Activating Single-Atom Ni Site via First-Shell Si Modulation Boosts Oxygen Reduction Reaction.

Atomically dispersed nitrogen-coordinated 3d transition-metal site on carbon support (M-NC) are promising alternatives to Pt group metal-based catalysts toward oxygen reduction reaction (ORR). However, despite the excellent activities of most of M-NC catalysts, such as Fe-NC, Co-NC et al., their durability is far from satisfactory due to Fenton reaction. Herein, this work reports a novel Si-doped Ni-NC catalyst (Ni-SiNC) that possesses high activity and excellent stability. X-ray absorption fine structure and aberration-corrected transmission electron microscopy uncover that the single-atom Ni site is coordinated with one Si atom and three N atoms, constructing Ni-Si1 N3  moiety. The Ni-SiNC catalyst exhibits a half-wave potential (E1/2 ) of 0.866 V versus RHE, with a distinguished long-term durability in alkaline media of only 10 mV negative shift in E1/2  after 35 000 cycles, which is also validated in Zn-air battery. Density functional theory calculations reveal that the Ni-Si1 N3  moiety facilitates ORR kinetics through optimizing the adsorption of intermediates.