Koyu Aoki
Toyota
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Publication
Featured researches published by Koyu Aoki.
Japanese Journal of Applied Physics | 2001
Takeshi Morikawa; Ryoji Asahi; Takeshi Ohwaki; Koyu Aoki; Yasunori Taga
TiO2-based powder, including 0.1 at% of N doped in the rutile lattice, has been synthesized by oxidation of TiN. As a result, a significant shift of the absorption edge to a lower energy in the visible-light region has been observed. The substitutional doping of N into the TiO2 lattice is found to be effective; its 2p states contribute to the band-gap narrowing by mixing with O 2p as shown in ab initio electronic structure calculations.
Physical Chemistry Chemical Physics | 2006
Y. Irokawa; Takeshi Morikawa; Koyu Aoki; Satoru Kosaka; Takeshi Ohwaki; Yasunori Taga
We report the photooxidation of toluene over nitrogen doped TiO(2) (TiO(2-x)N(x)) under visible light irradiation. The photocatalytic oxidation of toluene in air over TiO(2-x)N(x) powders was studied using diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS), gas chromatography (GC), ion chromatography (IC), and gas chromatography mass spectrometry (GC-MS), focusing on the photocatalytic decomposition processes of toluene. Results obtained indicate that toluene, weakly adsorbed on the catalyst surface, is initially photooxidized to benzaldehyde which adsorbs onto the TiO(2-x)N(x) surface more strongly, leading to the formation of ring-opening products such as carboxylic acids and aldehydes. No gaseous intermediates were detected during the photooxidation. Major intermediates adsorbed at the catalyst surface were oxalic acid, (COOH)(2), acetic acid, CH(3)COOH, formic acid, HCOOH, and pyruvic acid, CH(3)COCOOH, whereas more complicated carboxylic species, including propionic acid, CH(3)CH(2)COOH, isovaleric acid, (CH(3))(2)CHCH(2)COOH, and succinic acid, (CH(2)COOH)(2), were also found in the early stage of the photooxidation. These intermediate products were gradually photodegraded to CO(2) and H(2)O under visible light irradiation.
Japanese Journal of Applied Physics | 2016
Takeshi Ohwaki; Shu Saeki; Koyu Aoki; Takeshi Morikawa
Photocatalytic activities, as manifested in gas decomposition rates of volatile organic compounds under visible light irradiation, are well known to be enhanced by Cu or Fe compounds loaded onto the surface of nitrogen-doped titanium dioxide (N-TiO2). Antimicrobial properties are also known to be improved by Cu compounds loaded onto N-TiO2. In this study, the acetaldehyde gas decomposition rates and antimicrobial properties achieved by loading Cu or Fe compounds onto N-TiO2 have been investigated from a practical viewpoint. Enhancements of the photocatalytic activities have been confirmed, and the durability of the Cu- or Fe-modified N-TiO2 in acetaldehyde gas decomposition has been demonstrated. The enhancements have been rationalized by considering the valence states of the loaded material. The enhancements were inferred to be a result of increased amounts of oxidative species arising from the photo-Fenton reaction at the surface of the loaded metal compounds. With a view to expanding the range of indoor applications of such visible-light-sensitive photocatalysts, preparation processes, i.e., nanosizing of the powder and improvement of the immobilization on various substrates, are also discussed.
Science | 2001
Ryoji Asahi; Takeshi Morikawa; Takeshi Ohwaki; Koyu Aoki; Yasunori K.K. Toyota Chuo Kenkyusho Taga
Physical Chemistry Chemical Physics | 2006
Y. Irokawa; Takeshi Morikawa; Koyu Aoki; Satoru Kosaka; Takeshi Ohwaki; Yasunori Taga
Archive | 2004
Shin Yamaguchi; Toshihiro Sekiguchi; Keisuke Ikushima; Shoji Akahane; Koyu Aoki; Takeshi Morikawa; Takeshi Ohwaki; Yasunori Taga
Applied Catalysis B-environmental | 2009
Masaki Yoshinaga; Katsutoshi Yamamoto; Nobuaki Sato; Koyu Aoki; Takeshi Morikawa; Atsushi Muramatsu
Chemistry Letters | 2006
Koyu Aoki; Takeshi Morikawa; Takeshi Ohwaki; Yasunori Taga
Thermochimica Acta | 2004
Jhon Cuya; Nobuaki Sato; Katsutoshi Yamamoto; Atsushi Muramatsu; Koyu Aoki; Yasunori Taga
Archive | 2006
Shin Yamaguchi; Toshihiro Sekiguchi; Keisuke Ikushima; Shoji Akahane; Koyu Aoki; Takeshi Morikawa; Takeshi Ohwaki; Yasunori Taga