Enhanced durability and self-humidification of platinum catalyst through decoration with SnSi binary oxide

Abstract

Through decorating commercial Pt/C catalyst with a binary oxide of silicon and tin, a catalyst with significantly enhanced self-humidification capacity and ultra-high stability has been successfully prepared. After 5000 cycles, ECSA and ORR activity decay by only 30% and 28.4%, respectively, for our optimal decorated catalyst, compared with 75% and 99.9% for undecorated Pt/C under the same conditions. We attribute this improvement to the prevention of Pt nanoparticle aggregation and the synergistic effects between the Pt active component and the binary oxide. The decorated catalyst also exhibits excellent self-humidification. Under non-humidified operating conditions, a membrane electrode assembly (MEA) with a decorated Pt/C catalyst anode is discharged at 0.6 V for 8 h with only slight current density decay, whereas serious decay is observed for an MEA with a non-decorated Pt/C anode. The catalysts are characterized using XRD, SEM/TEM, XPS, and contacted angle measurement. We find that the dissolution, migration, and aggregation of Pt nanoparticles can be effectively prevented by decoration with the binary oxide, and that the contact angle is decreased by 56°, indicating great improvement in the catalyst’s wettability. The interactions between Pt and oxide, Sn and Si are revealed by XPS analysis. This work may provide a facile and effective way to address the durability and humidification issues of PEM fuel cells. An oxide modified Pt/C catalyst was prepared by decorating the commercial Tanaka Pt/C catalyst with a binary oxide of Sn and Si, the catalyst exhibited significantly enhanced stability/durability, slightly enhanced activity and excellent self-humidification property. The catalysts were characterized with HRTEM, XPS etc. The enhancements should be attributed to the prevention of the coated binary oxide to the aggregation of Pt, the corrosion of carbon support. And self-humidification may be resulted from the wettability of the silicon oxide.