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°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°C. Although the MeCpPtMe₃ chemisorption step occurred on the particle surfaces at 150°C, the ligand removal efficiency from the adsorbed Pt precursor was extremely low for O₂ dosing steps at temperatures below 200°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°C was optimal to maximize Pt surface dispersion and increased the photoactivity of TiO₂ nanoparticles threefold.