Laser-induced photocatalytic conversion of methane into methanol

The main aim of this dissertation work is the study of the photocatalytic process induced by laser light, for converting methane to methanol and for splitting water to hydrogen and oxygen. The catalysts, WO3, TiO2, NiO and alpha-Fe2O3 were investigated; TiO2, NiO and alpha-Fe2O3 were studied in pure form after pre-treatment whereas WO3 was studied in its pure as well as the surface modified forms.; The bandgaps of the synthesized photocatalysts were determined by UV-Visible absorption spectroscopy. Scanning electron microscopy (SEM) and electron x-ray dispersive spectroscopy (EDS) was used to study the morphology and composition of synthesized powders. The oxidation states of the doped metals at the surface of host WO3 were evaluated by x-ray photoelectron spectroscopy (XPS).; A 355 nm UV laser was employed as light source. The progress of the photocatalytic process was monitored by analyzing the yield in gas as well as liquid phase. The photonic efficiencies of all the processes were calculated to estimate photon harvesting. In addition, the effect of the dissolved metal ions on yield was investigated.; The influence of transition metals, as dopants, on the activity of WO 3 was evaluated by comparing the product yield and photonic efficiency of doped WO3 powders with that of pure WO3. The variations of pH during the course of reaction were found very useful in explaining the mechanism of photocatalytic processes.; The photonic efficiencies observed for both hydrogen and oxygen production during the photocatalytic splitting of water using laser as light source were found to be much higher than those obtained from conventional light sources. The study indicates a correlation between the photocatalytic splitting of water and conversion of methane in aqueous medium.