CO Oxidation with Atomically Dispersed Catalysts: Insights from the Energetic Span Model

Using density functional theory and the energetic span model (ESM), this work examines the activity of a single hollow site (H1) of atomically dispersed Pt on rutile TiO2 (110) toward low-temperature CO oxidation by enumerating all possible pathways and calculating the turnover frequencies (TOFs). Of the 12 distinct pathways spanning the Eley–Rideal (ER) mechanism, termolecular ER (TER) mechanism, Langmuir–Hinshelwood (LH) mechanism, Mars–van Krevelen (MvK) mechanism, and their combinations, the TER mechanism with CO-assisted CO2 desorption yields the highest TOF. However, this pathway is ruled out because Pt is unstable under the reaction conditions in an intermediate state when bound to two CO molecules, determined in a prior ab initio molecular dynamics study by our group. Combined with the fact that other pathways initiated with CO adsorption (including the MvK mechanism) exhibit negligibly low TOFs, we conclude that H1 exhibits little activity toward CO oxidation. By employing the ESM to calculate the TOFs for pathways proposed in prior mechanistic studies of several oxide-supported atomically dispersed catalysts, we identify the most active metal–support combinations for low-temperature CO oxidation.