3D urchin-like black TiO2−x/carbon nanotube heterostructures as efficient visible-light-driven photocatalysts

Abstract

3D urchin-like black TiO_2−x/CNT heterostructures are successfully fabricated via a facile one-pot solvothermal reaction combined with a subsequent in situ solid-state chemical reduction approach. The as-prepared photocatalysts are characterized in detail via X-ray diffraction, Raman spectroscopy, 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 TiO_2−x/CNT heterostructures exhibit a 3D urchin-like heterojunction structure, and Ti³⁺ is doped into the lattice of anatase TiO₂. This unique 3D structure with abundant active sites can enhance light scattering capability, and the Ti³⁺ self-doping defective TiO₂ with a narrow bandgap can promote visible-light photocatalytic activity. Therefore, the TiO_2−x/CNT heterostructures exhibit unparalleled high visible-light-driven photocatalytic activity and electrochemical properties. The visible-light-driven photocatalytic degradation rate for methylene orange is up to 99.6% and the hydrogen production rate is as high as 242.9 μmol h⁻¹ g⁻¹, which 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.