Optimal preparation of Pt/TiO2 photocatalysts using atomic layer deposition

Platinum (Pt) was deposited by atomic layer deposition (ALD) onto the surface of TiO2 photocatalyst nanoparticles in order to increase the rate of photocatalytic oxidation of methylene blue (MB). Methylcyclopentadienyl-(trimethyl) Platinum(IV) (MeCpPtMe3) and oxygen were used as precursors over a deposition temperature range of 150-400 degrees C. The Pt ALD reaction mechanism was studied using an in situ mass spectrometer. The effect of operating temperature on Pt deposition was explored, and the resulting effect on TiO2 photoactivity was measured. The lower temperature limit for Pt ALD was found to be approximately 200 degrees C. Although the MeCpPtMe3 chemisorption step occurred on the particle surfaces at 150 degrees C, the ligand removal efficiency from the adsorbed Pt precursor was extremely low for O-2 dosing steps at temperatures below 200 degrees C. Pt deposition via ALD resulted in a significant improvement in TiO2 photoactivity. It was determined that one Pt ALD cycle carried out at 320 degrees C was optimal to maximize Pt surface dispersion and increased the photoactivity of TiO2 nanoparticles threefold. (C) 2010 Elsevier B.V. All rights reserved.