A TiO2@Ni@C composite graphite felt electrode and its preparation method

Abstract

The application belongs to the field of electrode materials, and particularly discloses a TiO2@Ni@C composite graphite felt electrode and a preparation method thereof. The method comprises the following steps: S1: performing alkaline chemical oxidation etching surface pretreatment on the graphite felt to obtain pretreated graphite felt; S2: performing electrodeposition of NiTi-LDH on the pretreated graphite felt to obtain a NiTi-LDH graphite felt material; and S3: performing in-situ chemical reduction on the NiTi-LDH graphite felt material to obtain the TiO2@Ni@C composite graphite felt electrode. The method of the application performs surface modification on the graphite felt by using electrodeposition and in-situ chemical reduction, and has the characteristics of easy-to-realize reaction conditions, low energy consumption and high modification and activation efficiency.

Description

Technical Field

[0001] This invention belongs to the field of electrode materials, specifically relating to a TiO2@Ni@C composite graphite felt electrode and its preparation method. Background Technology

[0002] With the development of new energy technologies, large-scale energy storage technologies such as flow batteries have attracted increasing attention due to their inherent safety and long cycle life. Among various energy storage devices, carbon materials are considered a preferred option due to their good electronic conductivity and thermal / mechanical stability. However, problems such as small specific surface area, poor electrolyte wettability, and low catalytic activity limit their development and application in aqueous energy storage devices. For example, in the application of vanadium redox flow batteries, graphite felt is currently the mainstream electrode material. However, existing graphite felt electrode materials are not specifically developed and designed for vanadium batteries, and their existing specific surface area and vanadium ion catalytic activity both need to be improved.

[0003] To address the aforementioned issues, current methods primarily involve surface modification and activation of graphite felt electrode materials. Activation treatments mainly include the following: 1) High-temperature heat treatment: This involves controlling the temperature between 400 and 550°C for 4 to 30 hours to increase the number of oxygen-containing functional groups on the carbon material surface, as illustrated in Chinese Patent CN 109987604A; 2) Strong oxidizing acid treatment: Under high-temperature conditions such as hydrothermal / solvothermal, strong oxidizing acids are used to introduce oxygen-containing functional groups, improving the hydrophilicity of the carbon material, as illustrated in Chinese Patent CN 104018340A; 3) Plasmonic method: Under vacuum conditions, a plasma beam is used to bombard the surface of the carbon material, thereby introducing defects; 4) Electrochemical activation method, as illustrated in *Science in China: Chemistry*, 2014, 44, 1280-1288. However, these methods all have limitations to varying degrees, such as stringent reaction conditions, strict equipment requirements, and relatively low activation efficiency. Another approach is to use surface-supported catalysts to provide more catalytic active sites and improve catalytic reaction efficiency. However, ensuring the long-term stability of the catalyst on the graphite felt surface is a problem that urgently needs to be solved.

[0004] Therefore, existing technologies need to be improved. Summary of the Invention

[0005] The purpose of this invention is to provide a novel TiO2@Ni@C composite graphite felt electrode and its preparation method. This electrode can be used as an electrode for energy storage devices such as alkali metal secondary batteries, supercapacitors, and flow batteries.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] According to a first aspect of the present invention, a method for preparing a TiO2@Ni@C composite graphite felt electrode is provided, comprising the following steps:

[0008] S1: The graphite felt is subjected to alkaline chemical oxidation etching surface pretreatment to obtain pretreated graphite felt;

[0009] S2: Electrodeposit NiTi-LDH on the pretreated graphite felt to obtain NiTi-LDH graphite felt material;

[0010] S3: The NiTi-LDH graphite felt material is subjected to in-situ chemical reduction to obtain a TiO2@Ni@C composite graphite felt electrode.

[0011] As a further implementation, step S1 includes the following sub-steps:

[0012] S11: Dissolve an alkaline substance in water to obtain an alkaline solution;

[0013] S12: Dissolve the oxidizing substance in the alkaline solution to obtain an alkaline chemical oxidation etching solution;

[0014] S13: Immerse the graphite felt in the alkaline chemical oxidation etching solution to perform alkaline chemical oxidation etching surface pretreatment on the graphite felt, and obtain the pretreated graphite felt.

[0015] As a further implementation, in sub-step S11, the alkaline substance is one or more of sodium hydroxide, potassium hydroxide, and ammonia water.

