Study On Novel Catalysts For Fuel Cell Prepared By Hydrogen Evolution Assisted Electrodeposition

Direct methanol fuel cell(DMFC)has broad application prospects in the field of portable mobile power,because of its high efficient energy,zero pollution,rich in the source of methanol,high energy density and so on.Cathode catalyst and anode catalyst are the key factors to determine the performance,life and cost of direct methanol fuel cell.Three-dimensional porous materials are favored in the field of electrocatalysis due to its large specific surface area and faster mass transport.Hydrogen evolution assisted electrodeposition has been a common method for preparing 3D porous materials with adventages of structure control,low cost and easy preparation.In this project,we use hydrogen evolution assisted electrodeposition to prepare the novel 3D graphene with dentrite-like morphology and 3D porous Pt-based alloy with dentrite-like morphology,which are applied to cathode catalyst and anode catalyst for direct methanol fuel cell respectively.First of all,we use hydrogen evolution assisted electrodeposition to prepare nickel-rich 3D porous nickel-copper template comprised of dendrites,which would be used as substrate for depositing graphene by CVD.The influence of hydrogen source,additive,the concentration of Cu ion,current density and deposition time on the morphology and composition of nickel-copper template were studied in detail.The addition of Cu was crucial to the formation of porous structure and dendritic structure for nickel-copper template.By optimizing the deposition conditions,the nickel-rich(>90%)3D porous nickel-copper template with perfect dendritic structure was prepared successfully.The optimized electrodeposition conditions are as follows:electrodeposition solution 0.2M NiSO4+0.0075M CuSO4+2M(NH4)2SO4 + 0.3M Na3C6H5O7 + 0.4M H3BO3,current density 2A/cm2,deposition time 90S.Then,graphene was deposited on the nickel-rich 3D porous nickel-copper template comprised of dendrites.The influence of deposition temperature and CH4 flow on the preparation of graphene and catalytic activity of graphene for oxygen reduction reaction were studied in detail.In addition,the ORR catalytic activity of dendritic graphene and planar graphene was compared.The nickel-rich 3D porous nickel-copper template has stronger resistance to high temperature spherification than pure cu template.The higher the deposition temperature,the thicker the graphene,the better the crystallinity and quality,the more stable the dendritic structure.The higher the CH4 flow,the thicker the graphene,the more stable the dendrite structure.The dendritic graphene prepared at the deposition temperature of 900 ?and the CH4 flow of 10sccm exhibited the best catalytic activity toward oxygen reduction reaction because of its stable dendrite structure and high specific surface area.The ORR catalytic activity of dendritic graphene is far better than planar graphene.The good catalytic activity of dendritic graphene may be attributed to the existence of the unique curved surface structure.Finally,we use hydrogen evolution assisted electrodeposition to prepare the 3D porous Pt-based alloy catalysts comprised of dendrites for methanol electrooxidation.The influence of the content of Pt and Ni/Cu on the morphology,composition and the catalytic activity toward methanol electrooxidation were studied in detail.The addition of Cu was crucial to the formation of porous structure and dendritic structure for Pt-based alloy catalysts.The ternary Pt-based alloy porous catalyst comprised of nanodendrites prepared at the concentration of Pt2+ 5mM,Ni2+5mM,Cu2+2mM exhibited the best catalytic activity toward methanol electrooxidation,with its methanol oxidation peak potential of-3 01 mV vs Hg/HgO,shifting negatively for nearly 60 mV compared with commercial Pt/C(-241 mV vs Hg/HgO).Electronic effect,synergistic effect,and the porous structure with nanodendrites may all make some contribution to the enhanced electrocatalytic activity.