General and scalable strategy for synthesis of Pt-rare earth alloys as highly durable oxygen reduction electrocatalysts

Abstract

Platinum-rare earth (Pt-RE) alloys are effective oxygen reduction reaction (ORR) catalysts, which are promising to show robust durability in proton-exchange membrane fuel cells (PEMFCs). Whereas, the large difference in reduction potentials between the two kinds of metals and the very oxophilicity of RE elements bring big challenges in the controllable synthesis of Pt-RE alloys. Herein we propose a general and scalable strategy to synthesize Pt-RE catalysts with tunable compositions and microstructures. The as-obtained catalysts possess a lamellar structure with hierarchical pore sizes ranging from 4 to 8 nm and a typical face-centered cubic (FCC) crystalline structure, and the Pt and RE are homogeneously distributed in the alloys. The electronic structures of Pt are well modulated by incorporating RE atoms, resulting in the adjusted d band center for these Pt-RE alloys compare with Pt, which facilitates OH* adsorption behavior and accelerate the ORR kinetics. Furthermore, the energy barrier for Pt demetallation is enhanced by incorporating of RE into the Pt lattice, which significantly enhances ORR durability. Notably, the optimal Pt3Y catalyst exhibits a greatly improved catalytic activity, including a large half-wave potential (0.89 V, at an ultralow Pt loading of 7.8 μg cm−2), high mass activity (0.53 A mg−1 at 0.9 ViR-free) and robust stability (0.01 V decay after 60,000 cycles) exceeding the commercial Pt/C (0.06 V decay after 30,000 cycles). This study provides a new facile strategy for the controllable preparation of Pt-RE alloys, which might pave the way for the large-scale applications of PEMFCs.