[0016] As a further implementation, in sub-step S11, the concentration of the alkaline substance in the alkaline solution is 1~10 mol / L.

[0017] As a further implementation, in sub-step S12, the oxidizing substance is one or more of sodium persulfate, potassium persulfate, ammonium persulfate, potassium bromate, potassium chlorate, potassium perchlorate, potassium permanganate, and hydrogen peroxide.

[0018] As a further embodiment, in sub-step S12, the concentration of oxidizing substances in the alkaline chemical oxidation etching solution is 1~5 mol / L.

[0019] As a further implementation, in sub-step S13, the soaking temperature is room temperature to 100°C, and the soaking time is 1 to 24 hours.

[0020] As a further implementation, step S2 includes the following sub-steps:

[0021] S21: Prepare a mixed solution of nickel and titanium sources;

[0022] S22: Using the nickel-titanium source mixed solution as the electrolyte, a three-electrode system is adopted, with the pretreated graphite felt as the working electrode, NiTi-LDH is electrodeposited on the pretreated graphite felt in constant potential mode to obtain NiTi-LDH graphite felt material.

[0023] As a further implementation, in sub-step S21, the concentration of the nickel source in the nickel-titanium source mixed solution is 0.1~2 mol / L, the concentration of the titanium source is 0.1~1 mol / L, and the nickel-titanium molar ratio is 2~3:1.

[0024] As a further embodiment, the nickel source is one or more of nickel nitrate, nickel sulfate, and nickel chloride.

[0025] As a further embodiment, the titanium source is one or more of titanium sulfate, titanium tetrachloride, and titanium subsulfate.

[0026] As a further implementation, in sub-step S22, the electrodeposition potential is -0.8V to -1.5V, and the electrodeposition time is 300 to 800s.

[0027] As a further implementation, step S3 includes the following sub-steps:

[0028] S31: Dissolve the reducing agent and alkali in water to obtain a chemical reducing solution;

[0029] S32: The NiTi-LDH graphite felt material is placed in the chemical reduction solution for a chemical reduction reaction to obtain a TiO2@Ni@C composite graphite felt electrode.

[0030] As a further embodiment, in sub-step S31, the reducing agent is sodium hypophosphite, and the alkali is sodium hydroxide.

[0031] As a further implementation, in sub-step S32, the temperature of the chemical reduction reaction is 100~160℃, and the reaction time is 6~12h.

[0032] According to a second aspect of the present invention, a TiO2@Ni@C composite graphite felt electrode is provided, which is prepared by the above-described preparation method.

[0033] By adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art:

[0034] This invention constructs a unique TiO2@Ni@C composite hierarchical graphite felt electrode material through electrochemical deposition and in-situ chemical reduction. Based on the structural characteristics of hydrotalcite, a uniform distribution of Ni and Ti elements is achieved on the graphite felt electrode surface, which facilitates the full exposure of electrochemical active sites and enhances electrocatalytic reaction capabilities. Simultaneously, the in-situ reduced metallic nickel firmly immobilizes the TiO2 catalyst on the graphite felt surface, improving the stability of the catalytic active sites and increasing the specific surface area of ​​the electrode material. Furthermore, the high electronic conductivity of metallic Ni helps increase the overall conductivity of the composite graphite felt electrode material, resulting in excellent electrochemical performance.

[0035] The method of the present invention has the advantages of simple reaction conditions, easy implementation, low energy consumption, high efficiency and strong operability. The resulting composite electrode material has a stable structure, large specific surface area, good conductivity, good hydrophilicity and high electrocatalytic activity. It can be applied to electrode materials for energy storage devices such as alkali metal secondary batteries, supercapacitors and flow batteries. Attached Figure Description

[0036] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description of the present invention will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other embodiments can be obtained based on these drawings without creative effort.

