Hierarchical Z-scheme 1D/2D architecture with TiO2 nanowires decorated by MnO2 nanosheets for efficient adsorption and full spectrum photocatalytic degradation of organic pollutants

Abstract

Constructing composite photocatalysts with efficient photocatalytic activity, a wide optical response range and excellent stability has great significance for the removal of organic pollutants in water. Herein, we report a novel hierarchical Z-scheme 1D/2D architecture with TiO₂ nanowires decorated by MnO₂ nanosheets prepared using a simple vacuum freeze-drying method. X-ray diffraction (XRD), Raman, scanning electron microscopy (SEM), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), nitrogen adsorption–desorption, X-ray photoelectron spectroscopy (XPS) and UV-visible diffuse reflectance spectroscopy (UV-vis DRS) analyses confirmed its composition, morphology, surface structure, chemical state and light absorption properties. In comparison to pristine TiO₂ nanowires and sole MnO₂ nanosheets, the as-prepared composite exhibited significantly enhanced adsorption and full spectrum photocatalytic activity for the removal of typical organic contaminants in water. Illumination could not only accelerate the degradation of rhodamine B (RhB) in the solution but also promote the decomposition of RhB adsorbed on the composite surface. Thereby, the composite still retained excellent adsorption and photocatalytic stability after three recycling runs. On the basis of the hierarchical structure of the composite, the generation of hydroxyl radicals (·OH) and superoxide radicals (·O₂⁻) in the dark and the direct Z-scheme photocatalytic mechanism, the adsorption and photocatalytic performance enhancement of the composite was well elucidated. This work provides an effective approach to construct hierarchical 1D/2D photocatalysts for efficient adsorption and full spectrum photocatalytic degradation of organic contaminants in water.