A Pt/ZrO2 catalyst has been investigated by temperature-programmed red
uction and temperature-programmed desorption of hydrogen. Hydrogen spi
lls over from Pt onto the ZrO2 surface at about 550 degrees C. One par
t of spillover hydrogen is consumed by a partial reduction of zirconia
. The other part is adsorbed on the surface and is desorbed at about 6
50 degrees C. This desorption is a reversible one, i.e. it can be foll
owed by a renewed uptake of spillover hydrogen. No connection between
dehydroxylable OH groups and spillover hydrogen adsorption has been ob
served. The adsorption sites for the reversibly bound spillover hydrog
en were possibly formed during the reducing hydrogen treatment.