[0037] Figure 1 A flowchart illustrating the preparation method of the TiO2@Ni@C composite graphite felt electrode provided by this invention;

[0038] Figure 2 This is a schematic diagram illustrating the principle of the preparation method of the present invention;

[0039] Figure 3 This is a flowchart of a graphite felt pretreatment process provided in one embodiment of the present invention;

[0040] Figure 4 This is a flowchart illustrating the process of electrodepositing NiTi-LDH on a pretreated graphite felt according to one embodiment of the present invention;

[0041] Figure 5 This is a flowchart of the in-situ chemical reduction process of NiTi-LDH graphite felt material provided in one embodiment of the present invention;

[0042] Figure 6The graph shows a comparison of the polarization curves of the TiO2@Ni@C composite graphite felt electrode prepared in the embodiment of the present invention and a commercial graphite felt electrode in the positive electrolyte of a vanadium redox flow battery. In the graph, a represents the TiO2@Ni@C composite graphite felt electrode prepared in the embodiment of the present invention, and b represents the commercial graphite felt electrode.

[0043] Figure 7 The images show the contact angle test results of the TiO2@Ni@C composite graphite felt electrode prepared in the embodiment of the present invention and a commercial graphite felt electrode in the positive electrolyte of a vanadium redox flow battery. (a) is the contact angle test result of the commercial graphite felt electrode, and (b) is the contact angle test result of the TiO2@Ni@C composite graphite felt electrode prepared in the embodiment of the present invention. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0045] Specific embodiments of the invention are disclosed herein as needed; however, it should be understood that the embodiments disclosed herein are merely examples of the invention that may be implemented in various alternative forms. In the following description, various operating parameters and components are described in several contemplated embodiments. These specific parameters and components are provided as examples only and are not intended to be limiting.

[0046] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0047] The first aspect of this invention provides a method for preparing a TiO2@Ni@C composite graphite felt electrode, such as... Figure 1 As shown, the method includes the following steps:

[0048] S1: The graphite felt is subjected to alkaline chemical oxidation etching surface pretreatment to obtain pretreated graphite felt;

[0049] S2: NiTi-LDH is electrodeposited on pretreated graphite felt to obtain NiTi-LDH graphite felt material;

[0050] S3: In-situ chemical reduction of NiTi-LDH graphite felt material was performed to obtain TiO2@Ni@C composite graphite felt electrode.

[0051] The method of this invention utilizes electrodeposition and in-situ chemical reduction to modify the surface of graphite felt, featuring easily achievable reaction conditions, low energy consumption, and high modification and activation efficiency. The graphite felt electrode modified using this method exhibits a high specific surface area, good conductivity, and catalytic activity, making it suitable as an electrode material for energy storage devices such as alkali metal secondary batteries, supercapacitors, and flow batteries.

[0052] The TiO2@Ni@C composite graphite felt electrode prepared by the method of this invention uses a three-dimensional mesh graphite felt as the substrate framework, with TiO2@Ni core-shell structure active components loaded on the carbon fiber surface. The carbon fiber nanowires serve as the core structure, and metallic Ni is uniformly dispersed in the TiO2 layer as nanoparticles, forming a TiO2@Ni composite outer layer. The TiO2@Ni composite structure encapsulates the outer layer of carbon fiber nanowires, thus forming a TiO2@Ni@C core-shell structure. This core-shell structure is interconnected through the interwoven carbon fibers of the graphite felt, forming a three-dimensional, continuous, conductive, highly active, and corrosion-resistant composite electrode structure.

[0053] Figure 2 The diagram illustrates the principle of the preparation method of the present invention. The left diagram shows a schematic diagram of the carbon fiber structure of the graphite felt, the middle diagram shows a schematic diagram after NiTi-LDH nanosheets are electrodeposited on the carbon fibers, and the right diagram shows a schematic diagram after the NiTi-LDH nanosheets are transformed into a TiO2@Ni composite structure.

[0054] The present invention will be further described below for each step.

[0055] Step S1 involves alkaline chemical oxidation etching surface pretreatment of graphite felt, which aims to: on the one hand, introduce oxygen-containing hydrophilic functional groups such as sulfonic acid groups and hydroxyl groups on the surface of graphite felt through liquid-phase chemical oxidation, thereby improving the hydrophilicity of the graphite felt surface; on the other hand, while maintaining the good mechanical properties of graphite felt, increase the surface roughness of graphite felt and improve its specific surface area through in-situ etching.

[0056] Alkaline chemical oxidation etching (AOES) refers to the oxidation, erosion, and etching of material surfaces using oxidants in an alkaline environment.

