  In ceria-based catalysis, the shape of the catalyst particle, which
determines the exposed crystal facets, profoundly affects its reactivity. The
vibrational frequency of adsorbed carbon monoxide (CO) can be used as a
sensitive probe to identify the exposed surface facets, provided reference data
on well-defined single crystal surfaces together with a definitive theoretical
assignment exist. We investigate the adsorption of CO on the CeO2(110 and (111)
surfaces and show that the commonly applied DFT(PBE)+U method does not provide
reliable CO vibrational frequencies by comparing with state-of-the-art infrared
spectroscopy experiments for monocrystalline CeO2 surfaces. Good agreement
requires the hybrid DFT approach with the HSE06 functional. The failure of
conventional DFT is explained in terms of its inability to accurately describe
the facet- and configuration-specific donation and backdonation effects that
control the changes in the C-O bond length upon CO adsorption and the CO force
constant. Our findings thus provide a theoretical basis for the detailed
interpretation of experiments and open up the path to characterize more complex
scenarios, including oxygen vacancies and metal adatoms.
