Role of step sites on water dissociation on stoichiometric ceria surfaces

Abstract

The adsorption and dissociation of water on CeO 2 (111), CeO 2 (221), CeO 2 (331), and CeO 2 (110) has been studied by means of periodic density functional theory using slab models. The presence of step sites moderately affects the adsorption energy of the water molecule but in some cases as in CeO 2 (331) is able to change the sign of the energy reaction from endo-to exothermic which has important consequences for the catalytic activity of this surface. Finally, no stable molecular state has been found for water on CeO 2 (110) where the reaction products lead to a very stable hydroxylated surface which will rapidly become inactive.

Water‐Gas‐Shift over Metal‐Free Nanocrystalline Ceria: An Experimental and Theoretical Study

“…Ceria‐supported gold, platinum, and copper have been extensively studied, as well as supported nickel . The metals adsorb and activate CO, while the ceria serves to dissociate water . Nanostructured “metal‐free” ceria, especially sub‐10 nm nanoparticles, has recently become an interest for fundamental studies of the water‐gas shift reaction over the oxide .…”

“…Microscopy revealed the catalysts to be composed of spherical nanoparticle aggregates with 3–4 nm well‐defined truncated octahedral nanocrystals (Figure B–D) for which the (1 1 1) and (1 0 0) facets were exposed . Step defects on the nanocrystal surface, indicated by arrows, reveal the presence of under‐coordinated metals which may serve as active sites in the reaction . The catalyst with the highest specific activity (pre‐calcined to 450 °C) was selected for further investigation.…”

In Situ and Theoretical Studies for the Dissociation of Water on an Active Ni/CeO2 Catalyst: Importance of Strong Metal–Support Interactions for the Cleavage of O–H Bonds

“…13–16 Nevertheless, the molecular state can easily coexist with a OH‐pair‐like configuration (Figure 3 b), since these two configurations are separated by a small energy barrier barrier (≤0.15 eV) 14. 16–18 In contrast, the presence of O vacancies on the surface significantly enhances water dissociation (Figure 3 e) over molecular adsorption (Figure 3 d). 15, 16 This process is indeed quite exothermic by 1.15 eV and it is effectively barrierless16 (Figure 4), resulting in the water OH group readily healing the O vacancy and the remaining H atom being adsorbed on top of a nearest neighbor surface O atom.…”

Hydrophobic Properties of Al2O3 Doped with Rare‐Earth Metals: Ab Initio Modeling Studies

“…This approach is commonly used for metals with f or/and d states in metal oxides. The Hubbard parameters ( U eff ) of 4–6 eV for Ce, Eu, and Nd, respectively, were chosen to reproduce the electronic structures of REOs . The projector‐augmented wave method (PAW) was applied to describe the core‐valence interaction .…”

“…The Hubbard parameters (U eff ) of 4-6 eV for Ce, Eu, and Nd, respectively, were chosen to reproduce the electronic structures of REOs. [25][26][27][28][29][30] The projector-augmented wave method (PAW) was applied to describe the core-valence interaction. [31,32] An energy cutoff of 500 eV was set for plane-wave basis.…”