Interactions of hydrogen with CeO2

The interactions of hydrogen with ceria have been the subject of several ex perimental studies, but whether hydrogen atoms enter the bulk or are merely chemisorbed on the surfaces is disputed. We combine first-principles calcu lations with thermodynamic arguments and conclude that the uptake of small amounts of hydrogen by ceria is spontaneous below 665 K. The calculations a lso predict that hydrogen atoms within the bulk form hydroxyl groups and sl ightly expand the lattice. The predicted hydrogen content, OH vibrational f requency, and ceria lattice expansion upon hydrogen uptake are consistent w ith available data.