Importance of Acid–Base Equilibrium in Electrocatalytic Oxidation of Formic Acid on Platinum

Jiyong Joo, Taro Uchida, Angel Cuesta, Marc T. M. Koper, Masatoshi Osawa

Research output: Contribution to journalArticle

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Abstract

Electro-oxidation of formic acid on Pt in acid is one of the most fundamental model reactions in electrocatalysis. However, its reaction mechanism is still a matter of strong debate. Two different mechanisms, bridge-bonded adsorbed formate mechanism and direct HCOOH oxidation mechanism, have been proposed by assuming a priori that formic acid is the major reactant. Through systematic examination of the reaction over a wide pH range (0–12) by cyclic voltammetry and surface-enhanced infrared spectroscopy, we show that the formate ion is the major reactant over the whole pH range examined, even in strong acid. The performance of the reaction is maximal at a pH close to the pKa of formic acid. The experimental results are reasonably explained by a new mechanism in which formate ion is directly oxidized via a weakly adsorbed formate precursor. The reaction serves as a generic example illustrating the importance of pH variation in catalytic proton-coupled electron-transfer reactions.
Original languageEnglish
Pages (from-to)9991-9994
Number of pages4
JournalJournal of the American Chemical Society
Volume135
Issue number27
Early online date28 Jun 2013
DOIs
Publication statusPublished - 10 Jul 2013

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formic acid
Formic acid
Platinum
Oxidation
Electrocatalysis
Acids
Electrooxidation
Ions
Cyclic voltammetry
Infrared spectroscopy
Protons
Electrons

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Importance of Acid–Base Equilibrium in Electrocatalytic Oxidation of Formic Acid on Platinum. / Joo, Jiyong; Uchida, Taro; Cuesta, Angel; Koper, Marc T. M.; Osawa, Masatoshi.

In: Journal of the American Chemical Society, Vol. 135, No. 27, 10.07.2013, p. 9991-9994.

Research output: Contribution to journalArticle

Joo, Jiyong ; Uchida, Taro ; Cuesta, Angel ; Koper, Marc T. M. ; Osawa, Masatoshi. / Importance of Acid–Base Equilibrium in Electrocatalytic Oxidation of Formic Acid on Platinum. In: Journal of the American Chemical Society. 2013 ; Vol. 135, No. 27. pp. 9991-9994.
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abstract = "Electro-oxidation of formic acid on Pt in acid is one of the most fundamental model reactions in electrocatalysis. However, its reaction mechanism is still a matter of strong debate. Two different mechanisms, bridge-bonded adsorbed formate mechanism and direct HCOOH oxidation mechanism, have been proposed by assuming a priori that formic acid is the major reactant. Through systematic examination of the reaction over a wide pH range (0–12) by cyclic voltammetry and surface-enhanced infrared spectroscopy, we show that the formate ion is the major reactant over the whole pH range examined, even in strong acid. The performance of the reaction is maximal at a pH close to the pKa of formic acid. The experimental results are reasonably explained by a new mechanism in which formate ion is directly oxidized via a weakly adsorbed formate precursor. The reaction serves as a generic example illustrating the importance of pH variation in catalytic proton-coupled electron-transfer reactions.",
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note = "This work was supported by Japanese Society for the Promotion of Science (JSPS) KAKENHI Grants Nos. 24550143 and 24750117 and MEXT Project of Integrated Research on Chemical Synthesis. M.T.M.K. gratefully acknowledges the award of Long-Term Fellowship of JSPS (No. L-11527) and Visiting Professorship of Hokkaido University. T.U. acknowledges Grants-in-Aid for Regional R&D Proposal-Based Program from Northern Advancement Center for Science & Technology of Hokkaido, Japan. J.J. acknowledges scholarship of Asian Graduate School, Hokkaido University.",
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N2 - Electro-oxidation of formic acid on Pt in acid is one of the most fundamental model reactions in electrocatalysis. However, its reaction mechanism is still a matter of strong debate. Two different mechanisms, bridge-bonded adsorbed formate mechanism and direct HCOOH oxidation mechanism, have been proposed by assuming a priori that formic acid is the major reactant. Through systematic examination of the reaction over a wide pH range (0–12) by cyclic voltammetry and surface-enhanced infrared spectroscopy, we show that the formate ion is the major reactant over the whole pH range examined, even in strong acid. The performance of the reaction is maximal at a pH close to the pKa of formic acid. The experimental results are reasonably explained by a new mechanism in which formate ion is directly oxidized via a weakly adsorbed formate precursor. The reaction serves as a generic example illustrating the importance of pH variation in catalytic proton-coupled electron-transfer reactions.

AB - Electro-oxidation of formic acid on Pt in acid is one of the most fundamental model reactions in electrocatalysis. However, its reaction mechanism is still a matter of strong debate. Two different mechanisms, bridge-bonded adsorbed formate mechanism and direct HCOOH oxidation mechanism, have been proposed by assuming a priori that formic acid is the major reactant. Through systematic examination of the reaction over a wide pH range (0–12) by cyclic voltammetry and surface-enhanced infrared spectroscopy, we show that the formate ion is the major reactant over the whole pH range examined, even in strong acid. The performance of the reaction is maximal at a pH close to the pKa of formic acid. The experimental results are reasonably explained by a new mechanism in which formate ion is directly oxidized via a weakly adsorbed formate precursor. The reaction serves as a generic example illustrating the importance of pH variation in catalytic proton-coupled electron-transfer reactions.

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