[0057] In some embodiments, such as Figure 3 As shown, step S1 includes the following sub-steps:

[0058] S11: Dissolve an alkaline substance in water to obtain an alkaline solution;

[0059] S12: Dissolve oxidizing substances in an alkaline solution to obtain an alkaline chemical oxidation etching solution;

[0060] S13: Immerse the graphite felt in an alkaline chemical oxidation etching solution to perform alkaline chemical oxidation etching surface pretreatment on the graphite felt, and obtain pretreated graphite felt.

[0061] In this embodiment, by first preparing an alkaline chemical oxidation etching solution and then immersing the graphite felt in the alkaline chemical oxidation etching solution for modification and activation, oxygen-containing hydrophilic groups can be introduced onto the surface of the graphite felt, thereby improving the hydrophilic properties of the graphite felt surface. At the same time, while maintaining the integrity of the main structure of the graphite felt, the surface roughness of the graphite felt can be increased, thereby increasing the specific surface area of ​​the graphite felt.

[0062] Sub-step S11 can be implemented in the following way: weigh a certain mass of alkaline substance, dissolve it in deionized water, and prepare an alkaline solution.

[0063] Preferably, the alkaline substance is one or more of sodium hydroxide, potassium hydroxide, and ammonia water.

[0064] Preferably, the concentration of the alkaline substance in the alkaline solution is 1~10 mol / L. The concentration of the alkaline substance can typically, but not limited to, be set to 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L, or 10 mol / L.

[0065] Sub-step S12 can be implemented as follows: Weigh a certain mass of oxidizing substance, add it quickly to an alkaline solution at room temperature, and stir continuously until completely dissolved to obtain an alkaline chemical oxidation etching solution.

[0066] Preferably, the oxidizing substance is one or more of sodium persulfate, potassium persulfate, ammonium persulfate, potassium bromate, potassium chlorate, potassium perchlorate, potassium permanganate, and hydrogen peroxide.

[0067] Preferably, the concentration of the oxidizing agent in the alkaline chemical oxidation etching solution is 1~5 mol / L. The concentration of the oxidizing agent can typically, but not limited to, be set to 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, or 5 mol / L.

[0068] Preferably, the concentration ratio of alkaline substance to oxidizing substance in the alkaline chemical oxidation etching solution is 1:1 to 5:1. The concentration ratio of alkaline substance to oxidizing substance can typically, but not limited to, be set to 1:1, 2:1, 3:1, 4:1, or 5:1.

[0069] Sub-step S13 can be implemented by immersing the graphite felt in the above-mentioned alkaline chemical oxidation etching solution at a specified temperature for a specified time to perform alkaline chemical oxidation etching surface pretreatment on the graphite felt, thereby obtaining pretreated graphite felt.

[0070] Preferably, the specified temperature is room temperature to 100°C, and the specified time is 1 to 24 hours. The specified temperature can typically, but not limitedly, be set to room temperature, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, or 100°C, and the specified time can typically, but not limitedly, be set to 1 hour, 3 hours, 6 hours, 9 hours, 12 hours, 15 hours, 18 hours, 21 hours, or 24 hours.

[0071] Step S2 involves uniformly electrodepositing NiTi-LDH nanosheets onto the surface of a graphite felt pretreated with liquid-phase chemical oxidation using an electrochemical deposition method. NiTi-LDH is a nickel-titanium layered bimetallic hydroxide, composed of Ni... 2+ With Ti 4+ This invention constructs a two-dimensional layered material, belonging to the hydrotalcite family, which consists of positively charged hydroxide layers and interlayer fillings with exchangeable anions and water molecules. Based on the structural characteristics of hydrotalcite, this invention achieves a uniform distribution of Ni and Ti elements on the surface of a graphite felt electrode, which is beneficial for fully exposing electrochemical active sites and improving electrocatalytic reaction capabilities.

[0072] In some embodiments, such as Figure 4 As shown, step S2 includes the following sub-steps:

[0073] S21: Prepare a mixed solution of nickel and titanium sources;

[0074] S22: Using a mixed solution of nickel and titanium sources as the electrolyte, a three-electrode system is adopted, with pretreated graphite felt as the working electrode. NiTi-LDH is electrodeposited on the pretreated graphite felt in constant potential mode to obtain NiTi-LDH graphite felt material.

