In-situ grafting of CoO nanosheets onto hollow Co-N-C matrix for an enhanced bifunctional oxygen electrocatalyst

The pursuit of efficient non-noble metal electrocatalysts for zinc-air batteries continues to pose a significant challenge. Herein, we introduce a novel, efficient approach to create a robust interface bond between CoO and a Co-N-C matrix that stemming from the self-polymerization of ZIF-67. The optimized catalyst displays remarkable electrocatalytic activity for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), as well as in zinc-air battery applications. The active CoO decorating the Co-N-C matrix surface reduces the ORR half-wave-potential by approximately 70 mV, resulting in an onset ORR potential of 0.89 V (vs. reversible hydrogen electrode, RHE), a half-wave potential of 0.79 V (vs. RHE), and an OER overpotential of 400 mV at a current density of 10 mA cm-2 in 0.1 M KOH. Furthermore, the CoO@Co-N-C catalyst-powered zincair battery demonstrates minimal variations in charging and discharging processes after 210 cycles at 50 mA cm-2. This outstanding electrocatalytic performance can be attributed to the unique hollow heterojunction structure and the synergistic interplay between the surface-active CoO and the porous Co-N-C matrix.