Graphene electrocatalytic composite material with high catalytic activity and application thereof

Abstract

This invention discloses a graphene electrocatalytic composite material with high catalytic activity and its applications. It is prepared by mixing a metal salt corresponding to the electrocatalyst material with a silicon-containing precursor solution, directly dispersing graphene in the solution, and electrodepositing under rapid stirring. A three-electrode system is used, with a platinum sheet as the working electrode and a platinum mesh as the auxiliary electrode. A cathode potential is applied to the platinum sheet, causing the graphene powder to collide and contact with the platinum electrode, resulting in the electrodeposition of an electrocatalytic material containing a silica interlayer on the graphene surface. This invention overcomes the shortcomings of traditional techniques that struggle to directly electrodeposit electrocatalysts on the graphene surface. The prepared electrocatalyst has a quantum dot-sized particle size, and the silica interlayer exhibits excellent bonding with the graphene matrix, with adjustable thickness and a rough, porous structure, significantly improving the catalytic performance of the electrocatalytic material. It shows promising applications in electrode materials, electrocatalysis, and supercapacitors.

Description

Technical Field

[0001] This invention relates to the preparation of electrocatalytic materials, and more particularly to a method for preparing an electrocatalytic material with good binding strength and high electrocatalytic activity, and its applications. Background Technology

[0002] Graphene is a novel two-dimensional carbon nanomaterial with excellent properties such as large specific surface area and good electrical conductivity, and it is widely used in various fields such as photoelectrocatalysis, supercapacitors, nano-drug delivery, and metal corrosion and protection. Graphene can serve as an excellent carrier for various electrocatalytic active components, including metals, metal compounds, non-metal compounds, and single-atom catalysts. However, ordinary graphene has a smooth surface, lacks active groups, and is highly chemically inert, making it difficult to composite with electrocatalyst materials, which limits its applications.

[0003] Cobalt tetroxide, nickel, and nickel hydroxide possess excellent electrical properties and are inexpensive and easy to prepare, making them widely used in electrocatalysis, supercapacitors, electrochemical sensors, and other fields. Preparing nanoscale catalysts can increase specific surface area and thus improve catalytic activity; however, size reduction can lead to agglomeration, reducing catalytic activity and stability. By loading and immobilizing nanoscale catalysts on porous materials, such as graphene, a highly stable structure can be obtained while increasing the catalyst's specific surface area, effectively improving the utilization rate of the catalyst material and inhibiting the agglomeration and loss of the active catalyst components. Currently, graphene-based composite materials mostly use graphene oxide or reduced graphene oxide, and the prepared nano-electrocatalytic materials have relatively large particle sizes. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by proposing a graphene electrocatalytic composite material with high catalytic activity and its applications.

[0005] The objective of this invention is achieved through the following technical solution: A graphene electrocatalytic composite material with high catalytic activity is proposed. The electrocatalytic material is firmly bonded to the graphene surface, with a particle size as small as 2 nm; the thickness is adjustable, and it is rough and porous; it exhibits excellent electrocatalytic performance, reaching 10 mA·cm⁻¹. -2 The electrocatalytic Tafel slope can be as low as 45 mV / dec.

[0006] The highly catalytically active graphene electrocatalytic composite material is prepared by the following steps: 1) Preparation of precursor solution: Add 50~100 mL of anhydrous ethanol, 50~100 mL of deionized water, organosilane, and the metal salt solution corresponding to the electrocatalyst material, adjust the pH, stir well and set aside. 2) Add the prepared electrodeposition precursor solution to the three-electrode tank, then add 10~80 mg of graphene, and disperse it evenly by ultrasonication. Use Ag / AgCl as the reference electrode, platinum sheet as the working electrode, and platinum mesh as the auxiliary electrode. 3) Electrodeposition was performed while maintaining a stirring rate of 500-1000 rpm at a deposition temperature of 20-60 ℃. 4) The deposited product is washed with deionized water and anhydrous ethanol and then centrifuged and dried. The washing is repeated 1 to 5 times, the centrifugation speed is 1000 to 10000 rpm, the centrifugation time is 1 to 10 min, and the drying temperature of the deposited product is 50 to 100 ℃.

[0007] 5) The dried deposited product is calcined according to the procedure of heating in a muffle furnace for 1 to 5 hours, calcining at a constant temperature for 2 to 5 hours, and automatically cooling to room temperature.

[0008] The organosilane is one or more of tetramethyl silicate and tetraethyl silicate.

[0009] The metal salt is one or more of cobalt acetate, nickel sulfate, and nickel nitrate; the concentration of the metal salt is 0.01-0.5 M.

