In this work, the role of hydroxyl compounds during the anomalous NiFe elec
trodeposition is reinvestigated. It is found that the manner in which the b
oundary conditions are incorporated in existing NiFe models that lire based
on the chemical equilibrium of species in solution, is not correct and lea
ds to unphysical situations. In order to alleviate this problem, a kinetic
description of the homogeneous reactions in the solution is used to calcula
te the concentration profiles of the ionic species near electrodes. This sh
ows that even the fastest chemical reactions are nor in chemical equilibriu
m in the vicinity of the electrode. Also, the amount of generated hydroxyl
ions during proton reduction and hence the extent to which metal ions are h
ydrolyzed, is far less than assumed in existing models. This result is conf
irmed experimentally by polarization measurements. It is shown that the Ni-
H-2 and Fe-H-2 systems exhibit anomalous codeposition behavior as well and
that inhibition of the Ni and H reduction in the Ni-Fe-H-2 system cannot be
explained in terms of metal hydrolysis reactions. Therefore. it is conclud
ed from both the theoretical calculations and the experimental findings, th
at metal hydrolysis does not play a determining role in anomalous NiFe code
position. (C) 2000 The Electrochemical Society. S0013-4651(00)01-010-7. All
rights reserved.