Interfacial p–n coupling in Cu3N/1T-MoS2 heterojunctions drives efficient and durable acidic hydrogen evolution

Rational interfacial engineering is crucial to designing non-precious electrocatalysts for the hydrogen evolution reaction (HER). Here we report a Cu 3 N/1T-MoS 2 heterojunction in which ultrathin 1T-MoS 2 nanosheets are conformally grown on conductive p-type Cu 3 N nanocubes. Spectroscopy and microscopy reveal intimate lattice contact and interfacial strain, while XPS indicates charge redistribution across the junction. In 0.5 M H 2 SO 4 , the optimized 1:1 composite delivers an overpotential of 387 mV at 50 mA cm −2 and a Tafel slope of 57 mV dec −1 , outperforming both constituents (MoS 2 ≈ 456 mV; Cu 3 N inactive at this current density). Continuous operation for 150 h demonstrates excellent acid stability. Electrochemical impedance and double-layer capacitance analyses show the lowest charge-transfer resistance and the highest electrochemically active surface area among all samples (C dl = 103.6 mF cm −2 ), corroborating rapid electron transport and abundant accessible sites. The activity enhancement arises from a p–n heterojunction with a built-in field that promotes directional electron flow to MoS 2 active edges, together with strain-induced defect exposure. This work identifies Cu 3 N as an effective platform to stabilize conductive MoS 2 and provides design rules for interface-engineered HER catalysts.