N, P Co-doped Hierarchical Porous Graphene as a Metal-Free Bifunctional Air Cathode for Zn-Air Batteries

The development of high-efficiency Zn air batteries represents one of the emerging energy storage and conversion technologies. In this work, hierarchically structured N, P co-doped graphene (NPHG) has been synthesized through the chemical polymerization of aniline and phytic acid in the presence of SiO2 nanoparticles and applied as air cathodes for rechargeable Zn air batteries, owing to its high bifunctional oxygen electrocatalytic activities. The P-N bond, rather than P-C or P=N bonds, in NPHG is proposed to be responsible for the high catalytic activity. The rechargeable Zn-air batteries assembled from this NPHG exhibited much higher reversibility and better stability as compared with a benchmark Pt/C catalyst.