Special issue on “Ultrasound meets photocatalysis: recent trends in photocatalyst synthesis, hybrid processes, and piezo-enhanced strategies”

Highlights • This review focuses on the paths for Bi-based materials to profit from sonochemistry. • The roles of ultrasound in the process of material formation are introduced. • Inherent functionality of sonochemistry in photocatalysis is clarified. • Photocatalytic applications and status of enhanced Bi-based materials are discussed. • Future directions for ultrasonic synergistic Bi-based photocatalysts are presented.

Highlights • CoCr LDH was decorated on the graphene oxide and reduced graphene oxide. • Dimethyl phthalate was efficiently removed by photo-assisted sonocatalysis. • Hydroxyl radicals, holes, and superoxide anion radicals were known as efficient species. • he possible mechanism of decomposition of DMP into non-toxic compounds was proposed.

• Eu-doped BiOCl can be improved photocatalytic performance. • Sonophotocatalytic activity of Eu-doped BiOCl is also improved. • The synergistic effect of inhibiting carrier recombination, and expansion to the visible light absorption region. Bismuth oxychloride (BiOCl) has a unique layered structure and uneven charge distribution, resulting in an internal electric field under polarization, which promotes the efficient separation and migration of photogenerated carriers. BiOCl could be a candidate for sonophotocatalysts. However, the low utilization of visible light limits the application of BiOCl in photocatalysts. In this study, the photocatalytic performance of rare earth element (Nd, Sm, Eu, Er and Er)-doped BiOCl was studied by density functional theory (DFT) and experimentally to screen high-performance catalysts. The band structure, density of states, and optical properties were calculated by the DFT method to predict the photocatalytic activity of rare earth-doped BiOCl. The built-in electric field formed in Eu-doped BiOCl inhibiting electron and hole recombination can be observed. Subsequently, the activity of the photocatalyst and sonophotocatalysts was evaluated. The results show that the photocatalytic and sonophotocatalytic activity of Eu-doped BiOCl is improved, which is consistent with the theoretical prediction. Combining theoretical calculations with experiments, the sonophotocatalytic activity of Eu-doped BiOCl is enhanced, mainly due to the synergistic effect of inhibiting carrier recombination, and expansion to the visible light absorption region.