(46i) Dynamic Evolution of Atomically Dispersed Catalysts

Atomically dispersed catalysts have become popular due to the benefits gained by ease of separation due to the two phases of heterogeneous catalysts while maintaining the selectivity and efficiency of homogenous catalysts. However, the coordination environment and diffusivity of precious metal atoms on support surfaces are still not fully understood by experimental and static Density Functional Theory (DFT) studies. Sintering and dynamics of the support surface have been reported to be affected by conditions such as reactant partial pressures and reaction temperature, leading to the importance of studying the dynamical evolution of these systems. We utilize picoseconds timescale Ab Initio Molecular Dynamics (AIMD) simulations to better understand the coordination environment, diffusivity, and stability of Pt over rutile TiO₂ (110) support interface. With elevated temperature (1200K) 2ps AIMD simulations, we uncover eight new binding sites of Pt on the TiO₂ surface. To the best of knowledge, these sights have not been reported in static DFT studies because these structures are not intuitive and AIMD allows us to sample many configurations. These configurations have been selected based on criteria such as coordination number of Pt to the surface, migration events, and Bader charge of the Pt and nearby surface atoms. We have studied the dynamics of eight common Water-Gas Shift (WGS) adsorbates bound to both the Pt and support surface with lower temperature (500K) 5ps AIMD simulations. During these simulations, we observe the Pt diffuse to the unstable bridge sites of the surface while bound to COOH and CO₂, Pt diffusion along the basal plane via hydrogen bonding of OH to the support O atoms, and stabilization due to the formation of linear O-Pt-X complexes where O belongs to the support surface and X is the adsorbate during the simulation. We plan to analyze the chemical bounding of these near linear complexes to better understand what causes Pt stabilization, Pt oxidation state and how that determines catalytic activity, and uncover adsorbates that may induce/inhibit metal atom migration and target specific oxidataion states.