Abstract
Bimetallic alloys based on Pt and Y are potential cathode catalysts for proton exchange membrane fuel cells (PEMFCs) due to their high oxygen reduction reaction (ORR) activity. Nevertheless, the synthesis of carbon supported PtxY catalysts is challenging due to the low standard reduction potential of yttrium compared to platinum. Hence, extended electrochemical testing in actual PEMFCs remains elusive, especially with respect to catalyst degradation upon voltage-cycling. In this publication, we present the synthesis of a bimetallic PtxY/C catalyst via impregnation of commercial Pt/C with an yttrium halide precursor and subsequent heat-treatment in H2 at 1200°C. This catalyst showed a high specific ORR activity, at a mass activity similar to Pt/C due to its comparably low electrochemical surface area (ECSA). On the other hand, the large particle size of the here synthesized PtxY/C catalyst (≈10 nm) resulted in a significantly enhanced stability versus degradation in an accelerated stress test (AST) based on voltage-cycling between 0.6 and 1.0 VRHE at 50 mV s−1, showing a superior ECSA, ORR activity and H2/air performance after 30000 cycles compared to a standard Pt/C catalyst.
Highlights
FCs) are a major hurdle for their large-scale implementation in fuel cell electric vehicles (FCEVs).[1]
Evaluation of YCl3 reduction via Thermogravimetric analysis (TGA).—The synthesis of PtxY/C alloys, presented in this work, is based on the reduction of an yttrium halide precursor to metallic yttrium using H2 at elevated temperature and simultaneous alloying with platinum in its vicinity
For PtxY/C and Pt/C-HT, an activation procedure consisting of 50 potential cycles between 0.07 and 1.20 VRHE (based on the above described experiments in liquid electrolyte; the lower potential limit was increased by 20 mV to limit the hydrogen evolution reaction (HER) current and the temperature was raised to 40◦C) was applied after having executed an initial voltage-controlled MEA conditioning procedure; the commercial Pt/C catalyst was only subjected to the ramp-in procedure
Summary
FCs) are a major hurdle for their large-scale implementation in fuel cell electric vehicles (FCEVs).[1].
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