Metal oxide single-component light-powered micromotors for photocatalytic degradation of nitroaromatic pollutants

Mass transfer is a key parameter in heterogeneous reactions. Micro/nanomachines, a promising technology for environmental applications, significantly enhance the performance of conventional purification treatments because of the active motion ability and thus enhanced diffusion (superdiffusion) of these photocatalysts, which in turn leads to dramatically improved mass transfer and higher degradation capability compared to stationary microparticles. However, the design of micromotors generally involves noble metals, for instance, Au and Pt, to achieve an effective autonomous motion. Considering the expensive fabrication cost and complicated steps, we present Pt-free single-component light-powered WO3 micromotors capable of enhanced diffusion and effective degradation of nitroaromatic compounds in water. These microswimmers, synthesized by a hydrothermal method, which is highly scalable at low cost, followed by calcination, exhibit fuel-free light-driven motion due to asymmetric light irradiation. Picric acid (PA) and 4-nitrophenol (4-NP) were selected as representative nitroaromatic contaminants and photocatalytically decomposed by WO3 micromotors thanks to the close contact with the micromotors promoted by their self-propulsion. This work provides a low-cost, sustainable, scalable method for enhancing mass transfer by creating moving catalysts with broad application potential for water cleanup.