Improved Oxygen Reduction Activity on Biomass Derived Carbon Catalysts Via Microbial Fermentation Pre-Treatment and Oxygen Etching

Biomass-based carbon materials have been considered as promising catalysts for oxygen reduction reaction due to their abundant heteroatom, renewability, and low cost. However, their practical electrocatalytic applications face a series of challenges, including insufficient pore structure, active site density, and their uneven distribution. Herein, we report an ingenious strategy to fabricate the biomass-derived carbon materials with hierarchical structures and high nitrogen doping. More specifically, microbial fermentation was used to achieve efficient and homogeneous nitrogen introduction by degrading the compact structure of lignocellulosic biomass. In addition, the precise regulation of the pore structure for carbon material was achieved by further introduction of appropriate oxygen during the pyrolysis process. The carbon catalyst prepared by the cascading treatment exhibited better performance. Notably, the C-5 exhibited the highest surface area (858.17 m(2)g(-1)) and abundant nitrogen-containing active sites, and high graphitization degree, thus, the C-5 demonstrates an outstanding oxygen reduction reaction catalytic performance in a wide pH range (e.g., E-onset: 0.85 V vs. RHE in neutral pH) and microbial fuel cells performance (maximum power density of 741.6 mWm(-2)). This study provides new ideas for the activity regulation of carbon electrocatalysts derived from biomass and will open the door to its large-scale application.