In situ surface-enhanced Raman spectroscopic study of formic acid electrooxidation on spontaneously deposited platinum on gold

Abstract

Present formic acid fuel cell efficiency is limited by low kinetics at the anode, indicating the need for effective catalysts to improve the formic acid oxidation. As a prerequisite, the nature of adsorbed species and specifically the reaction intermediates formed in this process needs to be examined. This work focuses on the electrooxidation of formic acid and the nature of the intermediates at a platinum-modified gold surface prepared through spontaneous deposition using a combination of electrochemistry and in situ surface enhanced Raman spectroscopy (SERS). This Pt-modified gold electrode surface assists in oxidizing formic acid at potentials as low as 0.0 V vs. Ag/AgCl which is 0.15 V more negative than a bare Pt surface. The oxidation current obtained on the Pt-modified gold electrode is 72 times higher than on a bare Au surface and 5 times higher than on a bare Pt surface at the same potential. In situ SERS has revealed the involvement of formate at a low frequency as the primary intermediate in this electrooxidation process. While previous studies mainly focused on the formate mode at ca. 1322 cm(-1), it is the first time that a formate peak at ca. 300 cm(-1) was observed on a Pt or Pt-associated surface. A unique relationship has been observed between the formic acid oxidation currents and the SERS intensity of this formate adsorbate. Furthermore, the characteristic Stark effect of the formate proves the strong interaction between the adsorbate and the catalyst. Both electrochemical and spectroscopic results suggest that the formic acid electrooxidation takes place by the dehydrogenation pathway involving a low frequency formate intermediate on the Pt-modified gold electrode catalyst.

Insights into the Electrooxidation of Formic Acid on Pt and Pd Shells on Au Core Surfaces via SERS at Dendritic Au Rod Electrodes

“…Recently, Au-core Pd-shell Pt-cluster nanoparticles for enhanced electrocatalytic activity for FA electrooxidation were reported . It is necessary to elucidate the reaction mechanism of the electrooxidation of FA in order to develop highly active electrocatalytic electrode systems; however, the detailed mechanism is still unclear. ,, We performed the in-situ electrochemical SERS measurements for FA oxidation on DAR@Pt and DAR@Pd surfaces. Because these two electrodes had the same nanostructures, it was possible to elucidate the different spectroelectrochemical behaviors during FA oxidation on the Pt and Pd surfaces with same morphologies.…”

Recent Advances in Anode Electrocatalysts for Direct Formic Acid Fuel Cells – Part I – Fundamentals and Pd Based Catalysts

“…The direct pathway is generally preferred because it takes place at a lower potential and also a complete absence of any deactivation of the catalysts. The formation of HCOOad is the main intermediate that leads to mainly the direct pathway and indeed formate has been identified by in in situ surface enhanced Raman spectroscopy (SERS) as reported [49] …”

In situ surface enhanced Raman spectroscopy study of electrode–polyelectrolyte interfaces

“…6 that several Raman peaks obviously depend on the scanning potential, indicating that they were generated from the Pt-H 2 SO 4 (aq) interface, where the potential matters. The broad peak at 580 cm À1 is attributed to the Pt-O stretching mode, 19,20 which starts to appear at 1.2 V during Fig. 5 The CV curves obtained for the in situ Raman test device at a scanning rate of 50 mV s À1 with the electrodes of the SPEs not immersed in the solution or UP water but covered with a thin layer of the solution or UP water.…”