The Treatment And Functionalization Of Co₃O₄ Nanosheets By Plasma And Their Application For Oxygen Evolution Reaction

In recent years,with the increasing depletion of traditional fossil fuels such as coal and oil,the problem of the energy shortages and environmental pollution has become more and more serious.We need to find sustainable,clean and efficient energy to solve the problem of energy shortage and environmental pollution urgently.In many advanced energy production technologies,oxygen evolution reaction(OER)has played a key role.However,the catalytic efficiency of the OER has been limited by the expensiveness and the low storage of commercial catalyst RuO2 and IrO2.But,the development of OER catalyst with high performance,low cost and high storage capacity is the immediate task.A large number of studies have shown that the modified Co3O4 nanomaterials are good catalyst of OER and likely to replace the commercial catalysts such as RuO2 and IrO2.Therefore,in this thesis,we have modified the surface of Co3O4 nanomaterials by Ar,N2 and NH3 plasma in order to improve the performance of OER though the oxygen vacancies,N doping and high surface area.The main contents are as follows:(1)Treatment of Co3O4 nanosheets by Ar plasma for OERIn the room temperature,the Co3O4 nanosheets are treated by Ar plasma,after the electrochemical testing and characterization,it is found that the surface of the treated Co3O4 nanosheets produced oxygen vacancies and the surface area is higher than that of the untreated Co3O4 nanosheets,and the performance of OER is greatly improved.This is mainly because the Co3+ in the Co3O4 nanosheets is partly reduced to Co2+ with oxygen vacancies by the reduction effect of Ar plasma and the active site of OER in Co3O4 is cobalt oxyhydroxide(CoOOH)forming by Co2+.(2)Treatment of Co3O4 nanosheets by N2 plasma for OERIn the room temperature,the Co3O4 nanosheets are treated by N2 plasma,after the electrochemical testing and characterization,it is found that the treated Co3O4 nanosheets generate oxygen vacancies,dope N atoms and have higher surface area than the pristine Co3O4 nanosheets.This work leads to the introduction of nitrogen atoms at the same time as the generation of oxygen vacancies and high specific surface areas,resulting in a change in the electronic structure of Co3O4 nanosheets,which exposes more active sites and improves the catalytic performance of OER.(3)Treatment of Co3O4 nanosheets by NH3 plasma for OERIn the room temperature,the Co3O4 nanosheets are treated by N2 plasma,after the electrochemical testing and characterization,it is found that the treated Co3O4 nanosheets are reduced to CoO nanosheets,produce oxygen vacancies,dope N atoms and have a higher specific surface area than pristine Co3O4 nanosheets.This is mainly because the NH3 is reduction gas comparing Ar and N2.The Co3+ in Co3O4 nanosheets is reduced to Co2+ completely by NH3 plasma resulting in more active sites of OER.