Photocatalytic degradation of methylene blue by flowerlike rutile-phase TiO2 film grown via hydrothermal method

This paper presents the effects of operating parameters on the photocatalytic degradation of methylene blue using flowerlike rutile-phase TiO2 films synthesised by a hydrothermal method. The findings show that numerous parameters such as the catalyst morphology, the presence of oxygen vacancy/Ti3+ surface defects, initial pH of methylene blue solution, active species, and initial concentration of methylene blue influence the photocatalytic degradation of the dye. Based on the results obtained, the presence of oxygen vacancy/Ti3+ surface defects act as an electron trap that helps generate more electrons and holes, which contributes to the enhancement of the photocatalytic activity of the TiO2 film. This study reveals that the optimum concentration of Ti precursor was obtained at 0.10 M, which produced a flowerlike morphology with pristine rutile-phase that reached 42% methylene blue dye degradation. The effectiveness of the optimised film was boosted by 18% degradation by adjusting the initial pH of the methylene blue solution to 12. Under such conditions, the enhancement of the electrostatic attraction between the negatively charged TiO2 and the methylene blue molecules improved the degradation. No severe deactivation of the catalyst was found even after five photocatalysis reaction cycles. This study also demonstrates that there are multiple parameters involved in optimising the photocatalytic activity of TiO2.