Bio-inspired design: Inner-motile multifunctional ZnO/CdS heterostructures magnetically actuated artificial cilia film for photocatalytic hydrogen evolution

A novel inner-motile film for photocatalytic water splitting has been designed for the first time. The inner-motile photocatalyst film is a highly elaborate machinery and mainly integrates three functional modules - magnetically actuated artificial cilia, ZnO nanowires arrays and CdS quantum dots, which can work synergistically to enhance the photocatalytic hydrogen evolution activity. Through citing magnetically actuated artificial cilia, the inner-motile film can mimic ciliary motion like nature beating cilia under a rotational magnetic field. Hence it exhibits a singular ability of microfluidic manipulation, which is helpful to solve the stubborn problem of desorption of hydrogen and promotes release of active sites. In contrast to the traditional external magnetic-stirrer technologies, the photocatalytic activity can be greatly improved. Moreover, forest-like hierarchical structured ZnO nanowires arrays have been constructed by being grafted on magnetically actuated artificial cilia, which increase the surface area and light absorption. Furthermore, the photocatalytic modules - coupled ZnO/CdS heterostructures based on the Z-scheme mechanism has been devised to enhance electron-hole separation and interfacial charge transfer, in which ZnO and CdS serve as PS II and PS I, respectively. Consequently, the H₂ evolution rates of ZnO nanowires arrays/CdS heterostructures are about 2.7 times, 2.0 times of CdS substance and ZnO nanoparticles/CdS heterostructures, respectively. The design of the inner-motile system film is based on both nature cilia and photosynthesis, which would broaden the horizon for constructing artificial photocatalyst system and provide a new working prototype for photochemical hydrogen production.