Preparation And Electrochemical Performance Of Photo-chlorinated Graphene

Increasing environmental awareness and energy demand have driven the inevitable shift from traditional fossil fuels to clean renewable energy sources.However,the development of new energy with high energy density,such as regenerative fuel cells and rechargeable metal air batteries,is seriously hindered by the lack of electrocatalysts with ideal oxygen reduction reaction(ORR)and oxygen precipitation reaction(OER)catalytic kinetics..Existing catalysts exhibit a large overpotential,resulting in their relatively low energy density and high energy costs during charging.In addition,the widespread use of precious metal electrocatalysts commonly used in practical applications is obviously limited by high costs and poor durability.Therefore,the research and development of non-precious metal-based electrocatalysts came into being.Among them,non-metallic carbonaceous materials have caused great concern for their high theoretical activity,wide source,low cost,environmental protection,and long-term durability as dual-functional ORR and OER electrocatalysts.In this dissertation,monolayer graphene nanosheets and vertical oriented graphene were prepared by chemical vapor deposition,micro mechanical ablation and plasma enhanced vapor deposition.Chlorine photochlorination and UV assisted metal chloride decomposition and chlorination were used to design structural defects and covalent C-Cl bonds through the sp~2-to-sp~3 hybridization transition in graphene.It was confirmed by X-ray photoelectron spectroscopy(XPS)that graphene with a Cl coverage of 18 atom%was successfully prepared,and the changes of D,G,and2 D peaks were monitored by Raman spectroscopy after irradiation.The mobility of the graphene chloride field effect transistor decreased from 730.4 cm~2/(V·s)to 66.1cm~2/(V·s),showing obvious semiconductor properties and P-type doping characteristics.Raman spectroscopy indicates that defects and C-Cl bonds are closely related to the irradiation time,thus structural defects and compositions can be designed accordingly.Since the generation of active sites and the fast performance of ion and electron transmission,graphene chloride has met the requirements of electrocatalytic reaction characteristics.Measurement of chlorinated vertically-oriented graphene as an excellent bifunctional ORR and OER self-supporting electrode using a standard three-electrode system electrochemical workstation,showing an overpotential of370 mV for OER at 10 m A/cm~2,Tafel slope is 41 m V/dec,which exceeds commercial Ir/C.At the same time,the ORR reduction peak appears at 0.776 V vs.RHE,resulting in a more positive oxygen reduction voltage and a greater limited current density than the benchmark electrocatalysts such as carbon cloth and intrinsic graphene.In terms of durability,the current density loss of the graphene chloride electrode after a 12-hour chronoamperometry test was only 4.2%,superior to commercial Ir/C material.In this dissertation,two general chlorination methods were developed.Graphene chloride was successfully prepared by giving carbon-rich materials rich defects and polarized carbon as active sites.The excellent bifunctional ORR and OER electrocatalytic activities make graphene chloride materials aas a high application value in fuel cells and metal-air batteries.