Photoelectrocatalytic activity of mesoporous TiO2 films prepared using the sol-gel method with tri-block copolymer as structure directing agent

Mesoporous TiO2 films were synthesized using a sol-gel process with a tri-block copolymer (Pluronic F127) as a structure directing agent. The films were dip-coated onto conductive glass substrates followed by thermal treatment to remove the polymeric surfactant. The specific surface area, the pore size and morphology, and the crystallinity of the films were characterized. The analysis showed the structural properties of the films could be tailored by varying the surfactant concentration as well as the annealing temperature. The photocurrent responses of the prepared films were measured using a three-electrode photoelectrochemical cell in the presence of oxalic acid. When annealed at 450 degrees C, the dense electrode (control sample) had the strongest photoelectrocatalytic oxidation aptitude toward oxalic acid. The lower photocurrent response of the mesoporous electrodes compared to the dense electrode can be explained by poor inter-particle connectivity within the mesoporous TiO2 network, leading to high electron transport resistance. The mesoporous electrode annealed at 550 C, with improved connectivity, outperformed the dense electrode at a high oxalic concentration, as the lower surface area of the dense electrode restricted photoelectrocatalysis reactions on the surface. A further increase in annealing temperature to 650 degrees C resulted in a poor photocurrent response as the significant decrease in surface area outweighed the beneficial effect of improved connectivity.