High-Loading Single-Atom Chromium Catalysts on Graphullerene for Oxygen Reduction Reactions

Abstract

The oxygen reduction reaction (ORR) which is the cathodic reaction in many electric energy generators such as fuel cells, Li-air batteries and Zn-air batteries, requires a catalyst to enhance the reaction rate due to its inherently slow kinetics. Atomic dispersed catalysts have shown high metal utilization and catalytic activity. However, challenges such as low metal loading and easy agglomeration have limited their commercial applications. To address these issues, we employed density-functional theory (DFT) and microkinetic modeling to investigate the performance of transition metals atomically dispersed on a newly synthesized material, graphullerene (TM@gra) as ORR catalysts. Our findings reveal that Cr@gra exhibits considerable stability, with an overpotential as low as 0.389 V and a half-wave potential of 0.86 V, which outperforms the best commercial catalyst Pt. Besides, the Cr@gra catalyst demonstrates a high metal loading of 12.6%, outperforming most existing catalysts in terms of metal loading. The mechanism behind the outstanding performance of Cr@gra is analyzed, and a simplified descriptor for the overpotential of the TM@gra system is proposed. This work demonstrates construction of an efficient ORR catalyst and may promote various fields of clean energy.