CO oxidation on single Pt atom supported by two-dimensional ZnO monolayer: Reaction mechanism and precursor activation

Abstract

CO oxidation is an effective solution for controlling CO emissions, and supported single-atom catalysts have shown excellent catalytic reactivity for chemical reactions. CO oxidation on a single Pt atom supported by a two-dimensional ZnO monolayer is investigated by combing ab initio molecular dynamics and density functional theory calculations. Seven reaction mechanisms are identified, including two new trimolecular Elie-Riedel mechanisms; six of them, except for the Mars-van Krevelen mechanism, have rate-limiting step energy barriers between 0.31 and 0.47 eV, which is lower than the experimental activation barrier of 0.81 eV on single Pt atoms supported by bulk ZnO, and is much lower than that of about 1.0 eV on Pt(111) surface. Furthermore, two preferred reaction mechanisms are discovered, an Eley-Rideal mechanism and a trimolecular Eley-Rideal mechanism, both of which have rate-limiting step energy barriers as low as 0.31 eV. Our results show that the more antibonding orbitals are filled in the reaction precursor, the higher its activation level. Activation of precursors plays an important role in CO oxidation and leads to different mechanisms. These results provide insights into the design of efficient single-atom catalysts supported by two-dimensional materials for the removal of CO pollutants.