In situ electrochemical quartz crystal microbalance studies of water electrolysis at a palladium cathode in acidic aqueous media

Abstract

The in situ electrochemical quartz crystal microbalance (in situ ECQCM) technique has been applied to study water electrolysis at Pd film-coated quartz crystal cathodes in acidic aqueous media. Cyclic voltammetry, potential-step chronoamperometry and chronopotentiometry were employed as electrochemical methods. The resonance frequency of the Pd cathode was found to decrease and increase during the reduction and oxidation processes, respectively, with concomitant changes in the potential (or current). However, it became apparent that the observed frequency change (i.e., mass change) does not correspond simply to the absorption (and the reverse process) of hydrogen into (and out of) the Pd lattice. Some possibilities (morphology change of film surfaces, stress production in the film as a result of volume expansion due to hydrogen loading, etc.) resulting in mass changes of the electrode surface are discussed. The results demonstrate that the present technique can provide fruitful information concerning water electrolysis at Pd film cathodes which involves mass changes of the electrode surface due to the adsorption-desorption as well as the absorption and the reverse process of hydrogen.