Scalable synthesis of (Pd,Cu)@Pt core-shell catalyst with high ORR activity and durability

Abstract

• Pt shell is fabricated by galvanic replacement reaction of Cu by Pt. • The thickness of Pt shell is controlled by the different composition of Pd and Cu. • (Pd,Cu)@Pt/C catalysts show higher oxygen reduction reaction activity than that of PtPdCu/C. • Pd 2 Cu 1 @Pt/C catalyst exhibits superior long-term durability. Developing highly active and durable electrocatalysts for oxygen reduction reaction (ORR) remains a paramount challenge for the commercialization of proton exchange membrane fuel cells (PEMFCs). Core-shell nanoparticles (NPs) with Pt shells hold some promises for such catalysts. In this work, carbon-supported (Pd,Cu)@Pt core–shell NPs with tunable Pt shell thickness are synthesized by reacting pre-formed Pd x Cu y (x/y = 1/1, 2/1, 3/1) NPs with Pt(IV) ions. Pd x Cu y cores are synthesized by ultrasound-assisted polyol synthesis (UPS) method in a single step. The thickness of Pt shell and composition of (Pd,Cu)@Pt/C catalysts and, hence, their electronic structures are significantly influenced by the composition of Pd x Cu y NPs used. For comparison, PtPdCu/C catalyst is synthesized by a single-step UPS reaction. Electrochemical analysis reveals that (Pd,Cu)@Pt/C catalysts exhibit substantially enhanced catalytic activities compared to those of PtPdCu/C and Pt/C catalysts. Especially, Pd 2 Cu 1 @Pt/C catalyst with 0.4 nm thick Pt shell achieves the highest specific activity (SA) (1.923 mA cm Pt -2 ) and mass activity (MA) (0.678 A mg Pt -1 ) at 0.9 V, which are 4.0 and 3.1 times higher than those of Pt/C catalyst. More importantly, Pd 2 Cu 1 @Pt/C catalyst exhibits superior long-term durability. After 30,000 cycles of accelerated stress test (AST), it retains 87.8% of initial MA, much higher than Pt/C (36.1%) catalyst. The present synthesis route is facile and, in principle, scalable, by which it has the potential for large-scale production for real applications.