Humidity tuning CO oxidation on Ti decorated V2CO2 monolayer (MXene) catalyst: A density functional calculation study

Considering the high efficiency and low cost, original single-atom catalyst Ti/V2CO2 is used for CO catalytic oxidation in this work. Besides, density functional theory (DFT) calculations are adopted to explore H2O effects on performance and mechanisms of CO catalytic oxidation. Finally, the single atom of Ti is proven to be evenly distributed on V2CO2 monolayer. Also, it is discovered that CO oxidation cannot occur on Ti/V2CO2 in dry conditions. While, in humid conditions, water molecule is responsible for transferring charge to Ti atom, thus weakening O2 adsorption and causing lower activation energy of 0.71 eV. Rather than directly participating in CO oxidation by generating -OH groups with O2, it prefers to act as a co-catalyst with Ti/V2CO2. Consequently, the energy barrier of rate-limiting step based on Eley-Rideal (ER) mechanism is remarkably reduced from 1.79 to 0.57 eV, due to CO catalytic oxidation with the help of H2O in accelerating the interaction between single O atom and CO molecule. According to our findings, the existence of water can promote Ti/V2CO2 to be an effective single-atom catalyst for catalytic oxidation of CO in a humid environment.