Dipole-Induced Water Orientation at PtO x /NiO Heterostructures for Efficient Alkaline Hydrogen Evolution

The sluggish hydrogen evolution reaction (HER) in alkaline media is fundamentally limited by the high energy barrier of H2O dissociation, which is strongly governed by the orientation and hydrogen-bond environment of interfacial H2O molecules. Here, we reported a heterostructured electrocatalyst comprising PtOx nanoclusters anchored on NiO (PtOx/NiO) that overcomes this limitation by regulating the interfacial H2O configuration. Combined in-situ experimental and theoretical investigations revealed that PtOx/NiO established a strengthened dipole field, which induced a preferential H-down orientation of interfacial H2O, thereby lowering the H2O dissociation barrier. Meanwhile, partially oxidized Pt sites optimize hydrogen intermediate binding, increasing surface proton availability and facilitating subsequent HER. As a result, the PtOx/NiO delivered outstanding HER performance in alkaline electrolyte, requiring only 27 mV overpotential at 10 mA cm-2. This work establishes interfacial dipole engineering as an effective strategy for accelerating H2O activation, offering new mechanistic insight and a generalizable framework for designing high-efficiency alkaline HER electrocatalysts.