New insights into the single-atom-decorated Zr2CO2 (MXene) as an efficient catalyst for CO oxidation in incomplete combustion gas

Abstract

To design novel non-noble metal nano-catalysts for CO oxidation at low temperature and further understand the mechanism of CO oxidation in incomplete combustion gas (mainly containing CO, N2, CO2, and O2) with MXene-based materials, CO oxidation on Zr2CO2 with surface decoration by transition metal atoms was investigated by density functional theory (DFT) calculations. Sc and Ti atoms were preliminarily proven to be stably anchored on Zr2CO2 monolayer but O2 is easier to be dissociated into two O atoms on Ti/Zr2CO2. For CO, N2, and CO2, they are easy to automatically desorbe from the catalysts in presence of O2, what is beneficial for the CO oxidation reaction and preventing catalyst poisoning. On Sc/Zr2CO2, CO is difficult to be catalytically oxidized into CO2 with high reaction barriers. For Ti/Zr2CO2, the energy barrier to form the first CO2 in the ER mechanism is 0.58 eV, lower than that of the LH mechanism (0.7 eV) although their rate-determining barriers are same (0.8 eV). Furthermore, Ti/Zr2CO2 is also capable of resisting CO2 poison to enhance the reusability of the catalyst. Therefore, Ti/Zr2CO2 is a promising catalyst for CO oxidation at low temperature for incomplete combustion gas treatment.