Abstract
Atomically dispersed Pt species are advocated as a promising electrocatalyst for the oxygen reduction reaction (ORR) to boost noble metal utilization efficiency. However, when assembled on various substrates, isolated Pt single atoms are often demonstrated to proceed through the two-electron ORR pathway due to the unfavorable O─O bond cleavage thermodynamics in the absence of catalytic ensemble sites. In addition, although their distinct local coordination environments at the exact single active sites are intensively explored, the interactions and synergy between closely neighboring single atom sites remain elusive. Herein, atomically dispersed Pt monomers strongly interacting on a Mo(2) C support is demonstrated as a model catalyst in the four-electron ORR, and the beneficial interactions between two closely neighboring and yet non-contiguous Pt single atom sites (named as quasi-paired Pt single atoms) are shown. Compared to isolated Pt single atom sites, the quasi-paired Pt single atoms deliver a superior mass activity of 0.224 A mg(-1) (Pt) and near-100% selectivity toward four-electron ORR due to the synergistic interaction from the two quasi-paired Pt atom sites in modulating the binding mode of reaction intermediates. Our first-principles calculations reveal a unique mechanism of such quasi-paired configuration for promoting four-electron ORR.