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Title: Effect of Particle Size and Operating Conditions on Pt 3Co PEMFC Cathode Catalyst Durability

The initial performance and decay trends of polymer electrolyte membrane fuel cells (PEMFC) cathodes with Pt 3Co catalysts of three mean particle sizes (4.9 nm, 8.1 nm, and 14.8 nm) with identical Pt loadings are compared. Even though the cathode based on 4.9 nm catalyst exhibited the highest initial electrochemical surface area (ECA) and mass activity, the cathode based on 8.1 nm catalyst showed better initial performance at high currents. Owing to the low mass activity of the large particles, the initial performance of the 14.8 nm Pt3Co-based electrode was the lowest. The performance decay rate of the electrodes with the smallest Pt 3Co particle size was the highest and that of the largest Pt 3Co particle size was lowest. Interestingly, with increasing number of decay cycles (0.6 to 1.0 V, 50 mV/s), the relative improvement in performance of the cathode based on 8.1 nm Pt 3Co over the 4.9 nm Pt 3Co increased, owing to better stability of the 8.1 nm catalyst. The electron microprobe analysis (EMPA) of the decayed membrane-electrode assembly (MEA) showed that the amount of Co in the membrane was lower for the larger particles, and the platinum loss into the membrane also decreased with increasingmore » particle size. This suggests that the higher initial performance at high currents with 8.1 nm Pt 3Co could be due to lower contamination of the ionomer in the electrode. Furthermore, lower loss of Co from the catalyst with increased particle size could be one of the factors contributing to the stability of ECA and mass activity of electrodes with larger cathode catalyst particles. To delineate the impact of particle size and alloy effects, these results are compared with prior work from our research group on size effects of pure platinum catalysts. The impact of PEMFC operating conditions, including upper potential, relative humidity, and temperature on the alloy catalyst decay trends, along with the EMPA analysis of the decayed MEAs, are reported.« less
 [1] ;  [2] ;  [1] ;  [3] ;  [3] ;  [3] ;  [4] ;  [1]
  1. United Technologies Research Center, East Hartford, CT (United States)
  2. Johnson Matthey Technology Centre, Reading (United Kingdom)
  3. Univ. of Texas, Austin, TX (United States). Materials Science and Engineering Program
  4. Argonne National Lab., IL (United States)
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Additional Journal Information:
Journal Volume: 5; Journal Issue: 2; Journal ID: ISSN 2073-4344
Research Org:
Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Org:
Country of Publication:
United States
30 DIRECT ENERGY CONVERSION; Pt3Co catalyst; PEM fuel cells; in-cell performance; catalyst durability
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