Oxophilic NbO_xNanoisland-Confined Os Atomic Clusters for Practical Alkaline Water Electrolysis

Rational design of cost-effective atomic cluster (AC) catalysts with high mass activity and robust durability remains a huge challenge for the practical alkaline hydrogen evolution reaction (HER), primarily due to sluggish water dissociation kinetics at the electrolyte/electrode interface and inherent tendency of ACs to agglomerate. Herein, we report a design concept by employing NbO_x nanoislands anchored on fullerene-derived carbon (FDC) to spatially confine and stabilize Os ACs and enhance interfacial water dissociation ability for efficient alkaline HER catalysis in an anion exchange membrane water electrolysis (AEMWE). We find that the NbO_x nanoislands create a structurally confined environment that induces strong interfacial metal–support interactions for stabilizing the Os ACs against aggregation and enhancing the operational stability. Moreover, oxophilic NbO_x domains optimize interfacial water organization with enriched “free” hydrogen-bonded water at the reaction interface and strengthen the adsorption of hydroxyl species to accelerate water dissociation for a sufficient proton supplement. The resulting NbO_x–Os@FDC catalyst achieves an ultralow overpotential of 14 mV at 10 mA cm^–2 and an exceptional mass activity of 2.42 A mg_Os^–1 at −0.1 V vs RHE. Particularly, NbO_x–Os@FDC-based AEMWE with an ultralow Os loading realizes an industrial-level current density of 1 A cm^–2 at 1.74 V with high durability.