title: Investigation of local environments in Nafion-SiO(2) composite membranes used in vanadium redox flow batteries.
abstract: Proton conducting polymer composite membranes are of technological interest in many energy devices such as fuel cells and redox flow batteries. In particular, polymer composite membranes, such as SiO(2) incorporated Nafion membranes, are recently reported as highly promising for the use in redox flow batteries. However, there is conflicting reports regarding the performance of this type of Nafion-SiO(2) composite membrane in the redox flow cell. This paper presents results of the analysis of the Nafion-SiO(2) composite membrane used in a vanadium redox flow battery by nuclear magnetic resonance (NMR) spectroscopy, X-ray photoelectron spectroscopy (XPS), Fourier Transform Infra Red (FTIR) spectroscopy, and ultraviolet-visible spectroscopy. The XPS study reveals the chemical identity and environment of vanadium cations accumulated at the surface. On the other hand, the (19)F and (29)Si NMR measurement explores the nature of the interaction between the silica particles, Nafion side chains and diffused vanadium cations. The (29)Si NMR shows that the silica particles interact via hydrogen bonds with the sulfonic groups of Nafion and the diffused vanadium cations. Based on these spectroscopic studies, the chemical environment of the silica particles inside the Nafion membrane and their interaction with diffusing vanadium cations during flow cell operations are discussed. This study discusses the origin of performance degradation of the Nafion-SiO(2) composite membrane materials in vanadium redox flow batteries.
authors.affiliation: Pacific Northwest National Laboratory, Richland, WA 99352, USA. vijay@pnnl.gov
authors.forename: M
authors.initials: M
authors.lastname: Vijayakumar
authors.forename: Birgit
authors.initials: B
authors.lastname: Schwenzer
authors.forename: Soowhan
authors.initials: S
authors.lastname: Kim
authors.forename: Zhenguo
authors.initials: Z
authors.lastname: Yang
authors.forename: S
authors.initials: S
authors.lastname: Thevuthasan
authors.forename: Jun
authors.initials: J
authors.lastname: Liu
authors.forename: Gordon L
authors.initials: GL
authors.lastname: Graff
authors.forename: Jianzhi
authors.initials: J
authors.lastname: Hu
mesh_terms: D011211:Electric Power Supplies; D004566:Electrodes; D004735:Energy Transfer; D005465:Fluorocarbon Polymers / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008567:Membranes, Artificial; D010084:Oxidation-Reduction; D012822:Silicon Dioxide / Q000737:chemistry*
chemical_list: D005465:Fluorocarbon Polymers; D008567:Membranes, Artificial; C040402:perfluorosulfonic acid; D012822:Silicon Dioxide