Also,
further oxidation of thiourea could produce sulfate,
which was confirmed by the formation of
white precipitates after the addition of Ba2 fol-
lowing extensive oxidation 14. For the negative
scan, the current was largely suppressed in the
potential range for the reduction of oxygen. It can
be deduced that the adsorption of thiourea itself
or oxidation products formed in the positive scan
prohibit the reduction of oxygen