Boosting piezocatalytic hydrogen production via bismuth vacancy-engineered BiOCl–Bi2S3 heterojunctions fabricated by a light-induced deposition strategy

Abstract

This study presents a novel light-induced deposition strategy for constructing BiOCl–Bi₂S₃ heterojunctions enriched with bismuth vacancies (V_Bi) to enhance piezocatalytic hydrogen evolution. The heterojunction was synthesized by photodepositing Bi₂S₃ onto BiOCl nanosheets with exposed (001) facets. Structural characterization confirmed the formation of the heterojunction and revealed that the reaction between Bi³⁺ in BiOCl and S²⁻ generated V_Bi defects, leading to a dramatic enhancement of the piezoelectric coefficient (387 pm V⁻¹ vs. 151 pm V⁻¹ for pristine BiOCl). The optimal composite (BiOCl–Bi₂S₃-40) achieved an obviously enhanced hydrogen production rate of 678.67 µmol g⁻¹ h⁻¹ in pure water under ultrasonic vibration (45 kHz, 120 W), double that of pristine BiOCl (352.53 µmol g⁻¹ h⁻¹). In methanol solution, the rate further surged to 2717.33 µmol g⁻¹ h⁻¹, which is higher than those of the previously reported piezocatalysts. The catalyst retained high stability over five cycles. Mechanistic studies attribute the enhanced performance to the strong built-in electric field from piezoelectric polarization, which promotes charge separation. V_Bi act as electron traps, reducing interfacial charge-transfer barriers. Synergy between the heterojunction and V_Bi facilitates efficient carrier migration. This work not only demonstrates a high-efficiency piezocatalyst but also provides insights into the critical role of cationic vacancies in piezocatalysis.