Visualizing Labor Division in Oxygen Electrocatalysis: Fully Exposed Ni Clusters Enabling Dual-Site Catalysis via...

Fully exposed metal cluster catalysts combine the atomic precision of single-atom catalysts with the multi-site reactivity of nanomaterials; however, achieving both structural stability and site-specific bifunctionality remains challenging. Herein, we report a Janus-type bifunctional catalyst comprising fully exposed atomic-layered nickel clusters anchored on Co₂P nanocrystals (Ni_AC-Co₂P), demonstrating excellent oxygen reduction/evolution reaction (ORR/OER) performance. Leveraging an electronic metal-support interaction, interfacial charge redistribution fine-tunes the d-band centers, optimizes intermediate adsorption and promotes dual-site catalysis. Theoretical calculations show the Ni-P-Co bridge lowers the *OOH formation barrier in ORR (half-wave potential of 0.90 V), while Ni clusters facilitate *O to *OOH conversion in OER (overpotential of 260 mV), enabling efficient four-electron kinetics via spatially decoupled dual-site cooperation. Operando x-ray absorption spectroscopy further confirms this mechanism, revealing Ni sites at the Ni-P-Co bridge undergo reversible Ni-P coordination modulation and transient Ni-O bond formation during ORR, whereas Ni-Ni clusters transform into NiOOH-like species to drive OER. Importantly, Ni_AC-Co₂P-assembled Zn-air battery delivers a peak power density of 199.8 mW cm^-2 and stable cycling performance exceeding 1400 h (approximately 4200 cycles). This work introduces a dual-site catalysis paradigm in transition metal phosphide-supported, fully exposed cluster catalysts, providing a robust strategy for designing multifunctional catalysts for energy conversion.