A self-supporting cerium-doped spinel nanosheet electrocatalyst, a preparation method and application thereof

Abstract

This invention discloses a self-supporting cerium-doped spinel nanosheet electrocatalyst, its preparation method, and its application, belonging to the field of electrocatalytic nanomaterial synthesis technology. The electrocatalyst exhibits excellent catalytic activity and operational durability; moreover, the preparation process is simple, reproducible, and uses inexpensive reagents. This invention uses carbon cloth treated with concentrated nitric acid and modified with sodium dodecylbenzenesulfonate as the substrate material; cobalt, manganese, and cerium sources are dissolved in deionized water and stirred until homogeneous to obtain a pre-deposition solution; subsequently, carbon is arranged in the deposition solution for constant potential deposition, and after washing and drying, a precursor of cerium-doped cobalt-manganese oxide is obtained; the precursor sample is further annealed to obtain a cerium-doped spinel oxide electrocatalyst. The cerium-doped spinel oxide is loaded on the carbon fiber surface of the carbon cloth in a cross-linked nanosheet thin-layer structure, effectively increasing the specific surface area, which is beneficial for electron transport and improves the catalytic activity of the catalyst.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalytic nanomaterial synthesis technology, specifically relating to a self-supporting cerium-doped spinel nanosheet electrocatalyst, its preparation method, and its application. Background Technology

[0002] Hydrogen energy, with its clean, zero-carbon characteristics, excellent combustion performance, and abundant reserves, is a crucial component of future national energy systems. As the world transitions to low-carbon energy systems, hydrogen consumption will increase significantly. Current hydrogen production methods are categorized into "gray hydrogen," "blue hydrogen," and "green hydrogen" based on whether the process generates carbon emissions. "Gray hydrogen" and "blue hydrogen" utilize fossil fuels such as coal and oil, resulting in substantial carbon emissions. "Green hydrogen," primarily produced through water electrolysis, can achieve completely zero carbon emissions and represents a highly promising hydrogen energy development path.

[0003] Hydrogen production technologies via water electrolysis mainly include alkaline water electrolysis (AWE), proton exchange membrane water electrolysis (PEMWE), and anion exchange membrane water electrolysis (AEMWE). Among them, PEMWE has high energy conversion efficiency, rapid start-up and shutdown, and is easily adapted to the fluctuations in wind and solar power, making it a highly promising technology for hydrogen production via water electrolysis. However, the cost and lifespan of the anode catalyst are the main factors restricting its large-scale application. Currently, the most widely used anode catalysts are mainly noble metal-based catalysts, such as IrO2 and RuO2. Therefore, developing efficient and acid-stable non-noble metal-based electrocatalysts is of great significance.

[0004] In recent years, transition metal-based electrocatalysts (such as Fe, Co, Mn, and Ni) have attracted much attention due to their excellent catalytic performance and low cost. However, the difficulty in balancing catalytic activity and acid resistance remains a bottleneck for this class of non-noble metal-based electrocatalysts. Doping, by introducing heteroatoms into the catalyst lattice, can not only optimize the electronic structure of the catalyst to enhance electron transport and reduce ion dissolution, but also introduce additional active sites, which facilitates catalytic reactions. Therefore, doping is considered an important method for improving catalysts. Summary of the Invention

[0005] This invention provides a self-supporting cerium-doped spinel nanosheet electrocatalyst, its preparation method, and its application. The electrocatalyst exhibits high catalytic activity and durability in acidic media; moreover, the preparation process is simple to operate, requires no binder, has good repeatability, and uses inexpensive reagents.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A self-supporting cerium-doped spinel nanosheet electrocatalyst is based on modified carbon cloth, on which cerium-doped spinel oxide is deposited and loaded on the carbon fiber surface of the carbon cloth in a cross-linked nanosheet thin-layer structure.

[0007] The spinel material includes one or more of MnCo2O4, CoMn2O4, Co3O4, and Mn3O4.

