Enhanced piezocatalytic RhB degradation with ZnSnO Nanocube-modified BiTiO composite catalyst by harnessing ultrasonic energy.

With the increasing demand for effective methods to address environmental pollution, piezocatalysis has emerged as a promising approach for pollutant degradation under mechanical energy. However, the development of highly efficient piezocatalytic materials remains a challenge. This study aimed to increase the piezocatalytic activity of bismuth titanate (BiTiO) by modifying it with zinc stannate (ZnSnO) nanocubes. The composite catalysts were synthesized using a straightforward deposition and calcination process. The calcination process ensured the tight adhesion of ZnSnO nanocubes to the BiTiO surface, while facilitating strong interactions between ZnSnO and BiTiO, which enhanced electron transfer and heterojunction structure formation. Band structure analysis indicated that BiTiO has higher conduction band and valence band potentials than ZnSnO, forming a type-II heterojunction. BiTiO possesses a higher Fermi level than ZnSnO, resulting in interfacial electron drift and formation of a built-in electric field, which further promotes the directional transfer and separation efficiency of charge carriers within the composite catalyst. This hypothesis was confirmed by surface photovoltage spectroscopy, piezoelectric current response, and electrochemical analysis. Consequently, the ZnSnO/BiTiO composite exhibited significantly improved piezocatalytic performance in RhB degradation, achieving a degradation efficiency of 80 % within 90 min under ultrasonic vibration. The degradation rate of the optimal sample was 8.2 times that of BiTiO and 6.3 times that of ZnSnO. Additionally, experiments to detect reactive species were conducted to elucidate the mechanism behind the piezocatalytic RhB degradation. Holes and hydroxyl radicals were the main reactive species. This study may offer new insights into the design of efficient piezocatalytic materials.