REAL-TIME MEASUREMENTS OF HYDROGEN DESORPTION AND ABSORPTION DURING CO EXPOSURES OF PD - HYDROGEN STICKING AND DISSOLUTION

Combined real time measurements of hydrogen desorption and absorption show that both processes may be induced simultaneously by CO adsorptio n on a hydrogen-covered Pd surface. The induced absorption is found to be a kinetic effect, where the amount absorbed depends on the hydroge n desorption rate and the CO adsorption rate. In addition to simple si te blocking, adsorbed CO induces an increase in the hydrogen desorptio n energy and an activation barrier for hydrogen dissociation. Both inc rease linearly with CO coverage for theta(CO) > 0.18 ML. Below this co verage, the hydrogen dissociation is non-activated. (C) 1998 Elsevier Science B.V. All rights reserved.