[0010] The pH adjustment is performed using hydrochloric acid, nitric acid, or acetic acid; the pH range is 1 to 5.

[0011] The electrodeposition is cathodic electrodeposition with a deposition potential of -0.5 ~ -2.0 V.

[0012] The deposition time is 10 to 100 minutes.

[0013] The calcination temperature is 500~800 ℃.

[0014] The graphene electrocatalytic composite material with high catalytic activity described above can be applied to electrode materials, electrocatalysis, and supercapacitors.

[0015] The beneficial effects of this invention are: Compared with existing methods that use hydrothermal methods to combine electrocatalytic materials with graphene oxide or reduced graphene oxide, this invention achieves the one-step electrodeposition of silicon dioxide on ordinary graphene to prepare electrocatalyst-graphene composite materials with a size of only a few nanometers, which greatly improves the electrocatalytic activity. Attached Figure Description

[0016] Figure 1(a) shows the SEM image of graphene.

[0017] Figure 1(b) is a SEM image of graphene electrodeposited cobalt tetroxide in silica.

[0018] Figure 2 HRTEM images of graphene electrodeposited silica cobalt tetroxide at different magnifications.

[0019] Figure 3 This is the XRD pattern of nickel electrodeposited on graphene. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0021] This invention discloses a graphene electrocatalytic composite material with high catalytic activity, its preparation, and its application. It is prepared by mixing a metal salt corresponding to the electrocatalytic material with a precursor solution containing a silicon source, directly dispersing graphene in the solution, and electrodepositing under rapid stirring. A three-electrode system is used, with a platinum sheet as the working electrode and a platinum mesh as the auxiliary electrode. A cathode potential is applied to the platinum sheet, causing the graphene powder to collide and contact with the platinum electrode, resulting in the electrodeposition of an electrocatalytic material containing a silica interlayer on the graphene surface. This method overcomes the shortcomings of traditional techniques that struggle to directly electrodeposit electrocatalytic materials on the graphene surface. The prepared electrocatalytic material has a quantum dot-sized particle size, and the electrodeposited silica interlayer exhibits excellent adhesion to the graphene matrix, with adjustable thickness, a rough and porous structure, significantly improving the catalytic performance of the electrocatalytic material. Graphene-doped electrocatalytic materials hold promise for new applications in electrode materials, electrocatalysis, and supercapacitors.

[0022] The graphene electrocatalytic composite material prepared by silica-assisted electrodeposition on ordinary graphene proposed in this invention overcomes the limitations of conventional graphene-based nano-electrocatalytic composite materials, which can only be deposited on the surface of graphene oxide or reduced graphene oxide in a single step. The prepared nano-electrocatalytic material has a particle size of only a few nanometers, thus exhibiting superior electrocatalytic performance. This invention is based on a silica layer used in protective coating systems (a method for preparing silica-doped and modified protective coatings and its applications, CN108102447A) and the loading of silica and other nano-oxides (a method for directly loading nano-oxides onto graphene surfaces, CN105671611A). Silica is used as an intermediate template to assist in the preparation of metal particles and oxides. Furthermore, silica can be etched using cyclic voltammetry, making the remaining graphene electrocatalytic material more coarse and porous, resulting in even better electrocatalytic performance.

[0023] Example 1 1) Preparation of precursor solution: Add 50 mL anhydrous ethanol, 50 mL deionized water, 0.05 M CoAc2, 5 mL TMOS, adjust pH to 4.0, stir well and set aside. 2) Add the prepared electrodeposition precursor solution to the three-electrode tank, then add 20 mg of graphene, and sonicate for 20 min to disperse it evenly. The sonication power is 200 W. Use Ag / AgCl as the reference electrode, platinum sheet as the working electrode, and platinum mesh as the auxiliary electrode. The deposition temperature is 30 ℃, the deposition potential is -1.1 V, and the deposition time is 30 min.

[0024] 3) The deposited product was washed twice with deionized water and twice with anhydrous ethanol, centrifuged at 8000 rpm for 5 min, dried in an oven at 60℃, and calcined in a muffle furnace at 500℃ for 2 h.

[0025] The prepared samples were observed by scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). Figure 1(a) shows the SEM image of graphene. As can be seen from Figure 1(b), composite oxide materials were grown on the smooth graphene surface. Figure 2 The particles prepared by high-resolution transmission display in part (a) have extremely small particle sizes, around 2 nm. Figure 2 The lattice spacing of Co3O4 shown by the lattice fringes obtained under high-resolution transmission in part (b) indicates the synthesis of graphene electrodeposited cobalt tetroxide.

