Adjacent Atomic Pt Site Enables Single-Atom Iron with High Oxygen Reduction Reaction Performance.

Modulation effect has been widely investigated to tune the electronic state of single-atomic M-N-C catalysts to enhance the activity of oxygen reduction reaction (ORR). However, the in-depth study of modulation effect is rarely reported for the isolated dual-atomic metal sites. Interestingly, guided by the first-principles simulations, we find that the catalytic activities of Fe-N 4 moiety can be enhanced by the adjacent Pt-N 4 moiety through the modulation effect， in which the Pt-N 4 acts as the modulator to tune the 3 d electronic orbitals of Fe-N 4 active site and optimize ORR activity. Inspired by this principle, we design and synthesize the electrocatalyst that comprises isolated Fe-N 4 /Pt-N 4 moieties dispersed in the nitrogen-doped carbon matrix (Fe-N 4 /Pt-N 4 @NC) and exhibits a half-wave potential of 0.93 V vs. RHE and negligible activity degradation (∆E 1/2 = 8 mV) after 10000 cycles in 0.1 M KOH. We also demonstrate that the modulation effect is not effective for optimizing the ORR performances of Co-N 4 /Pt-N 4 and Mn-N 4 /Pt-N 4 systems. These results have refreshed the knowledge of adjacent dual metal sites at the atomic-level and provided rational guidance for the design of efficient electrocatalysts.