(A) study on size-controlled $Pt_3Co$ intermetallic catalyst using potassium chloride substrates

Abstract

The sluggish oxygen reduction reaction (ORR) at the cathode mainly increases overpotential of the polymer electrolyte membrane fuel cell (PEMFC). To improve ORR activity without increase of Pt usages, Pt-based catalysts have been extensively studied. Among them, Pt-based intermetallic catalysts have attracted attention with its enhancement in activity and stability. However, particle growth during high temperature heat treatment for ordered structure was major hurdle during synthesis. Here, we introduced potassium chloride (KCl) as a temporary substrate to synthesize $Pt_3Co$ intermetallic nanoparticles with keeping distances among the nanoparticles during the heat treatment. The size-controlled $Pt_3Co$ nanoparticles were sustained to 2.4 nm even with $Pt_3Co$ intermetallic phases. After all procedure, they were transported to carbon support with good dispersion. The prepared $Pt_3Co$/C catalysts showed 1.6-fold enhancement of mass activity and 6.3-fold enhancement of specific activity than commercial Pt/C. After 20k cycles of voltage cycling, the mass activity decreased only 0.8 % with extraordinary durability. Both intermetallic phases and the smaller particle sizes drew the synergy effect on the activity and stability. All the results revealed the possibilities of synthesis on KCl temporary substrate as well as development of $Pt_3Co$/C intermetallic catalysts.