IN-SITU FTIR STUDIES OF HIGH-TEMPERATURE ADSORPTION OF HYDROGEN ON ZIRCONIA

The interaction of hydrogen with ZrO2 at high temperatures (673-873 K) has been studied by using in situ FTIR spectroscopy. OH species are f ormed with O-H stretching frequencies at 3650 cm(-1) on the surface of monoclinic and at 3730 cm(-1) on the surface of tetragonal zirconia. The role of these hydroxy groups in the mechanism of hydrogen uptake a nd desorption at high temperatures, previously observed on monoclinic ZrO2, is discussed. According to our proposal, the nature of the hydro gen uptake of monoclinic zirconia consists of a heterolytic dissociati on of molecular hydrogen and the simultaneous formation of OH species and hydridic species at adjacent O2- and Zr3+ surface sites.