Electrode and preparation method thereof

Abstract

The invention provides an electrode and a preparation method thereof. The electrode provided by the invention comprises a carbon matrix and a SnO2 / CeO2 catalyst loaded on the surface of the carbon matrix. According to the electrode disclosed by the invention, a layer of SnO2 / CeO2 catalyst is loaded and deposited on the surface of the electrode, so that the specific surface area of the electrode can be effectively increased, and active sites of electrochemical reaction are increased. When the material is applied to a flow battery, such as an all-vanadium flow battery, the hydrogen evolution reaction in the battery can be inhibited, the charge-discharge efficiency of the flow battery is improved, the oxidation-reduction activity of vanadium ions is improved, and irreversible capacity loss caused by precipitation of the vanadium ions on the surface of an electrode is prevented.

Description

Technical Field

[0001] This application relates to the field of energy storage battery technology, and in particular to an electrode and its preparation method. Background Technology

[0002] With the depletion of fossil fuel resources and the increasing severity of environmental pollution, the search for new energy sources and energy storage technologies has become an urgent issue for energy development. Flow batteries, especially vanadium redox flow batteries, are a new type of high-efficiency electrochemical energy storage battery. They possess characteristics such as ultra-long cycle life, flexible capacity design and expansion, fast response rate, and intrinsic safety, making them widely recognized in the new energy field.

[0003] During the charge and discharge process of a flow battery, hydrogen evolution occurs on the surface of the negative electrode. This hydrogen evolution reaction competes with the main reaction in the flow battery, affecting its charge and discharge efficiency. Furthermore, the hydrogen evolution reaction also causes hydrogen ions in the electrolyte to rise. + Changes in ion concentration affect the conductivity of the electrolyte, and the generation of hydrogen gas can increase the internal pressure of the battery, affecting its structure and performance, and posing safety hazards. Furthermore, the charging and discharging process of vanadium redox flow batteries involves widespread redox reactions of vanadium ions under the influence of applied current. Since the electrodes of flow batteries use carbon-based materials, under the influence of applied current, the carbon in these materials combines with vanadium ions to form insoluble precipitates, consuming the active material of the electrolyte and causing irreversible capacity decay. This, to some extent, limits the industrialization and large-scale application of flow batteries. Therefore, developing an electrode that can effectively suppress the hydrogen evolution reaction during the operation of flow batteries has become a pressing technical problem for those skilled in the art. Summary of the Invention

[0004] The purpose of this application is to provide an electrode and its preparation method, which effectively suppresses the hydrogen evolution reaction during the operation of a flow battery, improves the charge and discharge efficiency of the flow battery, and prevents irreversible capacity loss caused by the precipitation of vanadium ions on the electrode surface. The specific technical solution is as follows:

[0005] A first aspect of this application provides an electrode comprising a carbon matrix and a tin oxide / cerium oxide (SnO2 / CeO2) catalyst supported on the surface of the carbon matrix.

[0006] In one embodiment of this application, the SnO2 / CeO2 catalyst has a mass percentage content of 0.1% to 10%, preferably 0.3% to 10%, based on the mass of the electrode.

[0007] In one embodiment of this application, the carbon matrix is ​​selected from at least one of graphite felt, carbon felt, carbon cloth, and carbon paper.

[0008] The second aspect of this application provides a method for preparing the electrode described in the first aspect of this application, comprising:

[0009] (1) Activate the carbon matrix to obtain the activated carbon matrix;

[0010] (2) SnCl2·2H2O, CeO2 nanoparticles and acid are mixed to prepare an electrolyte; the acid is selected from sulfuric acid or hydrochloric acid; in the electrolyte, the concentration of SnCl2·2H2O is 0.01-0.5 mol / L, the concentration of the acid is 0.05-2 mol / L, and the concentration of CeO2 nanoparticles is 0.1-10 g / L;

[0011] (3) Using the activated carbon matrix as the cathode electrode, immerse it in the electrolyte and electrochemically deposit SnO2 / CeO2 catalyst on the surface of the carbon matrix.

