Activity–Stability Relationship in Compositionally Tuned Magnetron Co‐Sputtered Bimetallic Catalysts for Proton Exchange Membrane Fuel Cells

ABSTRACT In the present study, magnetron‐sputtered Pt x M 100− x (M = Co, Cu, and Y; x = 25, 50, 75, and 100) bimetallic alloys were investigated as PEMFC cathodes. Accurate composition and layer thickness control enabled a systematic study of the correlation between the alloy composition, its activity, and stability. The catalysts underwent thorough characterization, employing a diverse portfolio of characterization techniques such as scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, X‐ray photoelectron spectroscopy, X‐ray diffraction, and cyclic voltammetry. The activity of all investigated alloys was tested directly in a fuel cell device, whereas stability was assessed through potentiodynamic cycling in a half‐cell. The activity–stability index, considering experimental results for both activity and stability, was calculated and compared for all investigated catalysts. All alloys exhibited a volcano‐type trend in the activity–stability index as a function of the concentration of the alloying element with maxima observed for Pt 50 Co 50 , Pt 50 Cu 50 , and Pt 75 Y 25 for respective alloys, surpassing that of monometallic platinum. Overall, Pt 50 Co 50 emerged as a catalyst with the highest activity–stability ratio.