O2 reduction on graphite and nitrogen-doped graphite: Experiment and theory

by Reyimjan A. Sidik, Alfred B. Anderson, Nalini P. Subramanian, Swaminatha P. Kumaraguru, Branko N. Popov
Journal of Physical Chemistry B ()
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Abstract

An experimental and theoretical study of electroreduction of oxygen to hydrogen peroxide is presented. The experimental measurements of nitrided Ketjenblack indicated an onset potential for reduction of approximately 0.5 V (SHE) compared to the onset potential of 0.2 V observed for untreated carbon. Quantum calculations on cluster models of nitrided and un-nitrided graphite sheets show that carbon radical sites formed adjacent to substitutional N in graphite are active for O2 electroreduction to H2O2 via and adsorbed OOH intermediate. The weak catalytic effect of untreated carbon is attributed to weaker bonding of OOH to the H atom-terminated graphite edges. Substitutional N atoms that are far from graphite sheet edges will be active, and those that are close to the edges will be less active. Interference from electrochemical reduction of H atoms on the reactive sites is considered, and it is shown that in the potential range of H2O2 formation the reactive sites are not blocked by adsorbed H atoms.

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