Enabling built‐in electric fields on rhenium‐vacancy‐rich heterojunction interfaces of transition‐metal dichalcogenides for pH‐universal efficient hydrogen and electric energy generation

Abstract Most advanced hydrogen evolution reaction (HER) catalysts show high activity under alkaline conditions. However, the performance deteriorates at a natural and acidic pH, which is often problematic in practical applications. Herein, a rhenium (Re) sulfide–transition‐metal dichalcogenide heterojunction catalyst with Re‐rich vacancies (NiS₂‐ReS₂‐V) has been constructed. The optimized catalyst shows extraordinary electrocatalytic HER performance over a wide range of pH, with ultralow overpotentials of 42, 85, and 122 mV under alkaline, acidic, and neutral conditions, respectively. Moreover, the two‐electrode system with NiS₂‐ReS₂‐V₁ as the cathode provides a voltage of 1.73 V at 500 mA cm⁻², superior to industrial systems. Besides, the open‐circuit voltage of a single Zn–H₂O cell with NiS₂‐ReS₂‐V₁ as the cathode can reach an impressive 90.9% of the theoretical value, with a maximum power density of up to 31.6 mW cm⁻². Moreover, it shows remarkable stability, with sustained discharge for approximately 120 h at 10 mA cm⁻², significantly outperforming commercial Pt/C catalysts under the same conditions in all aspects. A series of systematic characterizations and theoretical calculations demonstrate that Re vacancies on the heterojunction interface would generate a stronger built‐in electric field, which profoundly affects surface charge distribution and subsequently enhances HER performance.