Confined Tri-Functional FeOₓ @MnO₂ @SiO₂ Flask Micromotors for Long-Lasting Motion and Catalytic Reactions

Abstract

H2O2-fueled micromotors are state-of-the-art mobile microreactors in environmental remediation. In this work, a magnetic FeOx@MnO2@SiO2 micromotor with multi-functions is designed and demonstrated its catalytic performance in H2O2/peroxymonosulfate (PMS) activation for simultaneously sustained motion and organic degradation. Moreover, this work reveals the correlations between catalytic efficiency and motion behavior/mechanism. The inner magnetic FeOx nanoellipsoids primarily trigger radical species (• OH and O2 •−) to attack organics via Fenton-like reactions. The coated MnO2 layers on FeOx surface are responsible for decomposing H2O2 into O2 bubbles to provide a propelling torque in the solution and generating SO4 •− and • OH for organic degradation. The outer SiO2 microcapsules with a hollow head and tail result in an asymmetrical Janus structure for the motion, driven by O2 bubbles ejecting from the inner cavity via the opening tail. Intriguingly, PMS adjusts the local environment to control overviolent O2 formation from H2O2 decomposition by occupying the Mn sites via inter-sphere interactions and enhances organic removal due to the strengthened contacts and Fenton-like reactions between inner FeOx and peroxides within the microreactor. The findings will advance the design of functional micromotors and the knowledge of micromotor-based remediation with controlled motion and high-efficiency oxidation using multiple peroxides.