Synthesis of TiO2 hollow particles with highly dispersed CaCO3 template particulates and their photoactivity toward a VOC pollutant

Abstract

This brief article reports a suitable preparation of TiO2 hollow particles using titanium tetra-isopropoxide (TTIP) as a precursor and highly dispersed calcium carbonate (CaCO3) particle templates prepared from CaCl2 and dimethylcarbonate in the presence of the dispersing agent polyvinylpyrrolidone. The synthesis of TiO2 hollow particles was optimized considering certain experimental conditions: (a) the amount of TTIP, (b) the hydrolysis rate of TTIP in water/ethanol solvent, and (c) the mass of CaCO3 template particulates. The morphology and particle sizes of the resulting hollow particles (CaCO3 templates removed on addition of acid) were assessed by scanning electron microscopy (SEM and SEM-EDX); their crystalline phase (anatase) was determined by X-ray diffraction techniques and the specific surface area by the BET method. A formation mechanism of the TiO2 particles is described in terms of the TiO2 particulates generated under each experimental condition. The photoactivity of the TiO2 hollow particles was subsequently examined through the transformation of a volatile organic pollutant (iso-propanol) in air whose faster rate of photodegradation relative to TiO2 particles (synthesized without CaCO3) correlates with the greater specific surface area of these hollow particles (19.0 vs. 65.1 m2 g−1).