Preparation method and application of a carbon-based asymmetric wettability composite cathode for electrocatalytic production of hydrogen peroxide

Abstract

The present invention discloses a preparation method and application of an asymmetric wettability composite cathode with a three-dimensional porous high-oxygen-transport carbon-based substrate loaded with a highly active and inexpensive catalyst. An asymmetric wettability composite electrode is made by coating a cheap commercial catalyst (such as carbon black, activated carbon, acetylene black, and graphite powder) onto the carbon-based substrate through a binder, and can be applied to an electrochemical reactor to electrocatalytically produce alkaline hydrogen peroxide through oxygen reduction, belonging to the field of application of electrocatalytic materials. The purpose of the present invention is to solve the problems of the cumbersome and complex preparation process, high cost, and low mass transfer efficiency of the cathodes for most electrocatalytic hydrogen peroxide production at present. The beneficial effects of the present invention are: the process is simple, the prepared electrode has a high hydrogen peroxide yield and low power consumption, the cost is low, and using this as the cathode of an electrochemical reaction, the hydrogen peroxide concentration for pulp bleaching can be continuously produced in the reactor, having good development prospects.

Description

Technical Field

[0001] The present invention relates to a preparation method of a carbon-based asymmetric wettability composite electrode for high-performance electrocatalytic production of hydrogen peroxide, specifically a preparation method of an asymmetric wettability composite electrode with a high-activity and low-cost catalyst (any one of carbon nanotubes, graphene, carbon black, activated carbon, and graphite powder) loaded on a three-dimensional porous high-oxygen-transport carbon-based substrate and its application in the production of hydrogen peroxide in an electrochemical reactor, belonging to the field of electrocatalytic material applications. Background Art

[0002] Hydrogen peroxide (H 2 O 2 ) is an environmentally friendly oxidant that is efficient, harmless, and residue-free, and is widely used in industrial fields such as pulp bleaching, chemical synthesis, textile, and wastewater treatment. However, the current large-scale industrial production method of H 2 O 2 mainly relies on the energy-intensive anthraquinone process. Due to its cumbersome steps, large-scale equipment is required, and it has high energy consumption and carcinogens are generated during the production process. In addition, the instability of H 2 O 2 brings safety problems to transportation, so it does not meet the requirements of green chemistry. Therefore, a green, efficient, and low-cost hydrogen peroxide production method needs to be developed urgently.

[0003] Regarding the development of the electrochemical oxygen reduction reaction (ORR) to generate H 2 O 2 , it provides an attractive way for on-site production of H 2 O 2 and miniaturization of equipment. Moreover, the oxygen reduction method has attracted more and more attention due to its high degree of automation, low risk, mild reaction conditions, and environmental friendliness. This electrochemical selective oxygen reduction reaction to produce H 2 O 2 scheme can effectively solve the problems faced by the anthraquinone method. Currently, most of the catalysts for efficient oxygen reduction to produce H 2 O 2 are noble metal catalysts, but the characteristics of low earth reserves and high price limit their large-scale application. Compared with noble metals, carbon-based materials are low in price, rich in sources, environmentally friendly, and have unique surface and structural properties that can be fine-tuned, and are considered to be H 2 O 2The most promising family of materials to replace noble metals in electrochemical synthesis. Carbon felt is a typical three-dimensional structured electrode with a high specific surface area and high electrical conductivity close to that of metals. In addition, it has good chemical stability (excellent stability under strong acid / alkali conditions), an integral structure, is easy to process and scale up, and has a low cost. It is a highly potential carbon-based electrode material. A three-dimensional carbon aeration electrode for efficient hydrogen peroxide production invented by Ma Jun et al. selects commercial graphite felt as the electrochemical cathode. Oxygen-containing gas enters the three-dimensional pores of the three-dimensional carbon electrode through several hoses and diffuses from the three-dimensional pores of the three-dimensional carbon electrode to the outside and into the electrolyte of the reaction device, and finally produces H 2 O 2 , although the oxygen mass transfer is increased, the utilization efficiency of O 2 is extremely low, resulting in energy waste during the production process, and the concentration of H 2 O 2 electrochemically generated is low (patent number CN110408955 A). Cui Yi et al. improved the activity and selectivity of carbon materials used for H 2 O 2 production through surface oxidation of carbon catalysts. After oxidizing commercially available carbon nanotubes, they were used for electrocatalytic production of H 2 O 2 , but this preparation method is time-consuming, and there are great safety hazards in using concentrated nitric acid during the preparation, increasing the cost during actual application (patent number CN111465718 A). Zhou Minghua et al. invented an air-active diffusion type hydrogen peroxide electrochemical generation device, which has the characteristics of high efficiency and energy saving. However, the inner wall on one side of the reactor is hollowed out, and the electrode is placed at the hollowed-out place to form a closed reaction space, which may cause electrolyte penetration to a certain extent and cannot stably produce H 2 O 2 (patent number CN109913889 B).

