Abstract:
The oxygen reduction reaction (ORR) in low temperature fuel cells limits the obtainable output triggering
the necessity of screening the employable catalysts precisely. A nitrogen-containing carbon sphere
(NCS) catalyst was synthesized using a soft template and was studied for the oxygen reduction reaction.
The NCS catalyst was shown to have superior activity with an onset potential of 0.985 V (vs. RHE) and
a diffusion-limited current density of 6.16 mA cm 2
. The kinetic insight from the rotating disk electrode
(RDE) and rotating ring-disk electrode (RRDE) revealed an overall 4e reduction by a (2 + 2) electron
pathway with a rate constant of 4.6 10 4 cm s 1 at the onset potential. A fast screening of the
localized electrochemical activity using sample generation-tip collection (SG-TC) in combination with
a chronoamperometric multiple pulse technique was applied in the present study to trace the formation,
evolution and conversion of intermediate species using a Pt ultramicroelectrode. The local catalytic
activity of the NCS catalyst was successfully visualized by scanning electrochemical microscopy (SECM)
in highly alkaline medium.
