Yb. Mo et al., IN-SITU QUARTZ-CRYSTAL MICROBALANCE STUDIES OF NICKEL HYDROUS OXIDE-FILMS IN ALKALINE ELECTROLYTES, Journal of the Electrochemical Society, 143(1), 1996, pp. 37-43
The microgravimetric characteristics of electrodeposited nickel and co
mposite Ni/Co hydrous oxide films on Au electrodes in KOH electrolytes
were examined in situ with a combination of quartz crystal microbalan
ce (QCM) and voltammetric techniques. In the case of freshly prepared
alpha-Ni(OH)(2) hydrous oxide films, denoted as alpha-Ni(OH)(2)(hyd),
the mass increased during oxidation and then decreased upon subsequent
reduction. As the redox cycling was continued, however, this behavior
gradually reversed, i.e., the mass decreased upon oxidation and then
increased following further reduction. This unique effect could be cor
related with a shift in the position of the oxidation peak maximum (E(
p)(ox)) in the voltammogram toward more positive potentials, which has
been ascribed to the transformation of alpha-Ni(OH)(2)(hyd) into beta
-Ni(OH)(2)(hyd). Based on these findings, it can be concluded that the
mechanism of ionic charge transport in these two types of lattices is
markedly different. In contrast, composite Ni/Co (9:1) hydrous oxide
films displayed qualitatively the same behavior as pure freshly prepar
ed Ni(OH)(2)(hyd) in the same alkaline media regardless of the extent
of cycling. This observation provides evidence that the incorporation
of cobalt into Ni(OH)(2)(hyd) modifies the structural properties of th
e lattice during the oxidation/reduction process.