Engineering the Coordination Environment of Single Cobalt Atoms for Efficient Oxygen Reduction and Hydrogen Evolution Reactions
Tao Sun, Wenjie Zang, Huan Yan, Jing Li, Zhiqi Zhang, Yongfeng Bu, Wei Chen, John Wang, Jiong Lu, Chenliang Su
Abstract
The coordination environment of single-atom catalysts (SACs) plays a crucial role in determining the energy conversion efficiency of related electrochemical devices. Herein, the coordination environment of a series of Co-based SACs (Co1-SACs) was tuned to correlate the chemical structures of these catalysts with their electrocatalytic performance. The optimized Co1-SACs containing Co-S2N2 sites are electrocatalytically active in both the oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER), which were carried out in alkaline media. The Co1-SACs containing Co-S2N2 sites exhibit high ORR activity, with an onset potential of 0.99 V vs RHE and good stability, as well as have promising application in a zinc-oxygen battery with a high power density (260 mW cm-2) and open-circuit voltage (1.50 V), remarkable tolerance to large current density, and long-term operation. The ORR of the Co-S2N2 site is attributed to the optimized electron density of the Co atom through its cocoordination with adjacent S and N atoms. Moreover, the Co1-SACs efficiently catalyze the HER, exhibiting a low overpotential (121 mV at 20 mA cm-2), a low Tafel slope (47 mV dec-1), and long-term stability. This work also provides a facile heteroatom-doping strategy to engineer the desired coordination environments in SACs for efficient electrocatalysis. © 2021 American Chemical Society.