Reactivity of Hydroxyls and Water on a CeO₂(111) Thin Film Surface: The Role of Oxygen Vacancy

Abstract

The interaction of atomic hydrogen and H 2 O with stoichiometric and partially reduced CeO 2 (111) thin films deposited on a Cu(111) substrate was investigated by temperature programmed desorption and X-ray photoelectron spectroscopy. On stoichiometric CeO 2 (111) surface, the adsorption of atomic H(g) leads to the formation of surface hydroxyl (OH(a)) and H 2 O(a) as well as the reduction of Ce 4+ into Ce 3+ . On reduced CeO 2 (111) surfaces, the stability of OH(a) was enhanced by the presence of oxygen vacancies. Upon heating, surface hydroxyls undergo two competing reaction pathways: one is the associative desorption of OH(a) releasing H 2 O and creating oxygen vacancies (OH(a) + OH(a) → H 2 O(g) + O lattice + O vacancy ), and the other one is to produce H 2 via OH(a) + OH(a) → H 2 (g) + 2O lattice . The presence of oxygen vacancies in CeO 2 favors the reaction pathway of H 2 formation. At 115 K, reversible dissociation and molecular adsorption of H 2 O occur on stoichiometric CeO 2 (111) surface, but irreversible dissociation of H 2 O occurs on reduced CeO 2 (111) surfaces. These results deepen the fundamental understanding of the influence of oxygen vacancies on the reactivity of surface hydroxyls and water on CeO 2 surface.

Fast vacancy-mediated oxygen ion incorporation across the ceria–gas electrochemical interface

“…This impurity peak, which reaches a maximum atomic fraction of 14% of the oxygen photoelectron spectra, does not change appreciably with bias over the course of the experiment. Finally, the photoelectron peak with the highest binding energy (B2.2 eV higher than the lattice oxygen peak) is assigned to adsorbed OH À groups, consistent with prior photoemission and temperature-programmed desorption investigations [34][35][36][37] . We note, however, the binding energy is considerably larger than that reported by Zhang et al 32 Moreover, we observed that the binding energy difference between the OH and the lattice O changed with bias ( Supplementary Fig.…”

Isobutene from Ethanol: Describing the Synergy between In2O3 and m‐ZrO2

“…Chen et al . proposed that when water dissociates on the oxygen vacancies of the oxides, it generates H 2 and leaves oxygen occupying these vacancies.…”

Chemicals from ethanol: the acetone synthesis from ethanol employing Ce0.75Zr0.25O2, ZrO2 and Cu/ZnO/Al2O3

“…It was verified (not shown) that the molecular desorption of H 2 O occurs from low to high temperatures, which is related to the recombination of hydroxyls species [35]. The H 2 spectra show that both oxides generate this gas at low temperature (413 K).…”

“…Chen et al [35] studied the dissociation of H 2 O on CeO 2 . They showed that the adsorption of H 2 O on this oxide (reduced) creates hydroxyls species, which then react desorbing H 2 O and generating O lattice and O vacancy .…”