A Metal-Free N and P-Codoped Carbon Nanosphere as Bifunctional Electrocatalyst for Rechargeable Zinc-Air Batteries

Abstract

Developing metal-free electrocatalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are crucial for the large-scale application of fuel cells and metal-air batteries, which have attracted extensive attention. Herein, a facile and scalable route is developed to prepare N, P-codoped carbon nanospheres (NPCs) with the assistance of cesium chloride (NPC-"Cs"). After treatment with hot acid solution, no trace metals are left in the electrocatalyst, as determined by inductively coupled plasma atom emission spectrometry (ICP-AES). The obtained metal-free electrocatalyst exhibits outstanding bifunctional catalytic activity for ORR and OER. The half-wave potential is 0.85 V for ORR in 0.1 M KOH, and an overpotential of 0.34 V for OER in 1 M KOH is required to reach a current density of 10 mA cm(-2). Furthermore, zinc-air primary and rechargeable batteries assembled with the metal-free electrocatalyst show similar, or even better performance compared to precious metal-based devices containing Pt/C or IrO2 as catalysts. A facile strategy is developed to synthesize the metal free bifunctional electrocatalyst for ORR and OER that is beneficial for the development of new-energy technologies.