N, S-codoped porous carbon as metal-free electrocatalyst for oxygen reduction reaction

Preparing low-cost and metal-free catalysts with outstanding catalytic activity and high stability to replace noble metal catalysts is the current development trend. Herein, a facile and low-cost two-step carbonization is proposed for the preparation of N, S-codoped oxygen reduction reaction (ORR) electrocatalysts, PP350KOH800-S, from the biomass waste pomelo peel by introducing KOH and thiourea as activator. The prepared electrocatalysts have the high specific surface area and the hierarchical porous structure and exhibit excellent ORR catalytic activity with the half-wave potential of 0.87 V and the limiting diffusion current density of −7.2 mA cm−2 in alkaline media. The excellent ORR electrocatalytic activity largely depends on the large specific surface area, the porous structure, the high degree of defects, and the synergistic effect of nitrogen and sulfur atoms. The present work provides a reliable method for the preparation of cheap and effective electrocatalysts using biomass waste.