Early Stages during the Oxidation of HCOOH on Single-Crystal Pt Electrodes As Characterized by Infrared Spectroscopy

Abstract

Spectral data for HCOOH oxidation at Pt(111), Pt(100), and Pt(110) are presented and discussed. Spectra were taken shortly after the surfaces were contacted with a 0.1 M HCOOH/0.1 M HClO4 solution at a controlled potential of 0.05 V vs RHE and give information on the adsorption and oxidation processes at the early stages. The formation of on top and bridging CO on Pt(111) and Pt(100) is followed as a function of potential. Conversion of bridging into on top CO is observed at the Pt(100) surface in the low-potential region, while the parallel formation of both forms of adsorbed CO occurs at Pt(111) in the 0.1−0.4 V potential range. Only terminal CO is formed at Pt(110), this surface being the one presenting the highest level of poisoning at the initial potential. Very high values of the initial slopes of ν−E plots are observed for Pt(111) and Pt(100), which are rationalized in terms of lateral coupling due to adsorption in patches giving rise to high local coverages.

Langmuir−Blodgett Thin Films of Fe20Pt80 Nanoparticles for the Electrocatalytic Oxidation of Formic Acid

“…In this report, Fe 20 Pt 80 particle layers of varied thickness were prepared by the LB technique and the corresponding electrocatalytic activities for the oxidation of formic acid in an acidic electrolyte were examined by voltammetry and EIS. The voltammetric responses exhibited rather drastic variation with the particle layer thickness.…”

“…In the last decades, the mechanism of formic acid electro-oxidation on Pt and Pt-based alloys has been investigated extensively, and it is generally accepted that formic acid is oxidized to CO 2 via the so-called dual-pathway mechanism. [33][34][35] For Pt-based alloys (PtM), formic acid can be oxidized to CO 2 by the direct pathway, Alternatively, in the indirect pathway, HCOOH first reacts to form poisonous CO intermediate, which is then oxidized to CO 2 , In both cases, the overall reaction is It has been found in our previous study 25 that from the onset potential and current densities, dropcast films of Fe 20 Pt 80 nanoparticles exhibit very good electrocatalytic activities for HCOOH oxidation as compared to Pt and other metal alloys. [33][34][35] However, from the voltammetric currents of HCOOH oxidation in the positive and negative scans, the particles are found to be heavily poisoned by adsorbed CO species.…”

“…Oleic acid (0.5 mmol), oleyl amine (0.5 mmol), and Fe(CO) 5 (1.0 mmol) were added, and the mixture was heated to reflux (297°C) for 30 min. (Note: N 2 was kept flowing through the reaction system to ensure the Pt-rich Fe 20 Pt 80 nanoparticles were formed. This was different from the previous synthesis in which the reaction was run under a blanket of N 2 .)…”

“…Using formic acid as a model fuel, we have carried out an earlier study with a dropcast thick film of Fe 20 Pt 80 nanoparticles (average diameter ∼3 nm) and found that the particles exhibited very good electrocatalytic activities for formic acid electrooxidation, 25 as compared to Pt and other metal alloys. This was motivated, in part, by the fact that aqueous solutions of formic acid have been found to be an attractive potential fuel because of the ease of their handling, transportation, and storage in comparison to hydrogen.…”

Kinetic Study of the Formic Acid Oxidation on Steady State Using a Flow Cell

“…[2][3][4][5][6][7][8][9][10][11][12] There are some studies that have also used chronoamperometric measurements, 7-11,16 dynamic electrochemical impedance spectroscopy 17,18 and hydrodynamic impedance spectroscopy. 19 In the latter case, a no significant mass transfer effect was reported in the voltammetric anodic peak.…”