CN114774971A

CN114774971A - Preparation method of carbon-based electrocatalyst for synthesizing hydrogen peroxide through oxygen reduction reaction

Info

Publication number: CN114774971A
Application number: CN202210324814.5A
Authority: CN
Inventors: 李怡招; 盛剑平; 耿芹; 于洋洋; 董帆
Original assignee: Yangtze River Delta Research Institute of UESTC Huzhou
Current assignee: Yangtze River Delta Research Institute of UESTC Huzhou
Priority date: 2022-03-30
Filing date: 2022-03-30
Publication date: 2022-07-22
Anticipated expiration: 2042-03-30
Also published as: CN114774971B

Abstract

The invention discloses a preparation method of a carbon-based electrocatalyst for synthesizing hydrogen peroxide by oxygen reduction reaction. The carbon-based electrocatalyst has excellent performance and simple preparation method, can realize high-efficiency in-situ synthesis of hydrogen peroxide, and has a wide application prospect.

Description

Preparation method of carbon-based electrocatalyst for synthesizing hydrogen peroxide through oxygen reduction reaction

The technical field is as follows:

the invention relates to the technical field of electrocatalytic synthesis, in particular to a preparation method of a carbon-based electrocatalyst for synthesizing hydrogen peroxide by oxygen reduction reaction.

The background art comprises the following steps:

the hydrogen peroxide and the aqueous solution hydrogen peroxide thereof have strong oxidizing property and are widely applied to the aspects of papermaking, sewage treatment, disinfection and the like. The global demand of hydrogen peroxide is increasing day by day, but the traditional anthraquinone method has complex process, high cost and low efficiency, and the direct hydrogen-oxygen synthesis method has great potential safety hazard. Therefore, electrocatalytic oxygen reduction, a novel, green and safe method for in situ synthesis of hydrogen peroxide, has attracted much attention in recent years.

The oxygen reduction reaction is a multi-electron reaction, the intermediate is complex and difficult to measure, and the mechanism research is difficult. The oxygen reduction reaction has two competing reaction pathways, two electron pathways to yield hydrogen peroxide and four electron pathways to produce water. The reaction efficiency of the two-electron oxygen reduction reaction depends on the activity, selectivity and stability of the catalyst. At present, noble metal-based catalysts such as Au and Pd show good catalytic performance for two-electron oxygen reduction reaction, but the expensive and scarce characteristics limit the wide application of the noble metal-based catalysts. Therefore, there is a need to develop a non-noble metal-based two-electron oxygen reduction electrocatalyst in order to achieve efficient in-situ synthesis of hydrogen peroxide.

The carbon material has the advantages of abundant reserves, low price, good conductivity, controllable appearance and the like, and at present, a plurality of researches on the application of the carbon materials such as graphite, carbon black, carbon felt, carbon cloth and the like in the synthesis of hydrogen peroxide by electrocatalytic oxygen reduction reaction are carried out. Patent CN112225199A discloses treating carbon nanotubes with HCl and hydrogen peroxide to obtain oxidized carbon nanotubes, which can be used as an electrocatalyst to produce hydrogen peroxide. Patent CN113481004A discloses that carbon dots are obtained by using citric acid, urea and calcium chloride as precursors and calcining and purifying at high temperature in vacuum, the selectivity of the electrocatalyst to hydrogen peroxide reaches 95%, and the corresponding electron transfer number is 2.1. Patent CN107973282B carries out high-temperature carbonization on walnut kernel skins to obtain a carbon material, and the carbon material is coated on carbon cloth and used for electrocatalysis two-electron oxygen reduction reaction to show higher coulombic efficiency. Patent CN113292061A discloses that carbon aerogel is prepared by roasting resorcinol and formaldehyde under nitrogen after microwave reaction, and the selectivity of the carbon aerogel used as an electrocatalyst to hydrogen peroxide is 70-90%. Patent CN112442708A discloses that the selectivity of hydrogen peroxide synthesized by electrocatalytic oxygen reduction reaction can reach up to 90% by using glucose as carbon source and dicyanodiamine as nitrogen source through one-step thermal cracking to obtain nitrogen-doped carbon material. Patent CN109666949B discloses a multielement doped carbon catalyst prepared by annealing mesoporous activated carbon, divalent cobalt salt and melamine after mixing, and the current efficiency of the catalyst to electrosynthesis of hydrogen peroxide is 63.25%.

It can be seen that, although pure carbon materials and heteroatom-doped carbon materials exhibit certain activity for synthesizing hydrogen peroxide through electrocatalysis two-electron oxygen reduction reaction, the current preparation method of the carbon-based materials is complex, and the performance of the obtained electrocatalyst needs to be further improved.

The invention content is as follows:

in order to overcome the defects of the prior art, the invention provides a carbon-based electrocatalyst for synthesizing hydrogen peroxide by oxygen reduction reaction and a preparation method thereof. The chitosan is dissolved by glacial acetic acid aqueous solution, a salt template is introduced, and the nitrogen-doped porous carbon material rich in oxygen functional groups is prepared by heat treatment after freeze drying, is used as an oxygen reduction reaction electrocatalyst and has high selectivity and activity on hydrogen peroxide. The carbon-based electrocatalyst has excellent performance and simple preparation method, can realize high-efficiency in-situ synthesis of hydrogen peroxide, and shows great application prospect.

The technical scheme of the invention is as follows:

preparing a glacial acetic acid aqueous solution with the concentration of 2% -20%, mixing chitosan and the glacial acetic acid aqueous solution according to the mass ratio of 1: 50-1: 100, fully dissolving, adding salt (the mass ratio of the chitosan to the salt is 1: 5-1: 20), then performing freeze drying, performing heat treatment at 300-700 ℃ for 0.5-3 h at the heating rate of 1-5 ℃/min in argon or nitrogen, and washing and drying to obtain the oxygen-rich functional group nitrogen-doped porous carbon material.

