Investigation of the Interaction between Nafion Ionomer and Surface Functionalized Carbon Black Using Both Ultrasmall Angle X-ray Scattering and Cryo-TEM

Abstract

In making a catalyst ink, the interactions between Nafion ionomer and catalyst support are the key factors that directly affect both ionic conductivity and electronic conductivity of the catalyst layer in a membrane electrode assembly. One of the major aims of this investigation is to understand the behavior of the catalyst support, Vulcan XC-72 (XC-72) aggregates, in the existence of the Nafion ionomer in a catalyst ink to fill the knowledge gap of the interaction of these components. The dispersion of catalyst ink depends not only on the solvent but also on the interaction of Nafion and carbon particles in the ink. The interaction of Nafion ionomer particles and XC-72 catalyst aggregates in liquid media was studied using ultrasmall-angle X-ray scattering and cryogenic TEM techniques. Carbon black (XC-72) and functionalized carbon black systems were introduced to study the interaction behaviors. A multiple curve fitting was used to extract the particle size and size distribution from scattering data. The results suggest that the particle size and size distribution of each system changed significantly in Nafion + XC-72 system, Nafion + NH-XC72 system, and Nafion + SOH-XC-72 system, which indicates that an interaction among these components (i.e., ionomer particles and XC-72 aggregates) exists. The cryogenic TEM, which allows for the observation the size of particles in a liquid, was used to validate the scattering results and shows excellent agreement.

Tailoring Catalyst Morphology towards High Performance for Low Pt Loaded PEMFC Cathodes

“…25 For this reason, Pt/KB IW and Pt/KB TKK showed a mass activity of 249 ± 1 and 372 ± 29 A/g, while the Pt/KB PO and Pt/KB(NH x ) PO catalysts synthesized by the polyol method had lower mass activities of 220 ± 11 and 161 ± 2 A/g, respectively. The lower mass activity of the latter most likely arises from a better ionomer distribution of the KB(NH x ) support as shown in a previous publication, 15 where we argued that an increased interaction of the ionomer with the modified carbon black surface 33 would lead to a more homogeneous ionomer distribution, reaching more platinum particles and thus lowering their ORR mass activity. In addition, part of this effect may also derive from a somewhat larger fraction of Pt being deposited on the outer surface of the NH x -modified Ketjenblack due to a stronger Pt/support interaction during the deposition of Pt onto the surface-functionalized Ketjenblack.…”

Stretchable current collectors based on carbon embedded in a poly (acrylamide)/poly (N,N-methylenebisacrylamide) hydrogel modified with Nafion 117®

“…Listing one, it strongly lowers zeta potential on nanotubes in isopropanol suspensions [28]. An excellent ionic conductivity of Nafion 117 ® is another advantage and leads to improvement of electrochemical response (i.e., double-layer capacitance) of dispersed nanotubes [40,41]. This is related to the formation of percolated water channels that facilitate proton transport via a vehicular mechanism, which was analyzed by small angle neutron scattering (SANS) [42].…”

Inherent Acidity of Perfluorosulfonic Acid Ionomer Dispersions and Implications for Ink Aggregation

“…It has been demonstrated that these different solution-phase morphologies directly impact cast film properties; [6][7][8][9][10][11][12][13][14] ionomers maintain a memory of these structures. 15 These solvent effects must also change the interactions driving ionomer-particle aggregation/stability in an ink, because different water:alcohol ratio inks each exhibit different aggregate sizes, 7,[16][17][18][19][20][21][22] and once dried, different CL morphology, water uptake, conductivity, etc.…”