Formation and sintering of Pt nanoparticles on vicinal rutile TiO2 surfaces

Abstract

By means of scanning tunnelling microscopy (STM) the nucleation, growth and sintering of platinum nanoparticles (Pt NP's) was studied on vicinal and flat rutile titanium dioxide (TiO₂) surfaces. Utilising physical vapour deposition, the nucleation of Pt NP's on TiO₂ surfaces at room temperature (RT) was found to be random and invariant towards different surface morphologies and reduction states. Thus, the nucleation of Pt on TiO₂ at RT is rather insensitive to the surface structure and surface defects. Vacuum-annealing at 600 K, 700 K and 800 K, respectively, led to lower densities of Pt NP's as a result of sintering. Sintering occurred at different rates at the TiO₂ surfaces studied, indicating that the surface morphology and the amount of Ti³⁺ excess charge do have an influence on the particle stability. Observed changes in the NP distribution as a result of sintering can be explained inferring facile diffusion of Pt NP's along the [001] direction.