Finally, our research, as described in the first part of this review, shows that sonophotocatalysis is an effective method for treating wastewater, with advantages over both sonocatalysis and photocatalysis alone, such as shorter reaction times and higher removal rates. Second, ultrasonic and light irradiation work together synergistically to clean the catalytic surface in real time, addressing issues with catalyst opacity and porosity. Furthermore, sonophotocatalysis removes catalyst fouling, increases free radicals' production ( • OH, • O2 -), and removes resistance to mass transfer from the liquid phase to the catalyst surface. In terms of sonophotocatalysis for hydrogen production, the findings indicate that the impacts of ultrasound irradiation are primarily physical in nature. This is because the mass transfer of hydrogen from the catalyst surface to the bulk phase is improved, while charges are separated, leading to an increase in photoactivity. Consequently, hydrogen bubbles detach from the catalyst's surface. Additionally, the mechanical energy and shock waves produced when acoustic cavitation bubbles collapse further enhance adsorption characteristics and reactive sites. The introduction of ultrasonic vibration into the photocatalytic conversion of biomass for hydrogen generation has numerous benefits, including the acceleration of the photocatalytic process. On a larger scale, it would improve the process's efficiency and sustainability. From a kinetics perspective, the photocatalytic process can be improved by promoting the mixing of the photocatalyst with biomass, enhancing the formation and transfer of reactive oxygen species (ROS) to the biomass matter, and improving mass transfer as a result of shock waves and jetting phenomena. The oxidation of biomass and the creation of radical intermediates can be directly influenced by ROS production induced by ultrasound.