A comparative study of Pt/C cathodes in Sn_(0.9)In_(0.1)P_2O_7 and H_3PO_4 ionomers for high-temperature proton exchange membrane fuel cells

摘要

New Pt/C cathodes with many reaction sites for the oxygen reduction reaction as well as high tolerance to Pt corrosion have been designed for high-temperature proton exchange membrane fuel cells (PEMFCs), wherein a composite mixture ofSn_(0.9)In_(0.1)P_2O_7 (SIPO) and sulfonated polystyrene-b-poly(ethylene/butylene)-b-polystyrene (sSEBS) functioned as an ionomer. The microstructure of the Pt-SIPO-sSEBS/C cathode was characterized by homogeneous distribution of the ionomer over the catalyst layer and close contact between the ionomer and the Pt/C powder. As a result, the activation and concentration overpotentials of the Pt-SIPO-sSEBS/C cathode between 100 and 200 C were lower than those of an H_3PO_4-impregnated Pt/C cathode, which suggests that the present ionomer can avoid poisoning of Pt by phosphate anions and the limitation of gas diffusion through the catalyst layer. Moreover, agglomeration of Pt in the Pt-SIPO-sSEBS/C cathode was not observed during a durability test at 150 C for 6 days, although it was significant in the Pt-H_3PO_4/C cathode. Therefore, it is concluded that the Pt-SIPO-sSEBS/C electrode is a very promising cathode candidate for high-temperature PEMFCs.