[0012] In one embodiment of this application, the current density of the electrochemical deposition is 4–8 mA / cm². 2 The time is 0.5 to 1.5 hours.

[0013] In one embodiment of this application, the CeO2 nanoparticles have a size of 10–50 nm.

[0014] In one embodiment of this application, the carbon matrix is ​​selected from at least one of graphite felt, carbon felt, carbon cloth, and carbon paper.

[0015] In one embodiment of this application, the step of activating the carbon matrix includes:

[0016] The carbon matrix is ​​placed in deionized water and boiled for 1-2 hours; then placed in acid and treated at 80-120°C for 8-12 hours; rinsed with deionized water and dried to obtain the activated carbon matrix; the acid is selected from sulfuric acid or hydrochloric acid.

[0017] A third aspect of this application provides a flow battery comprising the electrode described in the first aspect of this application or the electrode prepared by the method described in the second aspect of this application.

[0018] The beneficial effects of this application are:

[0019] This application provides an electrode and its preparation method. The electrode of this application includes a carbon matrix and a SnO2 / CeO2 catalyst supported on the surface of the carbon matrix. Depositing a layer of SnO2 / CeO2 catalyst on the electrode surface can effectively increase the specific surface area of ​​the electrode and increase the active sites for electrochemical reactions. Compared with using SnO2 or CeO2 alone as a catalyst, the SnO2 / CeO2 catalyst of this application has more oxygen vacancies and better oxidation performance, while Sn...4+ / Sn 2+ With Ce 4+ / Ce 3+ The ion valence state transformation process between these processes provides more active electrons for the battery reaction. This environment with active electron aggregation is also beneficial for improving the redox activity of the SnO2 / CeO2 catalyst. Furthermore, the SnO2 / CeO2 catalyst has a high hydrogen evolution overpotential. When applied to flow batteries, such as vanadium redox flow batteries, it can suppress the hydrogen evolution reaction inside the battery, improving the charge-discharge efficiency. Additionally, loading the SnO2 / CeO2 catalyst onto the carbon-based electrode surface can prevent the precipitation of vanadium ions on the electrode surface, thus preventing irreversible capacity loss.

[0020] Of course, implementing any product or method of this application does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other embodiments can be obtained based on these drawings.

[0022] Figure 1 The discharge capacity variation curves of the all-vanadium redox flow batteries prepared in Examples 1 to 9 and Comparative Examples 1 to 3 are shown.

[0023] Figures 2A to 2B The figures show the coulombic efficiency variation curves of the all-vanadium redox flow batteries prepared in Examples 1 to 9 and Comparative Examples 1 to 3; wherein... Figure 2B for Figure 2A Enlarged image;

[0024] Figure 3 Cyclic voltammetry curves of the graphite felts with supported catalysts prepared in Examples 1, 3, 5, 6, 9, and Comparative Example 1. Detailed Implementation

[0025] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0026] A first aspect of this application provides an electrode comprising a carbon matrix and a SnO2 / CeO2 catalyst supported on the surface of the carbon matrix.

[0027] The inventors discovered that loading and depositing a SnO2 / CeO2 catalyst layer on the electrode surface can effectively increase the specific surface area of ​​the electrode and increase the active sites for electrochemical reactions. Compared with using SnO2 or CeO2 alone as a catalyst, the SnO2 / CeO2 catalyst of this application has more oxygen vacancies and better oxidation performance, while Sn... 4+ / Sn 2+ With Ce 4 + / Ce 3+ The ion valence state transformation process between these processes provides more active electrons for the battery reaction, and this environment with active electron aggregation is also beneficial for improving the redox activity of the SnO2 / CeO2 catalyst. Furthermore, the SnO2 / CeO2 catalyst has a high hydrogen evolution overpotential; when applied to flow batteries, such as vanadium redox flow batteries, it can suppress the hydrogen evolution reaction inside the battery, improving the charge-discharge efficiency. Additionally, loading the SnO2 / CeO2 catalyst onto the carbon-based electrode surface can prevent the precipitation of vanadium ions on the electrode surface, thus preventing irreversible capacity loss.

