Hierarchical Porous Manganese- and Nitrogen-Codoped Carbon Nanosheets Derived from Surface Modified Biomass as Efficient Oxygen Reduction Catalysts for Al-Air Batteries

Abstract

Oxygen reduction reaction (ORR) is essential for metal-air batteries and fuel cells, and it is urgent to develop non-precious metal catalysts with low cost and high performance for ORR. Here we propose a new general strategy for preparing hieratical porous manganese- and nitrogen-codoped carbon (Mn–N–C) derived from low cost biomass. This strategy demonstrates that pre-oxidation of the biomass with an optimized temperature plays an essential role in forming the unique structure of Mn–N–C due to the modification of surface functional groups on biomass. The resultant Mn–N–C displays superior ORR performance in both alkaline and neutral electrolytes, which is comparable or even higher than that of the commercial Pt/C catalyst. The superior electrocatalytic performance is ascribed to the intrinsically efficient Mn-Nx active sites and the high surface area together with the hieratical pores exposing more active sites, which is also confirmed by the density functional theory calculation. Furthermore, the Al-air battery based on the Mn–N–C cathode shows a high working voltage and maximum power density, demonstrating promising potential for practical application. This approach provides a new insight for low-cost and high performance electrocatalysts for metal-air batteries.