[0075] Preferably, in the nickel-titanium source mixed solution, the concentration of the nickel source is 0.1~2 mol / L, the concentration of the titanium source is 0.1~1 mol / L, and the nickel-titanium molar ratio is 2~3:1. The concentration of the nickel source can typically, but not limited to, be 0.1 mol / L, 0.2 mol / L, 0.4 mol / L, 0.6 mol / L, 0.8 mol / L, 1.0 mol / L, 1.2 mol / L, 1.4 mol / L, 1.6 mol / L, 1.8 mol / L, or 2 mol / L; the concentration of the titanium source can typically, but not limited to, be 0.1 mol / L, 0.2 mol / L, 0.4 mol / L, 0.6 mol / L, 0.8 mol / L, or 1.0 mol / L; and the nickel-titanium molar ratio can typically, but not limited to, be 2:1, 2.2:1, 2.4:1, 2.6:1, 2.8:1, or 3:1.

[0076] Preferably, the nickel source is one or more of nickel nitrate, nickel sulfate, and nickel chloride.

[0077] Preferably, the titanium source is one or more of titanium sulfate, titanium tetrachloride, and titanium sulfide.

[0078] Preferably, in sub-step S22, the electrodeposition potential is -0.8V to -1.5V, and the electrodeposition time is 300 to 800 s. The electrodeposition potential can typically, but is not limited to, be set to -0.8V, -0.9V, -1.0V, -1.1V, -1.2V, -1.3V, -1.4V, or -1.5V; the electrodeposition time can typically, but is not limited to, be set to 300 s, 400 s, 500 s, 600 s, 700 s, or 800 s. More preferably, the electrodeposition potential is -1.0V. In a specific example, step S2 is performed as follows: 100 ml of a mixed solution of 0.1~2 mol / L nickel source + 0.1~1 mol / L titanium source (Ni:Ti=2~3) is prepared as the electrolyte, Ag / AgCl is used as the reference, a platinum sheet is used as the counter electrode, and electrodeposition is performed for 300~800 s at a potential of -1.0V, thereby depositing NiTi-LDH on the surface of the graphite felt.

[0079] Step S3 involves the preparation of a TiO2@Ni@C composite graphite felt electrode through the reduction of chemically active NiTi-LDH. Specifically, an in-situ chemical reduction method is used to achieve the in-situ reduction transformation of NiTi-LDH on the graphite felt surface, thereby forming a multi-level TiO2@Ni@C structure. The in-situ reduced nickel can firmly fix the TiO2 catalyst on the graphite felt surface, improving the stability of the catalytic active sites and increasing the specific surface area of ​​the electrode material. Furthermore, thanks to the high electron conductivity of metallic Ni, the overall conductivity of the composite graphite felt electrode material is increased, resulting in excellent electrochemical performance. Utilizing the excellent electrocatalytic performance of TiO2 and the excellent electron transport performance of metallic Ni, the prepared electrode material exhibits good catalytic reaction capability.

[0080] In some embodiments, such as Figure 5 As shown, step S3 includes the following sub-steps:

[0081] S31: Dissolve the reducing agent and alkali in water to obtain a chemical reducing solution;

[0082] S32: NiTi-LDH graphite felt material is placed in a chemical reduction solution for chemical reduction reaction to obtain TiO2@Ni@C composite graphite felt electrode.

[0083] In an alkaline chemical reduction system, the reducing agent can reduce NiTi Ni in LDH layer 2+In-situ reduction to metallic Ni nanocrystals simultaneously induces dehydration, rearrangement, and phase transformation of the LDH structure, converting Ti species into TiO2 nanocrystals. During the reaction, a uniform TiO2@Ni layer is formed on the TiO2 and Ni surfaces; ultimately, atomically dispersed NiTi... LDH was in situ transformed into a composite shell structure with uniformly distributed metallic Ni and TiO2, which was then uniformly loaded onto the surface of carbon fiber nanowires on graphite felt, resulting in a TiO2@Ni@C composite graphite felt electrode. The presence of metallic Ni can greatly compensate for the poor conductivity of TiO2, while the core-shell structure design can improve the stability of the catalyst layer on the carbon nanofiber surface.

[0084] In some embodiments, the reducing agent is sodium hypophosphite, and the base is sodium hydroxide.