[0028] In one embodiment of this application, the mass percentage of the SnO2 / CeO2 catalyst is 0.1% to 10%, preferably 0.3% to 10%, based on the mass of the electrode. For example, the mass percentage of the SnO2 / CeO2 catalyst can be 0.1%, 0.3%, 0.5%, 1%, 3%, 5%, 8%, 10%, or a range of any two of these values, based on the mass percentage of the electrode. A mass percentage of SnO2 / CeO2 catalyst within the above range is more conducive to suppressing the hydrogen evolution reaction in the flow battery and improving the cycle performance of the flow battery.

[0029] In one embodiment of this application, the carbon matrix is ​​selected from at least one of graphite felt, carbon felt, carbon cloth, and carbon paper. This application does not impose a particular limitation on the thickness of the carbon matrix, as long as it achieves the purpose of this application; for example, the thickness of the carbon matrix is ​​1–5 mm.

[0030] The second aspect of this application provides a method for preparing the electrode described in the first aspect of this application, comprising:

[0031] (1) Activate the carbon matrix to obtain the activated carbon matrix;

[0032] (2) An electrolyte is prepared by mixing SnCl₂·2H₂O, CeO₂ nanoparticles, and an acid; the acid is selected from sulfuric acid or hydrochloric acid; in the electrolyte, the concentration of SnCl₂·2H₂O is 0.01–0.5 mol / L, the concentration of the acid is 0.05–2 mol / L, and the concentration of CeO₂ nanoparticles is 0.1–10 g / L; for example, the concentration of SnCl₂·2H₂O in the electrolyte can be 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, or 0.2 g / L. The concentration of the acid can be 0.05 mol / L, 0.1 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, or any two of these values; the concentration of the CeO2 nanoparticles can be 0.1 g / L, 1 g / L, 3 g / L, 5 g / L, 8 g / L, 10 g / L, or any two of these values.

[0033] (3) Using the activated carbon matrix as the cathode electrode, immerse it in the electrolyte and electrochemically deposit SnO2 / CeO2 catalyst on the surface of the carbon matrix.

[0034] This application does not impose any particular limitation on the anode electrode used in electrochemical deposition, as long as it can achieve the purpose of this application. For example, the anode electrode can be at least one of a platinum electrode and a titanium-based ruthenium-iridium electrode.

[0035] In one embodiment of this application, the process further includes rinsing and drying after electrochemically depositing the SnO2 / CeO2 catalyst on the carbon substrate surface. This application does not specifically limit the method of rinsing and drying; any method that achieves the purpose of this application is acceptable. For example, after electrochemically depositing the SnO2 / CeO2 catalyst on the carbon substrate surface, the catalyst can be rinsed with deionized water and dried in an oven at 50–80°C for later use.

[0036] In one embodiment of this application, the current density of the electrochemical deposition is 4–8 mA / cm². 2 The time is 0.5 to 1.5 hours. For example, the current density of the electrochemical deposition can be 4 mA / cm². 2 6mA / cm 2 8mA / cm 2The time can be any range of two values, such as 0.5 hours, 1 hour, 1.5 hours, or any range of two values. This application does not impose a particular limitation on the electrochemical deposition temperature; any temperature that achieves the purpose of this application is acceptable. For example, the electrochemical deposition temperature can be 10–40°C.

[0037] This application does not specifically limit the specific operation method of the electrochemical deposition. For example, electrochemical deposition can be carried out by a dual-cell electrolytic cell, and ultrasonic vibration or magnetic stirring can be used in the electrolysis process of the dual-cell electrolytic cell.

[0038] In one embodiment of this application, the CeO2 nanoparticles have a size of 10–50 nm. For example, the size of the CeO2 nanoparticles can be 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, or a range consisting of any two of these values. The size of the CeO2 nanoparticles within this application range is more conducive to their electrodeposition on a carbon substrate.

[0039] In one embodiment of this application, the carbon matrix is ​​selected from at least one of graphite felt, carbon felt, carbon cloth, and carbon paper. This application does not impose a particular limitation on the thickness of the carbon matrix, as long as it achieves the purpose of this application; for example, the thickness of the carbon matrix is ​​1–5 mm.

