Nanocoral architecture of TiO2 by hydrothermal process: Synthesis and characterization

[Display omitted] ► We synthesized novel TiO2 nanocorals by hydrothermal route at 120°C. ► The diameter of the circular corals is about 400–500nm, on top of which nanopolyps are nucleated and their average size is about 20nm. ► Such peculiar morphological feature is beneficial as it provides larger active surface area. ► Approximately 1.8μm thick nanocoral TiO2 films were achieved using MSH process exhibiting substantial increment in short circuit current density (Jsc=154μA). TiO2 thin films with novel nanocoral-like morphology were successfully grown directly onto the glass and conducting fluorine doped tin oxide coated glass substrates via multi-step hydrothermal (MSH) process. Titanium chloroalkoxide [TiCl2 (OEt)2 (HOEt)2)] precursor was used in an aqueous saturated NaCl in presence of 1mM HCl catalyst and HNO3 peptizer at 120°C. Reaction time varied from 3 to 12h. The morphological features and physical properties of TiO2 films were investigated by field emission scanning electron microscopy, high resolution transmission electron microscopy, X-ray diffraction, Fourier transform IR spectroscopy, Fourier transform Raman spectroscopy, room temperature photoluminescence spectroscopy and X-ray photoelectron spectroscopy. The surface morphology revealed the formation of TiO2 corals having nanosized (30–40nm) polyps. The photoelectrochemical properties of the TiO2 nanocoral electrodes were investigated in 0.1M NaOH electrolyte under UV illumination. The results presented in this study highlight two major findings: (i) ability to tune the photoelectrochemical response and photoconversion efficiency via controlled thickness of TiO2 nanocorals and (ii) the substantial increase in short circuit photocurrent (Jsc) due to the improved charge transport through TiO2 nanocorals prepared via MSH process. This approach would be quite useful for the fabrication of nanocoral architecture that finds key applications in photocatalysis, dye-sensitized solar cells and hybrid solar cells.