[0008] A method for preparing a self-supporting cerium-doped spinel nanosheet electrocatalyst includes the following steps: (1) The carbon cloth substrate was subjected to hydrophilic and anionic modification treatments in concentrated nitric acid and sodium dodecylbenzene sulfonate. (2) Dissolve a certain concentration of cobalt source, manganese source and cerium source in deionized water, stir and mix evenly to obtain a sedimentation solution; (3) Place the carbon cloth substrate treated in step (1) into the deposition solution of step (2) (the area of ​​the carbon cloth substrate below the liquid surface is 1 cm²). 2 A constant potential deposition was performed using a three-electrode system: the deposition potential range was -1.1 to -1.5 V. vs. Ag / AgCl, deposition time is 6~12 min; (4) Wash the sample obtained by electrodeposition in step (3) to remove the deposition liquid on the surface, and dry it in vacuum at 60°C for 5-6 hours; (5) The sample obtained by drying in step (4) is heated to 300-400℃ at a rate of 2-5℃ / min in an air atmosphere, kept at the temperature for 2-6h, and then naturally cooled to room temperature to obtain cerium-doped cobalt manganese oxide electrocatalyst.

[0009] In the steps described above, the cobalt source in step (2) is one or more of cobalt nitrate hydrate, cobalt chloride hydrate, cobalt acetate hydrate, and cobalt carbonate hydrate; the manganese source is one or more of manganese nitrate hydrate, anhydrous manganese chloride, manganese acetate hydrate, and cobalt carbonate hydrate; the cerium source is one or more of cerium nitrate hydrate, cerium chloride hydrate, cerium acetate hydrate, and cerium carbonate hydrate; and the molar ratio of cobalt source, manganese source, and cerium source in the electrodeposition solution in step (2) is 2:1:0.05~0.8.

[0010] Beneficial effects: This invention provides a self-supporting cerium-doped spinel nanosheet electrocatalyst, its preparation method, and its application, which have the following advantages compared with the prior art: 1. This invention incorporates cerium, a lanthanide element, into spinel cobalt-manganese oxide, utilizing the unique 4f... 1 5d 1 6s 2 The valence electron configuration enables flexible electron transfer, prevents excessive oxidation of cobalt, and enhances the durability of cobalt-manganese oxide electrocatalysts in acidic media. 2. The electrocatalyst prepared by this invention exhibits a cross-linked nanosheet thin-layer morphology, which effectively increases the specific surface area, facilitates electron transport, and improves the catalytic activity of the catalyst. 3. The preparation method of this invention is simple, efficient and requires no binder, making it easy to prepare on a large scale. While ensuring the morphology and structure of the catalyst, the deposition thickness and material composition can be flexibly adjusted, providing a new approach for the industrial application of non-precious metal-based electrocatalysts in water electrolysis. Attached Figure Description

[0011] Figure 1 This is a SEM image of Ce-MnCo2O4 obtained in Example 1 of the present invention; Figure 2 The image shows the XRD pattern of Ce-MnCo2O4 obtained in Example 1 of this invention. Figure 3 The XPS full spectrum of the electrocatalysts prepared in Example 1 and Comparative Example 1 of this invention; Figure 4 The LSV diagrams are of the electrocatalysts prepared in Examples 1-3 and Comparative Example 1 of this invention. Figure 5 The LSV diagrams are of the electrocatalysts prepared in Example 1 and Comparative Examples 1 and 2 of this invention. Figure 6 This is a durability diagram of the electrocatalysts prepared in Example 1 and Comparative Example 1 of the present invention in acidic media. Detailed Implementation

