Improving the Activity and Stability of PdSn Catalyst for Oxygen Reduction by Heat Treatment

Abstract

Carbon-supported PdSn catalysts were synthesized (ratio of about Pd:Sn = 1:1) by the NaBH4 reduction method for the oxygen reduction reaction (ORR) in HClO4 solution. The carbon support surface was previously activated with a sensitizing and activating pre-treatment. The as-prepared PdSn catalyst was then heat treated at 300 ºC in H2/N2 (3vol.% H2). The PdSn catalysts were characterized by SEM/EDX, XRD and TEM before and after the heat treatment. The electrochemical activity towards ORR was examined by cyclic and rotating disk electrode measurements and compared with that of Pd. The ORR catalytic activity of PdSn heat treated catalyst was about 25 and 4 times higher than that of as-prepared and Pd catalyst, respectively. Accelerated stability test (AST) by repetitive potential cycling indicated that PdSn heat treated was very stable in electrochemical environment.