The cobalt oxidation state in preferential CO oxidation on CoO/Pt(111) investigated by X-ray photoemission spectroscopy.

The combination of a reducible transition metal oxide and a noble metal such as Pt often leads to active low-temperature catalysts for the preferential oxidation of CO in excess H gas (PROX reaction). While CO oxidation has been investigated for such systems in model studies, the added influence of hydrogen gas, representative of PROX, remains less explored. Herein, we use ambient pressure scanning tunneling microscopy and ambient pressure X-ray photoelectron spectroscopy on a CoO/Pt(111) planar model catalyst to analyze the active phase and the adsorbed species at the CoO/Pt(111) interface under atmospheres of CO and O with a varying partial pressure of H gas.