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 (E1/2) of 0.78 V at 10 mA cm-2 and the OER overpotential of 360 mV at 10 mA cm-2. 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-1 at a current density of 10 mA cm-2, which was superior to that of the Pt/C&RuO2 catalyst-assembled battery (667 mAh g-1). 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.