High photopiezocatalytic energy conversion via effective charge separation and deformability in the asymmetric ternary heterojunction Bi4Ti3O12/PPy/TiO2

Abstract

Photopiezocatalysts can take advantage of both solar light and environmental mechanical energy, thus holding high significance in building a sustainable society. However, designing highly potent photopiezocatalysts remains challenging. In this study, we propose an asymmetric ternary heterojunction as an efficient strategy for achieving effective photopiezocatalysts. A BTO/PPy/TiO₂ catalyst composed of Bi₄Ti₃O₁₂ (BTO) and TiO₂ nanosheets and polypyrrole (PPy) nanoparticles presents both enhanced asymmetric interfacial charge separation and deformability under mechanical stimuli, which result in appealing photopiezocatalytic capabilities. The stresses applied to the piezoelectric material lead to charge separation, and the ternary BTO/PPy/TiO₂ heterojunction has a higher deformation capacity than the binary BTO/TiO₂ heterojunction, which leads to higher fluctuating electric fields. Therefore, the d₃₃ value of BTO/PPy/TiO₂ is 3.1 times higher than that of BTO/TiO₂. In situ synchrotron-radiation-IR measurements indicate that electric fields excite electrons to higher energy levels and lead to larger electron densities in the heterojunction. Piezoelectric fields also enhance charge separation. Using cycled assembly, ternary BTO/PPy/TiO₂ heterojunctions were facilely constructed on a copper mesh substrate, and their applications in effective photopiezocatalytic degradation reactions are demonstrated. BTO/PPy/TiO₂ degraded rhodamine B (RhB) solution by 96% with a k value 2.92 times higher than that of BTO/TiO₂. This study elucidates the mechanism underlying efficient energy conversion and application in photopiezocatalytically active asymmetric heterojunctions and inspires the design of efficient catalysts.