Water on ceria{111}: Comparison between 23 experimental vibrational studies in the literature and new modeling

Abstract

Theoretical and experimental vibrational signatures of H2O and OH− (dissociated water) adsorbed on stoichiometric ceria{111} surfaces are compared. The experimental ones were collected from low-coverage experiments in the literature, and the theoretical anharmonic frequencies were generated using density functional theory calculations employing the optPBE-vdW functional for coverages from 0.5 to a few monolayers. It is found that (i) the experiments and our calculations overall agree well, lending credibility to both; (ii) the calculations manage to resolve the large class of H-bonded motifs into frequency classes that can guide experimental assignments; (iii) it is possible to find a geometrical H-bond definition that also captures the OH vibrational frequency downshifts well: R(H⋯O) ≤2.5 Å and the O–H⋯O angle θ ≥ 100°; and (iv) the frequency vs electric field relations for water and hydroxides (i.e., dissociated water) follow different and well-separated curves.