The electrochemical study of different supported and unsupported Pt-based catalysts used in polymer electrolyte fuel cells (PEMFCs) has been made by means of thin film rotating disk electrode (RDE) method. The comparison of electrochemical surface area (ESA) was made using cyclic voltammetry measurements in H2SO4 or HClO4 at room temperature and scanning rates of 20 and 100mV∕s. Oxygen reduction activity for aerogel-supported and carbon-supported Pt catalysts was evaluated at various rotation speeds in the range of 0-2500rpm and compared to the catalytic activity of unsupported Pt-black catalyst. The calculated values of Levich constant for the oxygen reduction reaction (ORR) indicate dependence on the applied voltage and either 4 or 2–4 electron transfer mechanism. The hydrogen peroxide by-product formation was determined with a rotating ring disk electrode (RRDE) and was observed to take place mostly at voltages below 0.6V due to the limitations from mass transport effects. The results obtained at different Pt loadings in the range of 10-46.5wt% Pt demonstrated that XC-72 and aerogel-based catalysts are foreseen to have higher ESA in comparison to other tested supported and unsupported commercially available catalysts.
Silica impregnated expanded graphite–epoxy composites are developed as bipolar plates for proton exchange membrane (PEM) fuel cells. These composite plates were prepared by solution impregnation, followed by compression molding and curing. Mechanical properties, electrical conductivities, corrosion resistance, and contact angles were determined as a function of impregnated content. The plates show high flexural strength with 5% methyltrimethoxysilane (MTMS) addition (20 MPa) and in‐plane conductivity of 131 S cm−1 that meet the DOE target (>100 S cm−1). Corrosion current values as low as 1.09 μA cm−2 were obtained. The contact angle was found to be 80°. Power density of 1 W cm−2 was achieved with custom made expanded graphite–polymer composite plates. High efficiency values were obtained at low current regions.
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