Boosting Piezocatalytic Hydrogen Production via Bismuth Vacancy-Engineered BiOCl-Bi 2 S 3 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 (VBi) 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 VBi defects, leading to a dramatic enhancement of the piezoelectric coefficient (387 pm/V vs. 151 pm/V for pristine BiOCl). The optimal composite (BiOCl-Bi2S3-40) achieved a obviously enhanced hydrogen production rate of 678.67 μmol•g-1•h-1 in pure water under ultrasonic vibration (45 kHz, 120 W), doubling 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 previous reported piezocatalysts. The catalyst maintained 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. VBi acts as electron traps, reducing interfacial charge-transfer barriers. Synergy between the heterojunction and VBi facilitate 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.