Architecture Of Cobalt-based Electrocatalysts For Metal-air Batteries

Among electrochemical energy storage devices,metal-air batteries have triggered worldwide attention due to their ultra-high theoretical energy density,the catalytic reaction kinetics of ORR and OER is a key factor for the breakthrough of battery performance.Therefore,researchers have devoted themselves to exploring various highly efficient catalysts for reducing the polarization potential in ORR/OER reaction.In this article,we also constructed three cobalt-based catalysts,such as Co/N-C,Co P,Co_（1-x）S and Ti（PO₄）（Co PO₄）to improve the electrochemical performance of Li-air and Zn-air batteries.Firstly,we designed the Co/N-C catalyst with high catalytic activity from ZIF-67precursors.In this process,we used deionized water as the main solvent and DMEA as the inductive reagent to capture Co²⁺,the ZIF-67 with high crystallinity and high yield could be obtained by the action of ligand exchange.After carbonization at high temperature,Co/N-C with a large number of carbon nanotubes was achieved,and the surface defects produced by pickling greatly enhanced catalytic activity,even better than Pt/C.In Li-air batteries,it exhibits stability of 50 cycles at the current density of100 m A g^-1 and the cutoff specific capacity of 1000 m Ah g^-1,and the Zn-air batteries with Co/N-C can keep 150 h at the current density of 10 m A cm^-1.Secondly,based on the composite material ZIF-67@MWCNT,Na H₂PO₂ and TAA were used as phosphorus and sulfur sources,we obtained corresponding composite products Co P@MWCNT and Co_（1-x）S@MWCNT,respectively.Under the condition of100 m A g^-1 and 1000 m A g^-1 in Li-air batteries,they could separately work for 25 and40 cycles,and can also cycle for 75 h and 100 h under 10 m A cm^-2 in the Zn-air batteries.Finally,we prepared titanium phosphate Ti（PO₄）（H₂PO₄）by solvothermal method,which could be completely dissolved and stripped in a mixed solvent of DMEA/H₂O,and cobalt-containing catalyst Ti（PO₄）（Co PO₄）was precipitated again after reaction with Co²⁺.We composite it with MWCNT in situ to serve as conductive network and structural support,the final product Ti Co PO-40-250 can circulate stably for 25 cycles and 95 h in Li-air and Zn-air batteries,respectively.