Preparation Of Carbon-based Oxygen Electrode Catalyst And Study On Performance Of Zinc-air Battery

The oxygen reduction reaction/oxygen evolution reaction(ORR/OER)of the air electrode of rechargeable zinc air batteries(ZABs)is slow during charging and discharging,which directly restricts the development of commercial ZABs.The nitrogencontaining porous polymer has abundant pore structure and large specific surface area.The nitrogen atoms in the polymer are easy to coordinate with transition metal ions.After carbonization at high temperature,a carbon based bifunctional oxygen electrode catalyst with stable activity,high efficiency and low cost can be formed for ORR/OER.In this paper,porous nitrogen-containing polymers coordinated by transition metal ions were used as precursors.The preparation method,structure control and performance test of ORR/OER bifunctional carbon based oxygen electrode catalysts were studied in the following three aspects:1.Nitrogen containing conjugated microporous polymers(NCMPs)were synthesized by traditional methods.The nitrogen atoms in NCMPs were coordinated with Co2+to prepare Co-NCMPs.In the presence of carbon nanotubes,carbon nanotubes uniformly coated by Co-NCMPs can be obtained at one step After carbonization at high temperature,C-Co-NCMPs/CT containing Co-Nx as catalytic active species was obtained.C-Co-NCMPs/CT showed excellent ORR/OER catalytic activity and stability.ZABs with C-Co-NCMPs/CT as air electrode catalyst can stably discharge for 107 h at a constant current density of 5 mA cm-2,and its specific capacity can reach 750.0 mA h g-1.It has a good cycle charge-discharge stability of 68 h,superior to commercial air electrode catalyst Pt/C.2.Flower like porous polyacrylonitrile(PACN-F)was synthesized by hydrothermal method.The nitrogen atoms in PACN-F were coordinated with Fe2+.Cobalt base layered double hydroxide(Co-LDH)was grown on PACN-F containing Fe element by precipitation method Nitrogen doped carbon nanoflowers loaded with Fe3O4 and CoO nanoparticles coated by graphite layer(Fe3O4/CoO@CF)were prepared by high temperature carbonization as electrocatalysts.Fe3O4/CoO@CF showed excellent catalytic activity and stability for ORR/OER.Through the control experiment,it was verified that Fe3O4/CoO was the main active species for ORR/OER respectively.The results show that the ZABs with Fe3O4/CoO@CF as air electrode catalyst has excellent power density(137 mW cm-2)and 90 h cycle charge-discharge stability,superior to commercial air electrode catalyst Pt/C.3.Flower like porous polyamide(PA-F)was prepared by precipitation method.The nitrogen atom of PA-F was coordinated with Fe3+by imersion method.After carbonization at high temperature,flower like N-containing carbon skeleton loaded with graphite coated Fe3O4 nanoparticles(Fe3O4@CF)was prepared as the electrocatalyst.Fe3O4@CF showed excellent catalytic activity and stability for ORR/OER.Through the acid etching experiment,it was verified that Fe3O4 was the main catalytic active species for ORR/OER.When Fe3O4@CF was used as the air electrode catalyst of ZABs,the cell exhibited an open circuit voltage similar to that of commercial catalyst Pt/C,which was superior to Pt/C in discharge duration(112 h)and power density(136.82 mW cm-2),and had a good cycle charge-discharge stability of 90 h.