Single atom catalysts on the Cr₂NO₂ 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) via 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 ab initio 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.