Boost oxygen reduction reaction performance by tuning the active sites in Fe-N-P-C catalysts

Cost-effective atomically dispersed Fe-N-P-C complex catalysts are promising to catalyze the oxygen reduction reaction (ORR) and replace Pt catalysts in fuel cells and metal-air batteries. However, it remains a challenge to increase the number of atomically dispersed active sites on these catalysts. Here we report a highly efficient impregnation-pyrolysis method to prepare effective ORR electrocatalysts with large amount of atomically dispersed Fe active sites from biomass. Two types of active catalyst centers were identified, namely atomically dispersed Fe sites and Fe,P particles. The ORR rate of the atomically dispersed Fe sites is three orders of magnitude higher than it of Fe,P particles. A linear correlation between the amount of the atomically dispersed Fe and the ORR activity was obtained, revealing the major contribution of the atomically dispersed Fe to the ORR activity. The number of atomically dispersed Fe increases as the Fe loading increased and reaching the maximum at 1.86 wt% Fe, resulting in the maximum ORR rate. Optimized Fe-N-P-C complex catalyst was used as the cathode catalyst in a homemade Zn-air battery and good performance of an energy density of 771 Wh kg(zn)(1), a power density of 92.9 mW cm(-2) at 137 mA cm(-2) and an excellent durability were exhibited. (C) 2020 The Authors. Published by ELSEVIER B.V. and Science Press on behalf of Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences.

Automated summary

This study reports a highly efficient method for preparing ORR electrocatalysts with a large number of atomically dispersed Fe active sites, and reveals the major contribution of atomically dispersed Fe to the ORR activity.