Improving the electron transfer in the oxygen reduction reaction by N/S co-doping for high-performance of Zn-air batteries

Designing high-performance carbon-based oxygen reduction catalysts using a facile strategy is an attractive research direction in the field of energy conversion and storage. Herein, N/S co-doped carbon was prepared using kappa-carrageenan and melamine as precursors, in which melamine can be decomposed into nitrogen-containing gas for realizing nitrogen doping, and the sulfate groups in kappa-carrageenan can be converted for sulfur doping. Such an N/S doping strategy enables a carbon catalyst with a large specific surface area, hierarchical porous structure, and rich defective sites to be achieved, displaying a high positive onset potential (E-onset = 0.98 V) and half wave potential (E-1/2 = 0.89 V), excellent stability, and methanol tolerance. More importantly, S doping could increase the positive charge density of the carbon adjacent to the nitrogen, which is favorable for enhancing the chemisorption of O-2 and weakening the O-O bond, thereby promoting the reaction from O-2 to OH- and improving electron transfer. Furthermore, with this catalyst as the air cathode, the assembled aqueous Zn-air battery exhibits a high open-circuit potential of 1.53 V and a remarkable peak power density of 166.05 mW cm(-2), outperforming the Pt/C catalyst. This work gives a facile and effective strategy to construct high-performance ORR catalysts with four electron transfer for Zn-air batteries.

Automated summary

This study presents a facile and effective strategy for designing high-performance carbon-based oxygen reduction catalysts. The N/S co-doped carbon catalysts achieved a large specific surface area, hierarchical porous structure, and rich defective sites, exhibiting excellent oxygen reduction reaction activity and stability. Furthermore, the assembled zinc-air battery with this catalyst as the air cathode showed superior electrochemical performance compared to the traditional Pt/C catalyst.