Oxygen Vacancy-MediatedMicroflower-like Bi₅O₇I for Reactive OxygenSpecies Generation through Piezo-PhotocouplingEffect

Photocatalytic reactive oxygen species (ROS) evolution with Bi₅O₇I still suffers from sluggish charge carrier dynamics and limited light absorption. Herein, abundant oxygen vacancies (OVs) were introduced into the microflower-like Bi₅O₇I, and its ROS generation toward organic dye degradation under the synergistic effect of visible light and ultrasound irradiation was investigated. Benefiting from the broadened visible-light absorption range, stronger piezoresponse, and higher carrier transport efficiency in OV-enriched Bi₅O₇I (2-PEG-Bi₅O₇I), both its photocatalytic and piezocatalytic degradations were improved. More importantly, its piezo-photocatalytic degradation performance was greater than the sum of the corresponding photocatalysis and piezocatalysis, indicating a strong coupling effect. In addition, the piezo-photocatalytic yield of ^•O₂^– with 2-PEG-Bi₅O₇I was 1.5 times higher than that with Bi₅O₇I, and it was also 4.3 and 3.1 times higher than its single photocatalysis and piezocatalysis, respectively. Interestingly, no noticeable ^•OH was detected in the case of visible-light irradiation, while the piezocatalytic and piezo-photocatalytic yields of ^•OH were 3.6 and 5.3 μmol g^–1 h^–1, respectively, with OV-enriched Bi₅O₇I, surpassing the pristine Bi₅O₇I as well. This work advances the coupling effect between photocatalysis and piezocatalysis as a new strategy for efficient ROS generation and also discloses the positive role of oxygen vacancies in improving multiresponsive catalysis.