Preparation Of Cobalt-loaded And Heteroatoms Doped Carbon-based Catalysts And Their Application In Zinc-air Battery

Zinc-air battery has the advantages of high theoretical specific energy density,safety and pollution-free,simple structure and rich natural reserve in Zn resource.Therefore,it has become one of the representatives of the new generation of green batteries.However,the sluggish kinetics of oxygen reduction reaction（ORR）and oxygen evolution reaction（OER）involving in the air electrode of zinc-air battery require efficient and stable catalysts to ensure the performance.It is particularly important to find cheap catalysts that can replace precious-metal-based materials such as Pt,Pd,Ru,etc.A large number of studies have indicated that non-precious metals such as Fe and Co when combined with heteroatom-doped carbonaceous substrate can be employed as excellent ORR or OER catalysts,even as bifunctional catalyst materials.Starting from the abundant and inexpensive transition metal Co,the thesis selects carbon materials doped with different heteroatoms as porous substrate materials with excellent conductivity to compound with cobalt,and systematically studies the influence of components on catalytic performance.The main research contents of this thesis are as follows:（1）The waste biomass fish scales are used as carbon source and activated with KOH,then acted as carrier of ORR active sites.By utilizing the coordination between Co²⁺and 1,10-Phenanthroline（Phen）,the obtained Co-Phen complex has a strong adsorption effect and attaches to the carbon matrix in large quantities,and then generates abundant Co-N_x active sites in situ through pyrolysis.A 3D structure porous carbon material loaded with Co nanoparticles and highly active site of Co-N-C is prepared,and owns a half-wave potential of0.87 V used as an ORR catalyst.When the catalyst is applied to the air electrode of the home-made primary zinc-air battery,the maximum power density is 135 m W cm^-2,which was better than the commercial 20%Pt/C 98 m W cm^-2.（2）CoS_x(Co_1-xS and Co₉S₈)nanoparticles encapsulated in N,S co-doped carbon nanosheets were synthesized by sol-gel method.Urea acts as both carbon source and nitrogen source.Cobalt,nitrogen and carbon are integrated by the complexation of citric acid and Co²⁺.The influence of sulfur doping on catalytic performance and how the sulfidation temperature changes the composition of cobalt sulfide particles in the catalyst have been discussed.The experimental results show that the high content of pyridine nitrogen and graphitized nitrogen in the material and the possible synergistic effect in two-phase cobalt sulfide particles give it excellent bifunctional catalytic activity at the temperature of 800oC.The material is used as an air electrode catalyst for a rechargeable zinc-air battery.After 48 h of charge/discharge cycle,the performance decay is much lower than that of the Pt/C+RuO₂ catalyst-based battery.