Hydrogen adsorption kinetics on Pd/Ce 0.8 Zr0.2 O2

F.C.GENNARI; C.NEYERTZ; G.MEYER; T.MONTINI; P.FORNASIERO

PHYSICAL CHEMISTRY CHEMICAL PHYSICS

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Año: 2006 vol. 8 p. 2385 - 2395

1463-9076

Hydrogen adsorption on Pd/Ce0.8 Zr0.2 O2 was studied by temperature-programmed reduction, volumetric measurements and IR spectroscopy.Hydrogen uptake and reduction rate at 353 K are strongly dependent on the hydrogen pressure.At relatively high hydrogen partial pressure, reduction involves PdO,the surface and a signi .cant fraction of the bulk of the ceria based oxide. Formation of oxygen vacancies even at low temperature (<373 K) is observed. The hydrogen adsorption process is mainly irreversible,as is shown by an increase in the 2 F5/2 –> 2 F7/2 electronic transition of Ce3+ with hydrogen pressure and surface dehydroxylation.This ‘‘severe ’’ reduction has a negative efect on the subsequent hydrogen adsorption capability.The decrease of hydrogen uptake capacity and rate during adsorption can be associated with the partial loss of superficial OH and the presence of Ce3+,which deactivates Pd electronically