Rice grain-shaped TiO2 mesostructures—synthesis, characterization and applications in dye-sensitized solar cells and photocatalysis

Abstract

We report the synthesis, characterization and applications in dye-sensitized solar cells and photocatalysis of novel “rice grain-shaped” TiO₂ mesostructures by electrospinning, which is a well-established and cost-effective technique for large-scale production of 1-D nanostructures. The porous and crystalline rice grain-like structures produced at 500 °C are uniformly distributed with a high surface area of ∼60 m² g⁻¹ and with mixed crystal structure. The origin of the unique morphology is traced to the microscale phase separation between TiO₂ and the polymer during solvent evaporation owing to the solubility difference between the two. The morphology is excellently reproducible over a wide range of concentrations of the precursors and spinning conditions. Evolution of the unique morphology from fiber structures is probed by scanning electron microscopy analyses of systematically heated electrospun fibers. The rice grain morphology is stable up to 600 °C and with further increase in temperature, the shape distorts with accompanying changes to the anatase–rutile proportion and complete dominance of the rutile phase at 1000 °C. A comparison of the photovoltaic and photocatalytic performance of the material with P-25 TiO₂ showed that the rice grain-shaped structures are superior to commercially available P-25. We anticipate that the material would have wide range of applications in other areas too such as photonic crystals, chemical sensors, self-cleaning materials, UV-blockers, etc.