Preparation Of Carbon-Based Gas Diffusion Electrode Based On PVDF And Its Application In Electrochemical Reaction

The electrochemical reactions involving gas are very important reactions in the fields of energy and environment.For example,oxygen reduction reaction and hydrogen oxidation reaction have good application prospects in electrosynthesis of hydrogen peroxide at cathode and zinc reduction at anode,respectively.The three-phase reaction in gas diffusion electrode plays a key role in increasing reaction rate.Although many electrocatalytic materials have excellent intrinsic activity in electrochemical tests,their application to gas diffusion electrodes involves the preparation process and performance correlation problems.In this thesis,polyvinylidene fluoride（PVDF）resin was used as binder,and the hydrogen diffusion anode and oxygen diffusion cathode for electrodeposition of zinc and hydrogen peroxide were prepared by thermal pressing process.The research work of this thesis are as follows:The slurry of catalytic layer was prepared with PVDF as binder and carbon black as catalyst.The physical properties of the catalytic layer slurry were characterized,and the hot pressing processes such as hot pressing temperature,hot pressing time and hot pressing pressure were discussed.Finally,we determined the hot pressing temperature at 220°C for 10 minutes,and prepared the gas diffusion electrode.The smaller the hot pressing pressure,the greater the surface roughness of the gas diffusion electrode and the greater the apparent water contact angle of the electrode,which is independent of the size of water droplets.We added 20%commercial platinum carbon catalyst into the catalytic layer to obtain a gas diffusion electrode with a contact angle of about 130°.The total porosity of the electrode is 69.75%,and the porosity of primary and secondary pores is 11.33%.The gas diffusion electrode was used as a hydrogen diffusion anode to prepare metal zinc by electrodeposition.Within 24 hours,the cell voltage increased from 1.15 V to 1.3 V.the mass of zinc sheet obtained by electrodeposition was 22.2 g and the current efficiency was 95.4%.We have designed the gas diffusion layer of nickel foam based gas diffusion electrode,added anthraquinone and carbon black in the catalytic layer,and obtained gas diffusion electrode.The water contact angle of the gas diffusion electrode is about 130°,and the conductivity is about 1.4 S cm^-1.The total porosity of the electrode is 57.20%,and the porosity of primary and secondary pores is 23.87%.The electrode was used as a oxygen diffusion cathode to produce hydrogen peroxide in situ and phenol degradation.The working conditions in the electrolysis device of gas diffusion electrode modified by 1-amino-anthraquinone were discussed.It was found that p H 5,7 and 9 had no great influence on the generation of hydrogen peroxide.When the electrolyte concentration was 0.1 M Na₂SO₄,the cell voltage was relatively low and conducive to the generation of hydrogen peroxide.The generation of hydrogen peroxide and cell voltage increased with the increase of current density.The test showed that 1-amino-anthraquinone modified nickel foam based gas diffusion electrode had good long-term stability within 120 hours.The cell voltage was stable,and the current efficiency of H₂O₂ was maintained at 60%～70%.Combined with the hydrogen peroxide/ozone oxidation method,phenol wastewater with phenol content of 150 mg L^-1 could be degraded.At the current density of 10 m A cm^-2,the energy consumption was 6.7 W h g^-1_COD per gram COD（chemical oxygen demand）under the condition of ozone.The phenol removal rate reached 100%,and COD removal rate was 73.9%per hour,simultaneously.