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

Dual-atom catalysts (DACs) can be very effective for catalyzing bothoxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Herein, wepresent theoretical evidence of a new class of highly active DACs, namely, the double-atomembedded in nitrogen-doped graphene sheet 2M−N−C (M = Mn, Fe) on the basis ofdensity functional theory calculations. Importantly, we find that the double active sites of2M−N−C DACs entail an unconventional catalytic reaction pathway for ORR and OER.We also show that the local coordination environment of the active sites can significantlyaffect the stability and oxygen catalytic activity of 2M−N−C DACs. In particular, MnFe−N−C DAC not only exhibits good stability but also possesses outstanding bifunctionalORR/OER catalytic activity with the potential difference (ΔE) between the OER andORR as low as 0.34 V, notably lower than most bifunctional electrocatalysts reported inthe literature. This finding suggests a new strategy toward the design of stable and highlyactive bifunctional electrocatalysts for both ORR/OER.

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