Recent progress on sonochemical production for the synthesis of efficient photocatalysts and the impact of reactor design

•Sonochemical synthesis of photocatalysts is a promising green field for the removal of toxic substances.•Sonochemistry affects the structure of the synthesized nanoparticles in favour of photocatalytic experiments.•Batch and continuous flow reactors are the most studied systems.•Continuous flow reactors are used both for the synthesis and the photocatalytic experiments.•Microflow reactors offer commercial-scale advantages. Sonochemical-assisted synthesis has flourished recently for the design of photocatalysts. The main power used is ultrasound that allows the nanomaterials shape and size modification and control. This review highlights the effect in formation mechanism by ultrasound application and the most common photocatalysts that were prepared via sonochemical techniques. Moreover, the challenge for the suitable reactor design for the synthesis of materials or for their photocatalytic evaluation is discussed since the most prominent reactor systems, batch, and continuous flow, has both advantages and drawbacks. This work summarises the significance of sonochemical synthesis for photocatalytic materials as a green technology that needs to be further investigated for the preparation of new materials and the scale up of developed reactor systems to meet industrial needs.