Ab Initio Molecular Dynamics Reveals New Active Sites in Atomically Dispersed Pt1/TiO2 Catalysts
We present a multi-scale modeling study of atomically dispersed Pt on the (110) surface of rutile TiO2. Using density functional theory (DFT) and ab initio molecular dynamics (AIMD), we probe the dynamic evolution of the catalytic surface at elevated temperatures. We identify metal atom diffusion as well as support atom mobility as important dynamical phenomena that enable the formation of new active sites. Among the eight new dynamically formed sites that are distinct from prior experimental and DFT reports, two sites exhibit anionic, near-linear O−Pt−O configurations. Such configurations are neither intuitive nor easily located using static methods such as DFT. Therefore, DFT alone is not sufficient to obtain a complete, dynamic description of the catalytic surface. Furthermore, the near-linear O−Pt−O sites exhibit CO binding characteristics that are markedly distinct from their parent sites, with possibly higher activity towards CO oxidation and water-gas shift reactions. Based on the wide range of adsorbate affinities exhibited by the DFT and AIMD-generated sites in this study, our aim going forward is to probe site-sensitivity of water-gas shift kinetics with these catalysts.