Multilayered ordered mesoporous platinum/titania composite films: Does the photocatalytic activity benefit from the film thickness?

Abstract

Multilayered films of TiO2 with ordered cubic mesoporosity were grown via layer-by-layer deposition on a conductive FTO (F-doped SnO 2) substrate by dip-coating and subsequent calcination at 400°C. Since platinum nanoparticles are known to enhance the photocatalytic activity, they were introduced into the TiO2 mesopores by pulsed electrodeposition. Additionally, sandwich-like layers with up to five alternating TiO2 and Pt layers were prepared. The photocatalytic gas-phase oxidation of acetaldehyde served as a test reaction to characterize the activity in the gas phase of both pristine TiO2 as well as Pt/TiO2 single- and multilayer films. The ordered mesoporous pristine TiO2 and Pt/TiO2 nanocomposites exhibited significantly higher photoactivity than commercial Pilkington Activ™ glass and dense TiO2 films. Moreover for pristine TiO2 films, those consisting of three layers (about 650 nm in thickness), were shown to be sufficient to achieve a maximum photonic efficiency of ζ = 0.45%. For the Pt/TiO2 system, however, a single-layer film with a total thickness of only about 220 nm exhibited an almost identical activity. Moreover, repetitive experiments demonstrated that the newly prepared photocatalyst films did not suffer from a decrease in the photocatalytic activity, evincing their potential for practical applications. © 2011 The Royal Society of Chemistry.