[0040] In one embodiment of this application, the step of activating the carbon matrix includes:

[0041] The carbon matrix is ​​placed in deionized water and boiled for 1-2 hours; then placed in acid and treated at 80-120°C for 8-12 hours; rinsed with deionized water and dried to obtain the activated carbon matrix; the acid is selected from sulfuric acid or hydrochloric acid.

[0042] In this application, the concentration of acid in the carbon matrix activation step is not particularly limited, as long as it can achieve the purpose of this application. For example, concentrated sulfuric acid, i.e., sulfuric acid with a concentration greater than 98 wt%, or concentrated hydrochloric acid, i.e., hydrochloric acid with a concentration between 36 wt% and 38 wt%, can be used.

[0043] In the step of activating the carbon matrix, the carbon matrix is ​​placed in deionized water and boiled for 1 to 2 hours, which can better remove soluble impurities and dust from the carbon matrix; it is placed in acid and treated at 80 to 120°C for 8 to 12 hours, which can better remove acid-soluble metal impurities from the surface of the carbon matrix, while activating the carbon matrix and improving its hydrophilicity.

[0044] In this application, the drying temperature and method are not particularly limited, as long as they can achieve the purpose of this application. For example, drying can be carried out in an oven at 40 to 80 degrees Celsius.

[0045] A third aspect of this application provides a flow battery comprising the electrode described in the first aspect of this application or the electrode prepared by the method described in the second aspect of this application.

[0046] It should be noted that, in the specific embodiments of this application, a vanadium redox flow battery is used as an example of a flow battery to explain this application; however, the flow battery of this application is not limited to a vanadium redox flow battery. The specific technical solution is as follows:

[0047] The electrode described in this application can be used as either the positive or negative electrode of a flow battery, without any particular limitation. When the electrode described in this application is used as the negative electrode of a flow battery, the positive electrode can be either the electrode described in this application or a carbon matrix. This application does not specifically limit the carbon matrix, as long as it achieves the purpose of this application. For example, the carbon matrix can be selected from at least one of graphite felt, carbon felt, carbon cloth, and carbon paper. When the electrode described in this application is used as the positive electrode of a flow battery, the negative electrode can be either the electrode described in this application or a carbon matrix. This application does not specifically limit the carbon matrix, as long as it achieves the purpose of this application. For example, the carbon matrix can be selected from at least one of graphite felt, carbon felt, carbon cloth, and carbon paper. When the electrode described in this application is used as the positive electrode, it has a positive effect on improving the battery's charge and discharge efficiency. When the electrode is used as the negative electrode, in addition to improving the battery's charge and discharge efficiency, it also has the effect of inhibiting the hydrogen evolution reaction at the negative electrode.

[0048] This application does not impose any particular limitation on the thickness of the positive and negative electrodes, as long as the purpose of this application can be achieved. For example, the thickness of the positive electrode can be from 1 mm to 3 mm, and the thickness of the negative electrode can be from 1 mm to 3 mm.

[0049] In this application, the flow battery also includes a separator. This application does not impose any particular limitation on the separator, as long as it achieves the purpose of this application. For example, the separator material can be selected from, but is not limited to, at least one of perfluorosulfonic acid membranes and polyetheretherketone membranes. This application does not impose any particular limitation on the number of layers in the separator, as long as it achieves the purpose of this application; for example, the separator can be a single-layer thin film or a multi-layer composite thin film.

[0050] This application does not impose any particular limitation on the thickness of the diaphragm, as long as it achieves the purpose of this application. For example, the thickness of the diaphragm can be from 25 μm to 180 μm.

[0051] In this application, the flow battery also includes an electrolyte. This application does not impose any particular restrictions on the electrolyte, as long as it achieves the purpose of this application.

[0052] In one embodiment of this application, the electrolyte includes vanadium salt. This application does not have any particular limitation on the type of vanadium salt, as long as it can achieve the purpose of this application. For example, the vanadium salt can be selected from, but is not limited to, at least one of VOSO4, V2O5 and NH4VO3.

