Preparation And Application Of Black Titanium Dioxide/carbon Nanotube Composites

Among the myriad photocatalytic materials,TiO2,as one of the most suitable photocatalysts,has been widespread concern for its low cost,innocuity,good stability and commercial availability.Nevertheless,the unavoidable disadvantages of TiO2 photocatalyst include being limited to ultraviolet light of absorption spectrum and the rapid recombination of photogenerated electron-hole pairs.These issues lead to low solar-light utilization of TiO2 and reduce the photo-induced redox reaction.In order to enhance TiO2 activity in the visible light region,TiO2 is modified by transition metal additives,non-metals,rare earth metals,self-doping and sensitizers,combined with other semiconductors,etc.Recently,titanium dioxide self-doping can significantly improve its visible light catalytic ability in the reports.In addition,carbon nanotube(CNT)is one of the numerous studied materials with the benefit of large surface area,high conductivity,high chemical stability,high tensile strength,and the unique one-dimensional(1D)structure.This paper adopted a facile one-pot solvothermal reaction combined with thereafter in-situ solid-state chemical reduction approach.The aim is to prepare the black TiO2-x/CNT heterostructures,the black N,S-TiO2-x/CNT heterostructures and TiO2 photocatalyst.The as-prepared photocatalysts are characterized in detail via X-ray diffraction,Raman,Fourier transform infrared spectroscopy,scanning electron microscopy,transmission electron microscopy,X-ray photoelectron spectroscopy and UV-vis diffuse reflectance spectroscopy.The results demonstrate that the obtained black TiI2-x/CNT heterostructures and black N,S-TiO2-x/CNT heterostructures exhibit 3D urchin-like heterojunctions structure,and Ti3+ are doped into the lattice of anatase TiO2.Therefore,the TiO2-x/CNT heterostructures exhibit unparalleled high visible-light-driven photocatalytic activity and electrochemical property.The visible-light-driven photocatalytic degradation rate for methylene orange is up to 99.6%at 150 min,and the hydrogen production rate is as high as 242.9 μmol h-1 g-1.This result is ascribed to the 3D urchin-like structure offering abundant active sites,the heterostructures resulting in the separation of photogenerated charge carriers and the Ti3+ self-doping narrowing the bandgap and favoring visible light absorption.In addition,the N,S-TiO2-x/CNT exhibits excellent photocatalytic performance due to the presence of nitrogen and sulfur,the visible-light-driven photocatalytic degradation rate for methylene orange is up to 98.9%at 120 min,and the hydrogen production rate is as high as 260.9 μmol h-1g-1.