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

The 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. Now, the catalytic activities of Fe-N4 moiety can be enhanced by the adjacent Pt-N4 moiety through the modulation effect, in which the Pt-N4 acts as the modulator to tune the 3d electronic orbitals of Fe-N4 active site and optimize ORR activity. Inspired by this principle, we design and synthesize the electrocatalyst that comprises isolated Fe-N4 /Pt-N4 moieties dispersed in the nitrogen-doped carbon matrix (Fe-N4 /Pt-N4 @NC) and exhibits a half-wave potential of 0.93 V vs. RHE and negligible activity degradation (ΔE1/2 =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-N4 /Pt-N4 and Mn-N4 /Pt-N4 systems.