Photoelectrochemical characterisation of TiO2 thin films derived from microwave hydrothermally processed nanocrystalline colloids

Titanium dioxide (TiO2) thin films fabricated with different TiO2 colloids were characterised using photoelectrochemical techniques. TiO2 colloids were firstly prepared via hydrolysis of titanium butoxide and peptisation process with no hydrothermal process (labelled as NP). The resulting colloids were then subjected to different hydrothermal processes, i.e., 15-h convection hydrothermal (labelled as CH) treatment; 5-, 10- and 15-min microwave hydrothermal treatment (labelled as M5, M10 and M15, respectively). The colloids were used to prepare TiO2 thin films on conducting indium-doped tin oxide (ITO) substrates (i.e., CH, M15, M10, M5 and NP electrodes, respectively) using a controlled dip-coating technique. The experimental results demonstrate that the oxidation capacities of the electrodes for water and glucose are in the order of CH > M15 > M10 > M5 > NP. In contrast, the oxidation capacities of the electrodes for potassium hydrogen phthalate (KHP) are in the order of M15 > M10 > CH. It was also found that the CH electrode could be easily poisoned by high concentration of KHP, while microwave-processed electrodes (M15, M10 and M5) are immune from the KHP poisoning. The results presented demonstrate that microwave hydrothermal processing is a promising alternative method to the traditional convection hydrothermal treatment of colloids that provides electrodes with increased photocatalytic properties for the oxidation processes of adsorption-based organic compounds, such as KHP.