(676h) Effects of Site Distribution and Dynamic Character of Atomically Dispersed Catalysts on CO Oxidation Kinetics

Atomically dispersed catalysts (ADCs) reduce the cost of expensive noble metal utilization by delivering high selectivity and per-atom activity. Single atoms can attach to different locations on the surface where they exhibit unique electronic and chemical properties. These binding sites are sensitive to the reaction conditions and can dynamically change during a chemical reaction. Such phenomena are essential in understanding how reactions proceed over ADCs. In order to discover the effects of site distribution and the dynamic character of ADCs, we use density functional theory, ab initio molecular dynamics (AIMD), and (modified) energy span analysis. Recently, we thoroughly analyzed low-temperature CO oxidation pathways over the Pt₁/rutile-TiO₂ (110) catalyst and proposed twelve distinct mechanisms. Using AIMD, we assess the stability of all intermediates that occur during reactions and revisit the proposed reaction pathways. Although most intermediates are stable at the reaction conditions, the remaining can significantly change the reaction rate if that intermediate is associated with the rate-limiting step. Additionally, we expand our study to incorporate more Pt binding sites, including anionic and cationic vacancies and two stoichiometric sites. A significant impact of local coordination on the reaction kinetics is observed. The stoichiometric site with an O-Pt-O linear complex delivers the highest turnover frequency due to the ease of removing lattice oxygen. Our comprehensive study on reaction pathways highlights the importance of combining static, kinetic, and dynamic models to identify the reaction mechanisms. A complete atomic-level picture of ADCs can only be captured using these methods, along with the distribution of co-existing single-atom sites on the surface. Moving forward, we investigate PtO₂ on the TiO₂ surface. Such structures are a great avenue for ADCs since they are active for CO oxidation and have been shown to exist in mildly reducing conditions*.

*DeRita et al., Nat. Mater., 2019, 18, 746–751.