Transformation of 1D/2D High-Surface-Area Hierarchical Titanium Sulfate Structures to Stable, Morphology-Preserving Titania with Tailored Properties.

This report outlines a novel, facile process for the transformation of hierarchical enhanced surface area structures (HESAS) of titanium sulfate into titania. The transformation process preserves the HESAS morphology while providing tunable enhanced properties, based on the phase and degree of transformation. To demonstrate our process, a controlled thermo-chemical transformation strategy is implemented using four maximum temperatures (650, 750, 850, and 950 °C) in natural air or argon-rich environments, under various heating rates, and for two types of precursor HESAS. The resulting titania HESAS are characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and thin-film X-ray diffraction (XRD). Furthermore, both ab initio and semi-empirical quantum mechanics computational studies are conducted to provide insights into the diffusion mechanisms involved and the associated energetics. The transformed materials exhibit retention of the hierarchical features from the precursor HESAS. Furthermore, the degree of anatase or rutile formed is controlled based on the thermal kinetics of the process. Computational studies show that SO release is the main mechanism underlying the transformation, with the removal energy barrier increasing with the number of SO released. This work reveals a pathway for a scalable, low-cost manufacturing process for the design and fabrication of advanced titania-based photocatalytic materials with tailored properties.