[0004] In summary, the current preparation methods and applications of carbon-based electrodes have the following disadvantages: (1) The sources of catalytic materials are single and expensive, increasing the actual application cost to a certain extent; (2) The preparation process is complex and prone to secondary pollution; (3) Usually, complex devices are required and the long-term stability is poor. Summary of the Invention

[0005] The present invention aims to solve the deficiencies of high actual application cost, complex preparation process, and short electrode life of existing carbon-based electrodes, and provides a preparation method and application of an asymmetric wettability composite electrode with a three-dimensional porous high-oxygen transport carbon-based substrate loaded with a highly active and low-cost catalyst. The hydrophobic substrate is prepared by a calcination method, and the catalyst is bonded to the hydrophobic substrate through a binder to form a carbon-based composite cathode, which is placed in an electrochemical device to efficiently produce H 2 O 2, reaching the concentration of H that can be used for pulp bleaching 2 O 2 and can be directly used in the pulp papermaking process.

[0006] To solve the above problems and achieve the purpose of the present invention, the following technical solutions are adopted:

[0007] The preparation method and application of the carbon-based asymmetric wettability composite electrode with simple structure and no environmental pollution are characterized in that:

[0008] S1 Clean the impurities of the carbon-based substrate by ultrasonic method successively using acetone, ethanol, and deionized water, and then set aside;

[0009] S2 Immerse the cleaned carbon electrode in a polytetrafluoroethylene (PTFE) solution with a certain concentration for 2 min to 10 min, and then calcine it in a muffle furnace by a one-step calcination method to obtain a hydrophobic substrate;

[0010] S3 Prepare a binder through polyvinylidene fluoride and N,N-dimethylformamide, and bond the highly active catalyst to the hydrophobic substrate to make an asymmetric wettability composite electrode;

[0011] S4 The prepared carbon-based asymmetric wettability composite electrode is applied to an electrochemical reactor for highly efficient production of H 2 O 2 .

[0012] According to the above scheme, the asymmetric wettability composite electrode of a three-dimensional porous high-oxygen-transport carbon-based substrate loaded with a highly active and low-cost catalyst is characterized in that: the carrier material is one of carbon felt and graphite felt, and the industrial carrier material is one of carbon nanotubes, graphene, carbon black, activated carbon, acetylene black, and graphite powder. In the preparation method of the carbon-based asymmetric wettability composite electrode of the present invention, the concentration of the PTFE solution is 1% to 60%, and the catalyst loading is 10 to 2000 mg.

[0013] The specific preparation steps of the carbon-based asymmetric wettability composite electrode: Mix polyvinylidene fluoride and N,N-dimethylformamide in a certain proportion, and obtain a binder by ultrasonic stirring for a certain time. Mix carbon black and the binder to make a paste-like catalyst, coat it on one side of the hydrophobic substrate, immerse the coated catalyst side in water to remove the solvent, and then dry it naturally overnight.

[0014] The application of the carbon-based asymmetric wettability composite electrode is characterized in that: The three-dimensional porous high-oxygen-transport carbon-based asymmetric wettability composite electrode is used as the cathode of an electrochemical reactor and is placed in the reactor to continuously produce the concentration of H 2 O 2 for pulp bleaching.

[0015] The present invention has the following characteristics:

[0016] (1) The preparation method of the present invention is simple and low-cost, does not involve various chemical drugs and chemical synthesis methods, nor does it require high-energy-consuming processing processes and cumbersome processing techniques. It only needs to simply impregnate and calcine the materials and then coat them, which is energy-saving and environmentally friendly and has a large-scale application prospect in industry.

[0017] (2) The carbon-based asymmetric wettability composite cathode of the present invention has a simple process flow, low production of alkaline H 2 O 2 energy consumption, convenient operation, and has the characteristics of great safety and no environmental pollution.

