Mechanistic Study of Highly Active Bifunctional Double-Atom\nElectrocatalysts for Oxygen Reduction and Oxygen Evolution Reactions

Dual-atom\ncatalysts (DACs) can be very effective for catalyzing\nboth oxygen reduction reaction (ORR) and oxygen evolution reaction\n(OER). Herein, we present theoretical evidence of a new class of highly\nactive DACs, namely, the double-atom embedded in nitrogen-doped graphene\nsheet 2M–N–C (M = Mn, Fe) on the basis of density functional\ntheory calculations. Importantly, we find that the double active sites\nof 2M–N–C DACs entail an unconventional catalytic reaction\npathway for ORR and OER. We also show that the local coordination\nenvironment of the active sites can significantly affect the stability\nand oxygen catalytic activity of 2M–N–C DACs. In particular,\nMnFe–N–C DAC not only exhibits good stability but also\npossesses outstanding bifunctional ORR/OER catalytic activity with\nthe potential difference (Δ<i>E</i>) between the OER\nand ORR as low as 0.34 V, notably lower than most bifunctional electrocatalysts\nreported in the literature. This finding suggests a new strategy toward\nthe design of stable and highly active bifunctional electrocatalysts\nfor both ORR/OER.