Catalytic oxidation of carbon using TiO₂ based nanoparticles prepared using flame synthesis

Titanium dioxide (TiO₂) nanoparticles are used in numerous applications involving catalysis, photo-catalysis, water purification, electrode for Li-ion batteries, polymer fillers, and pigments. Multiple-diffusion flames are used to coat/dope the TiO₂ nanoparticles with various elements such as carbon, vanadium, silicon, and iron. The use of multiple diffusion flames offers several key advantages, such as uniform temperature and chemical species profiles and many of the limitations related to premixed flames such as flashback and flame speed are avoided. Crystal phase and size of the TiO₂ nanoparticles are determined using x-ray diffraction (XRD). The nanoparticles are further characterized using Raman spectroscopy, thermal gravimetric analysis (TGA), and Brunauer-Emmett-Teller (BET). The morphology and crystal structure of the samples are characterized using high-resolution transmission electron microscopy (HRTEM), with elemental mapping. With silicon precursors, the TiO₂ nanoparticles are coated in a layer of silica, while for vanadium, the nanoparticles are doped with vanadium oxide. An iron based precursor results in the formation of iron-oxide alongside the TiO₂ nanoparticles. Finally the iron based TiO₂ nanoparticles significantly improve the catalytic oxidation of carbon, where complete oxidation of carbon occurs at a temperature of 470°C (with iron) compared to 610°C (without iron).