Effect of adsorbed carbon monoxide on the kinetics of hydrogen electrosorption into palladium

Adsorption and electrooxidation of carbon monoxide on palladium (50 nm deposit, 50 μm foil and membrane) in 0.1 M H2SO4 have been examined using potentiostatic current transients, cyclic voltammetry and ac impedance measurements. During CO bubbling through solution, small current due to CO oxidation is observed at the adsorption potential of 0.6 V, however, in the solution saturated with CO or after removing it from the solution, the current is negligible. The shape of the CO stripping peak is strongly dependent on the sweep rate. The stripping charge is constant at the sweep rates 0.1–0.5 V s−1 and indicates that linear and bridged CO forms exist in equal quantities at Pd surface. The double layer capacitance decreases about three times in the presence of CO. The adsorbed CO layer allows of a very low H absorption current. In the hydrogen sorption potential range, the charge transfer resistance increases to tenths of kΩ cm2.