Effect of Different InO(111) Surface Terminations on CO Adsorption.

InO-based catalysts have shown high activity and selectivity for CO hydrogenation to methanol; however, the origin of the high performance of InO is still unclear. To elucidate the initial steps of CO hydrogenation over InO, we have combined X-ray photoelectron spectroscopy and density functional theory calculations to study the adsorption of CO on the InO(111) crystalline surface with different terminations, namely, the stoichiometric, reduced, and hydroxylated surface. The combined approach confirms that the reduction of the surface results in the formation of In adatoms and that water dissociates on the surface at room temperature. A comparison of the experimental spectra and the computed core-level shifts (using methanol and formic acid as benchmark molecules) suggests that CO adsorbs as a carbonate on all three surface terminations. We find that the adsorption of CO is hindered by hydroxyl groups on the hydroxylated surface.