Highly dispersed L10-PtZn intermetallic catalyst for efficient oxygen reduction

Abstract

Highly active and durable electrocatalysts with minimal Pt usage are desired for commercial fuel cell applications. Herein, we present a highly dispersed L10-PtZn intermetallic catalyst for the oxygen reduction reaction (ORR), in which a Zn-rich metal-organic framework (MOF) is used as an in situ generated support to confine the growth of PtZn particles. Despite requiring high-temperature treatment, the intermetallic L10-PtZn particles exhibit a small mean size of 3.95 nm, which confers the catalysts with high electrochemical active surface area (81.9 m2 gPt−1) and atomic utilization. The Pt electron structure and binding strength between Pt and oxygen intermediates are optimized through ligand effect and compressive strain. These advantages result in ORR mass activity and specific activity of 0.926 A mgPt−1 and 1.13 mA cm−2, respectively, which are 5.4 and 4.0 times those of commercial Pt/C. The stable L10 structure provides the catalysts with superb durability; only a halfwave potential loss of 11 mV is observed after 30,000 cycles of accelerated stress tests, through which the structure evolves into a more stable PtZn-Pt core-shell structure. Therefore, the development of a Zn based MOF as a catalyst support is demonstrated, providing a synergy strategy to prepare highly dispersed intermetallic alloys with high activity and durability.