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 Zn12O12 cluster and its assembled wire‐like (Zn12O12)n=2−4 structures were studied. It is revealed that O2 molecule is chemisorbed over the doped clusters while physisorbed over pristine (Zn12O12)n. Moreover, increasing the size of the nanocluster from AlZn11O12 to (AlZn11O12)4 enhances the O2 adsorption energy, although the amount of increase reduces as the cluster size grows. The adsorption energies of O2 over Al‐doped (Zn12O12)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 → CO2 + Oads) are around 0.30 eV, which are substantially lower than the energy barriers in the ER process. The possibility of using Al‐doped Zn12O12 monomer and its assembled wire‐like structures as noble metal‐free catalysts for CO oxidation is explored by density functional theory calculations. The findings demonstrate that the Al‐doped Zn12O12 cluster and its wire‐like structures have an interesting surface activity and catalytic performance in the CO oxidation process.