Favorable pore size distribution of biomass-derived N, S dual-doped carbon materials for advanced oxygen reduction reaction

Metal-free carbon materials offer prominent performance towards the oxygen reduction reaction (ORR). The pore size distribution of carbons plays the vital role in promoting the electrocatalytic property. Herein, a succession of N, S dual-doped carbons decorated with 3D interpenetrated hierarchically porous structure are successfully obtained through utilizing ZnCl2 and Zn(OH)2 as porogens during carbonizing biomass-wastes. The nanopore amounts with specific sizes can be manipulated through changing diverse biomass-wastes as precursors, while different pore sizes can be optimized by tuning the dosage ratios of ZnCl2 to Zn(OH)2. Accompany with the increased amounts of nanopores with sizes of 4.6, 12, 17 and 27 nm, the ORR activity of carbon materials has been significantly promoted. These suitable pore sizes ensure the highly effecient mass transfer through providing abundantly accessible delivery channels and reactive zones for ORR-related intermediates. The optimized catalyst delivers the excellent ORR activity with a half-wave potential of 0.83 V vs. RHE as well as the remarkable long-term stability and methanol resistance ability in alkaline medium. Moreover, two series-connected Zn-air batteries with the catalysts can continuously lighten 216 LEDs over 24 h. The application of biomass-wastes to synthesize N, S dual-doped hierarchical porous carbons is beneficial for achieving the goals of turning waste into treasure.