Beginning‐of‐lifeMEAperformance — efficiency loss contributions

Abstract

Beginning‐of‐life H 2 ‐fed fuel cell performance of membrane electrode assemblies (MEA) made using state‐of‐the‐art subcomponents (25–50 µm membranes, 47 wt% Pt on carbon, 0.15–0.4 mg cm −2 Pt cathode loading, ≤1100 equivalent weight (EW) ionomer/binder) was studied. Performance data were taken using small‐scale (50 cm 2 ) cells and a large‐scale (500 cm 2 , 22 cell) stack, and voltages were corrected for membrane resistance in order to isolate cathode polarization losses. Based on catalyst and MEA cyclic voltammetry and in‐situ testing with pure O 2 feed, we observed loading independent O 2 kinetic control up to 1.8 A cm −2 at 80 °C under fully humidified conditions; this indicates negligible effects of cathode layer proton transport limitations with pure O 2 . With air as the oxidant, we observed O 2 kinetic control below 0.2 A cm −2 and the onset of O 2 transport resistances at higher current densities. Results with helox (21% O 2 in helium) as the cathode feed revealed that the O 2 transport resistances were roughly evenly distributed between gas and solid phases. With incomplete reactant humidification, additional membrane resistance was observed and proton conductivity losses in the cathode layer became significant. Moreover, thin (25 µm) low‐equivalent weight (EW) MEAs outperformed thicker (50 µm) high EW MEAs even after correcting for membrane ohmic losses. This is due to faster water transport of the thinner low EW MEAs resulting in improved retention of cathode layer proton conductivity under dry conditions.

A Critical Review of Modeling Transport Phenomena in Polymer-Electrolyte Fuel Cells

“…Based on these component-level studies, models are developed in a simplified computational package that can be effectively used as an engineering tool, for assessment of the effects of material properties, design features, and operating conditions on PEFC performance. 26 Such models are often classified as 0-D, although they can contain more detailed descriptions of the physics from the experiments. Thus, the model is of the form [8] where η H O R is the kinetic loss from the HOR, η O R R is the kinetic loss from the ORR, η e − is the ohmic loss from electron transport, η H + is the ohmic loss from proton transport, and η tx is the mass-transport loss.…”

Nanostructuring Noble Metals as Unsupported Electrocatalysts for Polymer Electrolyte Fuel Cells

“…[87,93] In the absence of mass transport limitations, the reactivity of nanoparticles, expressed as a current density, can be described by the Butler-Volmer equation that relates current density and potential. [87,94] Looking at the mesoscale (tens of nm), the Pt-M nanoparticles are either located on the surface of carbon agglomerates [21] ; the line in (b) corresponds to an ORR activity improvement factor of 1.5. State-of-the art Pt/C and Pt alloy/C catalysts are included as benchmarks at the top of the chart and blank spaces correspond to missing data that was not provided in the references [77][78][79].…”

Evaluation of RuxWySez Catalyst as a Cathode Electrode in a Polymer Electrolyte Membrane Fuel Cell

“…The disc currents did not reach a plateau of the diffusion limited current and this is due to the small amount of catalysts (0.17 mg cm -2 ) on the thin film formed on the glassy carbon electrode, but it is clearly defined its dependency with the rotation rate. The percentage of hydrogen peroxide was evaluated from the following equation [20]:…”