In-situ engineering of 3D porous Co nanoparticles incorporated in B/N Co-doped carbon nanotube/nanofiber networks as integrated cathode materials for Zn-air batteries

Rational design and construction of low-cost and highly efficient bifunctional catalysts toward oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is crucial for the commercialization of the rechargeable Zn-air batteries (ZABs). Herein, a 3D self-standing bifunctional catalytic electrode has been successfully achieved by in-situ confinement of Co nanoparticles into B/N co-doped carbon nanotube/nanofiber well-integrated networks (Co-B/N-CNTs@CFs). The purpose of designing such a 3D network structure is to optimize the electronic structure of the active sites for high electrocatalytic activity, ensure continuous and fast electron and charge transfer for high utilization of active sites, and avoid the abscission and aggregation of nanocatalysts for high electrocatalytic stability, which is confirmed by a series of experimental, characterization, and theoretical studies. As a result, the Co-B/N-CNTs@CFs as integrated cathode materials deliver efficient and stable OER/ORR performance with a ΔE of 0.59 V, largely outperforming the benchmark Pt/C-RuO2 electrode (0.71 V), and hence leading to appealing applications in both the assembled aqueous and flexible solid-state ZABs. This study forges a new path for the production of integrated cathode while enhancing their superiority, allowing for the construction of energy storage devices.