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

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)-O-center dot and O-2(center dot-)) to attack organics via Fenton-like reactions. The coated MnO2 layers on FeOx surface are responsible for decomposing H2O2 into O-2 bubbles to provide a propelling torque in the solution and generating SO4 center dot- and (OH)-O-center dot for organic degradation. The outer SiO2 microcapsules with a hollow head and tail result in an asymmetrical Janus structure for the motion, driven by O-2 bubbles ejecting from the inner cavity via the opening tail. Intriguingly, PMS adjusts the local environment to control over-violent O-2 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.