Upcycling biomass tar into highly porous, defective and pyridinic-n-enriched graphene nanohybrid as efficient bifunctional catalyst for Zn-air battery

With quite limited use, biomass tar has been a long-standing issue that strongly impaired the cost-efficiency of biomass gasification. Here, a facile activation-annealing route for upcycling biomass tar into graphene nanohybrids with developed porosity and enriched pyridinic nitrogen was reported, whilst the metal-free product revealed with superior catalytic activities to the benchmark Pt/C and RuO 2 catalysts toward oxygen reduction reaction (ORR) and evolution reaction (OER). By associating the dual functionalities with products’ physiochemical properties, it was unveiled that those pyridinic-N and defects were accounted for the promoted oxygen reduction and evolution, respectively. Together with reinforced electric conductivity and hierarchical porosity and enlarged interface via ammonia annealing, the heterogeneously structured carbon catalyst finally endowed an assembled primary Zn-air battery with maximum energy density of 121 mW/cm −2 , in addition to robust stability against long-term running. This work highlights the great potential of biomass tar for advanced carbon materials , and therefore a novel strategy to address the tar-related challenges faced by gasification technologies.