Metal-Free Graphene Modified Nitrogen-Doped Ultra-Thin Hollow Carbon Spheres as Superior Cathodic Catalysts of Zn-Air Battery

Abstract

Developing efficient, low-cost and resource-abundant cathode catalysts plays a meaningful role for the practical application of some novel electrochemical power devices like zinc-air battery. Herein, poly-dopamine@SiO2 precursor adsorbed with graphene oxide (GO) was subjected to pyrolysis to obtain reduced GO (rG) modified ultra-thin nitrogen-doped hollow carbon sphere (NHCS) composites (2.5rG@NHCS, 5rG@NHCS and 10rG@NHCS) with different GO loadings. Among them, 5rG@NHCS performs the most efficient electroactivity for ORR in both alkaline and neutral conditions. The ORR half-wave potential are around −0.17 V for the 5rG@NHCS in 0.1 mol·l−1 KOH solution, while they are around 0.17 V for the 5rG@NHCS in a quasi-neutral solution of 4 mol·l−1 NH4Cl and 1 mol·l−1 KCl, respectively. In addition, home-made zinc-air battery with the prepared 5rG@NHCS as air electrode (cathode) catalyst performs excellent discharge capability and stability consistent with ORR results. Our work is expected to synthesize a novel metal-free catalyst with outstanding activity in both alkaline and neutral electrolytes by a versatile synthesis strategy.