Extending the Photoresponse of TiO₂ to the Visible Light Region:  Photoelectrochemical Behavior of TiO₂ Thin Films Prepared by the Radio Frequency Magnetron Sputtering Deposition Method

Abstract

TiO(2) thin films prepared by a radio frequency magnetron sputtering (RF-MS) deposition method were found to show an enhanced photoelectrochemical response in the visible light region. By controlling the temperature and the gaseous medium during the deposition step, it was possible to control the properties of these films. The photoelectrochemical behavior of the sputtered TiO(2) thin films was compared with that of a commercial TiO(2) sample, and the sputtered films showed higher incident photon to the charge carrier generation efficiency (IPCE of 12.6% at 350 nm) as well as power conversion efficiency (0.33% at 1.84 mW/cm(2)) than the commercial TiO(2) sample. Femtosecond transient absorption spectroscopy experiments have revealed that a major fraction of photogenerated electrons and holes recombine within a few picoseconds, thus limiting photocurrent generation efficiency. The mechanistic insights obtained in the present study should aid in designing semiconductor nanostructures that will maximize the charge separation efficiency and extend the response of the large band gap semiconductor TiO(2) into visible light regions.

Development of Well-Defined Visible Light-Responsive TiO2 Thin Film Photocatalysts by Applying a RF-Magnetron Sputtering Deposition Method

“…Figure 2 shows the UV-vis absorption (transmittance) spectra of the TiO 2 thin films prepared at different temperatures. The films prepared at low temperatures (T < 473 K) showed absorption edges at around 360 nm and clear interference fringes in visible light regions, similar to the TiO 2 thin films prepared by sol-gel (Heller 1995;Negishi et al 1995Negishi et al , 1998 or ionized cluster beam (ICB) deposition (Takeuchi et al 2000a, b;Yamashita et al 1998;Kikuchi et al 2006) (Chap. 2.1).…”

“…Moreover, this method was also effective in modifying transparent TiO 2 thin film photocatalysts to also absorb visible light. Studies in this novel metal ion-implantation method have provided valuable information on modifying the electronic properties of both TiO 2 powder and thin film photocatalysts (Anpo 1997(Anpo , 2000aAnpo et al 1998;Takeuchi et al 2000a;Yamashita et al 1998;Kikuchi et al 2006). However, since the complexity in the preparation processes impedes their mass production at low cost, less cumbersome preparation methods are strongly desired for widespread, global applications.…”

Synthesis of Nanowire TiO2 Thin Films by Hydrothermal Treatment and their Photoelectrochemical Properties

“…The photogenerated electrons can be readily collected at the conducting surface in a photoelectrochemical cell [23,27]. Photoelectrochemical measurements were performed using a standard three-electrode system consisting of a working electrode (TiO 2 /Ti, nw-TiO 2 (X)/Ti), Pt wire counter electrode and SCE reference electrode in an Ar-purged 0.25 M K 2 SO 4 aqueous solution.…”

“…The area of the working electrode exposed to light was about 0.2 cm 2 . The incident photon to current conversion efficiency (IPCE), defined as the number of electrons collected per incident photon, was determined by measuring the photocurrent (I ph ) of the electrodes at each excitation wavelength and by using the following equation [23,24]:…”

Photocatalytic Hydrogen Production from Water on Visible Light-Responsive TiO2 Thin Films Under Solar Light Irradiation

“…Figure 6 shows that the HF-Vis-TiO 2 /Ti electrode exhibits a much higher photocurrent than Vis-TiO 2 /Ti under both UV and visible light. Moreover, the apparent quantum efficiencies, that is, the incident photonto-current conversion efficiency (IPCE), of these electrodes are defined as the number of electrons collected per incident photon and determined by measuring the photocurrent (I ph ) of the electrodes at each excitation wavelength using the following equation (Kikuchi et al 2006):…”