Surface heterojunction between (001) and (101) facets of ultrafine anatase TiO2 nanocrystals for highly efficient photoreduction CO2 to CH4

Abstract

Shape-dependent ultrafine anatase TiO2 nanocrystals coexposed with (001) and (101) facets are synthesized in isopropanol by the simple solvothermal strategy. Nanotube titanic acid (NTA) was used as the Ti precursor, and hydrofluoric acid was the shape-control reagent. The nanotubular structure of NTA facilitated HF to adsorb on/into NTA, and made the shape-controlled process to be more economical and easier. The ratio of (001) facets of the obtained decahedral TiO2 nanocrystals can be adjusted from 5 to 51%, and the mean diameter of nanoparticles is about 10–30nm. The samples are characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscope, ultraviolet-visible diffuse reflectance spectrum, N2 adsorption-desorption isotherms, fluorescence and Raman spectroscopy. The truncated octahedral bipyramid TiO2 nanocrystals with 51% (001) and 49% (101) facets exposing showed the highest photoactivity for CO2 reduction to CH4. This remarkable photocatalytic efficiency is attributed to the surface heterojunction between (001) and (101) crystal facets, the small size and large surface area of the truncated octahedral bipyramid TiO2 nanocrystals.