Composition, surface segregation, and electrochemical properties of binary PtM/C (M = Co, Ni, Cr) catalysts

Abstract

The effect of the nature of transient metal and chemical treatment of binary cathodic PtM/C (M = Co, Ni, Cr) catalysts, which were prepared by high-temperature synthesis, on their structure, surface segregation, and characteristic properties (activity and stability) is studied. It is shown that, in the course of treatment in 0.5 M H2SO4 at the elevated temperature (60°C), the surface of nanoparticles becomes enriched in platinum with the formation of core-shell structures. The PtCo/C catalyst is the most efficient one. In this case, a compromise between the corrosion resistance and electrocatalytic activity is reached due to a higher, as compared with PtNi/C and PtCr/C, degree of alloy formation and enriching of surface in platinum in the course of corrosive attack. Thereby, the properties of platinum on the core surface change as a result of a pronounced ligand effect of the core. Thus, depending on the nature of transient metal, the binary cathodic PtM/C catalysts differ in their activity and stability, which depend on the degree of alloy formation and a possibility of formation of core-shell structure as a result of surface segregation in the course of synthesis and chemical treatment.