Competition between hydrogen and oxygen dissociation on palladium surfaces at atmospheric pressures

A large change in the surface and interface potential of Pd-films on SiO₂ is observed at a constant ratio between hydrogen and oxygen pressure in the ambient. This observation, which is most probably due to a competition between hydrogen and oxygen for the same dissociative adsorption sites, is described in this communication. Furthermore the potential measurements indicate the presence of another type of hydrogen adsorption sites on the oxygen covered surface.