V. Hermann et al., Mechanistic studies of oxygen reduction at La0.6Ca0.4CoO3-activated carbonelectrodes in a channel flow cell, ELECTR ACT, 46(2-3), 2000, pp. 365-372
The mechanism of the oxygen reduction reaction (orr) was studied in alkalin
e media at La0.6Ca0.4CoO3-activated carbon electrodes in a channel flow cel
l (CFC). The electrodes were made by depositing a mixture of the perovskite
(La0.6Ca0.4CoO3) powder as the catalyst, Vulcan XC 72 as the carbon, and T
riton X-100 as the binder on Ti substrates. The collection efficiency, N, o
f the double-electrode system in the CFC was evaluated in advance using the
ferro-ferricyanide couple. The results obtained for the ori show that the
mean number of electrons transferred per O-2 molecule, n(g), remains around
2, while the ratio k(1)/k(2) (the rate constants for direct reduction to O
H- and indirect reduction to HO2-) is much smaller than 1, both at nonactiv
ated and perovskite-activated carbon electrodes. This indicates that most o
f the oxygen was reduced via the two-electron pathway to HO2-. The hydrogen
peroxide ions appear to be stable at Vulcan, but are further reduced and/o
r chemically decomposed in part in the presence of the metal-oxide catalyst
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