[0012] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments: Example 1

[0013] A method for preparing a self-supporting cerium-doped spinel nanosheet electrocatalyst includes the following steps: Treatment of the carbon cloth substrate: The cut carbon cloth (2×1 cm in length and width) was refluxed in concentrated nitric acid for 3 h at a reflux temperature of 70 °C. After reflux, the carbon cloth was ultrasonically treated in acetone, ethanol, and deionized water for 15 min each, and then vacuum dried at 60 °C to obtain pretreated carbon cloth. To further increase the hydrophilicity of the carbon cloth, the pretreated carbon cloth was modified: The acid-treated carbon cloth was immersed in 0.01 M sodium dodecylbenzenesulfonate for 5 h at a immersion temperature of 60 °C. The immersed carbon cloth was then washed with deionized water and vacuum dried at 60 °C to obtain modified carbon cloth. Electrochemical deposition: Prepare an electrodeposition solution with the following concentrations: cobalt nitrate hexahydrate at 0.6 M, anhydrous manganese chloride at 0.3 M, and cerium nitrate hexahydrate at 0.02 M, 0.05 M, 0.1 M, 0.15 M, and 0.2 M, respectively. Construct a three-electrode system using the carbon cloth treated in step (1) as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode. The electrolyte is the aforementioned deposition solution. The electrodeposition is carried out at -1.5 V. vs. Electrodeposition was performed under constant potential conditions of Ag / AgCl for 8 min, and the intermediate obtained after electrodeposition was dried in a vacuum drying oven at 60℃ for 5 h. Annealing treatment: The intermediate obtained by electrodeposition in step (2) is heated to 300-400℃ at a rate of 2-5℃ / min in an air atmosphere, kept at the temperature for 2-6 h, and then naturally cooled to room temperature to prepare Ce-MnCo2O4 electrocatalyst. Example 2

[0014] The preparation method of the self-supporting cerium-doped spinel nanosheet electrocatalyst provided in this embodiment can be referred to in Example 1, except that the concentration of cerium nitrate hexahydrate is preferably 0.15M, and the deposition time of constant potential deposition is preferably 4, 6, or 8 min. Example 3

[0015] The method for preparing a self-supporting cerium-doped spinel nanosheet electrocatalyst provided in this embodiment can be referred to in Example 1, except that the concentration of cerium nitrate hexahydrate is preferably 0.15 M, and the deposition potential for constant potential deposition is -1.1, -1.3, -1.5, or -1.7 V. vs. Ag / AgCl.

[0016] Comparative Example 1 The preparation method of the self-supporting spinel cobalt manganese oxide electrocatalyst can be found in Example 1, except that cerium is not doped.

[0017] Comparative Example 2 The preparation method of IrO2 electrocatalyst includes the following steps: Weigh 2 mg IrO2 and 1.5 mg Super P, place them in a mortar, add 30 μl of PVDF; grind evenly and then coat the mixture onto the treated carbon cloth, with a coating area of ​​1 cm². 2 Then, place it in a vacuum drying oven at 80 ℃ and dry for 5 h.

[0018] To clarify the actual performance of the self-supported cerium-doped spinel nanosheet electrocatalysts prepared in the above embodiments, the following will describe the characterization and performance tests of the embodiments and comparative examples: Figure 1The images show SEM images of Ce-MnCo2O4 prepared in Example 1. As can be seen from Figures a and b, Ce-MnCo2O4 deposited by constant potential is loaded on the carbon fiber surface in the form of a cross-linked nanosheet thin layer structure.

[0019] Figure 2 The XRD patterns of the electrocatalysts prepared in Example 1 and Comparative Example 1 are shown in the figure. As can be seen from the figure, both sets of diffraction peaks correspond to the spinel phase of MnCo2O4, indicating that cerium doping did not change the main phase of MnCo2O4. Moreover, compared with MnCo2O4, the diffraction peaks of Ce-MnCo2O4 show a slight negative shift. This is because Ce has a larger atomic radius, and cerium doping causes lattice expansion.

[0020] Figure 3 The XPS full spectrum of the electrocatalysts prepared in Example 1 and Comparative Example 1 shows that cerium was successfully doped at the deposition potential.

[0021] Figure 4 The electrocatalysts prepared in Examples 1-3 and Comparative Example 1 were tested for their catalytic performance in the oxygen evolution reaction (OER) in acidic medium. In a three-electrode system, the prepared electrocatalyst was used as the working electrode, a platinum sheet as the counter electrode, and mercury / mercurous sulfate as the reference electrode. 0.1 M HClO4 was used as the test electrolyte, and the test temperature was 40 °C. The performance of the electrocatalysts was tested using linear voltammetry (LSV). As shown in Figure a, doping with an appropriate concentration of Ce can effectively reduce the overpotential of MnCo2O4 and improve its OER catalytic activity. The optimal cerium source concentration was 0.15 M (when the cerium source concentration was further increased, the catalytic activity of the electrocatalyst did not continue to improve; therefore, 0.15 M was selected as the optimal cerium source concentration). Figure 4 From b) and c), we can see that the optimal deposition time is 8 min and the optimal deposition potential is -1.5 V. vs. Ag / AgCl.

