Cc. Streinz et al., THE EFFECT OF TEMPERATURE AND ETHANOL ON THE DEPOSITION OF NICKEL-HYDROXIDE FILMS, Journal of the Electrochemical Society, 142(12), 1995, pp. 4051-4056
The objective of this work was to determine the effect of the temperat
ure and the ethanol content of the Ni(NO3)(2) solution on: (i) the eff
iciency of electrochemical deposition of nickel hydroxide; and (ii) th
e molecular weight of the deposited film. An electrochemical quartz cr
ystal nanobalance (EQCN) was used to measure the mass of films electro
chemically deposited from Ni(NO3)(2) solutions and constant current di
scharges were used to determine the electrochemical capacity of the fi
lms. The data indicates that increasing the temperature increases both
the efficiency of the deposition reaction and the molecular weight of
the deposited film. The increased efficiency at higher temperatures i
s attributed to a decrease in the concentration of a nickel complex at
the surface of the electrode. The lower complex concentration decreas
es the diffusion rate of this species away from the electrode surface
and hence increases the rate at which the complex precipitates from th
e solution. The increase in the molecular weight at higher temperature
is attributed to a combination of increased rate of deposition and an
increase in the lattice spacing of the active material. The data also
indicate that increasing the ethanol content of the solution had no n
oticeable effect on the efficiency of deposition, when water was prese
nt. In pure ethanol, however, the chemistry of deposition seemed to ch
ange considerably. However, increasing the ethanol content of the solu
tion resulted in an increase of the molecular weight of the film. Incr
ease in the molecular weight with an increase in the ethanol content o
f the solution is due to an increase in the relative percentage of eth
anol incorporated in the active material. The data also indicate that
the number of electrons in the discharge reaction is approximately 1.4
electrons per nickel atom.