Using Neutron Reflectometry to Quantify the Carbon-Nafion Interface for Proton Exchange Membrane Fuel Cell Applications

• DOI: 10.1149/ma2022-01351409mtgabs
• Publication Date: 2022-07-14T16:56:34Z
• Authors: Corey R. Randall; Joseph Dura; Lianfeng Zou; Melodie Chen-Glasser; Steven C. DeCaluwe
• Keywords: Nafion; Ionomer; Neutron reflectometry; Membrane electrode assembly

Due to its chemical stability in acidic environments and high ionic conductivity, Nafion has proven be an essential material proton exchange membrane fuel cell (PEMFC) designs. functions as both a – separating the two electrodes conductive binder each catalyst layer (CL). Nano-thin films of ionomer allow protons reach carbon-supported Pt catalysts. In addition protons, oxygen water also move through nano-thin from reactive sites. These physical transport processes directly impact PEMFC performance. Therefore, measuring determining ways improve upon these is critical development performance PEMFCs. regards thick membranes, conductivity diffusion measurements can readily performed most laboratories. on other hand prove more challenging study due experimental limitations. Nevertheless, neutron reflectometry (NR) been reported literature capable technique provide simultaneous quantitative structural composition profiles for thin-film [1-5]. Results at native silicon oxide interfaces show complex multi-layered structures forming distinct water-rich water-poor regions [1-3]. Despite advancements our understanding Nafion, it still unclear how observed may This because does not interface with CLs. Instead, carbon are primary secondary materials that ionomer. latter case, briefly studied shows significantly less structure than [4,5]. Beyond limited number studies Pt-Nafion interfaces, carbon-Nafion even scarce [5]. likely black (i.e. electron conductor CLs) too rough used NR. confidently assume trends NR work carbon-based samples need compiled compared, while considering their bonding surface chemistries. this work, we extend by testing four different substrates. Using (< 100 nm) deposited sample, was dry humidified environments. Fitting data experiments, results suggest variety polymer interface. include structures, similar those well simple homogenous little-to-no interfacial structure. During presentation, implications species CLs will discussed. Additionally, predictions incorporate learnings made using extended model earlier [6]. [1] S.C. DeCaluwe, A.M. Baker, P. Bhargava, J.E. Fischer, J.A. Dura, “Structure-property Relationships Thin-film Interfaces: Thickness Effects Hydration Anisotropic Ion Transport,” Nano Energy , vol. 46, pp. 91–100, 2018. [2] V.S. Murthi, M. Hartman, S.K. Satija, C.F. Majkrzak, “Multilamellar Interface Structures Nafion,” Macromolecules 42, no. 13, 4769–4774, 2009. [3] U.N. Shrivastava, H. Fritzsche, K. Karan, “Interfacial Bulk Water Ultrathin Films 3M PFSA, PFIA Ionomers Polycrystalline Platinum Surface,” 51, 23, 9839–9849, [4] J. S. C. “Water Uptake Interfacial Structural Changes Thin Film Membranes Measured Neutron Reflectometry PEM Fuel Cells,” ECS Transactions 16, 2, 2019. [5] D.L. Wood, Chlistunoff, Majewski, R.L. Borup, “Nafion Phenomena Carbon Interfaces,” Journal American Chemical Society, 131, 50, 18096–18104, [6] C.R. Randall “Physically Based Modeling Cathode Catalyst Layers: Effective Microstructure Ionomer Structure–Property Relationship Impacts,” Electrochemical Conversion Storage 17, 4, Jan. 2020.