Bulk Hydroxylation and Effective Water Splitting by Highly Reduced Cerium Oxide: The Role of O Vacancy Coordination

Abstract

Reactions of reduced cerium oxide CeO x with water are fundamental processes omnipresent in ceria-based catalysis. Using thin epitaxial films of ordered CeO x , we investigate the influence of oxygen vacancy concentration and coordination on the oxidation of CeO x by water. Upon changing the CeO x stoichiometry from CeO2 to Ce2O3, we observe a transition from a slow surface reaction to a productive H2-evolving CeO x oxidation with reaction yields exceeding the surface capacity and indicating the participation of bulk OH species. Both the experiments and the ab initio calculations associate the effective oxidation of highly reduced CeO x by water to the next-nearest-neighbor oxygen vacancies present in the bixbyite c-Ce2O3 phase. Next-nearest-neighbor oxygen vacancies allow for the effective incorporation of water in the bulk via formation of OH– groups. Our study illustrates that the coordination of oxygen vacancies in CeO x represents an important parameter to be considered in understanding and improving the reactivity of ceria-based catalysts.

Promoting ring-opening efficiency for suppressing toxic intermediates during photocatalytic toluene degradation via surface oxygen vacancies

“…The surface oxygen vacancies (OVs) can serve as the active sites for activating small molecules on the photocatalyst surface, which are of vital importance to enhance the performance in wastewater remediation, artificial synthesis, water oxidation and gaseous pollutants oxidation [19][20][21][22][23][24][25][26][27]. The OVs possess excess localized electrons and coordinatively unsaturated feature, thus they can provide specific sites to firmly bind with small molecules, then facilitating subsequent molecules activation by localized electrons [28][29][30][31].…”

Improved Electrocatalytic Water Splitting Reaction on CeO2(111) by Strain Engineering: A DFT+U Study

“…On excessively hydroxylated ceria, however, water dissociation and release of H2 might involve the formation of a Ce-H intermediate (H # O $%& + 2Ce '( + V ) → OH * + Ce +( + Ce 4+ * → # + 2Ce +( + O #* ) 17 . Both theoretical and experimental studies have found OH species 17,20 play an important role in limiting the WSR activity in ceria-based catalysis and demonstrated that the rate-determining step (RDS) of the WSR on ceria is associated with the oxidation of Ce 3+ to Ce 4+ during hydroxyl decomposition into H2. 3,17 To overcome the limitations of hydroxyl decomposition, strain engineering is a promising approach due to its significant influence on the local atomic structure and chemical reactivity.…”

Oxidation of Reduced Ceria by Incorporation of Hydrogen

“…[16] Furthermore,H 2 dissociation on at hin CeO 2 (111) film on Ru(0001) was observed at H 2 pressures in the mbar regime. [18] In this paper,w ed iscuss H 2 adsorption on reduced ceria surfaces (CeO 2Àx powder and CeO 2Àx (111) thin films) at different pressures and adsorption temperatures.T he combination of studies on atomically well-defined CeO 2Àx (111) thin films and morphologically complex CeO 2Àx powder allows us to extract information on chemical processes on amodel thin film and to verify their relevance on arealistic powder system. Ar eaction channel with bulk CeO 2Àx has recently also been identified for the incorporation of hydroxyls.…”