O2 Reduction on Graphite and Nitrogen-Doped Graphite:  Experiment and Theory

• Published in: The journal of physical chemistry. B 2006-02, Vol.110 (4), p.1787-1793
• Main Authors: Sidik, Reyimjan A, Anderson, Alfred B, Subramanian, Nalini P, Kumaraguru, Swaminatha P, Popov, Branko N
• Format: Article
• Language: English
• ISSN: 1520-6106; 1520-5207
• DOI: 10.1021/jp055150g

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.