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.