3 research outputs found
Ensemble Site Requirements for Oxidative Adsorption of Methanol and Ethanol on Pt Membrane Electrode Assemblies
No full textThe ensemble site requirements for the oxidative adsorption of
methanol and ethanol on platinum based membrane electrode assemblies
in operating liquid feed fuel cells were measured by CO stripping
voltammetry. At 30 °C and 0.2 V vs reference hydrogen electrode
(RHE), the CO<sub>ads</sub> coverage from directly dosed CO (CO<sub>CO</sub>), methanol (CO<sub>MeOH</sub>), and ethanol (CO<sub>EtOH</sub>) are 94%, 49%, and 39%, respectively. At 50 °C the CO<sub>MeOH</sub> and CO<sub>EtOH</sub> approach equality. The ratio of CO<sub>EtOH</sub>/CO<sub>MeOH</sub> was simulated with assumed ensemble site requirements
of 3 and 2 for ethanol and methanol respectively. Experimental and
simulated ratios of 0.79 and 0.78 suggest that high surface area fuel
cell Pt catalysts at 30 °C have adsorption properties similar
to that of a Pt (100) surface. Potential dependent infrared spectroscopy
of CO<sub>MeOH</sub> and CO<sub>EtOH</sub> from flash evaporated aqueous
alcohols delivered to a 50 °C fuel cell show lower CO<sub>EtOH</sub> relative to CO<sub>MeOH</sub> with Stark tuning rates below 10 cm<sup>–1</sup>/V
Ensemble Site Requirements for Oxidative Adsorption of Methanol and Ethanol on Pt Membrane Electrode Assemblies
No full textThe ensemble site requirements for the oxidative adsorption of
methanol and ethanol on platinum based membrane electrode assemblies
in operating liquid feed fuel cells were measured by CO stripping
voltammetry. At 30 °C and 0.2 V vs reference hydrogen electrode
(RHE), the CO<sub>ads</sub> coverage from directly dosed CO (CO<sub>CO</sub>), methanol (CO<sub>MeOH</sub>), and ethanol (CO<sub>EtOH</sub>) are 94%, 49%, and 39%, respectively. At 50 °C the CO<sub>MeOH</sub> and CO<sub>EtOH</sub> approach equality. The ratio of CO<sub>EtOH</sub>/CO<sub>MeOH</sub> was simulated with assumed ensemble site requirements
of 3 and 2 for ethanol and methanol respectively. Experimental and
simulated ratios of 0.79 and 0.78 suggest that high surface area fuel
cell Pt catalysts at 30 °C have adsorption properties similar
to that of a Pt (100) surface. Potential dependent infrared spectroscopy
of CO<sub>MeOH</sub> and CO<sub>EtOH</sub> from flash evaporated aqueous
alcohols delivered to a 50 °C fuel cell show lower CO<sub>EtOH</sub> relative to CO<sub>MeOH</sub> with Stark tuning rates below 10 cm<sup>–1</sup>/V
Thermal Processing as a Means to Prepare Durable, Submicron Thickness Ionomer Films for Study by Transmission Infrared Spectroscopy
No full textA high temperature solution processing method was adapted
to prepare
durable, freestanding, submicrometer thickness films for transmission
infrared spectroscopy studies of ionomer membrane. The materials retain
structural integrity following cleaning and ion-exchange steps in
boiling solutions, similar to a commercial fuel cell membrane. Unlike
commercial membrane, which typically has thicknesses of >25 μm,
the structural properties of the submicrometer thickness materials
can be probed in mid-infrared spectral measurements with the use of
transmission sampling. Relative to the infrared attenuated total reflection
(ATR) technique, transmission measurements can sample ionomer membrane
materials more uniformly and suffer less distortion from optical effects.
Spectra are reported for thermally processed Nafion and related perfluoroalkyl
ionomer materials containing phosphonate and phosphinate moieties
substituted for the sulfonate end group on the side chain. Band assignments
for complex or unexpected features are aided by density functional
theory (DFT) calculations