[0053] This application does not impose any particular limitation on the content of vanadium salt in the electrolyte, as long as the purpose of this application is achieved. For example, based on the mass of the electrolyte, the mass percentage content of vanadium salt is 18% to 38%.

[0054] The preparation method of the electrolyte in this application is not particularly limited, as long as it can achieve the purpose of this invention. For example, various solvents in the electrolyte can be mixed, and then electrolyte vanadium salts or other substances can be added and mixed evenly.

[0055] The preparation process of the vanadium redox flow battery of this application is well known to those skilled in the art, and this application has no particular limitations. For example, the preparation process of the vanadium redox flow battery may include, but is not limited to, the following steps: installing the positive and negative electrodes in the stack, installing the ion-conducting membrane between the positive and negative electrodes, fixing the stack with screws to ensure complete sealing; placing the electrolyte in the positive and negative electrolyte storage tanks of the flow battery respectively, connecting the electrolyte storage tanks to the installed stack through acid-resistant pipelines, and using a peristaltic pump to pump the electrolyte in the storage tanks to the stack for the charge and discharge reaction of the vanadium redox flow battery.

[0056] Example

[0057] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below. Furthermore, unless otherwise specified, "parts" and "%" refer to mass, and the temperature is room temperature, i.e., 20°C to 30°C.

[0058] Test methods and equipment:

[0059] Method for determining the mass percentage content of SnO2 / CeO2 catalyst

[0060] The electrodes before and after electrodeposition were weighed using an electronic balance. The mass of the SnO2 / CeO2 catalyst was calculated by the mass difference between the electrodes before and after electrodeposition. Based on the mass of the electrode after electrodeposition (the graphite felt on which the catalyst is supported), the mass percentage of the SnO2 / CeO2 catalyst was calculated.

[0061] Electrochemical testing

[0062] A three-electrode system was constructed to conduct electrochemical tests on the catalyst-loaded graphite felt using an electrochemical workstation, obtaining cyclic voltammetry results. A platinum electrode clamp was used to hold the catalyst-loaded graphite felt as the working electrode, a platinum sheet electrode as the auxiliary electrode, and a mercurous sulfate electrode as the reference electrode. The electrolyte was a vanadium electrolyte (1.5 mol / L VOSO4 solution). Electrochemical tests were conducted at room temperature and 101 kPa using a CHI604C electrochemical workstation. The voltage window for measurement was 0.3 V to 1.2 V, and the scan rate was 0.05 V / s.

[0063] Charge-discharge cycle test

[0064] The catalyst-loaded graphite felt was assembled into a vanadium redox flow battery for charge-discharge testing. Specifically, the vanadium redox flow battery was left to stand at room temperature and 101 kPa for 10 minutes, and then charged at 80 mA / cm². 2 Constant current charging and discharging were performed at a constant current density, with a voltage window ranging from 0.8V to 1.65V. The initial discharge capacity was recorded, and this constituted one charge-discharge cycle. This process was repeated up to nine cycles, and the charge-discharge capacity after the ninth cycle was recorded. Coulombic efficiency (CE) = charge capacity / discharge capacity. A Newway charge-discharge meter was used for testing.

[0065] Example 1

[0066] <Electrode Pretreatment>

[0067] A 3mm thick graphite felt was placed in deionized water and boiled for 1 hour. After being removed, it was placed in 98wt% concentrated sulfuric acid and treated at 100℃ for 8 hours. After being removed, it was rinsed with deionized water, dried, and cut to obtain a 3cm×3cm pretreated graphite felt for use.

[0068] <Catalyst Support>

[0069] SnCl2·2H2O, CeO2 nanoparticles (20 nm in size) were mixed with sulfuric acid to obtain an electrolyte. The concentration of SnCl2·2H2O in the electrolyte was 0.1 mol / L, the concentration of sulfuric acid was 0.1 mol / L, and the concentration of CeO2 nanoparticles was 1.0 g / L.

