Investigation of Pt, Pt₃ Co, and Pt₃ Co/Mo cathodes for the ORR in a microfluidic H₂ / O₂ fuel cell

We report on the performance and durability of four Pt-based cathode catalysts in a microfluidic H₂ / O₂ fuel cell: commercial unsupported Pt and Pt₃ Co as well as in-house acid-treated Pt ₃ Co (Pt₃ Co -at) and Pt₃ Co/Mo. Commercial Pt₃ Co was used as the starting material for both Pt₃ Co -at and Pt₃ Co/Mo. The composition of the resulting catalysts was confirmed via X-ray photoelectron spectroscopy analysis. In situ cathode studies were performed using an acidic microfluidic H₂ / O₂ fuel cell with an analytical platform. The electrolyte flow rate was optimized to minimize the effects of water management such that fuel cell performance is kinetically limited by the oxygen reduction reaction (ORR). In addition, electrolyte concentration was separately varied to determine cathode performance as a function of acidic pH. All four catalysts demonstrated good short-term activity and stability under fuel cell operating conditions in harsh acidic environments, with the Pt₃ Co/Mo alloy exhibiting the highest activity. Furthermore, both modified catalysts, Pt₃ Co/Mo and Pt ₃ Co -at, exhibited superior durability compared to commercially available Pt₃ Co and Pt in the accelerated cathode aging studies performed within the microfluidic fuel cell via potential cycling. In situ impedance analysis of the Pt₃ Co/Mo cathode revealed enhanced catalyst stability and electrode durability as the cause of the dramatic improvements in long-term performance.