In Situ 50°C FTIR Spectroscopy of Pt and PtRu Direct Methanol Fuel Cell Membrane Electrode Assembly Anodes

Abstract

A tandem surface-transmission Fourier transform infrared (FTIR) method permits the simultaneous investigation of adsorbed and desorbed species formed at the electrode surface of direct methanol fuel cell (DMFC) membrane electrode assemblies (MEAs). Potential dependent, in situ specular reflectance spectra and on-line transmission FTIR spectroscopy of adsorbed and desorbed species on working fuel cell electrode surfaces, confirm that linear bound CO, the primary intermediate on unsupported Pt and PtRu surfaces of fuel cell MEAs, have lower Stark tuning rates than the corresponding on arc-melted alloys. Two peaks corresponding to CO stretching modes were observed on a PtRu fuel cell anode surface prepared with Johnson Matthey catalysts. The higher frequency peak is ascribed to a Pt-rich alloy and the low frequency peak is ascribed to either pure Ru or an Ru-rich phase. The tandem technique confirms that a peak easily misassigned as a linear bound CO stretching mode false(2083 cm−1false) is a methanol overtone peak. In addition to CO2, methylformate is a major product of a gas fed DMFC, which is detected at the anode exhaust by on-line FTIR. © 2002 The Electrochemical Society. All rights reserved.

Vibrational Spectroscopy for the Characterization of PEM Fuel Cell Membrane Materials

“…In addition, studies that provide more detailed knowledge of vibrational mode assignments, such as those that combine computational methods and spectral measurements on model compounds [51], should continue, as they enable greater understanding to be derived from infrared spectra in relation to structure and function in PEM materials. Further use and development of in situ infrared methods for probing membrane-catalyst interactions in operating fuel cells [23,32,33] and on electrodes [21,22] would also be valuable.…”

“…Compared to in situ diffuse reflectance infrared sampling [23,32,33], Raman measurements can be less invasive. To develop the full potential of Raman spectroscopy for the study of fuel cell membrane materials, there is a need for greater access to instruments with sources that effectively reduce background fluorescence.…”

“…The sections below discuss the development of strategies for infrared transmission and ATR sampling of PEM materials. Also mentioned are more specialized approaches that include in situ techniques for probing membrane-electrode assemblies [21][22][23], Raman measurements [17,24], and ultrafast infrared vibrational lifetime measurements [25].…”

“…Smotkin and coworkers pioneered an approach for obtaining infrared spectra from membrane electrode assemblies (MEAs) in operating fuel cells [23,32,33]. A thermostatted single fuel cell was modified to accommodate an infrared transparent window ( Fig.…”

“…Diffuse reflectance optics are used to collect radiation emitted from the MEA. The researchers have used the cell mainly to investigate reactions over Pt and Pt alloy anode catalysts during direct methanol fuel cell operation [23,[32][33][34][35]. While studies have focused on the observation of spectral bands arising from methanol oxidation byproducts, the system also provides a means to probe the membrane-catalyst-gas three-phase boundary [34].…”