[0070] Pretreated graphite felt was used as the cathode electrode, and platinum was used as the anode electrode. The electrode was immersed in a dual-cell electrolytic cell containing electrolyte and electrochemical deposition was performed under ultrasonic vibration at a current density of 6 mA / cm². 2Electrodeposition was performed at room temperature for 1 hour to electrochemically deposit SnO2 / CeO2 catalyst on the surface of graphite felt (electrochemical reaction: SnCl2 + O2 → SnO2 + Cl2). The surface was then rinsed with deionized water and dried to obtain graphite felt with catalyst support. Based on the mass of the graphite felt with catalyst support, the mass percentage of SnO2 / CeO2 catalyst was 2.31%.

[0071] <Preparation of Electrolyte>

[0072] VOSO4 was dissolved in 3 mol / L sulfuric acid, resulting in a 1.5 mol / L VOSO4 solution. This VOSO4 solution was then placed in the cathode cell of an H-type electrolytic cell for electrolysis, while the anode cell contained 3 mol / L sulfuric acid. Electrolysis was performed at 50 mA / cm². 2 At a current density of 1.5 hours, after electrolytic reduction using graphite felt as an electrode, a negative electrode electrolyte is obtained in the cathode cell.

[0073] <Septum>

[0074] A perfluorosulfonic acid membrane with a thickness of 180 μm was used as the diaphragm.

[0075] <Preparation of all-vanadium redox flow batteries>

[0076] The prepared negative electrode electrolyte was placed in the negative electrode tank of the flow battery device, and a 1.5 mol / L VOSO4 solution was placed in the positive electrode tank of the flow battery device. The catalyst-loaded graphite felt was used as the negative electrode, the pretreated graphite felt as the positive electrode, and the perfluorosulfonic acid membrane as the separator. The separator was installed between the positive and negative electrodes, and the stack was fixed with screws to ensure complete sealing. The electrolyte tank was connected to the installed stack through an acid-resistant pipeline, and the electrolyte was pumped from the tank to the stack using a peristaltic pump for charge and discharge testing.

[0077] Examples 2 to 9

[0078] Except for adjusting the concentration A of catalyst modifier 1 and the concentration B of catalyst modifier 2 according to Table 1 in the <Catalyst Loading> step, and changing the mass percentage C of SnO2 / CeO2 catalyst accordingly, the rest is the same as in Example 1.

[0079] In Table 1, SnCl2·2H2O is designated as catalyst modifier 1, and CeO2 nanoparticles are designated as catalyst modifier 2; in the <catalyst loading> step, the concentration of SnCl2·2H2O in the electrolyte is designated as A, and the concentration of CeO2 nanoparticles is designated as B; based on the mass of the graphite felt supporting the catalyst, the mass percentage of the SnO2 / CeO2 catalyst is designated as C.

[0080] Comparative Example 1

[0081] Except for omitting the <catalyst loading> step and replacing the "pretreated graphite felt" obtained in <electrode pretreatment> with the "catalyst-loaded graphite felt" in <preparation of vanadium redox flow battery>, the rest is the same as in Example 1.

[0082] Comparative Example 2

[0083] The steps for <catalyst loading> are as follows: "SnCl2·2H2O is mixed with sulfuric acid to obtain an electrolyte; the concentration of SnCl2·2H2O in the electrolyte is 0.1 mol / L, and the concentration of sulfuric acid is 0.1 mol / L; pretreated graphite felt is used as the cathode electrode, and platinum is used as the anode electrode. The electrode is immersed in a dual-cell electrolytic cell containing the electrolyte and electrochemical deposition is performed under ultrasonic vibration at a current density of 6 mA / cm²." 2 Electrodeposition was performed at room temperature for 1 hour to electrochemically deposit SnO2 catalyst on the surface of graphite felt (electrochemical reaction: SnCl2 + O2 → SnO2 + Cl2). The surface was then rinsed with deionized water and dried to obtain graphite felt with catalyst support. Based on the mass of the graphite felt with catalyst support, the mass percentage of SnO2 catalyst was 2.21%.

[0084] The steps for <electrode pretreatment>, <electrolyte preparation>, <separator>, and <preparation of vanadium redox flow battery> are the same as in Example 1.

