Hydrogen Mass Transport in Fuel Cell Gas Diffusion Electrodes

Several experimental methods were used to identify the cause of the concurrent increase in kinetic and mass transfer overpotentials during the contamination of proton exchange membrane fuel cells outfitted with a commercially relevant cathode catalyst loading of 0.1 mg Pt per cm2. Neutron images demonstrated that the transport of liquid water through gas diffusion electrode materials was subtly affected by the presence of propene and methyl methacrylate in air at ppm levels (25 to 100 ppm propene, 12.5 to 50 ppm methyl methacrylate). Multioxidant polarization curves were obtained to isolate overpotentials (O2, 21% O2 + 79% He, and air). For all cases, neat air, 50 ppm propene in air, and 25 ppm methyl methacrylate in air, only kinetic and mass transfer overpotentials increased (O2 reduction on a Pt supported on C catalyst, O2 diffusion through the catalyst layer ionomer). Also, only the O2 mass transfer coefficient associated with diffusion in the catalyst layer ionomer increased in the presence of 50 ppm propene and 25 ppm methyl methacrylate. Contaminant species adsorbed on the catalyst decrease the active surface area and increase both the real current density and the O2 reduction kinetic overpotential. The smaller active surface area also brings the real current density closer to the limiting value, inducing an increase of the mass transfer overpotential connected with O2 movement in the ionomer layer covering the catalyst. This mechanism was supported by a mathematical contamination model focused on contaminant and O2 processes on the catalyst surface (adsorption, reaction, desorption).

show abstract

“…The p r / RTf term in eq is the inlet O 2 concentration c for a dilute oxidant stream . The combination of eqs and with eq yields …”

Section: Resultsmentioning

confidence: 99%

Contamination Mechanisms of Proton Exchange Membrane Fuel Cells - Mass Transfer Overpotential Origin

et al. 2020

View full text Add to dashboard Cite

show abstract

“…2) or ionomer phase (12). Generality is conserved by using a mass transport coefficient (13,14) for a gas/liquid phase rds: Figure 2. Mole fractions in gas/liquid and ionomer phases after contamination initiation and before a steady state is reached.…”

Section: Model Assumptionsmentioning

confidence: 99%

PEMFC Contamination Model: Neutral Species Sorption by Ionomer

St‐Pierre

2011

ECS Trans.

View full text Add to dashboard Cite

A mathematical and transient model was developed for the case of a neutral species penetrating an ionomer. It is assumed that transport in the gas or liquid water phases is rate determining. A limited number of equations are used to ensure that the model has an analytic solution. These equations include Fick's first law, a distribution of the neutral species between the gas/liquid phases and the ionomer phase described by a separation factor, a neutral species in the ionomer mass balance, an empirical relationship between the ionomer conductivity and the equivalent foreign neutral species mole fraction in the ionomer phase, and a cell voltage balance. Both separation factor and conductivity relations were experimentally validated. The model solution shows that the dimensionless current density reaches a steady state, recovery is eventually complete after removing the contaminant source, and, contamination and recovery time scales are equal.

show abstract

“…The continuous stirred tank reactor proposed in (1) also given previously does not apply here because in this work gas was transported through the cell in flow channels and not a plenum. The model proposed by Angelo et al (7) was similar to that previously proposed in (9) except that in (7) constant volumetric flow rate was assumed. The models in (7) and (9), however, did not account for different catalyst loadings or for the flow rate of all diluents when determining the mass transport coefficient.…”

Section: Introductionmentioning

confidence: 99%

Calculating Hydrogen Mass Transport Coefficients in a PEMFC at Different Operating Conditions Using a Hydrogen Pump Configuration

2013

View full text Add to dashboard Cite

A proton exchange membrane fuel cell system (PEMFCS) operated electroytically at its limiting current was proposed previously as a technology to separate H 2 and He through the electrochemical oxidation of H 2 . In this work the fraction of H 2 remaining in the effluent of two different sized PEMFCs with different flow field designs was studied at several operating conditions which included different: system temperatures, inlet relative humidity (R.H.), and system pressures to determine the most efficient operating condition. Experiments were performed at a fixed dry gas flow rate with an inlet H 2 dry gas fraction of 10 %. System performance was found to depend significantly on operating conditions with optimum performance attained at 60 ºC and 100 % R.H. for both system sizes. To assist in the performance modeling of each system a differential chemical reactor model was used to determine H 2 mass transport coefficients at each operating condition.

show abstract

Hydrogen Mass Transport in Fuel Cell Gas Diffusion Electrodes

Cited by 17 publications

References 41 publications

Contamination Mechanisms of Proton Exchange Membrane Fuel Cells - Mass Transfer Overpotential Origin

Contamination Mechanisms of Proton Exchange Membrane Fuel Cells - Mass Transfer Overpotential Origin

PEMFC Contamination Model: Neutral Species Sorption by Ionomer

Calculating Hydrogen Mass Transport Coefficients in a PEMFC at Different Operating Conditions Using a Hydrogen Pump Configuration

Contact Info

Product

Resources

About