Interfacial Electronic Modulation of Mo₅N₆/Ni₃S₂ Heterojunction Array Boosts Electrocatalytic Alkaline Overall Water Splitting

Bifunctional electrocatalysts with excellent activity and durability are highly desirable for alkaline overall water splitting, yet remain a significant challenge. In this contribution, palm-like Mo₅N₆/Ni₃S₂ heterojunction arrays anchored in conductive Ni foam (denoted as Mo₅N₆-Ni₃S₂ HNPs/NF) are developed. Benefiting from the optimized electronic structure configuration, hierarchical branched structure and abundant heterogeneous interfaces, the as-synthesized Mo₅N₆-Ni₃S₂ HNPs/NF electrode exhibits remarkably stable bifunctional electrocatalytic activity in 1 m KOH solution. It only requires ultralow overpotentials of 59 and 190 mV to deliver a current density of 10 mA cm^-2 for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 1 m KOH solution, respectively. Importantly, the overall water splitting electrolyzer assembled by Mo₅N₆-Ni₃S₂ HNPs/NF exhibits an exceptionally low cell voltage (1.48 V@10 mA cm^-2) and outstanding durability, surpassing most of the reported Ni-based bifunctional materials. Density functional theory (DFT) further confirms the heterostructure can optimize the Gibbs free energies of H and O-containing intermediates (OH, O, OOH) during HER and OER processes, thereby accelerating the catalytic kinetics of electrochemical water splitting. The findings provide a new design strategy toward low-cost and excellent catalysts for overall water splitting.