Preparation And Performance Study Of Co@NC New Electrocatalyst

With the rapid development of human society and the world economy,the increasing consumption of non-renewable energy such as coal,oil and natural gas and the deteriorating environment have become a serious problem facing mankind.There is an urgent need to develop new types of clean and renewable energy to reduce the limited The dependence of traditional fossil energy.Among them,the electrocatalytic electrolysis hydrogen production technology has become a research direction and hotspot of scientists in various countries due to its high energy conversion efficiency and environmental friendliness.The noble metal platinum catalyst exhibits the best activity and durability for HER in an acidic medium,but its high price and scarcity limit its large-scale use as an electrocatalyst in industrial production.In recent years,in order to improve the efficiency of electrocatalytic hydrogen production,the development of low-cost,earth-rich non-precious metal nanoelectrocatalysts to replace precious metal catalysts has gained widespread attention.This study designed and synthesized non-precious metal cobalt-based electrocatalysts and studied their hydrogen evolution performance.The main research contents include the following two aspects:(1)For the first time,a synthesis strategy of "self-template"was proposed:CoZn-ZIF was used as the precursor,and it was calcined and oxidized to Co3O4/ZnO at 350 0C.Then,the principle of "dissolution-generation" was used in Co3O4/ZnO.The surface of the nanoparticles is coated with a dense ZIF-8 shell structure in situ.By changing the different amounts of 2-methylimidazole,ZIF-8 shell thickness can be precisely controlled to obtain ZIF-8 shell with different thicknesses coated Co3O4/ZnO nanocomposites(Co3O4/ZnO@ZIF-8-x,x is ZIF-8 shell thickness);Finally,Co3O4/ZnO@ZIF-8-x were carbonized at 900 0C,different thicknesses of nitrogen-doped porous carbon coated metal Co nanoparticle electrocatalysts(Co NPs@NC-y,y is the thickness of the NC shell)were obtained,and The effect of the thickness of the nitrogen-doped porous carbon shell on the electrocatalytic activity of the inner transition metal nanoparticles was investigated in depth.The research shows that the designed and synthesized series of Co NPs@NC-y electrocatalysts show good hydrogen evolution activity and stability in 0.5 M H2SO4 solution,and the best hydrogen evolution performance of shell layer thickness is 1:1,which is about 250 mV.(2)A novel CoZn(bdc)2ted crystal was prepared by solvothermal method through the reaction of triethylenediamine,terephthalic acid,cobalt nitrate hexahydrate and zinc nitrate hexahydrate.Using this as a precursor,it was calcined at a high temperature in nitrogen atmosphere to prepare a cobalt-nitrogen co-doped porous carbon-based composite(Co NPs/NC),and exploring the effects of different carbonization temperatures and Co/Zn molar ratios on the electrocatalytic properties of synthetic materials.This synthesis method can be extended to electrocatalyst synthesis of other metals(such as Ni,Fe,Cu,etc.),which will provide a new idea for the preparation of nitrogen-doped porous carbon composite electrocatalysts.