[0022] Figure 5 The catalytic performance of the electrocatalyst prepared with the optimal cerium source concentration of 0.15 M in Example 1 and the electrocatalysts prepared in Comparative Examples 1 and 2 in the oxygen evolution reaction was tested in acidic medium. The test method is as follows: Figure 4 As shown in the figure, Ce-MnCo2O4 at 10 mA / cm 2 The overpotential at this point is only 220 mV, while the overpotential of undoped MnCo2O4 is 265 mV and the overpotential of IrO2 is 293 mV.

[0023] Figure 6 The durability of the electrocatalyst prepared with the optimal cerium source concentration of 0.15 M in Example 1 and the electrocatalyst prepared in Comparative Example 1 were tested under the following conditions: Figure 4Under the above conditions, the electrocatalyst was tested using a chronopotentiometric method. Figure 6 As shown, Ce-MnCo2O4 at 10 mA / cm 2 It can operate stably for more than 120 hours at a current density, and its durability is nearly 5 times better than that of undoped MnCo2O4.

[0024] The above description is merely a preferred embodiment of the present invention. It should be noted that the above embodiments are only for describing the present invention and are not restrictive. For those skilled in the art, making other similar embodiments of the present invention without inventiveness is within the protection scope of the present invention.

Claims

1. A self-supporting cerium-doped spinel nanosheet electrocatalyst, characterized in that, The electrocatalyst is used for the oxygen evolution reaction in an acidic medium during water electrolysis to produce hydrogen. The electrocatalyst is based on modified carbon cloth, on which cerium-doped spinel cobalt manganese oxide is deposited, wherein the spinel cobalt manganese oxide is MnCo2O4. The cerium-doped spinel cobalt manganese oxide is loaded on the surface of the carbon fibers of the carbon cloth in a cross-linked nanosheet thin layer structure. The modified carbon cloth has undergone hydrophilic and anionic modification treatment.

2. A method for preparing the self-supported cerium-doped spinel nanosheet electrocatalyst according to claim 1, characterized in that, Includes the following steps: (1) The carbon cloth substrate was subjected to hydrophilic and anionic modification treatments in succession; (2) Dissolve the spinel cobalt manganese oxide source and the cerium source in deionized water, stir and mix evenly to obtain a deposition solution. The spinel cobalt manganese oxide source is a cobalt source and a manganese source. The molar ratio of the cobalt source, manganese source and cerium source is 2:1:0.05~0.

8. (3) The modified carbon cloth substrate was placed in the deposition solution and constant potential deposition was performed in a three-electrode system; (4) Wash the electrodeposited sample to remove the surface deposit solution and then dry it; (5) The dried sample is heated to 300-400℃ at a rate of 2-5℃ / min in air atmosphere, kept at the temperature for 2-6h, and then naturally cooled to room temperature to obtain cerium-doped spinel cobalt manganese oxide electrocatalyst.

3. The method for preparing the self-supported cerium-doped spinel nanosheet electrocatalyst according to claim 2, characterized in that, The cobalt source is one or more of cobalt nitrate hydrate, cobalt chloride hydrate, cobalt acetate hydrate, and cobalt carbonate hydrate.

4. The method for preparing the self-supported cerium-doped spinel nanosheet electrocatalyst according to claim 2, characterized in that, The manganese source is one or more of manganese nitrate hydrate, anhydrous manganese chloride, manganese acetate hydrate, and cobalt carbonate hydrate.

5. The method for preparing the self-supported cerium-doped spinel nanosheet electrocatalyst according to claim 2, characterized in that, The cerium source is one or more of cerium nitrate hydrate, cerium chloride hydrate, cerium acetate hydrate, and cerium carbonate hydrate.

6. The method for preparing the self-supported cerium-doped spinel nanosheet electrocatalyst according to claim 2, characterized in that, The electrodeposition potential ranges from -1.1 to -1.5 V. vs. Ag / AgCl, deposition time is 6~12 min.

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