title: Photoelectrochemical oxidation of methanol on oxide nanosheets.
abstract: Photoelectrochemical oxidation of alcohol on various nanosheet electrodes such as Nb6O17, Ca2Nb3O10, Ti(0.91)O2, Ti4O9, and MnO2 system host layers were measured to evaluate the photocatalysis of water photolysis with alcohol as a sacrificial agent. The nanosheet electrodes were prepared by the layer-by-layer (LBL) method, using electrostatic principles. The highest photooxidation current density was observed in methanol solution for Nb6O17 and Ca2Nb3O10 nanosheets, while the density was lower for Ti(0.91)O2, Ti4O9, and MnO2 nanosheets in decreasing order. The rank in the photocurrent density was in agreement with that in the photocatalytic activity, which means that the degree of photooxidation of the alcohol determines the activity of the alcohol in the water photolysis process. The photocurrent was independent of the number of nanosheet layers on the electrode, indicating that only the mono-nanosheet layer attached directly on a substrate acts as a photoelectrocatalyst and that the interlayer space is not important. Consequently, higher photooxidation current on the Nb6O17 mono-nanosheet layer means that the charge separation of electron and hole under illumination is very large and that the hole-capturing process by CH3OH is very quick compared with the surface recombination on the Nb6O17 nanosheet. The adsorption of a transition metal cation on the nanosheet acted as the surface recombination center, because the photocurrent decreased after the adsorption. The photocatalytic mechanism has been discussed in detail in terms of various photoelectrochemical behaviors.
authors.affiliation: Department of Nano Science and Technology, Graduate School of Science and Technology, Kumamoto University, Kurokami 2-39-1, Kumamoto 860-8555, Japan. 049d8007@gsst.stud.kumamoto-u.ac.jp
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Izawa
authors.forename: Takashi
authors.initials: T
authors.lastname: Yamada
authors.forename: Ugur
authors.initials: U
authors.lastname: Unal
authors.forename: Shintaro
authors.initials: S
authors.lastname: Ida
authors.forename: Ozge
authors.initials: O
authors.lastname: Altuntasoglu
authors.forename: Michio
authors.initials: M
authors.lastname: Koinuma
authors.forename: Yasumichi
authors.initials: Y
authors.lastname: Matsumoto