Bifunctional Oxygen Electrocatalyst of Co₄N and Nitrogen-Doped Carbon Nanowalls/Diamond for High-Performance Flexible Zinc-Air Batteries

Rational design of heterogeneous catalysts with unique structural and electronic properties is one of the major challenges to improve the activity toward the reversible oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), the bottleneck in the construction of air cathodes for the next-generation flexible zinc-air batteries (ZABs). Herein, density functional theory calculations are combined with experimental attempts to exploit the roles of the electronic effects at the interface between Co4N nanoparticles and nitrogen-doped carbon nanowalls/diamond (d-NCNWs/D) toward the ORR and OER activities. The vacancy defect-induced Co-pyridinic N-C bond optimizes the electronic structure of Co 3d orbitals and balances the adsorption energies of intermediates along the reaction pathways. Consequently, as-synthesized Co4N@d-NCNWs/D composites exhibit superior bifunctional oxygen catalytic activity. The overpotential of the OER is as low as 340 mV at 10 mA cm(-2) and the high half-wave potential reaches 0.83 V for the ORR. As a binder-free and flexible ZABs cathode, this composite exhibits an open circuit voltage of 1.41 V and excellent bendable stability, proving its promising potential for the assembly of wearable devices. This work offers theoretical evidence and a controllable strategy to design high-performance ZAB cathodes for their application in smart electronic devices.