[0085] In a specific example, for instance, 1-5g of sodium hypophosphite and 1-5g of sodium hydroxide are dissolved in 40ml of deionized water to obtain a chemical reducing solution. In the alkaline chemical reducing system, sodium hypophosphite (NaH2PO2) acts as a reducing agent and undergoes an auto-oxidation-reduction reaction upon heating in the alkaline environment provided by NaOH, generating active hydrogen with strong reducing power (…). H) or reducing species such as phosphate; the above active reducing species can reduce NiTi Ni in LDH layer 2+ In situ reduction to metallic Ni nanocrystals simultaneously induces dehydration, rearrangement, and phase transformation of the LDH structure, transforming Ti species into TiO2 nanocrystals.

[0086] Preferably, in sub-step S33, the temperature of the chemical reduction reaction is 100~160℃, and the reaction time is 6~12h. The temperature of the chemical reduction reaction can typically, but not limitedly, be set to 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, or 160℃; the reaction time can typically, but not limitedly, be set to 6h, 7h, 8h, 9h, 10h, 11h, or 12h.

[0087] A second aspect of the present invention provides a TiO2@Ni@C composite graphite felt electrode, which is prepared by the above-described preparation method.

[0088] The present invention will be further explained and described below with reference to specific embodiments.

[0089] Example 1

[0090] 1) Weigh 10.0g of sodium hydroxide and dissolve it in 100mL of deionized water to prepare an alkaline solution. Weigh 2.8g of ammonium persulfate and add it to the alkaline solution at room temperature, stirring continuously until completely dissolved to obtain an alkaline chemical oxidation etching solution. Cut a 1×1 cm sample. 2Pretreated graphite felt can be obtained by immersing it in an alkaline chemical oxidation etching solution at 60°C for 6 hours.

[0091] 2) Prepare 100 ml of a mixed solution of 0.2 mol / L nickel nitrate and 0.1 mol / L titanium sulfate (Ni:Ti=2:1) ​​as the electrolyte, use Ag / AgCl as the reference, and use a platinum sheet as the counter electrode. Electrodeposit for 600 s at a potential of -1.0 V to obtain NiTi-LDH graphite felt material.

[0092] 3) Weigh 5g of sodium hypophosphite and 5g of sodium hydroxide and dissolve them in 40 ml of deionized water to prepare a chemical reducing solution. Immerse the graphite felt material obtained in step 2) in the chemical reducing solution and react at 160℃ for 6 hours. After taking it out, wash it 3 times with deionized water and dry it to obtain TiO2@Ni@C composite graphite felt electrode material.

[0093] Example 2

[0094] 1) Weigh 10.0g of sodium hydroxide and dissolve it in 100mL of deionized water to prepare an alkaline solution. Weigh 2.8g of ammonium persulfate and add it to the alkaline solution at room temperature, stirring continuously until completely dissolved to obtain an alkaline chemical oxidation etching solution. Cut a 1×1 cm sample. 2 Pretreated graphite felt can be obtained by immersing it in an alkaline chemical oxidation etching solution at 60°C for 6 hours.

[0095] 2) Prepare 100 ml of a mixed solution of 0.6 mol / L nickel sulfate and 0.2 mol / L titanium sulfate (Ni:Ti=3:1) as the electrolyte, use Ag / AgCl as the reference, and use a platinum sheet as the counter electrode. Electrodeposit for 500 s at a potential of -1.0 V to obtain NiTi-LDH graphite felt material.

[0096] 3) Weigh 3g of sodium hypophosphite and 2g of sodium hydroxide and dissolve them in 40ml of deionized water to prepare a chemical reducing solution. Immerse the graphite felt material obtained in step 2) in the chemical reducing solution and react at 120℃ for 8 hours. After taking it out, wash it 3 times with deionized water and dry it to obtain TiO2@Ni@C composite graphite felt electrode material.

[0097] Example 3

[0098] 1) Weigh 10.0 g of sodium hydroxide and dissolve it in 100 mL of deionized water to prepare an alkaline solution. Weigh 2.8 g of ammonium persulfate and add it to the alkaline solution at room temperature, stirring continuously until completely dissolved to obtain an alkaline chemical oxidation etching solution. Cut a 1×1 cm sample. 2Pretreated graphite felt can be obtained by immersing it in an alkaline chemical oxidation etching solution at 60°C for 6 hours.