[0085] Comparative Example 3

[0086] The steps for <catalyst loading> are as follows: "CeO2 nanoparticles (20 nm in size) are mixed with sulfuric acid to obtain an electrolyte; in the electrolyte, the concentration of sulfuric acid is 0.1 mol / L and the concentration of CeO2 nanoparticles is 1.0 g / L; pretreated graphite felt is used as the cathode electrode, and platinum is used as the anode electrode. The mixture is immersed in a dual-cell electrolytic cell containing the electrolyte and electrochemical deposition is performed under ultrasonic vibration at a current density of 6 mA / cm²." 2 Electrodeposition was performed at room temperature for 1 hour to electrochemically deposit CeO2 catalyst on the surface of graphite felt. The graphite felt was then rinsed with deionized water and dried to obtain a graphite felt with catalyst supported. Based on the mass of the graphite felt with catalyst supported, the mass percentage of CeO2 catalyst was 0.09%.

[0087] The steps for <electrode pretreatment>, <electrolyte preparation>, <separator>, and <preparation of vanadium redox flow battery> are the same as in Example 1.

[0088] The preparation parameters for each embodiment and comparative example are shown in Table 1.

[0089] Table 1

[0090] Catalyst Modification 1 A(mol / L) Catalyst Modification 2 B(g / L) C(％) Example 1 <![CDATA[SnCl2·2H2O]]> 0.1 <![CDATA[CeO2]]> 1.0 2.31 Example 2 <![CDATA[SnCl2·2H2O]]> 0.01 <![CDATA[CeO2]]> 1.0 0.46 Example 3 <![CDATA[SnCl2·2H2O]]> 0.05 <![CDATA[CeO2]]> 1.0 1.37 Example 4 <![CDATA[SnCl2·2H2O]]> 0.25 <![CDATA[CeO2]]> 1.0 3.7 Example 5 <![CDATA[SnCl2·2H2O]]> 0.5 <![CDATA[CeO2]]> 1.0 8.48 Example 6 <![CDATA[SnCl2·2H2O]]> 0.1 <![CDATA[CeO2]]> 0.1 2.17 Example 7 <![CDATA[SnCl2·2H2O]]> 0.1 <![CDATA[CeO2]]> 0.5 2.22 Example 8 <![CDATA[SnCl2·2H2O]]> 0.1 <![CDATA[CeO2]]> 5.0 2.36 Example 9 <![CDATA[SnCl2·2H2O]]> 0.1 <![CDATA[CeO2]]> 10 2.56 Comparative Example 1 / / / / / Comparative Example 2 <![CDATA[SnCl2·2H2O]]> 0.1 / / / Comparative Example 3 / / <![CDATA[CeO2]]> 1.0 /

[0091] In Table 1, " / " indicates that there are no relevant parameters.

[0092] The discharge capacity of the vanadium redox flow battery was obtained using the above charge-discharge cycle test method. Figure 1 The discharge capacity results of the all-vanadium redox flow batteries prepared in Examples 1 to 9 and Comparative Examples 1 to 3 are shown below. Figure 1 It can be seen that, compared with Comparative Examples 1 to 3, Examples 1 to 9 have higher discharge capacity, indicating that the electrode supported on SnO2 / CeO2 catalyst improves the redox activity and thus increases the battery capacity. At the same time, the catalyst prevents vanadium ions from precipitating on the electrode surface and causing irreversible capacity loss, thereby improving the battery capacity from these two aspects. Figure 2A and Figure 2B The coulombic efficiency results of the all-vanadium redox flow batteries prepared in Examples 1 to 9 and Comparative Examples 1 to 3 are shown below. Figure 2A and Figure 2B It can be seen that, compared with Comparative Examples 1 to 3, Examples 1 to 9 have higher coulombic efficiencies, indicating that the electrode using the SnO2 / CeO2 catalyst has more oxygen vacancies, which enhances the redox activity of vanadium ions in the vanadium redox flow battery, causing them to occur preferentially over side reactions, thereby improving the coulombic efficiency.

