Electrochemical behaviors of Pd/Mm rare earth film electrodes in KOH solution

Pd/Mm(mischmetal) rare earth films were prepared by magnetron sputtering technology, the crystal structure, morphology and electrochemical behavior of the as-prepared films were investigated by using XRD, AFM and electrochemical measurement techniques including cyclic voltammetry and AC impedance. The results showed that Pd coatings is a kind of island structure with 30 - 50 nm in size. The electrochemical reduction or oxidation of hydrogen only occurred on the Pd coatings. The electrochemical impedance spectra of Pd/Mm film electrodes was composed of two semi-circles, of which the low frequency zone is corresponded to the solid diffusion process of H atom in the film, and the high one to the electrochemical reaction on the surface of the electrode. The solid diffusion process of H atom in the inner rare earth layer is the rate-controlled step.