Photocatalytic Decomposition of Water on Double-Layered Visible Light-Responsive TiO2 Thin Films Prepared by a Magnetron Sputtering Deposition Method

Abstract

A radio-frequency magnetron sputtering (RF-MS) deposition method was applied to prepare a unique double-layered visible light-responsive TiO 2 thin film photocatalyst on a Ti foil substrate (DL-TiO 2 /Ti). The DL-TiO 2 /Ti consists of a UV light-responsive TiO 2 thin film (UV-TiO 2 ) deposited as the inner block layer on a Ti foil substrate and a visible light-responsive TiO 2 thin film (Vis-TiO 2 ) deposited as the outer layer. DL-TiO 2 /Ti exhibited higher photoelectrochemical and photocatalytic performance under both UV and visible light irradiation than a single-layered Vis-TiO 2 thin film photocatalyst deposited on a Ti foil substrate. The optimal thickness of the UV-TiO 2 film as the inner block layer of DL-TiO 2 /Ti was found be 100 nm in terms of the photoelectrochemical and photocatalytic performance. Expanding on this work, a novel double-layered TiO 2 thin film device, DL-TiO 2 /Ti/ Pt, was also prepared by the RF-MS method where DL-TiO 2 was deposited on one side of a Ti foil substrate and Pt was deposited on the other side. The separate evolution of H 2 and O 2 from H 2 O was successfully achieved by using an H-type glass cell consisting of two aqueous phases separated by the DL-TiO 2 /Ti/Pt and a protonexchange membrane. The separate evolution rate of H 2 and O 2 was found to be dramatically enhanced on DL-TiO 2 /Ti/ Pt as compared with a single-layered Vis-TiO 2 thin film device under white light irradiation from a solar simulator.Keywords Photocatalytic water splitting Á TiO 2 photocatalyst Á Separate evolution of H 2 and O 2 Á Visible light Á Double-layered thin film

Production of electricity and hydrogen by photocatalytic degradation of organic wastes in a photoelectrochemical cell

“…Water splitting in a PEC cell leads to hydrogen production, since the oxidation site, i.e. the photoanode, is spatially separated from the reduction site (cathode), thus O 2 and H 2 can be easily separated [11,12,15].…”

“…With titania on the photoanode electrode, the most frequently used electrolyte is NaOH or KOH [12,15,17,60,71,155,177,184,187]. The reason is to obtain high pH.…”

“…This is particularly important when an organic sacrificial agent is added, which is expected to be photodegraded during PEC cell operation [17,71,187]. When the cell is structured in two compartments, a basic electrolyte is frequently introduced in the anode compartment and an acidic electrolyte (H 2 SO 4 ) in the cathode compartment thus offering chemical bias to the cell [15,60,136,184,201], according to Eq. (1).…”

“…The most celebrated scientific publication that affected the development of the field was the work by Fujishima and Honda [1] in 1972, describing photocatalytic water splitting in a PEC cell using a semiconductor (rutile single crystal) electrode. This work has been the point of reference for many later research efforts [2][3][4][5][6][7][8][9][10], including the recent ones [11][12][13][14][15][16][17]. Since then, a huge amount of research has been published.…”

Enhanced Visible-light Response and Conductivity of the TiO2/reduced graphene oxide/Sb2S3 Heterojunction for Photoelectrochemical Water Oxidation

“…Recently, the heterojunction between TiO 2 and the semiconductors with a narrow band gap has been proposed as the highly active photocatalysts for water oxidation with responses to the visible light [9,11,12]. Naik et al used a soft chemical homogeneous co-precipitation route to fabricate the Bi 2 O 3 / TiO 2Àx N x nanocomposite, which presented high photocatalytic activity under the visible light illumination [9].…”