Semi-transparent nanofilms of plasmonic Au/TiO2 for visible-light photocatalysis

Conventionally supported nanoparticle (NP) of plasmonic Au/TiO2 performs well under visible light, however the problem with cost, activity and durability inevitably remains. Here we demonstrate a semi-transparent nanofilm of plasmonic Au/TiO2 by deposition-precipitation and atmospheric chemical vapor deposition methods. Onto a synthetic TiO2 nanofilm (bottom layer), Au NP is allocated (top layer) for direct exposure to light with enhanced utilization efficiency (low cost). Compared to the conventional coating film from NPs, its growth nanofilm formed from molecular assembly is considered more durable. Effects of localized surface plasmon resonance (LSPR) and Fabry-Pérot (F–P) interference are evidenced by UV–vis absorption spectra. To identify and further utilize separation efficiency of charge carriers, photoluminescence spectra and visible-light photocurrent experiment in a three-electrode electrochemical cell were conducted. Using formaldehyde oxidation as reaction model, visible-light photocatalysis over plasmonic Au/TiO2 nanofilm is conceptually verified. The presence and size of Au NP promotes light absorption, separation of charge carriers and photocurrent. Au/TiO2 exhibits up to 10 times photocurrent at applied potential compared to TiO2. Inspiringly, over Au/TiO2 nanofilm, apparent rate constant, kapp (ca. 0.49 s−1) is unprecedentedly achieved ca. 3-4 orders of magnitude larger than TiO2-based thin films reported in literatures. Our growth nanofilm of Au/TiO2, achieves reaction rate of 5.0 × 10−7 mol s−1·gcat−1 under green LED that is even higher than the conventional supported NP, which is of significance to be considered more durable with the improved interface. Consequently, our semi-transparent nanofilm of plasmonic Au/TiO2 addresses cost, activity and durability for visible-light photocatalysis, for which it may pave a way to large-scale application from a practical perspective.