Review of 3D printing in photocatalytic substrates and catalysts

Photocatalysis with semiconductor materials provides a new way of solar energy utilization, which has been widely investigated in the environmental and energy fields. There-dimensional (3D) printing is a rapid preparation technology of photocatalysis materials that provides a low-cost and versatile alternative to design photocatalysts and tunable structured photocatalytic substrates. The flexible operation of 3D printing technology can expand the specific surface area of catalytic/photocatalytic materials and precisely control active components. Besides, it can also realize the optimization and molding of complex substrate structures and reduce the manufacturing costs. The substrate structure affects the catalyst loading, quality, and light transmission performance, thus plays a crucial role in photocatalysis. Meanwhile, the transparent substrates could be manufactured by 3D printing to improve the light quantum transport efficiency in the reaction system. However, a systematic summary of 3D printing photocatalytic materials and substrate structures is still lacking. This paper reviews various printing techniques and printing materials for photocatalysis applications. Besides, the effects on the catalytic performances of integral printing and the printed photocatalytic substrates modified by post processing are discussed. Also, the regulation mechanism between the type and structure of photocatalytic substrate and the catalytic performance is revealed. Finally, the design methods of 3D printing complex topology for future applications are discussed.