Carbon-based Electrocatalyst For Biomass Preparation And Analysis Of Catalytic Performance Of Oxygen Reduction And Water Decomposition

In the recent years,traditional precious metals（Pt,Ru,and Ir）,hydroxides,transition metal（Fe,Ni,Co,and Cu）,and oxide supported porous carbon material has been widely used in emerging energy storage and conversion fields such as proton exchange membrane fuel cells,metal-air batteries and total water decomposition.Considering the complex and difficult conditions for the preparation of graphene,vapor-grown carbon fibers（VGCF）,carbon nanotubes（CNTs）and their hybrids,high pollution,low yield,the research on the preparation of carbon materials using biomass as a carbon precursor is receiving increasing attention.Therefore,this study uses low cost,easily available and renewable biomass aquatic scindapsus and waste distiller grain as raw materials to synthesize biochar which is supported transition metal and its heteroatom-doped composite materials.The relationship between the morphology,structure,formation process of the samples and electrocatalytic activity（including oxygen reduction,hydrogen evolution reaction and oxygen evolution reaction）was investigated by various characterization means.The main contents and conclusions of this thesis include the following two parts:（1）Explore the high specific surface area and high activated carbon-based catalysts used in fuel cell devices.This study proposes an inexpensive and environmentally friendly scalable method for the synthesis of N-doped porous carbon（SD-T-N）.Compared with the materials SD-700-N and SD-900-N or SD-800 and Pre-500,comprehensive electrochemical studies have shown that SD-800-N has achieved good effect at the limiting current density and starting potential.Among them,the ORR starting potential and the limiting diffusion current density are-0.003 V and-5.60 m A cm^-2,respectively,which are equivalent to the noble metal Pt/C.The oxygen reduction reaction carbon-based catalyst SD-800-N has better stability and methanol resistance.After 3000 cycles of voltammetry,SD-800-N has a limit diffusion current density loss rate of only 5.45%;it has multiple attractive properties including high catalytic activity,excellet durability,low cost and scalable production function.The developed oxygen reduction reaction carbon-based catalyst SD-800-N has broad prospects in the development of practical next-generation fuel cell cathode electrocatalysts.（2）Development of low-cost and high-efficiency catalysts for oxygen evolution reaction（OER）and hydrogen evolution reaction（HER）in the field of water decomposition.As carbon and nitrogen sources,distiller grain achieve nitrogen-doped and cobalt nanoparticles-loaded by sodium carbonate activation,while obtaining composite catalyst（Co（15）-DS-4）.Under Co（15）-DS-4 catalysis,the electrode in alkaline electrolyte needs 0.42 V overvoltage to reach a current density of 10 m A cm^-2,which is much lower than the commercially valuable catalyst Ru O₂（≈0.5 V）.In addition,Co（15）-DS-4 has excellent water decomposition stability.After 3000 cycles of cyclic voltammogram,the OER limiting diffusion current density of Co（15）-DS-4 can still maintain 97.5%（The HER limiting diffusion current density could still be maintained at 98.3%）.This composite catalyst constructed from distiller grain promise huge application potential in the field of water decomposition.In summary,a carbon-based functional electrocatalyst with catalytic activity for oxygen reduction,oxygen evolution,and hydrogen evolution was prepared using biomass as a precursor.This research not only provides a new method for the high-value utilization of waste biomass,but also provides theoretical support for the development of new energy storage and conversion technologies such as proton exchange membrane fuel cells,metal-air batteries and total water decomposition.