Hydrogen peroxide reduction in the oxygen vacancies of ZnO nanotubes

The adsorption of a H2O2 molecule on the pristine and O-vacancy defected ZnO nanotubes was investigated by means of density functional calculations. It was found that the molecule prefers to attach to two zinc atoms of the tube from its two oxygen atoms with the adsorption energy of 254.1 kJ/mol. Attachment of the H2O2 to the wall of the tube does not have any significant influence on its highest occupied molecular orbital/lowest unoccupied molecular orbital gap (Eg). The presence of oxygen vacancy defect causes a decrease in the Eg of the tube and, as a consequence, may cause an increase in the conductivity of the tube. The zinc atoms of the defect are more reactive toward H2O2 reduction to H2O than perfect ones with the adsorption energy of 617.4 kJ/mol. During the adsorption process, the H2O2 was reoriented in such a way that its O atom has diffused into vacancy site, so that OO and OH bonds of the molecule were dissociated and an H2O is formed. Thus, we think that ZnO-NTs may be a candidate for electrochemical reduction and detection of H2O2.