A quartz crystal microbalance study on a metallic nickel electrode

Electrochemical processes taking place on a Ni electrode have been investigated with the electrochemical quartz crystal microbalance. At potentials negative of ca. −500 mV vs. SCE, a closed frequency loop is observed without irreversible changes in the mass of the electrode. The phase transition α- → β-Ni(OH)2, taking place at potentials positive to −500 mV vs. SCE, is accompanied by an irreversible increase in the mass of the electrode. When Ni(OH)2 is further oxidized, the frequency increase is followed by a decrease, indicating the transport of various species in both directions, i.e. from and into the electrode. During the Ni(OH)2 oxidation reaction the transport of species responsible for the mass increase is slower than the charge transfer process.