Bubble-propelled plasmon-reinforced Pt-ZnIn2S4 micromotors for stirring-free photocatalytic water purification

Abstract

In recent years, self-propelled micro/nanomotors have attracted great attention in environmental remediation. However, their progress in real-world applications is still constrained by crucial issues such as manufacturing processes, low yields, poor adaptability, and poor motion ability. In this work spherical bubble-propelled micromotors (i.e., Pt-ZnIn₂S₄) were fabricated with a strong motion ability and photocatalytic performance to replace conventional mechanical stirring for photocatalytic water purification. A simple, efficient, and highly productive ultraviolet reduction method is employed to deposit Pt on the ZnIn₂S₄ microspheres assembled by nanosheets. The Pt nanoparticles (NPs) can promote the separation and migration of photogenerated carriers between semiconductor interfaces and enhance their visible light absorption due to their strong electron-accepting ability (Cocatalyst) and localized surface plasmon resonance effect (Plasmonic metal NPs). In addition, due to the asymmetrical structure of the Pt-ZnIn₂S₄ micromotor, Pt NPs can decompose H₂O₂ to produce oxygen bubbles, driving the micromotor to move rapidly (Engine), up to a maximum speed of 970 ± 150 μm s⁻¹. Compared with traditional photocatalysts, the movement of the Pt-ZnIn₂S₄ micromotor and the migration and collapse of the generated bubbles increase the solution stirring effect and mass transfer effect, thereby achieving efficient and rapid degradation of methyl orange (MO) and tetracycline hydrochloride (TCH) without mechanical stirring. The degradation mechanism of organic pollutants is mainly based on the production of reactive oxygen species in photocatalytic processes. This study shows that the combination of photocatalysts, plasmonic metal NPs, and the strong motion ability of bubble-propelled micromotors presented the potential for practical environmental pollution remediation.