High performance layer-by-layer Pt(3)Ni(Pt-skin)-modified Pd/C for the oxygen reduction reaction

Bimetallic Pt–Ni with Pt on the outermost layer and an innermost layer enriched in Ni, referred to as Pt(3)Ni(Pt-skin), is a promising configuration of an electrocatalyst for the oxygen reduction reaction (ORR) in fuel cells. We prepare a core (Pd)/shell (Pt(3)Ni(Pt-skin)) catalyst (Pt(3)Ni(Pt-skin)/Pd/C) from Zn underpotential deposition (UPD) on a Ni UPD modified Pd/C catalyst, facilitating Pt atomic layer-by-layer growth on the Ni surface through the galvanic replacement process. Pt(3)Ni(Pt-skin)/Pd/C shows the best ORR performance, with a Pt specific activity of 16.7 mA cm(–2) and Pt mass activity of 14.2 A mg(Pt)(–1), which are 90- and 156- fold improvements over commercial Pt/C catalysts. The Pt(3)Ni(Pt-skin) structure effectively inhibits Ni leaching to improve the durability in two accelerated durability test modes mimicking the catalyst lifetime and start-up/shut-down cycles.