Annealing-free preparation of anatase TiO2 nanopopcorns on Ti foil via a hydrothermal process and their photocatalytic and photovoltaic applications

Uniform and well-defined nanopopcorns of the tetragonal anatase TiO2 having an average diameter of 670 nm have been facilely grown on Ti foil via a hydrothermal method and characterized by analyzing electron microscopic images and electron diffraction patterns as well as X-ray photoelectron, photoluminescence, and Raman spectra. The morphology of TiO2 nanostructures on Ti foil has been controlled well by adjusting the volume ratio of H2O2 : HF : H2O, VR(H2O2 : HF : H2O). Truncated tetragonal pyramidal TiO2 nanocrystals exposing the {001} and {101} facets have grown on the surface of TiO2 nanostructures exposing the {001} facets to produce anatase TiO2 nanopopcorns. Without being treated via any annealing process, our well-defined TiO2 nanopopcorns on Ti foil have been directly employed for photocatalytic materials and dye-sensitized solar cells. Among our prepared samples, anatase TiO2 nanopopcorns grown on Ti foil at a VR(H2O2 : HF : H2O) of 1 : 1 : 1000 have shown the most reduced oxygen vacancy luminescence, the highest photocatalytic activity for the degradation of methylene blue, and the highest photovoltaic conversion efficiency of 3.98% as the working electrode of a dye-sensitized solar cell.