Ceria (CeO2) has risen to prominence in recent years as a key material in modern heterogeneous catalysis, finding applications as both a support and a catalyst itself. Its catalytic efficacy is in part a consequence of its high oxygen storage capacity, the ability of a material to store oxygen under oxidising conditions and release oxygen under reducing conditions. This stems in ceria from the relatively facile reversible reduction of Ce(IV) ions to Ce(III) upon the removal of oxygen ions. An advancement in the area has been the novel approach of �noble metal ionic catalysis�, whereby the divalent ions of noble metals which typically sit atop the ceria support in three-way catalysts are instead incorporated into the lattice[1].To determine the fundamental reasons for the catalytic activity of these systems, the substitution of ten divalent ions (Be, Mg, Sr, Ca, Ba, Ni, Pd, Pt, Cu, Zn) into the ceria bulk is investigated with density functional theory, using the PBE general gradient approximation functional[2] with a +U correction to account for on-site Coulombic repulsion. By testing a number of structural configurations, it is shown that the dopants preferentially adopt the coordination of their parent oxides, which when different from the cubically coordinated Ce(IV), results in under-coordinated or weakly bound oxygen ions that are more easily removed than those in pure ceria[3]. Low index surfaces of ceria ({100}, {110}, and {111}) are then doped with those ions that give rise to the lowest reduction energies (Pd and Pt), and the positions of the dopant and oxygen vacancies adjusted to determine the most stable surfaces, over which the reductions of CO and NO2are analysed.[1] Hegde et al., Acc. Chem. Res. 42, 704-712 (2009)[2] Perdew et al., Phys. Rev. Lett. 77, 3865-3868 (1996)[3] Kehoe et al., Chem. Mater. 23, 4464-4468 (2011)

Enhancing the reducibility of CeO<sub>2</sub>: The role of divalent dopants

246th National Meeting (2013)

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Enhancing the reducibility of CeO2: The role of divalent dopants

Enhancing the reducibility of CeO₂: The role of divalent dopants