In Situ Surface-Enhanced Raman Spectroscopic Studies of Nafion Adsorption on Au and Pt Electrodes

Abstract

Understanding interactions between Nafion (perfluorosulfonic acid) and Pt catalysts is important for the development and deployment of proton exchange membrane fuel cells. However, study of such interactions is challenging and Nafion/Pt interfacial structure remains elusive. In this study, adsorption of Nafion ionomer on Au and Pt surfaces was investigated for the first time by in situ surface-enhanced Raman spectroscopy. The study is made possible by the use of uniform SiO(2)@Au core-shell particle arrays which provides very strong enhancement of Raman scattering. The high surface sensitivity offered by this approach yields insightful information on interfacial Nafion structure. Through spectral comparison of several model compounds, vibration assignments of SERS bands were made. The SER spectra suggest the direct interaction of sulfonate group with the metal surfaces, in accord with cyclic voltammetric results. Comparison of present SERS results with previous IR spectra was briefly made.

Impact of Polymer Electrolyte Membrane Degradation Products on Oxygen Reduction Reaction Activity for Platinum Electrocatalysts

“…The sulfonate anion, as mentioned previously, has been shown to effectively adsorb onto Pt surfaces under proper conditions. [44][45][46] Initial carboxylate adsorption in this case may allow the sulfonate group to reach the surface in such a way where bond formation is more preferable (in contrast to the non-adsorbing nature of the lone perfluorinated sulfonate species reported above). Secondary bonding would thus lead to less Pt sites available for molecular oxygen to adsorb.…”

“…However, there were other CV, LSV, and surface enhanced Raman spectroscopy studies that reported chemisorption of the sulfonate ion when a Nafion ionomer film was applied to a polycrystalline Pt surface. [44][45][46] It was suggested that film crystallization from the ionomer film application method enhanced the interaction between sulfonate groups and the Pt substrate. 43 Low concentrations and different structural nature (ionomer fragments in solution as opposed to an applied film) of the compound used in this study may also contribute to differences in the observations.…”

Etherification of 5‐Hydroxymethylfurfural to Biofuel Additive Catalyzed by Aquivion® PFSA Modified Mesoporous Silica

“…Whatever the Aquivion® loading, all of the characteristic bands due to PFSA resin are well‐visualized in the composites by Raman spectra after immobilization by silica (Figure ), even if the silica support is present. The Aquivion®/ m ‐SiO 2 catalysts show the typical bands for the CF 2 –CF 2 stretching mode and the skeletal C–C–C symmetric stretching mode of the backbone of the PFSA polymer . In addition, two bands associated with the CF 2 deformation mode are visualized.…”

Plasmonic Core/Satellite Heterostructure with Hierarchical Nanogaps for Raman Spectroscopy Enhanced by Shell‐Isolated Nanoparticles

“…[1][2][3][4][5][6] SERS-active substrates based on the coinage metals (Au, Ag, and Cu) provide strong enhanced Raman scattering. [9][10][11][12][13][14][15][16] A typical example would be tip-enhanced Raman spectroscopy (TERS)-a breakthrough for SERS versatility; TERS, which was fi rst introduced in 2000, involves a nanoscale gold tip above a generic substrate to achieve SERS signals. [9][10][11][12][13][14][15][16] A typical example would be tip-enhanced Raman spectroscopy (TERS)-a breakthrough for SERS versatility; TERS, which was fi rst introduced in 2000, involves a nanoscale gold tip above a generic substrate to achieve SERS signals.…”

“…[ 7,8 ] Over the past couple of decades, various SERS-active substrates have been developed through top-down and bottom-up approaches; these substrates include Ag triangular nanoprisms, Au nanoshell arrays, and Au metal tips. [9][10][11][12][13][14][15][16] A typical example would be tip-enhanced Raman spectroscopy (TERS)-a breakthrough for SERS versatility; TERS, which was fi rst introduced in 2000, involves a nanoscale gold tip above a generic substrate to achieve SERS signals. [ 11 ] Although TERS is capable of imaging a single molecule based on the strong localized plasmonic fi elds generated at the metal tip, [ 12 ] TERS spectra from a certain number of target molecules have a relatively low signal-to-noise ratio within a nanometer-sized region compared to that of conventional SERS spectra acquired from a large amount of molecules at a micrometer-sized laser spot.…”