In situ construction of MOF derived CoNC anchored on N-doped carbon xerogel sphere as efficient bifunctional ORR/OER electrocatalyst for Zn-air batteries.

Electrocatalytic materials with dual functions of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) have received increasing attention in the field of zinc-air batteries (ZABs) research. In this study, bifunctional CoNC@NCXS catalysts were prepared by anchoring Co and N co-doped CoNC on N-doped carbon xerogel sphere (NCXS) based on the spatially confined domain effect and in-situ doping technique. CoNC@NCXS exhibited excellent ORR/OER activity in alkaline electrolytes with the ORR onset potential of 0.99 V, the half-wave potential (E) of 0.78 V at 10 mA cm and the OER overpotential of 360 mV at 10 mA cm. These excellent catalytic activities were derived from constructing composite active structures and enhancing electrocatalytic efficiency. The ZAB assembled with CoNC@NCXS catalyst had a discharge specific capacity of 710 mAh g at a current density of 10 mA cm, which was superior to that of the Pt/C&RuO catalyst-assembled battery (667 mAh g). After running for 150 h, the charge and discharge efficiency of the CoNC@NCXS battery decreased by only 12.8%, which confirmed the excellent stability of the CoNC@NCXS catalyst. The free energy diagrams showed that, CoNC@NCXS has lower energy barriers and higher potential than CoNC in key reaction steps. This study provides a new perspective for the structural design of highly active composite catalysts in energy storage and conversion.