Abstract
The electrocatalytic oxidation of formic acid (HCOOH) and formate (HCOO−) to CO2 on platinum has been studied over a wide range of pH (0–12) by surface-enhanced infrared absorption spectroscopy (SEIRAS) coupled with cyclic voltammetry. The peak current of HCOOH/HCOO− oxidation exhibits a volcano-shaped pH dependence peaked at a pH close to the pKa of HCOOH (3.75). The experimental result is reasonably explained by a simple kinetic model that HCOO− oxidation is the dominant reaction route over the whole pH range. HCOOH is oxidized after being converted to HCOO− via the acid-base equilibrium. The ascending part of the volcano plot at pH < 4 is ascribed mostly to the increase of the molar ratio of HCOO−, while the descending part at pH > 4 is ascribed to the suppression of HCOO− oxidation by adsorbed OH or oxidation of the electrode surface. In acidic media, HCOOH is adsorbed on the electrode as formate with a bridge-bonded configuration. The bridge-bonded adsorbed formate is stable and suppresses HCOO− oxidation by blocking active site. However, the suppression is not fatal because bridge-bonded adsorbed formate enhances the oxidation of HCOO− at high potential by suppressing the adsorption of OH or surface oxidation. The complex cyclic voltammograms for HCOOH/HCOO− oxidation also can be well interpreted in terms of the simple kinetic model. The experimental results presented here serve as a generic example illustrating the importance of pH variations in catalytic proton-coupled electron transfer reactions.
Original language | English |
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Pages (from-to) | 127-136 |
Number of pages | 10 |
Journal | Electrochimica Acta |
Volume | 129 |
Early online date | 25 Feb 2014 |
DOIs | |
Publication status | Published - 20 May 2014 |
Keywords
- electrocatalysis
- formic acid
- oxidation
- platinum
- infrared spectroscopy
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Dive into the research topics of 'The effect of pH on the electrocatalytic oxidation of formic acid/formate on platinum: A mechanistic study by surface-enhanced infrared absorption spectroscopy coupled with cyclic voltammetry'. Together they form a unique fingerprint.Profiles
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Angel Cuesta Ciscar
- School of Natural & Computing Sciences, Chemistry - Personal Chair
- Centre for Energy Transition
Person: Staff, Academic