High temperature polymer electrolyte membrane fuel cell performance of PtxCoy/C cathodes

Carbon-supported Pt–Co alloy nanoparticles of varying Pt:Co atomic ratios of 1:1, 2:1, 3:1 and 4:1 are prepared, characterized and tested in high temperature PEM fuel cell intend to reduce the Pt loading. These electrocatalysts are prepared by borohydride reduction method in the presence of citric acid as stabilizing agent. Face-centered cubic structure of Pt is evident from XRD. The positive shift of Pt diffraction peaks with increasing cobalt content in the PtxCoy/C catalysts indicated the solubility of Co in Pt lattice. The average crystallite size is found to be 6 nm in all the prepared catalysts. The electrochemical active surface area (EAS) of the catalysts from CO-stripping voltammetry is calculated to be 65.2, 51.4, 47.7, 41.5 and 38.3 m2 g−1 Pt for Pt/C, Pt–Co(4:1)/C, Pt–Co(3:1)/C, Pt–Co(2:1)/C and Pt–Co(1:1)/C, respectively. These catalysts are used as cathode in the fabrication of polybenzimidazole-based membrane electrode assembly (MEA) and the polarization curves are recorded at 160 and 180 °C. The results indicate the good performance of Pt–Co alloys than that of Pt under the PEM fuel cell conditions. Among the investigated electrocatalysts, Pt–Co(1:1)/C and Pt–Co(2:1)/C exhibited good fuel cell performance. Durability tests also indicated the good stability of Pt–Co(1:1)/C and Pt–Co(2:1)/C compared to Pt/C.