Issue 31, 2010

Effects of p-substituents on electrochemical COoxidation by Rh porphyrin-based catalysts

Abstract

Electrochemical CO oxidation by several carbon-supported rhodium tetraphenylporphyrins with systematically varied meso-substituents was investigated. A quantitative analysis revealed that the p-substituents on the meso-phenyl groups significantly affected CO oxidation activity. The electrocatalytic reaction was characterized in detail based on the spectroscopic and X-ray structural results as well as electrochemical analyses. The difference in the activity among Rh pophyrins is discussed in terms of the properties of p-substituents along with a proposed reaction mechanism. Rhodium tetrakis(4-carboxyphenyl)porphyrin (Rh(TCPP)), which exhibited the highest activity among the porphyrins tested, oxidized CO at a high rate at much lower potentials (<0.1 V vs. a reversible hydrogen electrode, at 60 °C) than the present PtRu catalysts. This means that CO is electrochemically oxidized by this catalyst when a slight overpotential is applied during the operation of a proton exchange membrane fuel cell. This catalyst exhibited little H2 oxidation activity, in contrast to Pt-based catalysts.

Graphical abstract: Effects of p-substituents on electrochemical CO oxidation by Rh porphyrin-based catalysts

Associated articles

Supplementary files

Article information

Article type
Paper
Submitted
02 Dec 2009
Accepted
12 Apr 2010
First published
07 Jun 2010

Phys. Chem. Chem. Phys., 2010,12, 8968-8976

Effects of p-substituents on electrochemical CO oxidation by Rh porphyrin-based catalysts

S. Yamazaki, Y. Yamada, S. Takeda, M. Goto, T. Ioroi, Z. Siroma and K. Yasuda, Phys. Chem. Chem. Phys., 2010, 12, 8968 DOI: 10.1039/B925413G

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