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

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.