Theoretical Verification of Photoelectrochemical Water Oxidation Using Nanocrystalline TiO2 Electrodes

Molecules

Shozo Yanagida²  Susumu Yanagisawa⁴  Koichi Yamashita¹  Ryota Jono¹  Hiroshi Segawa³ 

[1] Department of Chemical System Engineering, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan; E-Mails:;Frontier Research Institute, Osaka University, 2-1, Yamada-oka, Suita, Osaka 565-0871, Japan;Research Center for Advance Science and Technology, The university of Tokyo, 4-6-1, Komaba, Meguro-ku, Tokyo 153-8904, Japan; E-Mail:;Department of Physics and Earth Sciences, Faculty of Science, University of the Ryukyus, 1, Senbaru, Nishihara, Okinawa 903-0213, Japan; E-Mail:

关键词: DFT;    HOMO;    LUMO;    spin density;    conductivity;    TiO₂ photocatalysis;    DSC;    Honda/Fujishima effect;   

DOI  :  10.3390/molecules20069732

来源: mdpi

【 摘 要 】

Mesoscopic anatase nanocrystalline TiO₂ (nc-TiO₂) electrodes play effective and efficient catalytic roles in photoelectrochemical (PEC) H₂O oxidation under short circuit energy gap excitation conditions. Interfacial molecular orbital structures of (H₂O)₃ &OH(TiO₂)₉H as a stationary model under neutral conditions and the radical-cation model of [(H₂O)₃&OH(TiO₂)₉H]⁺ as a working nc-TiO₂ model are simulated employing a cluster model OH(TiO₂)₉H (Yamashita/Jono’s model) and a H₂O cluster model of (H₂O)₃ to examine excellent H₂O oxidation on nc-TiO₂ electrodes in PEC cells. The stationary model, (H₂O)₃&OH(TiO₂)₉H reveals that the model surface provides catalytic H₂O binding sites through hydrogen bonding, van der Waals and Coulombic interactions. The working model, [(H₂O)₃&OH(TiO₂)₉H]⁺ discloses to have a very narrow energy gap (0.3 eV) between HOMO and LUMO potentials, proving that PEC nc-TiO₂ electrodes become conductive at photo-irradiated working conditions. DFT-simulation of stepwise oxidation of a hydroxide ion cluster model of OH⁻(H₂O)₃, proves that successive two-electron oxidation leads to hydroxyl radical clusters, which should give hydrogen peroxide as a precursor of oxygen molecules. Under working bias conditions of PEC cells, nc-TiO₂ electrodes are now verified to become conductive by energy gap photo-excitation and the electrode surface provides powerful oxidizing sites for successive H₂O oxidation to oxygen via hydrogen peroxide.

【 授权许可】

CC BY   
© 2015 by the authors; licensee MDPI, Basel, Switzerland.