High-performance carbon/MnO₂ micromotors and their applications for pollutant removal

The wide applications of particulate micromotors in practice, especially in the removal of environmental pollutants, have been limited by the low production yields and demand on high concentration of fuel such as H₂O₂. Carbon/MnO₂ micromotors were made hydrothermally using different carbon allotropes including graphite, carbon nanotube (CNT), and graphene for treatment of methylene blue and toxic Ag ions. The obtained micromotors showed high speed of self-propulsion. The highest speed of MnO₂-based micromotors to date was observed for CNT/MnO₂ (>2 mm/s, 5 wt% H₂O₂, 0.5 wt% surfactant). Moreover, different from previous studies, even with low H₂O₂ concentration (0.5 wt%) and without surfactant addition, the micromotors could also be well dispersed in water by the O₂ stream released from their reaction with H₂O₂. The carbon/MnO₂ micromotors removed both methylene blue (>80%) and Ag ions (100%) effectively within 15 min by catalytic decomposition and adsorption. Especially high adsorption capacity of Ag (600 mg/g) was measured on graphite/MnO₂ and graphene/MnO₂ micromotors.