New-type electrochemical oscillation caused by electrode - Surface inhomogeneity and electrical coupling as well as solution stirring through electrochemical gas evolution reaction
Y. Mukouyama et al., New-type electrochemical oscillation caused by electrode - Surface inhomogeneity and electrical coupling as well as solution stirring through electrochemical gas evolution reaction, J PHYS CH B, 105(44), 2001, pp. 10905-10911
The appearance mechanism of an electrochemical oscillation (previously call
ed oscillation B), observed for Pt electrodes in H2O2-containing acidic ele
ctrolytes in a potential region of hydrogen evolution, has been investigate
d. Though it is reported that electrochemical oscillations in general appea
r in potential regions of negative differential resistance (NDR) or hidden
NDR (HNDR), impedance analyses have shown that no NDR or HNDR is present in
the potential region of oscillation B. Besides, oscillation B is observed
only for Pt electrodes with atomically roughened surfaces, not for electrod
es with atomically flat surfaces. A possible explanation is proposed by ass
uming the presence of small local "active" areas in the electrode surface,
in which the H2O2 reduction is not prevented by a full coverage of under-po
tential deposited hydrogen, contrary to the other normal "nonactive" areas
occupying the major part of the electrode surface. The appearance of oscill
ation B is reproduced by mathematical simulation based on the model, togeth
er with the consideration of electrical coupling between the active and non
active areas as well as solution stirring by hydrogen-gas evolution. Oscill
ation B can be classified into a new category of oscillators, which may be
called "coupled NDR" oscillators.