[0099] 2) Prepare 100 ml of a mixed solution of 1.0 mol / L nickel nitrate and 0.5 mol / L titanium tetrachloride (Ni:Ti=2:1) ​​as the electrolyte, use Ag / AgCl as the reference, and use a platinum sheet as the counter electrode. Electrodeposit for 400 s at a potential of -1.0 V to obtain NiTi-LDH graphite felt material.

[0100] 3) Weigh 3g of sodium hypophosphite and 1g of sodium hydroxide and dissolve them in 40 ml of deionized water to prepare a chemical reducing solution. Immerse the graphite felt material obtained in step 2) in the chemical reducing solution and react at 100℃ for 12 hours. After taking it out, wash it 3 times with deionized water and dry it to obtain TiO2@Ni@C composite graphite felt electrode material.

[0101] Figure 6 This is a comparison of the polarization curves of the TiO2@Ni@C composite graphite felt electrode prepared in Example 1 of this invention and a commercial graphite felt electrode in the positive electrode electrolyte (1.6 mol / L VOSO4) of a vanadium redox flow battery. In the figure, a represents the TiO2@Ni@C composite graphite felt electrode prepared in Example 1 of this invention, and b represents the commercial graphite felt electrode. Figure 6 As can be seen, compared with ordinary commercial graphite felt electrode materials, the TiO2@Ni@C composite graphite felt electrode prepared in Example 1 of this invention has a higher slope and exhibits better electronic / ionic conductivity, which is conducive to achieving better electrochemical performance.

[0102] Table 1 shows the specific surface area (BET) test results of the TiO2@Ni@C composite graphite felt electrode prepared in Example 1 of this invention and the commercial graphite felt electrode, wherein the specific surface area of ​​the commercial graphite felt electrode is 1.3 m². 2 / g, while the specific surface area of ​​the TiO2@Ni@C composite graphite felt electrode prepared in Example 1 of this invention reaches 6.1 m². 2 / g, with a larger specific surface area.

[0103] Table 1. Specific surface area test of the TiO2@Ni@C composite graphite felt electrode prepared in Example 1 and the commercial graphite felt electrode.

[0104]

[0105] Figure 7The images show contact angle test results of the TiO2@Ni@C composite graphite felt electrode prepared in Example 2 of this invention and a commercial graphite felt electrode in the positive electrode electrolyte (1.6 mol / L VOSO4) of a vanadium redox flow battery. (a) shows the contact angle test result of the commercial graphite felt electrode, and (b) shows the contact angle test result of the TiO2@Ni@C composite graphite felt electrode prepared in this embodiment of the invention. Figure 7 As can be seen, compared with ordinary commercial graphite felt electrode materials, the TiO2@Ni@C composite graphite felt electrode prepared in Example 2 of this invention has a smaller contact angle and better electrolyte wettability.

[0106] Table 2 compares the peak currents of the TiO2@Ni@C composite graphite felt electrode prepared in Example 2 of this invention with those of a commercial graphite felt electrode. A higher peak current indicates a higher redox catalytic reaction capability. The peak current of the commercial graphite felt electrode is 0.23 A / cm². 2 Under the same testing conditions, the peak current of the TiO2@Ni@C composite graphite felt electrode prepared in Example 2 of this invention can reach 0.34 A / cm. 2 It exhibits more beneficial catalytic reaction performance.

[0107] Table 2. Peak current comparison between the TiO2@Ni@C composite graphite felt electrode prepared in Example 2 and the commercial graphite felt electrode.

[0108]

[0109] In summary, this invention utilizes electrodeposition and in-situ chemical reduction methods for surface modification of graphite felt. By leveraging the excellent electrocatalytic properties of TiO2 and the superior electron transport properties of metallic Ni, the prepared electrode material exhibits excellent catalytic reactivity. The preparation method of the TiO2@Ni@C composite graphite felt electrode provided by this invention is simple, uses readily available and inexpensive raw materials, has low energy consumption, high efficiency, and is easily scaled up. The structural and performance advantages of the composite graphite felt material obtained by this invention make it promising to overcome the current limitations of carbon-based materials in modification, activation, and as electrode materials for energy storage applications, thus promoting the application prospects of carbon materials in energy storage fields such as alkali metal secondary batteries, supercapacitors, and flow batteries.

