Metal alloy catalysts (e.g., Pt–Co) are widely used in fuel cells for improving the oxygen reduction reaction kinetics. Despite the promise, the leaching of the alloying element contaminates the ionomer/membrane, leading to poor durability. However, the underlying mechanisms by which cation contamination affects fuel cell performance remain poorly understood. Here, we provide a comprehensive understanding of cation contamination effects through the controlled doping of electrodes. We couple electrochemical testing results with membrane conductivity/water uptake measurements and impedance modeling to pinpoint where and how the losses in performance occur. We identify that (1) ∼44% of Co2+ exchange of the ionomer can be tolerated in the electrode, (2) loss in performance is predominantly induced by O2 and proton transport losses, and (3) Co2+ preferentially resides in the electrode under wet operating conditions. Our results provide a first-of-its-kind mechanistic explanation for cation effects and inform strategies for mitigating these undesired effects when using alloy catalysts.
BT - ACS Applied Materials & Interfaces DA - 08/2022 DO - 10.1021/acsami.2c07085 IS - 31 LA - eng N2 -Metal alloy catalysts (e.g., Pt–Co) are widely used in fuel cells for improving the oxygen reduction reaction kinetics. Despite the promise, the leaching of the alloying element contaminates the ionomer/membrane, leading to poor durability. However, the underlying mechanisms by which cation contamination affects fuel cell performance remain poorly understood. Here, we provide a comprehensive understanding of cation contamination effects through the controlled doping of electrodes. We couple electrochemical testing results with membrane conductivity/water uptake measurements and impedance modeling to pinpoint where and how the losses in performance occur. We identify that (1) ∼44% of Co2+ exchange of the ionomer can be tolerated in the electrode, (2) loss in performance is predominantly induced by O2 and proton transport losses, and (3) Co2+ preferentially resides in the electrode under wet operating conditions. Our results provide a first-of-its-kind mechanistic explanation for cation effects and inform strategies for mitigating these undesired effects when using alloy catalysts.
PY - 2022 SP - 35555 EP - 35568 ST - ACS Appl. Mater. Interfaces T2 - ACS Applied Materials & Interfaces TI - Toward a Comprehensive Understanding of Cation Effects in Proton Exchange Membrane Fuel Cells UR - https://pubs.acs.org/doi/10.1021/acsami.2c07085 VL - 14 SN - 1944-8244 ER -