Effect of interfacial oxide thickness on the photocatalytic activity of magnetron-sputtered TiO2coatings on aluminum substrate

Abstract

The influence of the coating/substrate interface on the photocatalytic behavior of Al-TiO2 coatings was investigated. The TiO2 coatings were prepared by magnetron sputtering. The nanoscale structure of the coating was analyzed using X-ray diffraction; atomic force microscopy; scanning electron microscopy; andtransmission electronmicroscopy. Thephotocatalytic behavior was investigated through optical spectrophotometry studies and electrochemical experiments; as photo voltage; photocurrent; and electrochemical impedance measurements. Consistent results from both optical and electrochemical measurements showed a maximum UV-light absorption by titanium dioxide occurring slightly prior to the energy of the maximum photocurrent. The photocurrent of titanium dioxide decreases with increasing thickness of the aluminum oxide interface layer. Aluminumoxide acts as an insulator; disfavoring the electron transport between the coating and the metallic substrate. The highest photocurrents were indeed obtained when the thickness of interfacial aluminum oxide could be reduced by sputtering a thin Ti layer prior to TiO2 coating. [GRAPHICS] Photocurrent plotted for different photon energy for a TiO2 coating on a Ti interlayer consisting of both rutile and anatase. Two photon-excitation peaks from the TiO2 coating (anatase and rutile) are observed at a potential of 0.34V versus SHE, while only one peak was observed at a potential 0.14V versus SHE closer to the conduction band. (C) 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim