Non-precious-metal
catalysts have been investigated as alternatives
to Pt-based oxygen reduction reaction catalysts for more than 50 years.
While the incorporation of a metal is known to be necessary to generate
a catalyst with high activity, the exact role of the metal is still
not well-understood. In this work, we prepare an active oxygen reduction
reaction catalyst containing Fe and then selectively remove the Fe
from the catalyst while preserving the carbon and nitrogen species.
By comparing the oxygen reduction reaction activity of the catalyst
before and after treatment, we show that in the absence of Fe the
carbon and nitrogen sites in the catalyst exhibit a larger overpotential
and lower selectivity for the 4e
– reduction of oxygen in both acidic and alkaline conditions. These
findings reveal the direct involvement of the metal in the active
site of non-precious-metal catalysts and provide important guidance
for future catalyst improvements.
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