CO oxidation mediated by Al‐doped ZnO nanoclusters: A first‐principles investigation

Using density functional theory the reaction pathways of CO oxidation mediated by Al‐doped Zn 12 O 12 cluster and its assembled wire‐like (Zn 12 O 12 ) n =2−4 structures were studied. It is revealed that O 2 molecule is chemisorbed over the doped clusters while physisorbed over pristine (Zn 12 O 12 ) n . Moreover, increasing the size of the nanocluster from AlZn 11 O 12 to (AlZn 11 O 12 ) 4 enhances the O 2 adsorption energy, although the amount of increase reduces as the cluster size grows. The adsorption energies of O 2 over Al‐doped (Zn 12 O 12 ) n clusters range from −1.83 to −2.14 eV, which are more negative than those of CO molecule (≈−0.80 eV). The Eley–Rideal (ER) and Langmuir–Hinshelwood (LH) pathways are used to investigate the oxidation mechanisms of the CO molecule. The energy barriers for the rate limiting step in the LH mechanism (i.e., OCOO → CO 2 + O ads ) are around 0.30 eV, which are substantially lower than the energy barriers in the ER process.