Low-temperature oxidation of methane mediated by Al-doped ZnO cluster and nanowire: A first-principles investigation

Abstract

Abstract The oxidation of methane over aluminum (Al)-doped Zn12O12 cluster and (Zn12O12)2 nanowire is investigated using first-principles calculations. The impact of Al impurity on the geometry, electronic structure and surface reactivity of Zn12O12 and (Zn12O12)2 are thoroughly studied. It is found that N2O is highly activated on these systems to provide an activated *O species. Though, the oxidation of CH4 is almost impossible over pristine ZnO counterparts due to less activation of N2O or CH4 over these systems, however, the addition of an Al atom helps the dissociation of N‒O bond of N2O. The conversion of CH4 into CH3OH over AlZn11O12 and (AlZn11O12)2 requires an activation energy of 0.45 and 0.29 eV, respectively, indicating it can be easily performed at normal temperatures. Besides, the overoxidation of methanol into formaldehyde cannot take place over the AlZn11O12 and (AlZn11O12)2, due to the high energy barrier needed to dissociate C-H bond of the CH3O intermediate.