[0110] Finally, it should be noted that the embodiments described above are only some, not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for preparing a TiO2@Ni@C composite graphite felt electrode, characterized in that, Includes the following steps: S1: The graphite felt is subjected to alkaline chemical oxidation etching surface pretreatment to obtain pretreated graphite felt; S2: Electrodeposit NiTi-LDH on the pretreated graphite felt to obtain NiTi-LDH graphite felt material; S3: The NiTi-LDH graphite felt material is subjected to in-situ chemical reduction to obtain a TiO2@Ni@C composite graphite felt electrode. The obtained TiO2@Ni@C composite graphite felt electrode uses a three-dimensional mesh graphite felt as the substrate framework and loads TiO2@Ni core-shell structure active components on the carbon fiber surface. In this case, carbon fiber nanowires serve as the core structure, and metallic Ni is uniformly dispersed in the TiO2 layer in the form of nanoparticles to form a TiO2@Ni composite structure. The TiO2@Ni composite structure is wrapped around the outer layer of carbon fiber nanowires, thereby forming a TiO2@Ni@C core-shell structure.

2. The method for preparing the TiO2@Ni@C composite graphite felt electrode according to claim 1, characterized in that, Step S1 includes the following sub-steps: S11: Dissolve an alkaline substance in water to obtain an alkaline solution; S12: Dissolve the oxidizing substance in the alkaline solution to obtain an alkaline chemical oxidation etching solution; S13: Immerse the graphite felt in the alkaline chemical oxidation etching solution to perform alkaline chemical oxidation etching surface pretreatment on the graphite felt, and obtain the pretreated graphite felt.

3. The method for preparing the TiO2@Ni@C composite graphite felt electrode according to claim 2, characterized in that, The alkaline substance is one or more of sodium hydroxide, potassium hydroxide, and ammonia water, and the concentration of the alkaline substance in the alkaline solution is 1~10 mol / L; the oxidizing substance is one or more of sodium persulfate, potassium persulfate, ammonium persulfate, potassium bromate, potassium chlorate, potassium perchlorate, potassium permanganate, and hydrogen peroxide, and the concentration of the oxidizing substance in the alkaline chemical oxidation etching solution is 1~5 mol / L.

4. The method for preparing the TiO2@Ni@C composite graphite felt electrode according to claim 2, characterized in that, In sub-step S13, the soaking temperature is room temperature to 100℃, and the soaking time is 1 to 24 hours.

5. The method for preparing the TiO2@Ni@C composite graphite felt electrode according to claim 1, characterized in that, Step S2 includes the following sub-steps: S21: Prepare a mixed solution of nickel and titanium sources; S22: Using the nickel-titanium source mixed solution as the electrolyte, a three-electrode system is adopted, with the pretreated graphite felt as the working electrode, NiTi-LDH is electrodeposited on the pretreated graphite felt in constant potential mode to obtain NiTi-LDH graphite felt material.

6. The method for preparing the TiO2@Ni@C composite graphite felt electrode according to claim 5, characterized in that, In sub-step S21, the nickel source and titanium source mixed solution has a nickel source concentration of 0.1~2 mol / L, a titanium source concentration of 0.1~1 mol / L, and a nickel-titanium molar ratio of 2~3:

1. The nickel source is one or more of nickel nitrate, nickel sulfate, and nickel chloride, and the titanium source is one or more of titanium sulfate, titanium tetrachloride, and titanium subsulfate.

7. The method for preparing the TiO2@Ni@C composite graphite felt electrode according to claim 5, characterized in that, In sub-step S22, the electrodeposition potential is -0.8V to -1.5V, and the electrodeposition time is 300 to 800s.

8. The method for preparing the TiO2@Ni@C composite graphite felt electrode according to claim 1, characterized in that, Step S3 includes the following sub-steps: S31: Dissolve the reducing agent and alkali in water to obtain a chemical reducing solution; S32: The NiTi-LDH graphite felt material is placed in the chemical reduction solution for a chemical reduction reaction to obtain a TiO2@Ni@C composite graphite felt electrode.

9. The method for preparing the TiO2@Ni@C composite graphite felt electrode according to claim 8, characterized in that, In sub-step S31, the reducing agent is sodium hypophosphite and the base is sodium hydroxide; in sub-step S32, the temperature of the chemical reduction reaction is 100~160℃ and the reaction time is 6~12h.

10. A TiO2@Ni@C composite graphite felt electrode, characterized in that, It is prepared by any one of the preparation methods described in claims 1-9.

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