The insight into the critical role of photoexcitation in manipulating charge carrier migration in piezo-photocatalytic S-scheme heterojunction

Piezo-photocatalytic S-scheme heterojunctions, consisting of a piezoelectric N-type semiconductor and a conventional N-type semiconductor, have garnered substantial interest due to their capacity for facilitating charge carrier separation and transport within piezo-photocatalytic processes. However, previous studies on the piezo-photocatalytic of S-scheme heterojunctions primarily focus on the coupling mechanism between piezoelectricity and semiconductor properties, aimed at manipulating charge carrier migration. This leaves scant attention to the modulation mechanism induced by photoexcitation. In this work, we aim to investigate the photoexcitation-induced modulation mechanisms in piezo-photocatalytic S-scheme heterojunctions of ZnO/Cs₂AgBiBr₆ nanorod array (ZC NRA) for the first time, using a light-tailoring irradiation strategy. ZnO is a rational choice for constructing the heterojunctions due to its wide band gap (3.23 eV), which allows the photoexcitation state to be modulated by UV irradiation. The degradation kinetic constant of optimized ZC NRA under simulated sunlight irradiation with ZnO excitation is 2.52 times higher than that under visible light (λ > 420 nm) without ZnO excitation. The piezo-polarization induced band bending structures that underlie the enhanced mechanisms of piezo-photocatalytic S-scheme heterojunctions are switched with the presence or absence of ZnO photoexcitation. This study reveals the photoexcitation-induced modulation mechanisms in piezo-photocatalytic S-scheme heterojunctions, complementing the neglected piece in the puzzle of piezo-phototronics effect. It also paves the way for the use of lead-free halide double perovskite in piezo-photocatalytic conversion of solar and mechanical energy.