Infrared study of hydrogen adsorbed on ZrO2
Abstract
The adsorption of H2 and D2 at various temperatures and the isotope effect have been studied in detail over a ZrO2 catalyst by means of FTIR. Four different types of adsorbed hydrogen were observed as follows: (1) molecularly adsorbed hydrogen, H2(a), was observed below 173 K and was easily desorbed by evacuation; (2) homolytic dissociative adsorption produces Zr[graphic omitted] species was observed below 373 K and was stable below 178 K; (3) heterolytic dissociative adsorption which forms OH and ZrH was observed in the temperature range 223–373 K and the isotope effect of adsorption between H2 and D2 was also found; (4) the adsorption which generates two OH bands at 3778 and 3668 cm–1 takes place above room temperature. For the heterolytic dissociative adsorption of H2 and D2, both the kinetic and the equilibrium isotope effects were observed. The magnitude of these isotope effects is in good agreement with the values calculated via IR data.