Pt–Co electrocatalyst with varying atomic percentage of transition metal

A series of Platinum–Cobalt bimetallic catalyst supported on carbon (Vulcan XC-72R) were prepared by sequential deposition using an organic salt of cobalt for use as cathode in Phosphoric Acid Fuel Cell (PAFC). The atomic percent of non noble metal with respect to Pt in the alloy was varied from 5 to 100 and the composition of alloy catalyst was confirmed by chemical analysis and SEM – EDS spectra. Electrochemical performance of the catalyst was studied in half cell and unit cells. The exchange current densities for oxygen reduction reaction (ORR), for alloys with different concentration of non noble metal was evaluated from current-potential curves, which showed values close to 10−5 A/cm2 and the mass activity and specific activity, for the (ORR), were found to be higher for Pt–Co/C compared to that of 10% Pt/C catalysts. The catalyst was tested for its stability in unit cell for a period of 500 h using air as an oxidant which showed higher performance for Pt–Co/C containing 0.5 at% Co. The nature of hydrogen adsorption and dominant crystal plane was also evaluated from cyclic voltammetry. XPS analysis was carried out to determine the surface species present. Results show significant enhancement of electro catalytic activity of Pt by alloying with Co, with maximum activity at ca 0.5 at% Co.