Hierarchical MnOx@PVDF/MWCNTs tree-like nanofiber membrane with high catalytic oxidation activity

A hierarchical MnOx@polyvinylidene fluoride (PVDF)/multiwalled carbon nanotubes (MWCNTs) tree-like nanofiber membrane (TLNM) was developed for dye degradation under natural sunlight irradiations, which was prepared by in situ hydrothermal growth of MnOx nanoflakes on the electrospun PVDF/tetrabutylammonium chloride (TBAC)/MWCNTs TLNM. The specific surface area of the MnOx@PVDF/MWCNTs composite catalyst was significantly enhanced by the tree-like structure and MnOx nanoflakes and the catalyst presented good absorption of both ultraviolet light and visible light. Noticeably, the MnOx@PVDF/MWCNTs TLNM exhibited excellent catalytic activity for several different dyes under sunlight and even in the dark condition. Electron spin resonance (ESR) technology and reactive oxidative species scavenging experiments demonstrated that superoxide radicals ([rad]O2−) was the major active ingredient during catalytic degradation process. More importantly, the capacity of manganese with three oxidation states (II/III/IV) could massively enhance the electron transfer and the synergistic oxidation of [rad]O2− and Mn(IV) accelerated the degradation of dyes. Meanwhile, MWCNTs act as electron transfer channels which could effectively facilitate the catalytic efficiency. This study will supply a new scheme for construction of new catalysts with enhanced catalytic activity in pollutant degradation under both sunlight and dark conditions. © 2018 Elsevier B.V.