High-temperature low-humidity proton exchange membrane with “stream-reservoir” ionic channels for high-power-density fuel cells

Abstract

The perfluorosulfonic acid (PFSA) proton exchange membrane (PEM) is the key component for hydrogen fuel cells (FCs). We used in situ synchrotron scattering to investigate the PEM morphology evolution and found a “stream-reservoir” morphology, which enables efficient proton transport. The short-side-chain (SSC) PFSA PEM is fabricated under the guidance of morphology optimization, which delivered a proton conductivity of 193 milliSiemens per centimeter [95% relativity humidity (RH)] and 40 milliSiemens per centimeter (40% RH) at 80°C. The improved glass transition temperature, water permeability, and mechanical strength enable high-temperature low-humidity FC applications. Performance improvement by 82.3% at 110°C and 25% RH is obtained for SSC-PFSA PEM FCs compared to Nafion polymer PEM devices. The insights in chain conformation, packing mechanism, crystallization, and phase separation of PFSAs build up the structure-property relationship. In addition, SSC-PFSA PEM is ideal for high-temperature low-humidity FCs that are needed urgently for high-power-density and heavy-duty applications.

All-Perfluorosulfonated-Ionomer Composite Membranes Containing Blow-Spun Fibers: Effect of a Thin Fiber Framework on Proton Conductivity and Mechanical Properties

“…The composite membranes containing 10 and 15 wt % PFSA thin fibers showed higher proton conductivity in the wide range of temperature. The activation energy ( E a ) of the proton conductivity through the thin fiber composite membranes (7.7–9.8 kJ mol –1 ) compares with that through the pristine Aquivion membranes (8.5 kJ mol –1 ) (these values also compare with the reported E a value for the short-side-chain PFSA of 6.7 kJ mol –1 ), indicating intrinsic superior proton conduction of the solid-state Aquivion with and without fiber framework. On the contrary, the composite membrane containing 15 wt % ion-insulating PVDF thin fibers showed the lower proton conductivity and higher E a value of 22 kJ mol –1 more than expected (the temperature dependence of the proton conductivity is shown in Figure S8).…”

Colloidal Nafion Particles: Are Cylinders Ubiquitous?

“…In summary, we demonstrate that commonly reported, cylindrical morphologies are not ubiquitous among Nafion dispersions and assuming such may provide incomplete information. − Specifically regarding the dispersing technique, redispersing precast Nafion results in incomplete separation of the polymer strands and manifests in scattering peak, which complicates the deduction of morphology. Our SANS analyses using model-dependent and model-independent techniques combined with MD simulations demonstrate highly solvated, gel-like particles best describe Nafion particles in NMP, which is in stark contrast to the commonly assumed cylindrical morphology.…”

“…Perfluorosulfonic acids (PFSAs) are widely used in electrochemical systems for proton transport . For decades, PFSAs have been on the leading edge of proton exchange membrane (PEM) technologies and are an essential part of research efforts to improve device performance. − PFSA ionomer dispersions are used to fabricate solution-cast membranes as well as thin-film electrodes, and the PFSA dispersion morphology directs the final nanoscale structure of those membranes and electrodes, ultimately determining their performance. − Recent studies focusing on the correlation between PFSA membrane morphology and device performance have highlighted the critical importance of PFSA morphology prior to membrane formation in fuel cells, , CO 2 capture, and redox flow batteries . Therefore, understanding the PFSA dispersion morphology is crucial to enable the tailored interface design for electrochemical devices.…”

Molecular Complexation of Polymers and Metal Oxide Clusters for Semicrystalline, Thermoplastic Anhydrous Proton Exchange Membranes in Fuel Cells

“…Because PEG–SiW 12 nanocomposites are prone to material softening and deformation under realistic test conditions above 80 °C and high gas back pressure thus leading to device failure, we explore the performance of a H 2 /O 2 fuel cell with PEG400–80%SiW 12 as the proton exchange membrane at 45, 55, and 70 °C without a humidifier. The obtained maximum open-circuit voltage and maximum power density are 0.96 V and 476 mW cm –2 at 70 °C, respectively, implying that the PEG–POM nanocomposites have potential for further development in the field of anhydrous PEMFCs (Figure d). − …”