Enhanced oxygen reduction electrocatalysis on PtCoSn alloy nanocatalyst mediated by Ta-doped SnO2 support for polymer electrolyte fuel cells

For polymer electrolyte fuel cells (PEFCs), platinum-based catalysts for the air cathode supported on metal oxides such as SnO 2 exhibit highly promising durability. Yet, the activity for the oxygen reduction reaction (ORR) has still not been sufficiently high toward widespread application. Here, we report a new type of catalyst with significantly boosted ORR activity, based on PtCoSn alloy nanostructures formed on Ta-doped SnO 2 support (PtCoSn/Ta-SnO 2 ). The ORR activity of the PtCoSn/Ta-SnO 2 catalyst is evaluated in acidic media (0.1 M HClO 4 ) from 20 to 80 °C. The apparent rate constants ( k app ) for the ORR on PtCoSn/Ta-SnO 2 are found to be about 4.5 and 1.5 times greater than those of commercial Pt and Pt 3 Co alloy catalysts supported on carbon black (c-Pt/C and c-Pt 3 Co/C), respectively, and increase with temperature, in accordance with an Arrhenius-type relation from 20 to 60 °C. The enhanced ORR rates of the PtCoSn/Ta-SnO 2 catalyst can be correlated with an increase in the preexponential factor of the Arrhenius equation, together with a lowered activation energy. Experimental and density functional theory results reveal that the incorporation of Sn facilitates O 2 adsorption and dissociation, which is beneficial to overcome the kinetic limitation of ORR. Moreover, the durability of PtCoSn/Ta-SnO 2 examined by potential-step cycling between 0.6 and 1.0 V at 80 °C has been found to be much higher as compared with c-Pt/C and c-Pt 3 Co/C.