Proximity Electronic Effect of Ni/Co Diatomic Sites for Synergistic Promotion of Electrocatalytic Oxygen Reduction and Hydrogen Evolution

The modulation effect manifests an encouraging potential to enhance the performance of single-atom catalysts; however, the in-depth study about this effect for the isolated diatomic sites (DASs) remains a great challenge. Herein, a proximity electronic effect (PEE) of Ni/Co DASs is proposed that is anchored in N-doped carbon (N-C) substrate (NiCo DASs/N-C) for synergistic promoting electrocatalytic oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER). Benefiting from the PEE of adjacent Ni anchored by four nitrogen (Ni-N-4) moiety, NiCo DASs/N-C catalyst exhibits superior ORR and HER activity. In situ characterization results suggest Co anchored by four nitrogen (Co-N-4) as main active site for O-2 adsorption-activation process, which promotes the formation of key *OOH and the desorption of *OH intermediate to accelerate the multielectron reaction kinetics. Theoretical calculation reveals the adjacent Ni-N-4 site as a modulator can effectively adjust the electronic localization of proximity Co-N-4 site, promoting the *OH desorption and *H adsorption on Co-N-4 site, thereby boosting ORR and HER process significantly. This work opens a new opportunity for rationally regulating the electronic localization of catalytic active centers by proximity single-atom moiety, as well as provides guidance for designing high-efficiency bifunctional electrocatalysts for promising applications.