High-Performance Fuel Cell Operable at 120 °C Using Polyphenlyene Ionomer Membranes with Improved Interfacial Compatibility

Abstract

While the performance and durability of proton exchange membrane fuel cells (PEMFCs) have been considerably improved over the last decade, high-temperature operation (above 100 °C) is still an issue. We designed a sulfonated polyphenylene containing tetrafluorophenylene groups (SPP-QP-f) for high-temperature and low-humidity operation of PEMFCs. Compared to state-of-the-art perfluorinated PEMs and the previous polyphenylene ionomer membrane with no fluorine-containing groups, the SPP-QP-f membrane exhibited superior proton conductivity under all testing conditions (80−120 °C, 20−95% RH). Because of the improved interfacial compatibility with the catalyst layers, the SPP-QP-f membrane induced high cathode catalytic activity. These attractive properties of the SPP-QP-f membrane resulted in high fuel cell performance (390 mW cm −2 maximum power density) at 120 °C and 30% RH. The durability was confirmed under accelerated degradation conditions (100 °C, 30% RH) for 1000 h.

ePTFE reinforced, sulfonated aromatic polymer membranes enable durable, high-temperature operable PEMFCs

“…The higher IEC contributed to more developed phase-separated morphology. Compared with that (3.0–3.5 nm) of SPP-QP-f membranes ( Long and Miyatake, 2021 ), the domain size of the SPP-TP-f with the similar IECs (3.1–4.1 mequiv g −1 ) was slightly smaller because of the smaller TP-f groups. The hydrophilic/hydrophobic domains were much smaller than the pore size of the ePTFE substrate (400–700 nm), implying that the nano-morphology of the ionomer would not be interfered by the substrate in the reinforced membrane.…”

“…The chemical structure of TP-f monomer and SPP-TP-f was confirmed by 1 H and 19 F NMR spectra in Figures S1 and S2 . Compared with our previous SPP-QP-f containing tetrafluoro-quinquephenyl groups as the hydrophobic moiety ( Long and Miyatake, 2021 ) (Mw = 196–211 kDa, Mn = 51–54 kDa), SPP-TP-f polymers were obtained as higher molecular weight (Mw = 237.2–924.3 kDa, Mn = 40.7–51.9 kDa) ( Table 1 ) because the tetrafluorophenylene groups to effectively improve the polymerization reactivity were closer to the terminal Ph-Cl. These polymers possessed excellent solubility in polar organic solvents such as DMSO and DMF to provide flexible membranes by solution casting.…”

“…There was an incompatibility issue with the Nafion-based catalyst layers for SPP-QP ( Ahn et al., 2018 ). To address the issues, tetrafluorophenylene groups were introduced to prepare SPP-QP-f membranes more recently ( Long and Miyatake, 2021 ). Compared with Nafion NRE 211 membrane, SPP-QP-f possessed superior proton conductivity, catalytic performance and fuel cell performance at a wide range of temperature (80–120°C) and humidity (30–100% RH).…”

Hydrocarbon-based Pemion™ proton exchange membrane fuel cells with state-of-the-art performance

“…The work of Holdcro, Kreuer and Miyatake are the most well-known ones in developing hydrocarbon (membrane) ionomers for low to mid-temperature fuel cells (<150 C) to-date and have published many articles on benchmark hydrocarbon-based MEAs. 6,33,49,50 Not shown in Fig. 3 is, for instance, the excellent work of Long et al 50 with sulfonated poly(phenylene) containing additional tetrauorophenylene groups in the membrane, but with Naon™ as electrode electrolyte.…”

“…6,33,49,50 Not shown in Fig. 3 is, for instance, the excellent work of Long et al 50 with sulfonated poly(phenylene) containing additional tetrauorophenylene groups in the membrane, but with Naon™ as electrode electrolyte. The power density at 0.6 V was 0.9 W cm À2 , which is higher than the to-date reported fully hydrocarbon cells (0.7 W cm À2 ) at the same potential.…”