Study of the process of black TiO2 turning white and its molecular adsorption and photocatalytic behavior

Abstract

Black titanium dioxide (TiO₂) with anatase structure was prepared in this paper. Surface oxygen molecule (O₂) adsorption and photocatalytic behavior during the conversion of black titanium dioxide to white were investigated using density functional theory (DFT) and electrochemical impedance spectroscopy (EIS) techniques. Theoretical simulations show that two O₂ molecules are chemically adsorbed on the black TiO₂ surface and one O₂ molecule is physically adsorbed after the transformation into white, which suggests that the defective state of the black TiO₂ is beneficial to the loading of O₂, a result that is confirmed by the EIS experimental data. Theoretical calculations show that the poor hydrophilicity of black TiO₂ at room temperature meant that rhodamine B (RhB) in water could not be transported closer to the crystal surface for redox reaction with adsorbed oxygen, and the photocatalytic degradation performance was reduced compared with that of white TiO₂. However, based on the advantages of high oxygen adsorption of black TiO₂ and high degradation of white TiO₂, the synergistic effect of the two will greatly enhance the photocatalytic efficiency. The experiments of photocatalytic degradation of RhB confirmed this result. Studying the adsorption behavior of gas molecules on the crystal plane is an important insight for the construction of more efficient photocatalytic degradation interfaces and optimization of the performance of gas sensors.