Nitrogen-doped vertical graphene nanosheets by high-flux plasma enhanced chemical vapor deposition as efficient oxygen reduction catalysts for Zn–air batteries

Abstract

Nitrogen-doped vertical graphene (NVG) nanosheets have attracted enormous attention as promising metal-free electrochemical catalysts for the oxygen reduction reaction (ORR). However, the conventional synthesis of NVG nanosheets by plasma enhanced chemical vapor deposition (PECVD) suffers from high costs caused by high temperature and a complex process. Herein, we introduce a one-step strategy to fabricate NVG nanosheets in a lab-built high-flux plasma enhanced chemical vapor deposition (H-PECVD) system at low temperature. The obtained NVG nanosheets possess a vertically interconnected structure with moderate defects. The beneficial morphology and structure endow the optimal catalyst (NVG-30) with a comparable ORR activity and much superior stability to the commercial Pt/C catalyst. Ultraviolet photoelectron spectroscopy (UPS) measurements suggest a low work function of NVG-30 with an excellent electron-donating capability. Moreover, the NVG-30 catalyst shows a superior discharge performance with high energy density and discharge durability in an assembled Zn–air battery. This work not only proposes a feasible strategy to fabricate NVG nanosheets but also demonstrates effective metal-free catalysts for the ORR and metal–air batteries.