Self-Asymmetric Yolk–Shell Photocatalytic ZnO Micromotors

Abstract

Large-scale fabrication of self-propelled micromotors is crucial to reach practical applications, but batch processes in manufacture make it challenging. Here, a novel ZnO yolk-shell structure from large-scale synthesis is introduced as photocatalytic micromotor. The self-asymmetry of the yolk-shell structure enables them to create asymmetric gradients, leading to autonomous motion. Benefiting from the inner void space, the ZnO micromotors possess higher incident light utilization and a larger surface area for photocatalytic reactions. Moreover, when exposed to hydrogen peroxide, ZnO partially transforms into ZnO2 forming a beneficial ZnO2/ZnO heterojunction for separation of photo-generated carriers, enhancing the photochemical reactions and thereby the motion. This combination of yolk-shell structure and ZnO2/ZnO heterojunction formation provides a prospective approach for large-scale asymmetric micromotor fabrication and may open new horizons for designing versatile photocatalytic micromotors.