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Oxygen-Hydrogen Reciprocal Titration on Thin Rh Film Surfaces

Duś R., Nowicka E., Nowakowski R.

Polish Journal of Chemistry

2008

Vol. 82, nr 10

1911-1922

Oxygen-hydrogen reciprocal titration on thin Rh film was examined for the purpose of applying this reaction to determine the active area of rhodium in selected catalytic processes. Simultaneous measurements of work function changes Delta Fi and pressure P were carried out to study the adsorption of pure gases O2 and H2 and then for "in situ" investigation of the catalytic reaction between of oxygen and hydrogen adatoms in the course of recip rocal titration. Combining Delta Fi data with the measured amount of reagents actually consumed for adsorption and reaction in comparison with the amount expected to be used according to the model of the reaction allows to suggest the mechanism of succes sive steps of the catalytic process and to estimate the extent of poisoning of the surface by the products which remain on the surface under defined experimental conditions.

Adsorption and Desorption States of Deuterium on Sintered Thin Gold Films

Duś R., Nowicka E.

Polish Journal of Chemistry

2005

Vol. 79 / nr 7

1205-1216

Interaction of atomic deuterium, thermally generated on hot tungsten filament with thin Au polycrystalline film was studied. The surface topography, preferential crystallographic orientation and real area of the films were determined on the basis of AFM, XRD and BET data. The experiments with deuterium were carried out measuring the change of the adsorbent resistance _R during D atoms adsorption under isothermal conditions (78 or 87 K). It has been found that the rate of adsorption occurs according to Eley-Rideal (ER) model. One adsorption state exists, characterized by sticking probability S0 = 0.25 and ER recombination probability _ = 0.22. Measurements of the resistance changes _R of thin gold films with deuterium deposit caused by an increase of temperature were applied to study desorption phenomena. Differentiation of delta R against temperature T in the course of thermal desorption reveals the existance of two desorption states with maxima of desorption rates around 120 and 170 K. We suggest that the first one corresponds to desorption of (D-D) ad-dimers, and the second one to associative desorption due to recombination of D ad-atoms. Thus the adsorption and desorption states of atomic deuterium on thin gold films differ.