[0026] Example 2 1) Preparation of precursor solution: Add 50 mL anhydrous ethanol, 50 mL deionized water, 0.1 M Ni2SO4, 0.1 M H3BO3 solution, and 5 mL TMOS, stir well and set aside. 2) Add the prepared electrodeposition precursor solution to the three-electrode tank, then add 20 mg of graphene, and sonicate for 20 min to disperse it evenly. The sonication power is 200 W. Use Ag / AgCl as the reference electrode, platinum sheet as the working electrode, and platinum mesh as the auxiliary electrode. The deposition temperature is 30 ℃, the deposition potential is -1.1 V, and the deposition time is 40 min.

[0027] 3) The deposited product was washed twice with deionized water and twice with anhydrous ethanol, centrifuged at 8000 rpm for 5 min, and finally dried in an oven at 60℃ to obtain graphene-silica-nickel composite electrocatalytic material.

[0028] from Figure 3 The XRD pattern showed obvious Ni-related diffraction peaks, indicating the synthesis of graphene-nickel composite material.

[0029] Example 3 The specific implementation steps are similar to those in Example 1. By changing the deposition potential in Example 1, graphene with different cobalt tetroxide loadings of silica was obtained, exhibiting different electrocatalytic performances (0.6 V (vs SCE)), as shown in Table 1. Compared to unmodified graphene, the electrocatalytic performance is significantly improved.

[0030] Table 1 Effect of electrodeposition potential .

[0031] Example 4 The specific implementation steps are similar to those in Example 1. By changing the silicon source in Example 1, graphene with different cobalt tetroxide loadings of silicon dioxide was obtained, which showed different electrocatalytic performances (0.6 V (vs SCE)), as shown in Table 2.

[0032] Table 2 Effect of silane precursors .

[0033] The above embodiments are only used to explain the present invention and are not intended to limit the present invention. Any modifications and changes made to the present invention within the spirit and scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A graphene electrocatalytic composite material with high catalytic activity, characterized in that, The electrocatalytic material is firmly bonded to the graphene surface, with a particle size as small as 2 nm; its thickness is adjustable, and it is rough and porous; it exhibits excellent electrocatalytic performance, reaching 10 mA·cm⁻¹. -2 The electrocatalytic Tafel slope can be as low as 45 mV / dec; The highly catalytically active graphene electrocatalytic composite material is prepared by the following steps: 1) Preparation of precursor solution: Add 50~100 mL of anhydrous ethanol, 50~100 mL of deionized water, organosilane, and the metal salt solution corresponding to the electrocatalyst material, adjust the pH, stir well and set aside for use; 2) Add the prepared electrodeposition precursor solution to the three-electrode tank, then add 10~80 mg of graphene, and disperse it evenly by ultrasonication. Use Ag / AgCl as the reference electrode, platinum sheet as the working electrode, and platinum mesh as the auxiliary electrode. 3) Electrodeposition was performed while maintaining a stirring rate of 500-1000 rpm at a deposition temperature of 20-60 ℃. 4) The deposited product is washed with deionized water and anhydrous ethanol and then centrifuged and dried. The washing is repeated 1 to 5 times, the centrifugation speed is 1000 to 10000 rpm, the centrifugation time is 1 to 10 min, and the drying temperature of the deposited product is 50 to 100 ℃. 5) The dried deposited product is calcined according to the procedure of heating in a muffle furnace for 1 to 5 hours, calcining at a constant temperature for 2 to 5 hours, and automatically cooling to room temperature.

2. The graphene electrocatalytic composite material with high catalytic activity according to claim 1, characterized in that, The organosilane is one or more of tetramethyl silicate and tetraethyl silicate.

3. The graphene electrocatalytic composite material with high catalytic activity according to claim 1, characterized in that, The metal salt is one or more of cobalt acetate, nickel sulfate, and nickel nitrate; the concentration of the metal salt is 0.01-0.5M.

4. The graphene electrocatalytic composite material with high catalytic activity according to claim 1, characterized in that, The pH adjustment is performed using hydrochloric acid, nitric acid, or acetic acid; the pH range is 1 to 5.

5. The graphene electrocatalytic composite material with high catalytic activity according to claim 1, characterized in that, The electrodeposition is cathodic electrodeposition with a deposition potential of -0.5 ~ -2.0 V.

6. The graphene electrocatalytic composite material with high catalytic activity according to claim 1, characterized in that, The deposition time is 10 to 100 minutes.

7. The graphene electrocatalytic composite material with high catalytic activity according to claim 1, characterized in that, The calcination temperature is 500~800 ℃.

8. The application of the graphene electrocatalytic composite material with high catalytic activity according to claim 1, characterized in that, Applications include electrode materials, electrocatalysis, and supercapacitors.

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