Efficient Catalytic Production of Reactive Oxygen Species through Piezoelectricity in Bismuth Sulfide Rich in Sulfur Vacancies

Sulfur (S) vacancies in metal sulfides are of interest in electrocatalysis and photoelectronics, but their effect on the generation of reactive oxygen species (ROS) during mechanical catalysis is unclear. This study investigates the impact of S-vacancies in defective bismuth sulfide (Bi₂S_3-<i>x</i>) on ROS production under ultrasonic irradiation and organic contaminant decomposition. S-vacancies disrupt the centrosymmetric structure of intrinsic Bi₂S₃, inducing piezoelectric effects and enhancing the electrical energy in Bi₂S_3-<i>x</i>. The positively charged S-vacancies in Bi₂S_3-<i>x</i> promote the separation of ultrasound-activated electron-hole pairs by capturing electrons. As a result, the optimal rate of H₂O₂ formation and the reaction rate constant for degrading Rhodamine B dye on Bi₂S_3-<i>x</i> are found to be 1.9 and 37 times higher, respectively, than those on Bi₂S₃ under ultrasonic irradiation. The nonzero catalytic efficiency in centrosymmetric Bi₂S₃ is due to the flexoelectric catalytic effect from nonuniform strain. These results guide the piezocatalyst design and elucidate mechanical catalysis mechanisms.