Study on Degradation of the Pt-Ru Anode of PEFC for Residential Application (3): Interpretation of AC Impedance Analyses of MEAs and the Nature of CO Poisoning on Anode of PEFC

Proton exchange membrane fuel cells (PEMFCs) are being developed and sold commercially for multiple near term markets. Ballard Power Systems is focused on the near term markets of backup power, distributed generation, materials handling, and buses. Significant advances have been made in cost and durability of fuel cell products. Improved tolerance to a wide range of system operation and environmental noises will enable increased viability across a broad range of applications. In order to apply the most effective membrane electrode assembly (MEA) design for each market, the system requirements and associated MEA failures must be well understood. The failure modes associated with the electrodes and membrane degradation are discussed with respect to associated system operation and mitigating approaches. A few key system considerations that influence MEA design include expected fuel quality, balance-of-plant materials, time under idle or open circuit operation, and start-up and shut-down conditions.

Section: Discussionmentioning

confidence: 99%

PEMFC MEA and System Design Considerations

Knights

Rajesh

et al. 2011

“…Combined with reduced cost, durability improvement is one of the major challenges for both stationary and automotive applications (1,2). Wide adoption of fuel cell technology in the near and mid-term market will be significantly facilitated by increased fuel flexibility, including durable, efficient operation on reformed fuels (3)(4)(5)(6).…”

Section: Introductionmentioning

confidence: 99%

Impacts of Cathode Loading on Ru Crossover Related PEFC Durability

Rajesh¹,

He²,

Wessel³

et al. 2011

The use of platinum-ruthenium anode catalyst to improve tolerance of fuel cells to carbon monoxide present in reformed fuels can result in additional durability concerns, due to instability of the Ru. The degradation of Ru from PtRu/C catalyst is not only a problem for the anode but also for the cathode, as degraded Ru dissolves and crosses over to the cathode, resulting in degraded performance over the fuel cell lifetime. In the current study we investigated how the Ru crossover related performance issues is exacerbated if the cathode Pt loading is varied from 0.4 mg/cm 2 to 0.1mg/cm 2 Pt for a constant anode PtRu/C loading of 0.1 mg/cm 2 through Ballard's anode stress test protocols mimicking the anode degradation due to air-air start-up/shut-down (SU/SD). Unacceptable performance losses have been observed with lower Pt loadings in H 2 /air polarizations. The Ru crossover was systematically characterized and quantified using both electrochemical and physiochemical techniques.

“…In addition, it was clarified that the flooding in the anode affected the CO tolerance performance 3) . And, the quantitative model of CO poisoning characteristic was proposed 4) .…”

Section: Introductionmentioning

confidence: 99%

Establishment of Accelerated Degradation Method of PEFC Stacks (NEDO Project: Fundamental Research of Degradation of PEFC Stacks)

Shintaku¹,

Oomori²,

Tabata³

2008

Long-term continuous operation test under the actual operation condition in the system was carried out for more than 24,000 hrs using full-size cell stack manufactured by Sanyo Electric Corp.. Degradation tendencies of CO tolerance of anode and gas diffusivity of cathode were evaluated quantitatively by measuring the voltage drop by high concentration CO poisoning and air utilization dependence on the voltage. Accelerated degradation method concerning the gas diffusivity of cathode developed by Sanyo was verified. Accelerated magnifying power of gas diffusivity was calculated as about 2,100.