Activation of Oxygen Species on Ag/CoAlO Catalysts to Promote CO Oxidation by Enhancing Metal-Support Interactions

Ag catalysts supported on cobalt-aluminum hydrotalcite derivative (CoAlO) nanosheet for CO oxidation are reported. A facile pre-reduction treatment on reducible CoAlO support was employed to construct more oxygen vacancies for anchoring Ag sites to tune metal-support interactions (MSI) and improve metal dispersion. The results show that directly loading Ag on CoAlO (Ag/CoAlO) can significantly promote the generation of active oxygen species by three times. Pre-reduction of CoAlO enhances MSI of the Ag catalyst (Ag/CoAlO-R), which further enlarges quantity of active oxygen species. Besides, the kinetic results demonstrate that compared with Ag/CoAlO, Ag/CoAlO-R shows the additional advantages of the lower activation energy, the higher intrinsic activity of Ag sites, and especially the decreased reaction order of O-2 from 0.20 to 0. The latter one indicates that enhancing MSI can readily activate gaseous oxygen at the interface of Ag and CoAlO, and the reaction mechanism obeys a typical Mars-van Krevelen route.

Automated summary

This study reports the use of Ag catalysts supported on cobalt-aluminum hydrotalcite derivative (CoAlO) nanosheet for CO oxidation. A pre-reduction treatment on the reducible CoAlO support was employed to enhance metal-support interactions (MSI) and improve metal dispersion. The results show that the pre-reduction treatment increases the generation of active oxygen species, leading to higher catalytic activity of the Ag catalyst. Kinetic studies also reveal that the pre-reduction treatment lowers the activation energy and modifies the reaction order of oxygen.