In-situ electrochemical quartz crystal microbalance studies of water electrolysis at a palladium cathode

The in-situ electrochemical quartz crystal microbalance (EQCM) technique has been applied to study electrolysis of water containing 0.2 M LiClO4 at Pd cathode. Decrease in resonant frequency was observed during the electrolysis. The decrease was attributed to the mass change involving hydrogen absorption into the palladium and lithium underpotential deposition, the mechanical stress change in the electrode, and the change in roughness of the electrode surface. The stress change, which may be caused by hydrogen uptake, was estimated using palladium film-coated AT- and BT-cut quartz crystal oscillators. The surface roughness change was observed by scanning electron microscopy and a number of cracks and holes were found. Underpotential deposition of lithium was observed in propylene carbonate containing 0.1 M LiClO4 and 16 mg L-1 water. Contributions of respective factors to the total frequency change was estimated. (author)