A cyclic voltammogram of 1,4-benzoquinone showed a couple of redox waves in
aqueous solution. Upon adding a trace amount of silver ion, the cyclic vol
tammogram exhibited an anomalous behavior: a shift of the reduction peak to
ward a negative potential and the appearance of a new re-oxidation peak at
a much more positive potential. This anomalous electrochemical behavior was
investigated in terms of both interactions in bulk and on the electrode su
rface using some kinds of metal-ion additives and some working-electrode ma
terials. It is suggested that the underpotential deposition of silver ion i
s primarily responsible for the anomalous electrochemical behavior of 1,4-b
enzoquinone. This was demonstrated by a measurement of cyclic voltammograms
using a silver-deposited electrode at an underpotential.