Ionic liquids (ILs) have shown to be promising additives to the catalyst layer to enhance oxygen reduction reaction in polymer electrolyte fuel cells. However, fundamental understanding of their role in complex catalyst layers in practically relevant membrane electrode assembly environment is needed for rational design of highly durable and active platinum-based catalysts. Here we explore three imidazolium-derived ionic liquids, selected for their high proton conductivity and oxygen solubility, and incorporate them into high surface area carbon black support. Further, we establish a correlation between the physical properties and electrochemical performance of the ionic liquid-modified catalysts by providing direct evidence of ionic liquids role in altering hydrophilic/hydrophobic interactions within the catalyst layer interface. The resulting catalyst with optimized interface design achieved a high mass activity of 347 A g−1Ptat 0.9 V under H2/O2, power density of 0.909 W cm−2under H2/air and 1.5 bar, and had only 0.11 V potential decrease at 0.8 A cm−2after 30 k accelerated stress test cycles. This performance stems from substantial enhancement in Pt utilization, which is buried inside the mesopores and is now accessible due to ILs addition.
We report a new catalytic system by partially covering the uniform Pt nanocrystals on a carbon support with an ultrathin film derived from polyacrylonitrile (PAN). The use of Pt nanocrystals uniform in both size and shape effectively suppresses Ostwald repining, while partially covering them with a PAN‐derived film prevents migration, aggregation, and detachment from the support. In addition, the pyridinic N atoms on the edges of the thermally‐treated PAN film can also weaken the O=O bond, accelerating the reduction of oxygen. Upon optimization, the new catalyst exhibits a mass activity of 0.51 mA ⋅ μg−1Pttoward oxygen reduction, substantially enhanced relative to the same catalyst without PAN (0.22 mA ⋅ μg−1Pt) and a commercial Pt/C (0.41 mA ⋅ μg−1Pt). The mass activity is essentially retained after 10,000 cycles of accelerated durability test between 0.6 V and 1.1 V in oxygen‐saturated HClO4. Even after aging in H3PO4at 220 °C for one week, the electrochemical surface area of the catalyst is still maintained. This catalytic system holds great promise for use in various types of fuel cells with a long lifetime.
more » « less- Award ID(s):
- 1804970
- PAR ID:
- 10236092
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- ChemCatChem
- Volume:
- 12
- Issue:
- 19
- ISSN:
- 1867-3880
- Page Range / eLocation ID:
- p. 4817-4824
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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