10.1021/jp064893e.s001 Masaaki Kitano Masaaki Kitano Keisho Funatsu Keisho Funatsu Masaya Matsuoka Masaya Matsuoka Michio Ueshima Michio Ueshima Masakazu Anpo Masakazu Anpo Preparation of Nitrogen-Substituted TiO<sub>2</sub> Thin Film Photocatalysts by the Radio Frequency Magnetron Sputtering Deposition Method and Their Photocatalytic Reactivity under Visible Light Irradiation<sup>†</sup> American Chemical Society 2006 TiO 2 lattice radio frequency magnetron XPS light irradiation lattice O atoms 550 nm XRD UV scanning electron microscopy SEM concentration Radio Frequency Magnetron Sputtering Deposition Method film photocatalysts TiO 2 2006-12-21 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Preparation_of_Nitrogen_Substituted_TiO_sub_2_sub_Thin_Film_Photocatalysts_by_the_Radio_Frequency_Magnetron_Sputtering_Deposition_Method_and_Their_Photocatalytic_Reactivity_under_Visible_Light_Irradiation_sup_sup_/3040045 Nitrogen-substituted TiO<sub>2</sub> (N−TiO<sub>2</sub>) thin film photocatalysts have been prepared by a radio frequency magnetron sputtering (RF-MS) deposition method using a N<sub>2</sub>/Ar mixture sputtering gas. The effect of the concentration of substituted nitrogen on the characteristics of the N−TiO<sub>2</sub> thin films was investigated by UV−vis absorption spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and scanning electron microscopy (SEM) analyses. The absorption band of the N−TiO<sub>2</sub> thin film was found to shift smoothly to visible light regions up to 550 nm, its extent depending on the concentration of nitrogen substituted within the TiO<sub>2</sub> lattice in a range of 2.0−16.5%. The N−TiO<sub>2</sub> thin film photocatalyst with a nitrogen concentration of 6.0% exhibited the highest reactivity for the photocatalytic oxidation of 2-propanol diluted in water even under visible (λ ≥ 450 nm) or solar light irradiation. Moreover, N−TiO<sub>2</sub> thin film photocatalysts prepared on conducting glass electrodes showed anodic photocurrents attributed to the photooxidation of water under visible light, its extent depending on wavelengths up to 550 nm. The absorbed photon to current conversion efficiencies reached 25.2% and 22.4% under UV (λ = 360 nm) and visible light (λ = 420 nm), respectively. UV−vis and photoelectrochemical investigations also confirmed that these thin films remain thermodynamically and mechanically stable even under heat treatment at 673 K. In addition, XPS and XRD studies revealed that a significantly high substitution of the lattice O atoms of the TiO<sub>2</sub> with the N atoms plays a crucial role in the band gap narrowing of the TiO<sub>2</sub> thin films, enabling them to absorb and operate under visible light irradiation as a highly reactive, effective photocatalyst.