The sticking probability of hydrogen on Ni, Pd and Pt at a hydrogen pressure of 1 bar

A technique for measurements of the sticking probability of hydrogen on metal surfaces at high (ambient) pressure is described. As an example, measurements for Ni, Pd and Pt at a hydrogen pressure of 1 bar and temperatures between 40 and 200 °C are presented. The sticking probabilities are extracted from measurements of the local gas composition over the catalytic surface, with the help of a model for the H–D exchange reaction. The sticking probability is lowest for Ni and similar for Pd and Pt. The apparent energies of desorption derived from the adsorption rates decrease in the order Ni, Pd, Pt. The transition between β- and α-phase in the H–Pd system has a significant effect on the activity for Pd.