Rational Design of Diatomic Active Sites for Elucidating Oxygen Evolution Reaction Performance Trends.

Diatomic catalysts, especially those with heteronuclear active sites, have recently attracted significant attention for their advantages over single-atom catalysts in reactions with relatively high energy barrier, e.g. oxygen evolution reaction. Rational design and synthesis of heteronuclear diatomic catalysts are of immense significance but have so far been plagued by the lack of a definitive correlation between structure and catalytic properties. Here, we report macrocyclic precursor constrained strategy to fabricate series of transition metal (M, Ni, Co, Fe, Mn, or Cu)-noble (M, Ir or Ru) centers in carbon material. One notable performance trend is observed in the order of Cu-M<Mn-M<Fe-M<M<Co-M<Ni-M. Meanwhile, the pathway has been not altered, still following the traditional adsorption reaction mechanism. The effect of the M atoms on the performances could possibly originate from the distinct adsorption/desorption behaviors of key intermediates (i.e. *OH, *O and/or *OOH), strongly implying that ΔG-ΔG could be used as the performance descriptor. We believe that our work provides useful strategy for synthesis of diatomic active sites with sole coordination configuration and varied composition, and in-depth insight to their catalytic mechanism, which could be used for further optimization of diatomic catalysts towards oxygen electrocatalysis.