TiO2‑Nanoparticle-Shelled Light-Driven Microcleaner for Fast and Highly Efficient Degradation of Organic Pollutants

High emissions of hazardous pollutants into the environment potentially lead to water shortages. New cost-effective water-treatment techniques with high degradation efficiencies are therefore needed. Here, we design an “open-mouth,” hollow, TiO2-nanoparticle-shelled (OMHTNPS), light-induced-bubble-propelled microcleaner for efficiently degrading organic pollutants. OMHTNPS microcleaners with asymmetric structures can be obtained via a facile sol–gel method, with subsequent removal of carbon microspheres by a simple sintering process. The shells of the prepared OMHTNPS microcleaners mainly consist of 20 nm anatase–TiO2 nanoparticles. When exposed to UV light, the OMHNPS microcleaners moved rapidly because of the photocatalytic decomposition of H2O2. The propulsion mechanism was investigated in detail. The OMHNPS microcleaner velocity can be conveniently controlled by the UV irradiation intensity and H2O2 concentration. Light-triggered on/off motion of the prepared microcleaners was also demonstrated. The combination of photocatalysis, self-propulsion, and a specific hollow nanoparticle-shelled structure gave a rhodamine B removal rate of 98% in the first 10 min. This is approximately 11 and 3 times higher than those achieved with a static pattern and solid TiO2 microcleaners, respectively. Deposition of magnetic Fe3O4 particles enabled convenient recycling and reuse of the microcleaners. These novel OMHTNPS microcleaners show outstanding capabilities for the removal of organic pollutants with fast speed and confirm that high efficiency can be achieved through the structure design of the microcleaner. The strategy proposed here provides potential approaches to the large-scale fabrication of asymmetric micromotors and the design of versatile photocatalytic micromotors.