Single atom catalysts on the Cr ₂ NO ₂ MXene for CO oxidation

Using density functional theory, this work investigates the adsorption of carbon monoxide (CO) molecules and their subsequent oxidation to carbon dioxide (CO₂) on the MXene Cr₂NO₂ decorated with a single atom of transition metal (Sc, V, and Ti) <i>via</i> the Eley-Rideal mechanism. The dynamic stability of the MXene is evaluated through phonon calculations, and the thermal stability of the structure is determined by <i>ab initio</i> molecular dynamics simulations. First, an oxygen (O₂) molecule is adsorbed onto the metal atom. Sc and Ti induce a partial dissociation, while V causes a full decomposition into atomic O. For the first CO oxidation, all transition metals favor CO oxidation, with Ti and V providing higher and lower activation energies, respectively. However, in the second CO oxidation, the V site is poisoned since the CO₂ molecule is unstable compared to the adsorbed CO. In the case of Ti and Sc, CO₂ formation is feasible, with Sc providing the lowest activation energies. Thus, the present study demonstrates Sc SACs on Cr₂NO₂ as improved catalysts for CO oxidation reactions.