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

Abstract

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.

Tailoring Metal/TiO2 Interface to Influence Motion of Light‐Activated Janus Micromotors

“…Recently, photoactive quantum dots are attracting great attention among scientists for the preparation of visible‐light‐driven micromotors . ZnO/Pt microrobots, ZnO/Pt microrods, and ZnO microrockets with coated Ni layer have also been demonstrated as excellent photoactive materials, exhibiting autonomous motion under UV light, as well as steerable motion.…”

Toward High‐Performance Triboelectric Nanogenerators by Engineering Interfaces at the Nanoscale: Looking into the Future Research Roadmap

“…[ 1,100,109 ] However, the same ZnO particles (with controlled facets) on another application, i.e., photocatalyst micromotors, have shown improved charge transfer at the interface layer with noble metals and both photocatalytic and motion were enhanced. [ 110–112 ] Generally, interlayer interactions are a versatile design method for obtaining high‐performance TENG devices. [ 113–116 ]…”

Titania-Based Micro/Nanomotors: Design Principles, Biomimetic Collective Behavior, and Applications

“…Following these reports, a variety of metals have been used in combination with TiO 2 to form TiO 2 / metal hybrid structures [24][25][26][27][28][29][30][31]. To examine the effect of incorporating different metals in TiO 2 / metal MNMs, 40 nm thickness layers of Pt, Cu, Fe, Ag, and Au were sputtered, respectively, on TiO 2 microspheres and their velocities were compared under UV irradiation in the absence of fuel [32].…”