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

Abstract

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.