Modifying the Electrocatalyst–Ionomer Interface via Sulfonated Poly(ionic liquid) Block Copolymers to Enable High-Performance Polymer Electrolyte Fuel Cells

Abstract

Polymer electrolyte membrane fuel cell (PEMFC) electrodes with a 0.07 mg Pt cm −2 Pt/Vulcan electrocatalyst loading, containing only a sulfonated poly(ionic liquid) block copolymer (SPILBCP) ionomer, were fabricated and achieved a ca. 2× enhancement of kinetic performance through the suppression of Pt surface oxidation. However, SPILBCP electrodes lost over 70% of their electrochemical active area at 30% RH because of poor ionomer network connectivity. To combat these effects, electrodes made with a mix of Nafion/ SPILBCP ionomers were developed. Mixed Nafion/SPILBCP electrodes resulted in a substantial improvement in MEA performance across the kinetic and mass transport-limited regions. Notably, this is the first time that specific activity values determined from an MEA were observed to be on par with prior half-cell results for Nafion-free Pt/Vulcan systems. These findings present a prospective strategy to improve the overall performance of MEAs fabricated with surface accessible electrocatalysts, providing a pathway to tailor the local electrocatalyst/ionomer interface.

Cathode Design for Proton Exchange Membrane Fuel Cells in Automotive Applications

“…Some ILs possess excellent oxygen solubility and diffusivity, although not as good as Nafion ionomer, they can penetrate the small pores that cannot be reached by the large ionomer cluster thus enhancing catalyst utilization ratio. Li et al [69] introduced a sulfonated poly(ionic liquid) block copolymer (SPILBCP) as an additive to Nafion ionomer in the catalyst layer. From an electrode structure point of view illustrated in Fig.…”

“…This resistance can be significantly reduced by improving the ionomer distribution to form a homogeneous thin layer on the catalyst surface. Potential strategies include modifying the catalyst support (e.g., NH 3 or N-groups functionalizing carbon support), using SSC ionomer or even combining with ILs, [12,64,69,80] which have been discussed in Sect. 2.…”

Emerging Applications of Solid Catalysts with Ionic Liquid Layer Concept in Electrocatalysis

“…Most recently, an attempt on implementation of ILs in MEAs was made by Neyerlin et al., who studied the MEA performance of Pt/C catalyst in presence of a sulfonated poly IL block copolymer (SPILBCP). [ 117 ] First, they found that the SPILBCP can replace the conventional Nafion as an ionomer, and the fabricated MEA (Nafion‐free) exhibited a two times higher specific activity (@0.9 V) relative to that using pristine Pt/C catalyst, which was comparable to that obtained using RDE. The IL boosting effect was assumed to benefit from the suppressed formation of Pt oxide in the presence of the IL.…”

<i>Operando</i> X-ray Absorption Spectroscopic Study on the Effect of Ionic Liquid Coverage upon the Oxygen Reduction Reaction Activity of Pd-core Pt-shell Catalysts

“…Apart from tuning the active sites, the Pt-electrolyte interface has an important role in ORR. 21,22 A hydrophobic ionic liquid (IL) modification of Pt surface has recently emerged as another method to enhance the activity of Pt-based catalysts for ORR. [23][24][25] Many groups have investigated the ability of IL modifications to enhance ORR activity with a variety of IL.…”