improving the catalyst's OER activity.
[0046] Example 3: Preparation of bimetallic CoNi catalyst
[0047] Weigh 4.7930 g (0.01646 mol) of cobalt nitrate hexahydrate and 2.0520 g (0.00705 mol) of nickel nitrate hexahydrate, and add 12.7476 g (0.0703 mol) of 5-aminoisophthalic acid to obtain a solid mixture. Dissolve the solid mixture in a mixed solution consisting of 252 ml of deionized water, 252 ml of ethanol, and 252 ml of N-dimethylformamide, and sonicate until the solid is completely dissolved. Transfer the mixed solution to a high-pressure reactor lined with polytetrafluoroethylene, seal the reactor, and place it in an oven. The oven temperature is gradually increased to 80 °C at a rate of 5 °C / min, and the mixture is run at 80 °C for 48 h. After natural drying, grind the solid mixture into a solid powder using a mortar and pestle. 1g of solid powder was placed in a porcelain boat and calcined in a tube furnace under a nitrogen atmosphere. The temperature of the tube furnace was increased to 800℃ at a rate of 9℃ / min and held at 800℃ for 20min. After the tube furnace was allowed to cool naturally, the in-situ carbon-doped cobalt-based catalyst was obtained. Its scanning electron microscope image is shown below. Figure 5 and Figure 6 As shown, the cobalt-based catalyst has a micron-sized, near-spherical particle size and a high specific surface area. The larger the specific surface area, the more active sites are exposed on the catalyst powder surface, resulting in better catalytic performance and ultimately improving the catalyst's OER activity.
[0048] Example 4: Preparation of bimetallic CoCr catalyst
[0049] Weigh 6.1624 g (0.0212 mol) of cobalt nitrate hexahydrate and 0.9409 g (0.00235 mol) of chromium nitrate nonahydrate, and add 12.7476 g (0.0703 mol) of 5-aminoisophthalic acid to obtain a solid mixture. Dissolve the solid mixture in a mixed solution consisting of 252 ml of deionized water, 252 ml of ethanol, and 252 ml of N-dimethylformamide, and sonicate until the solid is completely dissolved. Transfer the mixed solution to a high-pressure reactor lined with polytetrafluoroethylene, seal the reactor, and place it in an oven. The oven temperature is gradually increased to 80 °C at a rate of 5 °C / min, and the reactor is run at 80 °C for 48 h. After the oven heating program is completed, the oven and reactor are cooled to room temperature. Open the reactor, and centrifuge the solid obtained, which is the cobalt-based catalyst precursor. Wash it three times with deionized water and ethanol, and after air drying at room temperature, grind it into a solid powder using a mortar and pestle. Take 1g of solid powder in a ceramic boat and calcine it at high temperature in a tube furnace under a nitrogen atmosphere. The tube furnace is heated to 800℃ at a rate of 9℃ / min and held at 800℃ for 20min. After the tube furnace is naturally cooled down, the in-situ carbon-doped cobalt-based catalyst is obtained.
[0050] Example 5: Preparation of ternary metal CoNiMn catalyst
[0051] Weigh 4.7930 g (0.01646 mol) of cobalt nitrate hexahydrate, 1.3680 g (0.00469 mol) of nickel nitrate hexahydrate, and 0.4680 g (0.00236 mol) of manganese chloride tetrahydrate, and add 12.7476 g (0.0703 mol) of 5-aminoisophthalic acid to obtain a solid mixture. Dissolve the solid mixture in a mixed solution consisting of 252 ml of deionized water, 252 ml of ethanol, and 252 ml of N-dimethylformamide, and sonicate until the solid is completely dissolved. Transfer the mixed solution to a high-pressure reactor lined with polytetrafluoroethylene, seal the reactor, and place it in an oven. The oven temperature is gradually increased to 80 °C at a rate of 5 °C / min, and the reactor is run at 80 °C for 48 h. After the oven heating process is completed, the oven and reactor are cooled to room temperature. The reactor is opened, and the solid obtained by centrifugation is the cobalt-based catalyst precursor. It is washed three times with deionized water and ethanol, and then naturally dried at room temperature. It is then ground into a solid powder using a mortar and pestle. 1g of the solid powder is placed in a porcelain boat and calcined at high temperature in a tube furnace under a nitrogen atmosphere. The temperature of the tube furnace is increased to 800℃ at a rate of 9℃ / min, and held at 800℃ for 20min. After the tube furnace is naturally cooled, the in-situ carbon-doped cobalt-based catalyst is obtained.
