Tailoring structural properties of carbon via implanting optimal co nanoparticles in n-rich carbon cages toward high-efficiency oxygen electrocatalysis for rechargeable zn-air batteries

Rational construction of carbon-based materials with high-efficiency bifunctionality and low cost as the substitute of precious metal catalyst shows a highly practical value for rechargeable Zn-air batteries (ZABs) yet it still remains challenging. Herein, this study employs a simple mixing-calcination strategy to fabricate a high-performance bifunctional composite catalyst composed of N-doped graphitic carbon encapsulating Co nanoparticles (Co@NrC). Benefiting from the core-shell architectural and compositional advantages of favorable electronic configuration, more exposed active sites, sufficient electric conductivity, rich defects, and excellent charge transport, the optimal Co@NrC hybrid (Co@NrC-0.3) presents outstanding catalytic activity and stability toward oxygen-related electrochemical reactions (oxygen reduction and evolution reactions, i.e., ORR and OER), with a low potential gap of 0.766 V. Besides, the rechargeable liquid ZAB assembled with this hybrid electrocatalyst delivers a high peak power density of 168 mW cm⁻², a small initial discharge-charge potential gap of 0.45 V at 10 mA cm⁻², and a good rate performance. Furthermore, a relatively large power density of 108 mW cm⁻² is also obtained with the Co@NrC-0.3-based flexible solid-state ZAB, which can well power LED lights. Such work offers insights in developing excellent bifunctional electrocatalysts for both OER and ORR and highlights their potential applications in metal-air batteries and other energy-conversion/storage devices.