The role of fuel to oxidizer ratio in solution combustion synthesis of TiO2 and its influence on photocatalysis

Recently, solution combustion synthetic approach has emerged as a potential route to synthesize a wide range of catalytic oxides. Nano TiO2 was synthesized by solution combustion methods using glycine, urea, and oxalyldihydrazide as fuels. X-ray diffraction and field emission scanning electron microscopy analyses revealed the structural and morphological differences of TiO2 synthesized with different fuels. The oxidizer to fuel ratio from lean to rich conditions also played a crucial role in determining the polymorphic percentage concentration in the synthesized TiO2 powders. However, diffuse reflectance spectroscopy and photoluminescence spectroscopy studies did not show any significant differences in the electronic properties of the synthesized TiO2. As the polymorphic composite phases synergistically influence the catalytic performances, photodegradation of methylene blue (MB) and photo hydrogen production were studied with the synthesized catalysts. The synergistic role crucially depended on the specific reaction. The presence of different TiO2 polymorphs due to difference in fuels during combustion controlled the photocatalytic efficiency of the catalysts toward MB degradation and hydrogen production.