The oxygen–water reaction on Pd(100): Observation of a precursor complex.

The oxygen–water reaction on Pd(100) has been studied by electron energy loss spectroscopy (EELS) and low energy electron diffraction. A precursor complex for hydroxyl formation was identified in the ν(O–H) loss region of the vibrational spectrum when water was adsorbed on the Pd(100) p(2×2)O surface. The observations indicate that the precursor complex contains several water molecules. The formation of the water–oxygen precursor complex and thus the reaction is inhibited by the presence of hydrogen on the surface. The reaction is demonstrated to start at the defects of the p(2×2)O structure. Water does not adsorb on the perfect p(2×2)O structure above 140 K, at low pressures. [ABSTRACT FROM AUTHOR]