The salt is one of sodium sulfate, potassium sulfate, sodium chloride and potassium chloride.

The obtained carbon material is rich in oxygen functional groups, including hydroxyl, carboxyl and oxygen bridge bonds; the nitrogen atom doping type is pyridine nitrogen, pyrrole nitrogen and graphitized nitrogen doping; it has a hierarchical pore structure of micropores, mesopores and macropores; the initial potential of the catalyst used for electrocatalytic oxygen reduction reaction in an alkaline electrolyte is 0.65-0.85V (relative to a reversible hydrogen electrode), and the selectivity to hydrogen peroxide is 80-95% under 0-0.5V (relative to the reversible hydrogen electrode).

Compared with the prior art, the invention has the following advantages:

the chitosan is used as a raw material, the source of the chitosan is wide, the chitosan simultaneously contains carbon, nitrogen and oxygen elements, the nitrogen-doped carbon material rich in oxygen functional groups can be obtained without adding a heteroatom source, and nitrogen and oxygen heteroatoms can provide active sites for the electrocatalyst.

Salt is taken as a template agent, and freeze drying is combined to prepare the hierarchical porous carbon material with micropores, mesopores and macropores. The abundant pore structure is beneficial to the ion conduction and mass transfer process of the electrocatalytic reaction.

The carbon-based electrocatalyst is simple in preparation method, and has high activity and selectivity when being used for two-electron oxygen reduction reaction.

The chitosan is dissolved by glacial acetic acid aqueous solution, a salt template is introduced, and the nitrogen-doped porous carbon material rich in oxygen functional groups is prepared by heat treatment after freeze drying, is used as an oxygen reduction reaction electrocatalyst, and has high selectivity and activity on hydrogen peroxide. The carbon-based electrocatalyst has excellent performance and simple preparation method, can realize high-efficiency in-situ synthesis of hydrogen peroxide, and shows great application prospect.

Description of the drawings:

FIG. 1 is a linear scanning voltammogram of the oxygen functional group-rich nitrogen-doped porous carbon material prepared in example 1 in a 0.1M KOH electrolyte.

FIG. 2 shows that the nitrogen-doped porous carbon material rich in oxygen functional groups prepared in example 1 has selectivity to hydrogen peroxide at 0-0.5V (relative to a reversible hydrogen electrode).

The specific implementation mode is as follows:

the invention is further illustrated by the following specific examples. These examples are to be construed as merely illustrative and not limitative of the remainder of the disclosure in any way whatsoever. Various changes or modifications of the present invention based on the principle of the present invention after reading the contents of the present invention also fall within the scope of the present invention defined by the appended claims.

Example 1

Preparing a glacial acetic acid aqueous solution with the concentration of 2%, mixing chitosan and the glacial acetic acid aqueous solution according to the mass ratio of 1:60, adding sodium sulfate (the mass ratio of the chitosan to the sodium sulfate is 1:10) after fully dissolving, then carrying out freeze drying, then carrying out heat treatment for 2h at 500 ℃ at the heating rate of 5 ℃/min in argon, and washing and drying to obtain the nitrogen-doped porous carbon material rich in oxygen functional groups.

The obtained carbon material is rich in oxygen functional groups, including hydroxyl, carboxyl and oxygen bridge bonds; the nitrogen atom doping type is pyridine nitrogen, pyrrole nitrogen and graphitized nitrogen doping; it has a hierarchical pore structure of micropores, mesopores and macropores; the initial potential for electrocatalytic oxygen reduction reaction in alkaline electrolyte is 0.67V (relative to a reversible hydrogen electrode, see figure 1), and the selectivity to hydrogen peroxide is about 91% under 0-0.5V (relative to the reversible hydrogen electrode) (see figure 2).

Claims

1. A preparation method of a carbon-based electrocatalyst for synthesizing hydrogen peroxide by oxygen reduction reaction is characterized by comprising the following steps:

dissolving chitosan in a glacial acetic acid aqueous solution, and adding salt into the solution;

step two, freeze-drying the mixed solution, and carrying out heat treatment in inert gas;

and step three, washing and drying to obtain the nitrogen-doped porous carbon material rich in oxygen functional groups.

2. The method for preparing a carbon-based electrocatalyst for synthesis of hydrogen peroxide by oxygen reduction reaction according to claim 1, wherein: the oxygen-containing functional group comprises hydroxyl, carboxyl and an oxygen bridge bond, the nitrogen atom doping type is pyridine nitrogen, pyrrole nitrogen and graphitized nitrogen doping, and the nitrogen-doped porous carbon material has a hierarchical pore structure of micropores, mesopores and macropores.

3. The method for preparing a carbon-based electrocatalyst for synthesis of hydrogen peroxide by oxygen reduction reaction according to claim 1, wherein: the concentration of the glacial acetic acid aqueous solution in the first step is 2% -20%, the mass ratio of the chitosan to the glacial acetic acid aqueous solution is 1: 50-1: 100, and the mass ratio of the chitosan to the salt is 1: 5-1: 20.

4. A method for preparing a carbon-based electrocatalyst for synthesis of hydrogen peroxide by oxygen reduction reaction according to claim 1 or 3, wherein: the salt added in the first step is one of sodium sulfate, potassium sulfate, sodium chloride and potassium chloride.

5. The method for preparing a carbon-based electrocatalyst for synthesis of hydrogen peroxide by oxygen reduction reaction according to claim 1, wherein: and the heat treatment condition of the third step is to carry out heat treatment for 0.5-3 h at the temperature rise rate of 1-5 ℃/min to 300-700 ℃ in argon or nitrogen.