Research ArticleELECTROCHEMISTRY

Critical advancements in achieving high power and stable nonprecious metal catalyst–based MEAs for real-world proton exchange membrane fuel cell applications

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Science Advances  23 Mar 2018:
Vol. 4, no. 3, eaar7180
DOI: 10.1126/sciadv.aar7180
  • Fig. 1 Polarization analysis obtained under air and oxygen for MEAs prepared from the three different catalyst loadings.

    Polarization curves obtained under (A) air and (B) O2 at 100% relative humidity (RH) (anode/cathode). (C) Kinetic overpotential (assuming Butler-Volmer kinetics) for the three different catalyst loadings.

  • Fig. 2 Polarization and performance curves obtained under air or O2.

    Performance obtained under (A) air and (B) O2 for the 4.0-mg/cm2 CCL design with 35 or 40 wt % ionomer. (C) Performance (corrected for ohmic losses) obtained under O2 (inset shows performance achieved at 0.044 A/cm2).

  • Fig. 3 Stability of the three catalyst loadings during galvanostatic experiments at 0.5 A/cm2.

    The stability test was performed under air/H2, 100% RH (cathode/anode). (A) The performance at 0.5 A/cm2 is normalized to the beginning-of-test (BOT) performance at 0.5 A/cm2. (B) Absolute differences in BOT versus end-of-test (EOT) performances.

  • Fig. 4 Comparison of the change in double layer charge for each MEA between beginning of test (BOT) and end of test (EOT).

    (A) CVs obtained before and after the stability test. The inset highlights the pseudocapacitive peaks for the 1.0-mg/cm2 design. (B) Percent increase in double-layer charge following the stability test for each of the three loadings. (C) Measured (scanning electron microscopy cross section) CCL thickness and estimated depth of oxidation into the CCL.

  • Table 1 Peak power for the 35 and 40 wt % ionomer designs under air or O2 for the 4.0-mg/cm2 CA#1 loaded CCLs.
    Oxidant gas35 wt % ionomer40 wt % ionomer
    Air570 mW/cm2395 mW/cm2
    O2750 mW/cm2678 mW/cm2
  • Table 2 Mechanisms and corresponding predictions.
    MechanismStability affected
    by loading
    Carbon oxidation
    affected by loading
    Mechanism 2 (attack by H2O2)ExpectedExpected
    Mechanism 3 (active-site
    protonation/anion binding)
    Not expectedNot expected
    Mechanism 4 (micropore
    flooding)
    ExpectedNot expected

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/4/3/eaar7180/DC1

    Supplementary Text

    fig. S1. In situ CVs obtained for three different loadings of CA#1.

    fig. S2. Difference in performance under air versus O2 at 1 A/cm2 for each of the three designs.

    fig. S3. CCL conductance versus ionomer EW.

    fig. S4. Schematic depiction of how CCL degradation may be expected to proceed in the case of attack by H2O2.

    fig. S5. N2 gas sorption analysis of CA#1.

    fig. S6. Transmission electron microscopy images of CA#1 obtained at various magnifications.

    fig. S7. X-ray photoelectron spectroscopy characterization of CA#1.

    fig. S8. Polarization curves at beginning of test (BOT) (solid lines) and end of test (EOT) (dashed lines) for MEAs prepared from the three different catalyst loadings.

    table S1. Double-layer charge normalized to the charge obtained for the 1.0 mg/cm2 design.

    table S2. XPS characterization of CA#1.

    table S3. Gas sorption analysis.

    table S4. Fe and Zn content based on inductively coupled plasma measurements of CA#1.

  • Supplementary Materials

    This PDF file includes:

    • Supplementary Text
    • fig. S1. In situ CVs obtained for three different loadings of CA#1.
    • fig. S2. Difference in performance under air versus O2 at 1 A/cm2 for each of the three designs.
    • fig. S3. CCL conductance versus ionomer EW.
    • fig. S4. Schematic depiction of how CCL degradation may be expected to proceed in the case of attack by H2O2.
    • fig. S5. N2 gas sorption analysis of CA#1.
    • fig. S6. Transmission electron microscopy images of CA#1 obtained at various magnifications.
    • fig. S7. X-ray photoelectron spectroscopy characterization of CA#1.
    • fig. S8. Polarization curves at beginning of test (BOT) (solid lines) and end of test (EOT) (dashed lines) for MEAs prepared from the three different catalyst loadings.
    • table S1. Double-layer charge normalized to the charge obtained for the 1.0 mg/cm2 design.
    • table S2. XPS characterization of CA#1.
    • table S3. Gas sorption analysis.
    • table S4. Fe and Zn content based on inductively coupled plasma measurements of CA#1.

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