Stabilization of platinum nanoparticle electrocatalysts for oxygen reduction using poly(diallyldimethylammonium chloride)

Abstract

A long-chain polyelectrolyte, poly(diallyldimethylammonium chloride) (PDDA), has been employed to stabilize platinum nanoparticles for oxygen reduction in polymer electrolyte membrane (PEM) fuel cells. Pt nanoparticles are synthesized by reducing H₂PtCl₆ with NaBH₄ in the presence of PDDA and then deposited on a carbon support (PDDA-Pt/C). Transmission electron microscope images show that Pt nanoparticles of PDDA-Pt/C are uniformly dispersed on the carbon support with a mean size of about 2.2 nm (2.1 nm for commercial Etek-Pt/C). PDDA-Pt/C exhibits a higher activity towards oxygen reduction reaction (ORR) than Etek-Pt/C. The durability of PDDA-Pt/C is improved by a factor of 2 as compared with Etek-Pt/C. X-ray photoelectron spectroscopy characterization of PDDA-Pt/C reveals the interaction between Pt nanoparticles and PDDA, which increases Pt oxidation potential and prevents Pt nanoparticles from migrating/agglomerating on or detaching from carbon support. This provides a promising strategy to improve both the durability and activity of electrocatalysts for fuel cells.