An FTIR study of surface ceria hydroxy groups during a redox process with H2

Two ceria samples with differing specific surface areas and porosities have been investigated by IR spectroscopy. A ν(OH) band at ca. 3510 cm–1 was found to be due to cerium oxyhydroxide impurities within the ceria pores. One-, two- and three-coordinated OH species were observed. Doubly bridging OH species in the vicinity of surface oxygen vacancies were found to be very reactive towards D2 dissociation at 423 K, when the reduction is surface limited. At 673 K, doubly bridging OH species and hydrogen-bonded ones were formed when the already reduced ceria surface was exposed to H2. These OH species were not stable upon evacuation and are proposed to be responsible for the so-called reversible H2-reduction of ceria.