| With the gradual increase of the world’s population base,it has also brought large scale energy use and consumption.The burning of traditional energy sources such as fossil fuel will cause a series of problems such as global warming and environmental pollution.Therefore,it is necessary to develop and use clean,high energy density and sustainable new energy sources to replace traditional fossil fuel.The theoretical energy density of the rechargeable zinc-air battery reaches 1084 wh kg-1.During the reaction,water is directly generated from O2,which will not pollute the environment and comply with the requirements of green energy.Since the charge-discharge reactions of zinc-air batteries are oxygen evolution reaction（OER）and oxygen reduction reaction（ORR）,noble metal catalysts are currently the most bifunctional catalytically active materials,but they have high costs and limited reserves and cannot be used on a large scale.Transition metal matrix composites have a variety of valence states and crystalline structures,and exhibit the same electrocatalytic activity as Ru O2 and Ir O2,so they have potential application prospects in zinc-air batteries.Based on the above analysis,this thesis successfully synthesized Co,Fe,Mn-based electrocatalysts by electrodeposition method and has good bifunctional activity.The research content is divided into the following three aspects:1.A simple electrodeposition method was used to grow Co（OH）2 nanosheets on the carbon cloth substrate,and the NC-Co3O4/CC self-supporting electrode was successfully obtained through subsequent air calcination and carbon coating processes.This material has excellent bifunctional catalytic activity.Further assembled into a zinc-air battery,it was found that the activity and stability of the electrode after carbon coating have been significantly improved,which proves that the coating of the carbon layer is beneficial to improve conductivity and avoid dissolution in the alkaline electrolyte of the catalyst.2.The ORR performance based on the single metal oxide catalyst can still be improved,and the Fe Mn LDH precursor was grown on the carbon cloth by electrodeposition method,and the Fe Mn-based catalyst was obtained by carbonization with dicyandiamide as the carbon source.Electrochemical tests indicate that this catalyst has ORR and OER catalytic activity comparable to commercial Pt/C and Ru O2.As a positive electrode material,the assembled zinc-air battery has better potential difference and better cycle stability.3.Three-dimensional lamellar Co Fe LDH was grown on the carbon cloth substrate by a constant current electrodeposition method,followed by the successful trapping of polypyrrole.The pyrolysis resulted in a carbon-encapsulated Co Fe alloy nanoparticle structure.The special structure is beneficial to reduce the ohmic polarization of the reaction and effectively improve the stability of the catalyst.The synergistic effect of metal-O bond and metal-N bond in the catalyst has been proved by synchrotron radiation to give it excellent bifunctional OER/ORR electrocatalytic activity.Based on its excellent dual-function activity assembled rechargeable zinc-air battery,at a current density of 10 m A cm-2,the charge-discharge potential difference is0.77V,and has excellent cycle stability,far superior to commercial Pt/C+Ru O2 catalyst.The assembled flexible all-solid battery has good flexibility and longevity,and has shown certain application prospects in flexible electronic devices. |
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