H2-oxidation driven by its behavior of losing an electron over B-doped TiO2 under UV irradiation

Abstract

In this work, TiO₂ was modified by doping the electron-deficient B element, and then the gas-sensing response of B-TiO₂ to H₂ under UV irradiation at room temperature in a N₂ atmosphere and the oxidation of H₂ over B-TiO₂ under corresponding conditions were tested. It was found that H₂ would accept an electron when adsorbed on the TiO₂ surface, while H₂ would donate an electron when adsorbed on the B-TiO₂ surface. Correspondingly, H₂ could not be oxidized over TiO₂, but could be oxidized over B-TiO₂. This indicated that the oxidation of H₂ was dependent on the electron-transfer behavior between H₂ and the surface of TiO₂ or B-TiO₂. Based on the relevant characterization results, it was proposed that H₂ could accept an electron from TiO₂ due to the higher Fermi level of TiO₂, while H₂ could donate an electron to B-TiO₂ due to the lower Fermi level of B-TiO₂ induced by doping B. This indicated that the electron-transfer behavior between H₂ and TiO₂ could be changed by adjusting the Fermi level of TiO₂, while the electron-transfer behavior would further affect the photocatalytic activity of oxidizing H₂. This result shows that the doable H₂ photocatalytic oxidation in thermodynamics can be controlled by a kinetics factor (H₂ losing-an-electron behavior). This work can be applied to provide an understanding of the photocatalytic oxidation behavior of other reactants over semiconductor materials.