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.

Keywords

built-in electric field / electrocatalysts / hydrogen evolution reaction / self-powered system / water splitting / Zn–H₂O cell