[0052] Example 6: Preparation of a ternary metal CoNiFe catalyst
[0053] Weigh 4.7930 g (0.0164 mol) of cobalt nitrate hexahydrate, 1.3680 g (0.0047 mol) of nickel nitrate hexahydrate, and 0.9557 g (0.0024 mol) of ferric nitrate nonahydrate, and add 12.7476 g (0.0703 mol) of 5-aminoisophthalic acid to obtain a solid mixture. Dissolve the solid mixture in a mixed solution consisting of 252 ml of deionized water, 252 ml of ethanol, and 252 ml of N-dimethylformamide, and sonicate until the solid is completely dissolved. Transfer the mixed solution to a high-pressure reactor lined with polytetrafluoroethylene, seal the reactor, and place it in an oven. The oven temperature is gradually increased to 80 °C at a rate of 5 °C / min, and the reactor is run at 80 °C for 48 h. After the oven heating process is completed, the oven and reactor are cooled to room temperature. The reactor is opened, and the solid obtained by centrifugation is the cobalt-based catalyst precursor. It is washed three times with deionized water and ethanol, and then naturally dried at room temperature. It is then ground into a solid powder using a mortar and pestle. 1g of the solid powder is placed in a porcelain boat and calcined at high temperature in a tube furnace under a nitrogen atmosphere. The temperature of the tube furnace is increased to 800℃ at a rate of 9℃ / min, and held at 800℃ for 20min. After the tube furnace is naturally cooled, the in-situ carbon-doped cobalt-based catalyst is obtained.
[0054] Example 7: Testing the electrochemical performance of cobalt-based catalysts
[0055] A three-electrode system was constructed, using the in-situ carbon-doped cobalt-based catalysts from Examples 1-6, uniformly distributed on hydrophilic carbon paper, as the working electrode, with a catalyst loading of 3 mg / cm³. 2 A carbon rod was used as the counter electrode, and an Hg / HgO electrode was used as the reference electrode. The electrolyte was 1 mol / L KOH.
[0056] The LSV polarization curves of the cobalt-based catalysts obtained according to Examples 1-6 of the present invention are as follows: Figure 7 As shown, at a current density of 10 mA / cm² 2 At that time, the overpotential η of the bimetallic CoMn catalyst in Example 2 10 =E i -E t (Theoretical voltage value) = 1.57 - 1.23 = 0.34V = 340mV, the overpotential η of the bimetallic CoCr catalyst in Example 2 10 =E i -E t =1.585 - 1.23 = 0.355V = 355mV. Therefore, with an electrolyte of 1 mol / L KOH and a current density of 10 mA / cm², the voltage is 355mV. 2 Under these conditions, the overpotential is 340mV-355mV.
[0057] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention. Various variations can be made to the above embodiments of the present invention. That is, all simple and equivalent changes and modifications made based on the claims and description of this invention fall within the protection scope of the claims of this patent. All aspects not described in detail in this invention are conventional technical content.
Claims
1. A method for preparing an in-situ carbon-doped cobalt-based catalyst, characterized in that, The preparation method includes the following steps: S1, a solid mixture is obtained by mixing a metal source and an organic ligand, and then the solid mixture is dissolved in a mixed solvent to obtain a mixed solution, wherein the metal source consists only of Co. 2+ Composed of, or made of Co 2+ and Cr 3+ Composed of, or made of Co 2+ and Mn 2+ Composition, Co from metal source 2+ The molar ratio is 70%-100%, and the metal source is Cr. 3+ or Mn 2+ The molar ratio is 0%-30%, the organic ligand is 5-aminoisophthalic acid, and the mixed solvent is composed of deionized water, ethanol and N,N-dimethylformamide in a volume ratio of 1:1:
1. S2, the mixed solution was prepared into an organometallic framework precursor by hydrothermal method at 70℃-90℃; S3. The organometallic framework precursor is placed in a ceramic boat and calcined in an inert atmosphere in a tube furnace. The tube furnace is heated to 800℃-1000℃ at a rate of 8℃ / min-10℃ / min and then held at that temperature. The organometallic framework precursor is calcined at 800℃-1000℃ and then naturally cooled to obtain an in-situ carbon-doped cobalt-based catalyst. The particle size of the cobalt-based catalyst is in the micrometer range and is spherical.
2. The preparation method according to claim 1, characterized in that, In step S2, the mixed solution is transferred to the reactor, the reactor is sealed and placed in an oven, the oven is heated to 70℃-90℃ and kept at that temperature, the oven and reactor are cooled to room temperature, the reactor is opened and centrifuged to obtain the organometallic framework precursor.
3. An in-situ carbon-doped cobalt-based catalyst obtained by the preparation method according to claim 1 or 2.
4. The application of the in-situ carbon-doped cobalt-based catalyst according to claim 3 in alkaline water electrolysis for hydrogen production, characterized in that, The cobalt-based catalyst is used as the anodic oxygen evolution reaction catalyst in alkaline water electrolysis for hydrogen production.
5. The application according to claim 4, characterized in that, With an electrolyte of 1 mol / L KOH and a current density of 10 mA / cm², 2 Under these conditions, the overpotential for the oxygen evolution reaction is 340mV-355mV.