Preparation And Properties Of Electrochemical Catalysts With Carbon-based Composite

The extensive use of traditional fossil energy has led to the increasingly serious problem of environmental pollution.Therefore,the demand for renewable resources is constantly increasing.Hydrogen,which has a high energy density and only prodeces water after combustion,is considered as an ideal alternative to fossil fuels.Although some progress has been made in industrial hydrogen production,methane reforming and coal gasification are still the main approaches.In addition,these two approaches result in hydrogen with low purity,as well as problems of environmental pollution.Water electrolysis has high efficiency and environmental benignity for production of hydrogen,hence,it becomes a focus in the field of hydrogen production.However,due to the low reaction rate of the two half reactions of water electrolysis,i.e.,oxygen evolution reaction（OER）and hydrogen evolution reaction（HER）,efficient electrocatalysts are needed to accelerate the reaction process.Presently,precious metal based catalysts（Pt,Ir,Ru）are the main commercial electrocatalysts,but they are expensive and are rather scarce.In this thesis,cobalt oxide/nitrogen doped carbon nanofibers（Co_xO_y/NCNF）composites and nitrogen doped coal-based activated carbon（Ni₃N/Ru/NCAC）composite,which were modified with Ruthenium and nickel nitride nanoparticles were prepared,and their electrocatalytic properties were studied as follows:（1）Nitrogen-doped carbon nanofibers were prepared by a total biomass method the following ammonia annealing.After the nitrogen doped carbon nanofibers were filtered,the resulting NCNF network could be used as an oil/dye dual-functional filter membranes to remove crude oil,methylene blue and reactive violet K-3R from water at the same time.The filtration flux could reach 4950 L m^-2 h^-1,and the efficiency was as high as 99.82%.After deposition of Co_xO_y nanoparticles on NCNF,the OER electrocatalytic activity of Co_xO_y/NCNF composite were superior to that of commercial iridium oxide.We attributed this to the synergy of cobalt oxide,nitrogen doping,and carbon nanofibers.（2）Ni₃N/Ru/NCAC composites were synthesized by simply annealing mixtures of cheap coal-based activated carbon（CACs）,ruthenium chloride and nickel chloride in ammonia.Due to the large surface area of coal activated carbon(853 m² g^-1),the synergistic effects of N,Ru and Ni₃N,the composites had excellent OER and HER bifunctional electrocatalytic activeities.When Ni₃N/Ru/NCAC composites were used as both anodes and cathodes of electrolyzers for overall water splitting,only 1.55V voltage was needed to yield the current density of 10m A cm^-2.