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 H 2 O dissociation, which is strongly governed by the orientation and hydrogen-bond environment of interfacial H 2 O molecules. Here, we reported a heterostructured electrocatalyst comprising PtO x nanoclusters anchored on NiO (PtO x /NiO) that overcomes this limitation by regulating the interfacial H 2 O configuration. Combined in-situ experimental and theoretical investigations revealed that PtO x /NiO established a strengthened dipole field, which induced a preferential H-down orientation of interfacial H 2 O, thereby lowering the H 2 O dissociation barrier. Meanwhile, partially oxidized Pt sites optimize hydrogen intermediate binding, increasing surface proton availability and facilitating subsequent HER. As a result, the PtO x /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 H 2 O activation, offering new mechanistic insight and a generalizable framework for designing high-efficiency alkaline HER electrocatalysts.