Catalytic and Light-Driven ZnO/Pt Janus Nano/Micromotors: Switching of Motion Mechanism via Interface Roughness and Defect Tailoring at the Nanoscale

The first models of mesoporous ZnO/Pt Janus micromotors that show fuel-free and light-powered propulsion depending on the interface roughness are shown. Two models of ZnO semiconducting particles with distinct surface morphologies and pore structures are synthesized by self-aggregation of primary nanoparticles and nanosheets into nanoscale rough and smooth microparticles, respectively. The self-assembled nanosheet model (smooth) provides a large surface for the formation of a continuous Pt layer with strong adherence, whereas the discontinuous Pt species take place inside the inter-nanoparticles pores in the self-assembled nanoparticle model (rough). The effects of the interface, surface porosity, defect, and charge transfer on the light-powered motion for both well-designed mesoporous ZnO/Pt Janus micromotors are investigated and compared to find the underlying propulsion mechanisms. The degradation of two model pollutants is demonstrated as a proof-of-concept application of these carefully engineered Janus micromotors. In this work, it is shown that by discreet material fabrication together with semiconductor/metal interface charge transport interpretation, it would be possible to develop new light-driven Janus micromotors based on other photocatalysts containing active surfaces such as TiO₂.