[0018] (3) The composite electrode of the present invention is applied to an electrochemical reactor, has high reaction efficiency and long service life, solves the safety and economic problems of H 2 O 2 transportation and storage, and realizes the instant production and use of H 2 O 2 in the pulp bleaching process. Detailed implementation manners

[0019] Those skilled in the art can easily understand that the present invention will be described more comprehensively and detailedly below in combination with embodiments. The following are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

[0020] Example 1

[0021] A preparation method of an asymmetric wettability composite cathode with a three-dimensional porous high-oxygen-transport carbon-based substrate loaded with a highly active and low-cost catalyst, the specific steps are as follows:

[0022] Immerse the ultrasonically cleaned carbon felt in a polytetrafluoroethylene solution, and calcine it in a muffle furnace at a heating rate of 5 °C / min for 0.5 h. Add a polyvinylidene fluoride binder to the carbon black to prepare a paste-like catalyst, coat it on the calcined carbon felt, immerse the coated catalyst side in water for a certain time to remove the solvent, and then dry it naturally overnight.

[0023] Example 2

[0024] Electrocatalytic oxygen reduction of asymmetric wettability composite electrodes with different carbon black loadings to produce H 2 O 2The application steps are as follows: Anode material: graphite plate; Cathode materials, electrodes with carbon black loadings of 100, 200, 300, 400, and 500 mg (CF-100, CF-200, CF-300, CF-400, and CF-500) are used as working electrodes, and the effective working area of the electrode is 20 cm 2 , there is a polyester diaphragm between the anode and cathode plates, the cathode chamber and the anode chamber are 0.1 mol / L KOH solution, and the current density is 10 mA / cm 2 , and the reaction time is 2 h. The experimental results are shown in Table 1.

[0025] Table 1 Comparison of the effects of composite cathodes with different carbon black loadings

[0026]

[0027] Example 3

[0028] Electrocatalytic oxygen reduction to produce H 2 O 2 by an asymmetric wettability composite electrode under different current density conditions. The application steps are as follows: Anode material: graphite plate; Cathode material, CF-400 is used as the working electrode, and the effective working area of the electrode is 20 cm 2 , there is a Nafion diaphragm between the anode and cathode plates, the cathode chamber is 0.1 mol / L KOH solution, and the anode chamber is 0.5 mol / L H 2 SO 4 solution, the current density is 10 - 60 mA / cm 2 , and the reaction time is 1 h. The experimental results are shown in Table 2.

[0029] Table 2 Comparison of the effects of the composite cathode under different current density conditions

[0030]

[0031] It can be seen from Table 2 that the concentration of H 2 O 2 increases with the increase of the current density. When the current density is 50 mA / cm 2 , the concentration of H 2 O 2 reaches the maximum, which is 30856 mg / L, and the current efficiency is 97%. The alkaline H 2 O 2 solution obtained by the present invention does not need to purify H 2 O 2 and can be directly used to reach the concentration (2% - 3%) that can bleach pulp.

Claims

1. A preparation method of an asymmetric wettability composite cathode with a three-dimensional porous high-oxygen-transport carbon-based substrate loaded with a highly active and inexpensive catalyst, the specific steps are as follows: Immerse the ultrasonically cleaned carbon felt in a polytetrafluoroethylene solution, and calcine it in a muffle furnace at a heating rate of 5 °C / min for 0.5 h; add a polyvinylidene fluoride binder to carbon black to prepare a paste-like catalyst, and coat it on the calcined carbon felt. Immerse the coated catalyst side in water to remove the solvent, and dry it naturally overnight. The carbon black loading is 400 mg.

2. An asymmetric wettability cathode prepared by the preparation method of the asymmetric wettability composite cathode with a three-dimensional porous high-oxygen-transport carbon-based substrate loaded with a highly active and inexpensive catalyst as described in claim 1.

3. An application of the asymmetric wettability cathode as described in claim 2 in electrocatalytic oxygen reduction to produce hydrogen peroxide, the specific steps are as follows: The anode material is a graphite plate, the cathode material is the asymmetric wettability cathode as described in claim 2, there is a polyester diaphragm between the anode and cathode plates, and the cathode chamber and the anode chamber are filled with 0.1 mol / L KOH solution.

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