TiC and TiN supported platinum monolayer as high-performance catalysts for CO oxidation: A DFT study

The reactivity toward CO oxidation of Pt monolayer supported on TiC(001) and TiN(001) is studied by using empirical dispersion-corrected density functional theory calculations. A number of possible reaction pathways for CO oxidation, including the Eley-Rideal (ER) and Langmuir-Hinshelwood (LH) mechanisms, between adsorbed O₂ and CO molecules considering the cases that the adsorbed O₂ dissociates first or directly reacts with CO. It is found that the dissociation adsorption of O₂ molecules as the initial step is more favorable with lower activation barriers compared with the direct reaction mode. Hence the dissociation of adsorbed O₂ molecules plays a very key role in the CO oxidation reaction. For both Pt monolayer systems, our analyses also reveal that the reaction is most likely predominant via the initial ER mechanism and the subsequent LH mechanism. Furthermore, by comparing the activation barriers of the rate-limiting steps, CO oxidation on Pt_ML/TiN(001) shows a higher catalytic activity than that on Pt_ML/TiC(001), showing the important role that the support would play in the catalytic reactions. The present results suggest that the TiN supported monolayer Pt catalyst appears to be a good candidate for CO oxidation at low-temperature.