Using decomposed Nafion ionomers to anchor Pt nanoparticles and improve their durability during methanol electro-oxidation

Abstract

Nafion ionomers were partially decomposed to produce oxygenated functional groups on Vulcan XC72R (XC72R) that enabled increased Pt ion adsorption when the functionalized XC72R was immersed in a 5 mM aqueous H2PtCl6 solution. X-ray absorption spectroscopy spectra indicated that the oxidation state for the Pt ions remained unchanged upon adsorption on the functionalized XC72R whereas a notable reduction in the oxidation state was recorded when the Pt ions were adsorbed onto untreated XC72R. After a hydrogen reduction treatment, the Pt nanoparticles on the functionalized XC72R demonstrated impressive mass activities and durability retention during the methanol electro-oxidation reaction (MOR), compared to those of commercial E-TEK Pt/C samples. After the durability test, transmission electron microscope images showed that the Pt nanoparticles on the functionalized XC72R exhibited significantly reduced agglomeration, and X-ray photoelectron spectra confirmed that the functional groups from the decomposed Nafion ionomers were still present. We attributed the notable durability improvement to the anchoring effect of decomposed Nafion ionomers that prevented the Pt nanoparticles from contacting XC72R directly, thus minimizing the undesirable migration and detachment of Pt nanoparticles during repeated MOR cycles. (C) 2013 Elsevier B.V. All rights reserved.