It is well-known that the catalytic oxidation of CO molecule into CO2 is one of the most important strategies for the removing of this toxic gas from the atmosphere. In the present study, we investigate the reaction pathways and energy barriers for the oxidation of CO by O2 molecule over the Si-doped C3N nanosheet. According to our results, doping of C3N nanosheet with a Si atom could greatly modify its surface reactivity and electronic structure. Due to the large positive charge on the Si, this atom acts as the most active site to adsorb CO and O2 molecules. Three possible reaction mechanisms are studied for the CO oxidation, namely the Eley–Rideal (ER), Langmuir-Hinshelwood (LH) and new Eley–Rideal (NER). Comparing the activation energies indicates that the CO oxidation reaction proceeds via the LH mechanism over the title surface. The energy barrier needed to remove the activated oxygen atom (O*) from the Si atom is only 0.22 eV, which is most likely to overcome at room temperature. The results of this study may be useful to fabricate noble-metal free catalysts to remove toxic CO molecules from the atmosphere.
