Catalytic Pollutant Upgrading to Dual-Asymmetric MnO₂@polymer Nanotubes as Self-Propelled and Controlled Micromotors for H₂O₂ Decomposition

Abstract

Industrial and disinfection wastewater typically contains high levels of organic pollutants and residue hydrogen peroxide, which have caused environmental concerns. In this work, dual-asymmetric MnO2 @polymer microreactors are synthesized via pollutant polymerization for self-driven and controlled H2 O2 decomposition. A hollow and asymmetric MnO2 nanotube is derived from MnO2 nanorods by selective acid etching and then coated by a polymeric layer from an aqueous phenolic pollutant via catalytic peroxymonosulfate (PMS)-induced polymerization. The evolution of particle-like polymers is controlled by solution pH, molar ratios of PMS/phenol, and reaction duration. The polymer-covered MnO2 tubing-structured micromotors presented a controlled motion velocity, due to the reverse torque driven by the O2 bubbles from H2 O2 decomposition in the inner tunnels. In addition, the partially coated polymeric layer can regulate the exposure and population of Mn active sites to control the H2 O2 decomposition rate, thus avoiding violent motions and massive heat caused by vigorous H2 O2 decomposition. The microreactors can maintain the function of mobility in an ultra-low H2 O2 environment (<0.31 wt.%). This work provides a new strategy for the transformation of micropollutants to functional polymer-based microreactors for safe and controlled hydrogen peroxide decomposition for environmental remediation.