Engineering Local and Global Structures of Single Co Atoms for a Superior Oxygen Reduction Reaction
Xiao Hai, Xiaoxu Zhao, Na Guo, Chuanhao Yao, Cheng Chen, Wei Liu, Yonghua Du, Huan Yan, Jing Li, Zhongxin Chen, Xing Li, Zejun Li, Haomin Xu, Pin Lyu, Jia Zhang, Ming Lin, Chenliang Su, Stephen J. Pennycook, Chun Zhang, Shibo Xi, Jiong Lu
Abstract
The ability to tune both local and global environments of a single-metal active center on a support is crucial for the development of highly robust and efficient single-atom electrocatalysts (SAECs) that can surmount both thermodynamic and kinetic constraints in electrocatalysis. Here, we designed a core–shell-structured SAEC (Co1-SAC) with superior oxygen reduction reaction (ORR) performance. Co1-SAC consists of a locally engineered single Co-N3C1 site on a N-doped microporous amorphous carbon support enveloped by a globally engineered highly conductive mesoporous graphitic carbon shell. Theoretical calculations reveal that Co-N3C1 exhibits near-Fermi electronic states distinct from those of Co-N2C2 and Co-N4, which facilitate both the electronic hybridization with O2 and the subsequent protonation of adsorbed O2* toward the formation of OOH*. Engineering Co-N3C1-SAC into a micro/mesoporous core–shell structure dramatically enhances the mass transport and electron transfer, which further boosts the ORR and Zn-air battery performance (slightly outperforming Pt/C). Our findings open an avenue toward engineering of the local and global environment of SACs for a wide range of efficient electrochemical conversions.