To overcome these activity and stability challenges, unsupported bimetallic Pt-alloy aerogels consisting of a 3D nanochain network (~ 30 m2ECSA/gPt) were synthesized (see Figure 1 for a TEM image of Pt3Ni aerogel) [4, 5]. Both Pt-Ni and Pt-Cu aerogels meet the US Department of Energy ORR activity target for 2017 of 440 A/gPt at 0.9 VRHE when tested in liquid half cells. Considering that this outstanding performance needs to be demonstrated in an actual PEFC, Pt‑Ni and Pt-Cu aerogels were processed into membrane electrode assemblies (MEAs) and characterized in a differential PEFC .
In this contribution, we present the MEA optimization process for unsupported Pt‑alloy aerogel ORR catalysts and compare cell performance and durability (start-stop cycles, load cycles) to a conventional Pt/C benchmark. To explain the outstanding stability of Pt-alloy aerogel catalysts for start-stop cycling (see Figure 1), catalyst layers were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX) at beginning-of-life and end-of-life.
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