In-Plane Mott–Schottky Effects Enabling Efficient Hydrogen Evolution from Mo₅N₆-MoS₂ Heterojunction Nanosheets in Universal-pH Electrolytes

Cost-effective electrocatalysts for the hydrogen evolution reaction (HER) spanning a wide pH range are highly desirable but still challenging for hydrogen production via electrochemical water splitting. Herein, Mo₅N₆-MoS₂ heterojunction nanosheets prepared on hollow carbon nanoribbons (Mo₅N₆-MoS₂/HCNRs) are designed as Mott–Schottky electrocatalysts for efficient pH-universal HER. The in-plane Mo₅N₆-MoS₂ Mott–Schottky heterointerface induces electron redistribution and a built-in electric field, which effectively activates the inert MoS₂ basal planes to intrinsically increase the electrocatalytic activity, improve electronic conductivity, and boost water dissociation activity. Moreover, the vertical Mo₅N₆-MoS₂ nanosheets provide more activated sites for the electrochemical reaction and facilitate mass/electrolyte transport, while the tightly coupled HCNRs substrate and metallic Mo₅N₆ provide fast electron transfer paths. Consequently, the Mo₅N₆-MoS₂/HCNRs electrocatalyst delivers excellent pH-universal HER performances exemplified by ultralow overpotentials of 57, 59, and 53 mV at a current density of 10 mA cm⁻² in acidic, neutral, and alkaline electrolytes with Tafel slopes of 38.4, 43.5, and 37.9 mV dec⁻¹, respectively, which are superior to those of the reported MoS₂-based catalysts and outperform Pt in overall water splitting. This work proposes a new strategy to construct an in-plane heterointerface on the nanoscale and provides fresh insights into the HER electrocatalytic mechanism of MoS₂-based heterostructures.