Three-dimensional nitrogen and phosphorous Co-doped graphene aerogel electrocatalysts for efficient oxygen reduction reaction

The development of efficient electrocatalysts for oxygen reduction reaction（ORR） is of importance for fuel cells and metal-air batteries. Herein, three-dimensional nitrogen and phosphorous co-doped graphene aerogel（NPGA） was prepared via the pyrolysis of polyaniline（PANi） coated graphene oxide aerogel synthesized by oxidative polymerization of aniline on graphene oxide（GO） sheets in the presence of phytic acid. The uniform coating of PANi thin layer on the surface of GO sheets enables the formation of highly porous composite aerogel of PANi and GO. The subsequent thermal treatment is able to prepare the porous NPGA due to the carbonization of PANi and phytic acid as nitrogen and phosphorous resources. When used as electrocatalysts,the as-prepared NPGA electrocatalysts exhibited good catalytic activity to ORR via an efficient four-electron pathway with good stability, benefiting from the highly porous structure and the heteroatom co-doping. More importantly, Zn-air batteries operated in ambient air have been fabricated by coupling a Zn plate with the NPGA electrocatalyst in an air electrode, demonstrating the maximal power density as high as 260 W/g and a good long-term stability with slightly potential decay for over 450 h. The facile method for preparing efficient carbon based ORR electrocatalysts would generate other potential applications including fuel cells and others.