Confined Tri-Functional FeO x @MnO 2 @SiO 2 Flask Micromotors for Long-Lasting Motion and Catalytic Reactions.

H 2 O 2 -fueled micromotors are state-of-the-art mobile microreactors in environmental remediation. In this work, a magnetic FeO x @MnO 2 @SiO 2 micromotor with multi-functions is designed and demonstrated its catalytic performance in H 2 O 2 /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 FeO x nanoellipsoids primarily trigger radical species ( • OH and O 2 •- ) to attack organics via Fenton-like reactions. The coated MnO 2 layers on FeO x surface are responsible for decomposing H 2 O 2 into O 2 bubbles to provide a propelling torque in the solution and generating SO 4 •- and • OH for organic degradation. The outer SiO 2 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 H 2 O 2 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 FeO x 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.