Recent progresses in the synthesis of MnO₂ nanowire and its application in environmental catalysis

Nanostructured MnO₂ with various morphologies exhibits excellent performance in environmental catalysis owing to its large specific surface area, low density, and adjustable chemical properties. The one-dimensional MnO₂ nanowire has been proved to be the dominant morphology among various nanostructures, such as nanorods, nanofibers, nanoflowers, etc. The syntheses and applications of MnO₂-based nanowires also have become a research hotspot in environmental catalytic materials over the last two decades. With the continuous deepening of the research, the control of morphology and crystal facet exposure in the synthesis of MnO₂ nanowire materials have gradually matured, and the catalytic performance also has been greatly improved. Differences in the crystalline phase structure, preferably exposed crystal facets, and even the length of the MnO₂ nanowires will evidently affect the final catalytic performances. Besides, the modifications by doping or loading will also significantly affect their catalytic performances. This review carefully summarizes the synthesis strategies of MnO₂ nanowires developed in recent years as well as the influences of the phase structure, crystal facet, morphology, dopant, and loading amount on the catalytic performance. Besides, the cutting-edge applications of MnO₂ nanowires in the field of environmental catalysis, such as CO oxidation, the removal of VOCs, denitrification, etc., have been also summarized. The application of MnO₂ nanowire in environmental catalysis is still in the early exploratory stage. The gigantic gap between theoretical investigation and industrial application is still a great challenge. Compared with noble metal based traditional environmental catalytic materials, the lower cost of MnO₂ has injected new momentum and promising potential into this research field.