PtCoCr catalysts for fuel cell cathodes: Electrochemical activity, Pt content, substrate nature, structure and corrosion properties

Abstract

Creation of multicomponent catalytic systems is the main way to decrease the content of or completely replace Pt in fuel cell cathodes. Compared to the conventional catalytic systems, production of PtCoCr catalysts on different substrates (XC-72 carbon nanotubes, TiO2) differs in high-temperature conditions and the use of nitrogen-containing transient-metal precursors. According to electrochemical and structural studies, during synthesis and subsequent treatment, alloy nanoparticles with a core-shell structure enriched in platinum are formed on a carbon material doped with nitrogen. The ligand effect of the alloy core results in an increase in the electron density of the platinum d-level, acceleration of oxygen reduction, and deceleration of water molecule discharge and platinum corrosion. A architecture of membrane electrode assembly involving PtCoCr-based active layers of varying composition is developed for fuel cells operating at a temperature of 65°C in hydrogen-air and hydrogen-oxygen environments. In both cases, the use of PtCoCr instead of monoplatinum catalysts enabled us to halve the platinum consumption at the same discharge current density and specific power. The results of life testing and potential cycling of membrane electrode assemblies under severe conditions showed that the resistance of PtCoCr systems is not inferior to platinum.