Light-Driven Sandwich ZnO/TiO₂/Pt Janus Micromotors: Schottky Barrier Suppression by Addition of TiO₂ Atomic Interface Layers into ZnO/Pt Micromachines Leading to Enhanced Fuel-Free Propulsion

Conventional binary light-driven micromotors, based on semiconducting photocatalysts and metal junctions, have mostly shown limited speed and charge separation/transport due to their not well-designed interfaces. Here ZnO/Pt Janus micromotors with atomically smooth interfaces are introduced, which show fast light-driven and fuel-free propulsion (15 body-length s⁻¹). Furthermore, the speed of ZnO/Pt micromotors is increased by ≈60% with a few atomic amorphous TiO₂ photocatalyst interlayers. The new photocatalysts' interfaces, i.e., ZnO/TiO₂, provide type II heterojunctions, leading to an increase in the number of electron/hole pairs and then improving the electron transfer to Pt metal. This effective charge separation/transfer results in a faster electrophoretic motion of the novel ternary ZnO/TiO₂/Pt micromotors. The concept of the type II heterojunction, which is well known in photocatalysis communities, is used in light-driven micromotors as a new approach and paves the way for the next-generation of faster fuel-free “green” micromotors.