Durability Of PEM Fuel Cells Research Articles

Oxygen Reduction at the Pt/Recast-Nafion Film Interface. Effect of the Polymer Equivalent Weight.

ORR at the interface between platinum and recast Nafion® with 1100 and 950 equivalent weights (N1100 and N950) was studied employing smooth Pt and Pt-black-covered ultramicroelectrodes. At 100% relative humidity, the diffusion coefficient and solubility of oxygen in N950 are correspondingly higher and lower than in N1100, in accordance with the smaller volume fraction occupied by the hydrophobic component in N950. The ionomer surface restructuring, where the hydrophobic component is coming into contact with Pt with an increase in ORR overpotential (1) is more significant for N950. The inhibition of ORR caused by the restructuring is dramatically reduced at Pt-black-covered electrodes, where the complex interfacial geometry obstructs molecular motions, but the higher tendency of N950 to push out the hydrophobic component is reflected in the overall smaller accessible Pt black surface area for this ionomer. The potential consequences of restructuring on PEM fuel cell durability are discussed.

PEM Fuel Cell Durability With Transportation Transient Operation

PEM fuel cell durability testing is performed with tests conducted using steady-state conditions, with dynamic conditions using power cycling simulating a vehicle drive cycle and by accelerated testing methods. The long-term performance characteristics of MEAs, Electrocatalysts and Gas Diffusion Layers (GDLs) and their impact on PEMFC durability are evaluated in terms of their associated degradation mechanisms. Testing simulating automotive drive cycles show a greater rate of particle growth than do tests in which the cell potential is held constant. The loss of electroactive Pt surface area is shown to be due primarily to the growth in platinum particle size; particle growth appears to have multiple growth mechanisms. Cathode particle size growth is dependent on temperature, relative humidity and potential. Cell performance degradation due to mass transport limitations correlates with changing hydrophobicity of GDL materials.

Mechanical endurance of polymer electrolyte membrane and PEM fuel cell durability

AbstractThe life of proton exchange membrane fuel cells (PEMFC) is currently limited by the mechanical endurance of polymer electrolyte membranes and membrane electrode assemblies (MEAs). In this paper, the authors report recent experimental and modeling work toward understanding the mechanisms of delayed mechanical failures of polymer electrolyte membranes and MEAs under relevant PEMFC operating conditions. Mechanical breach of membranes/MEAs in the form of pinholes and tears has been frequently observed after long‐term or accelerated testing of PEMFC cells/stacks. Catastrophic failure of cell/stack due to rapid gas crossover shortly follows the mechanical breach. Ex situ mechanical characterizations were performed on MEAs after being subjected to the accelerated chemical aging and relative humidity (RH) cycling tests. The results showed significant reduction of MEA ductility manifested as drastically reduced strain‐to‐failure of the chemically aged and RH‐cycled MEAs. Postmortem analysis revealed the formation and growth of mechanical defects such as cracks and crazing in the membranes and MEAs. A finite element model was used to estimate stress/strain states of an edge‐constrained MEA under rapid RH variations. Damage metrics for accelerated testing and life prediction of PEMFCs are discussed. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2346–2357, 2006

Effect of Water Activity on the Durability of PEM Fuel Cells. II. H2O2 Kinetics on Pt Alloys

not Available.

PEM Fuel Cell Durability With Transportation Transient Operation

not Available.

Effect of Water Activity on the Durability of PEM Fuel Cells. I. Hydrogen Peroxide Kinetics

not Available.

Limiting Factors in PEM Fuel Cell Durability

not Available.

Multi-scale modeling considerations for PEM fuel cell durability

not Available.