[0093] Comparative Examples 2 and 3 demonstrate the battery performance under conditions with only one catalyst. SnO2 has numerous oxygen vacancies both on its surface and inside; however, its conductivity at room temperature and without doping is not as good as graphite. Therefore, the performance enhancement effect is not significant when SnO2 is used as the only catalyst. CeO2, on the other hand, has oxygen vacancies on its surface. When CeO2 is used as the only catalyst, oxygen transport within the material is weak, which is detrimental to redox reactions. Therefore, CeO2 is also unsuitable as a catalyst. The SnO2 / CeO2 catalyst of this application exhibits an interaction between the two substances that optimize each other's performance deficiencies, improving both conductivity and redox activity, thereby enhancing battery performance.

[0094] The cyclic voltammetry results of the electrode of this application obtained using the above electrochemical testing method are as follows: Figure 3 As shown, Figure 3 The graphite felt cyclic voltammetry results for the supported catalysts prepared in Examples 1, 3, 5, 6, 9, and Comparative Example 1 are shown. Examples 1, 3, and 5 represent the effect of changing the SnO2 concentration on the hydrogen evolution reaction, while Examples 1, 6, and 9 represent the effect of the CeO2 concentration on the hydrogen evolution reaction. Figure 3 It can be seen that, compared with Comparative Example 1, the graphite felt with catalyst supported in this application has a higher hydrogen evolution overpotential, indicating that the graphite felt with catalyst supported in this application can suppress the hydrogen evolution reaction inside the battery.

[0095] In summary, when the electrode of this application is applied to a vanadium redox flow battery, it suppresses the hydrogen evolution reaction inside the battery, improves the charge and discharge efficiency of the flow battery, enhances the redox activity of vanadium ions, and prevents vanadium ions from precipitating on the electrode surface and causing irreversible capacity loss.

[0096] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. An electrode comprising a carbon matrix and a SnO2 / CeO2 catalyst supported on the surface of the carbon matrix.

2. The electrode according to claim 1, wherein, Based on the mass of the electrode, the mass percentage of the SnO2 / CeO2 catalyst is 0.1% to 10%.

3. The electrode according to claim 1, wherein, Based on the mass of the electrode, the mass percentage of the SnO2 / CeO2 catalyst is 0.3% to 10%.

4. The electrode according to claim 1, wherein, The carbon matrix is ​​selected from at least one of graphite felt, carbon felt, carbon cloth, and carbon paper.

5. A method for preparing an electrode according to any one of claims 1 to 4, comprising: (1) Activate the carbon matrix to obtain the activated carbon matrix; (2) SnCl2·2H2O, CeO2 nanoparticles and acid are mixed to prepare an electrolyte; the acid is selected from sulfuric acid or hydrochloric acid; in the electrolyte, the concentration of SnCl2·2H2O is 0.01-0.5 mol / L, the concentration of the acid is 0.05-2 mol / L, and the concentration of CeO2 nanoparticles is 0.1-10 g / L; (3) Using the activated carbon matrix as the cathode electrode, immerse it in the electrolyte and electrochemically deposit SnO2 / CeO2 catalyst on the surface of the carbon matrix.

6. The preparation method according to claim 5, wherein, The current density of the electrochemical deposition is 4–8 mA / cm². 2 The time is 0.5 to 1.5 hours.

7. The preparation method according to claim 5, wherein, The CeO2 nanoparticles have a size of 10–50 nm.

8. The preparation method according to claim 5, wherein, The carbon matrix is ​​selected from at least one of graphite felt, carbon felt, carbon cloth, and carbon paper.

9. The preparation method according to claim 5, wherein, The step of activating the carbon matrix includes: The carbon matrix is ​​placed in deionized water and boiled for 1-2 hours; then placed in acid and treated at 80-120°C for 8-12 hours; rinsed with deionized water and dried to obtain the activated carbon matrix; the acid is selected from sulfuric acid or hydrochloric acid.

10. A flow battery comprising an electrode according to any one of claims 1 to 4 or an electrode prepared by any one of claims 5 to 9.

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