(27f) Understanding the Effect of Surface Deposited Pt On the Photoactivity of TiO2

It is well know that Pt can be utilized to enhance the photoactivity of TiO₂. We have produced Pt coated TiO2 via Atomic Layer Deposition (ALD) and tested its ability to degrade methylblue. At low Pt loadings Pt increases the photodegredation rate by three times at a 1% Pt loading, but the photoactivity decreases at higher Pt loadings. We have additionally used density functional theory to develop an understanding of the processes that cause the initial increase and subsequent decrease in photoactivity as the Pt coverage increases. We study O₂’s interaction with a pure TiO₂ surface and a Pt cluster on a TiO₂ surface, as well as interactions of both simulated holes and excited electrons. Pt allows O2 to interact with the TiO2 surface by providing adsorption sites, which are rare on pure TiO2 surfaces. However, Pt clusters always act as electron hole recombination centers. The initial rise and subsequent fall in TiO₂’s photoactivity with Pt loading results from the competition between enhanced electron scavenging due to increased O₂ adsorption and increased electron-hole recombination.