Nature-inspired diatomic Zn-Cu pairs trigger active two OH* -involved oxygen reduction reaction

Abstract

Diatomic site catalysts (DASCs) are advanced as a more promising candidate among atom-scale catalysts for oxygen reduction reaction (ORR) benefiting from the synergistic catalysis. However, it is still challenging towards clarifying synergistic mechanisms behind faster kinetics. Here, a Zn-Cu-based DASC (ZnCuN₆/C) with Zn-Cu pairs has been deliberately designed and synthesized using a planar organometallic molecular approach, followed by confinement within π-π molecules and ZIF-8. The as-prepared ZnCuN₆/C catalyst have shown an impressive ORR activity with 200-fold higher mass activity of 2.8 A mg⁻¹_{total metal} at 0.9 V than that of benchmarking Pt/C (0.0140 A mg⁻¹_Pt), comparable with most advanced noble metal catalysts. A detailed theoretical calculation furtherly demonstrates that the introduction of the adjacent Cu sites in diatomic Zn-Cu pairs facilitates the competitive Zn 3d-O 2p orbital overlap, strengthening the O–O bond cleavage and preferring OH* release on active Zn sites via a more advanced two OH* -involved mechanism that bypasses the conventionally involved O* intermediate in the ORR process. The present work contributes a promising methodology for the experimental creation of DASCs and provides insightful understanding into their catalytic mechanisms.