TiO_xN_y/TiO₂ Photocatalyst for Hydrogen Evolution under Visible Light Irradiation II Degradation of Photocatalytic Activity of TiO_xN_y/TiO₂ with Mild Oxidation

Abstract

We have studied degradation of photocatalytic activity of TiOxNy for water splitting under visible light irradiation with heat treatment in O2/N2 mixed gas. The reduction of the N content by oxidation through the formation of O–N–O species (NOx) was confirmed as the result of the reduction of the catalytic activity. The catalytic activity is not simply related to the amount of N remained but that of N taking the chemical state of O–Ti–N in TiOxNy, which is the active species for visible light responsiveness on hydrogen evolution. N in TiOxNy is first oxidized to NO2 species during the oxidation, which reduces the activity. Then, O–N–O species (NOx) is removed as NOx gas from the surface. Because the formation of O–N–O in TiOxNy could induce an impurity energy level to enhance charge recombination, the loss of catalytic activity might be influenced by the formation of O–N–O species (NOx) rather than the loss of the N content from TiOxNy.

Novel axial substituted subphthalocyanine sensitized titanium dioxide H12SubPcB‐OPh2OH/TiO2 photocatalyst: Synthesis, density functional theory calculation, and photocatalytic properties

“…[3] Some semiconductor materials such as TiO 2 , SnO 2 , CuO, ZnO, WO 3 , ZrO 2 , and g-C 3 N 4 have been studied by researchers to degrade organic contaminants. [9][10][11][12][13][14][15][16][17][18][19][20] Among them, TiO 2 is a potential candidate due to its advantages of chemical stability, low cost, high reaction rate, no secondary pollution, nontoxicity, strong oxidation ability, and so forth. [21][22][23][24] However, the photocatalytic technology based on titanium dioxide semiconductor also has problems such as low quantum decomposition, low light utilization, and difficulty in recycling.…”