The 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 ads coverage from directly dosed CO (CO CO ), methanol (CO MeOH ), and ethanol (CO EtOH ) are 94%, 49%, and 39%, respectively. At 50 °C the CO MeOH and CO EtOH approach equality. The ratio of CO EtOH /CO MeOH 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 MeOH and CO EtOH from flash evaporated aqueous alcohols delivered to a 50 °C fuel cell show lower CO EtOH relative to CO MeOH with Stark tuning rates below 10 cm −1 /V.
Operando
high-throughput evaluation of heterogeneous catalysts
by laser-activated membrane introduction mass spectrometry (LAMIMS)
elucidates the Pt loading dependence of methylcyclohexane dehydrogenation
on platinized γ-alumina beads. A CO2 marking laser
rapidly and sequentially heats catalyst beads positioned on a heat-dissipating
carbon paper support that overlays a silicone membrane, separating
the bead library reaction zone from a quadrupole mass analyzer. The
toluene m/z peak varies logarithmically
with Pt loading, suggesting that reactivity includes factors that
are negatively correlated to Pt loading. These factors may include
the Pt/γ-Al2O3 surface interfacial region
as one component of a heterogeneous catalytically active surface area/mass.
This work demonstrates LAMIMS as a broadly applicable high-throughput
operando screening method for heterogeneous catalysts.
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