Single Zn atom catalyst on Ti2CN2 MXenes for efficient CO oxidation

Carbon monoxide (CO) oxidation is an efficient way to purify CO. Herein, the geometrical properties, electronic structure and CO oxidation catalytic activity of Zn single atom catalyst (SAC) on pristine Ti2CT2 (T = N/O/F) MXenes and defective ones (Tv/Ti2CT2) with a functional-group vacancy (Tv) were calculated by using density functional theory (DFT) calculations. The results revealed that Ti2CN2 may serve as an excellent substrate to stabilize single Zn atom catalyst, compared to Ti2CT2 (T = O/F) and Tv/Ti2CN2 (T = N/O/F). The catalytic oxidation mechanism of CO on the surface of Zn–Ti2CN2 has been systematically studied. The Eley–Rideal (ER) mechanism was identified as the most preferential pathway with the smallest rate-determining energy barrier of 0.06 eV, since the Zn atom can considerably promote the activation of O2 molecule and weaken the O–O bond. Electronic structure analysis confirmed the synergistic effects of adsorbed single Zn atom and substrate in regulating electron transfer, activating the adsorbed small molecule reactants and enhancing CO oxidation activity. Overall, this work reveals that Zn–Ti2CN2 could be a promising low-temperature CO oxidation candidate and probably provides a new theoretical guidance and inspiration for the experimental and theoretical research to design more effective single atom catalysts with nonprecious metals.