Reduction of Oxygen on
Dispersed Nanocrystalline CoS<sub>2</sub>
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Abstract
The electrocatalytic properties of nanocrystalline CoS<sub>2</sub> have been investigated for the oxygen reduction reaction
(ORR) in
0.1 M HClO<sub>4</sub>. CoS<sub>2</sub> with pyrite structure was
prepared by hydrothermal synthesis and attached to a glassy carbon
electrode from solution with a mixture of carbon and Nafion. The prepared
CoS<sub>2</sub> electrode layers showed high activity toward the ORR
and very good stability under oxygen reducing conditions. Selectivity
of the ORR toward H<sub>2</sub>O<sub>2</sub> was determined by rotating
(ring) disk electrode measurements, and relatively high selectivity
was obtained with up to 80% H<sub>2</sub>O<sub>2</sub> formation around
0.4 V (vs Ag/AgCl), but this dropped to zero for potentials below
0.0 V. The amount of H<sub>2</sub>O<sub>2</sub> produced between 0.6
and 0.0 V was dependent on the quality of the CoS<sub>2</sub> dispersion
within the electrode layer, and decreasing CoS<sub>2</sub> particle
size resulted in significant improvement in the ORR electrocatalytic
activity, both by increasing the turnover frequency and through decreasing
the selectivity toward H<sub>2</sub>O<sub>2</sub> production