Highly exposed discrete Co atoms anchored in ultrathin porous N, P-codoped carbon nanosheets for efficient oxygen electrocatalysis and rechargeable aqueous/solid-state Zn–air batteries

Abstract

Single atom catalysts (SACs) exhibit desirable catalytic properties in key renewable energy reactions and devices. However, rational design of SACs and boosting their performances for oxygen electrocatalysis and rechargeable Zn–air batteries (ZABs) are still crucial yet challenging. Herein, single Co atoms anchored in ultrathin N, P-codoped porous carbon nanosheets (Co_SA/NPC) were prepared by an in situ confinement pyrolysis strategy. The ultrathin nanosheet structure provides an ideal platform for high exposure of the generated Co active sites and extremely shortens the electron transport pathways. Both experimental and theoretical results demonstrate that the N/P coordinated Co sites enable optimized charge distribution and facilitate oxygen intermediate adsorption/desorption. Such a Co_SA/NPC catalyst exhibits high oxygen reduction reaction (ORR) activity with a half-wave potential (E_1/2) of 0.87 V and oxygen evolution reaction (OER) activity with a low potential of 1.67 V at 10 mA cm⁻². As an air electrode in ZABs, it demonstrates a high peak power density of 204.3 mW cm⁻² and excellent long-term stability in aqueous ZABs. It also reveals superior flexibility and stability in solid-state ZABs. Thus, Co_SA/NPC is a promising bifunctional electrocatalyst for practical applications in aqueous and flexible solid-state ZABs.