• Energy Research

Abstract We demonstrate that small and narrow hydrophilic conducting domain morphology in sulfonated aromatic membranes leads to much better fuel cell performance at medium temperature and low humidity conditions than those with larger hydrophilic domains. A comparison of three types of sulfonated poly(arylene ether sulfone)s (SPAES) with random, block, and graft architecture indicates that small hydrophilic domain sizes ( 100 °C) fuel cell applications. The graft copolymer outperformed both a random copolymer and multiblock copolymer at 120 °C and 35% RH fuel cell operating conditions due to capillary condensation of water within the 3–5 nm hydrophilic domains.

An ultramicroporous membrane provides highly selective ion transport, enabling power generation from solutions with/without salinity difference, or potentially from wastewater. This extends the concept of extracting Gibbs energy from solution mixing.

Abstract Sulfonated poly(phthalazinone ether ketone nitrile) copolymers (SPPEKN) were prepared by copolymerization of disodium 3,3′-disulfonate-4,4′-difluorobenzophenone (SDFB-Na), 2,6-difluorobenzonitrile (2,6-DFBN), and 4-(4-hydroxyphenyl)-1(2H)-phthalazinone (DHPZ) at 160 °C in N-methyl-2-pyrrolidione containing anhydrous potassium carbonate. The polymerization reactions proceeded smoothly and in high yield giving high molecular weight SPPEKN copolymers with different sulfonic acid content (SC) values. The polymer structures were defined by 1H NMR and FT-IR. Membrane films of SPPEKN copolymers in both salt and acid forms, prepared at SDFB-Na to 2,6-DFBN feed ratios up to 60/40 mol/mol, were cast from the N,N-dimethylacetamide (DMAc) polymer solutions. The presence of highly polar nitrile groups are expected to increase inter-chain molecular forces, contributing to the observed reduction in water swelling over previously prepared sulfonated poly(phthalazinone ether ketone) (SPPEK) copolymers. Membranes containing nitrile groups are expected to show improved adhesion between polymer and catalyst when utilized in a fuel cell. All SPPEKN copolymers exhibited tensile strength higher than that of Nafion®117. The proton conductivities of acid form SPPEKN copolymers (SPPEKNH)s, prepared at the sulfonated/unsulfonated monomer feed ratio above 0.35 mol/mol, were around 10−1 S/cm at 80 °C, which is close to or higher than that of Nafion®117 under same measurement conditions.

Abstract This paper reports the fuel cells (DMFC and PEMFC) performance using sulfonated poly(arylene ether ether nitrile) (SPAEEN) copolymers containing sulfonic acid group arranged in structurally different ways. The membrane electrode assembly (MEA) fabricated from SPAEEN containing 60 mol% of angled naphthalenesulfonic acid group (m-SPAEEN-60) had superior performance over those derived from pendent naphthalenesulfonic acid group (p-SPAEEN) or sulfonated hydroquinone (HQ-SPAEEN) in H2/air and/or DMFC conditions. For example, the current density of the MEA using m-SPAEEN-60 at 0.5 V and 2.0 M methanol was 250 mA/cm2, whereas the current densities of the MEAs using p-SPAEEN-50 and HQ-SPAEEN-56 were 185 and 190 mA/cm2, respectively. In addition, compared with the sulfonated polysulfone (BPSH-35) and Nafion membranes, the copolymer containing nitrile group showed the improved cell performance. For example, the power density of the MEA using m-SPAEEN-60 at 250 mA/cm2 and 2.0 M methanol was 125 mW/cm2, whereas the power densities of the MEAs using sulfonated polysulfone (BPSH-35) and Nafion were 115 and 113 mW/cm2, respectively. m-SPAEEN-60 showed stable cell performance during extended operation (>100 h).

Abstract Highly fluorinated poly(arylene ether)s containing sulfonic acid groups meta to ether linkage (SPAE), intended for fuel cell applications as proton electrolyte membrane materials, were synthesized by potassium carbonate mediated nucleophilic polycondensation reactions of commercially available monomers: 2,8-dihydroxynaphthalene-6-sulfonated salt (2,8-DHNS-6), hexafluorobisphenol A (6F-BPA), and decafluorobiphenyl (DFBP) in dimethylsulfoxide (DMSO) at 160–170 °C. FT-IR and 1 H NMR were used to characterize the structures. The sulfonate or sulfonic acid contents (SC), expressed as a number per repeat unit of polymer and ranged from 0 to 0.79, were calculated from 19 F NMR. The proton conductivities of acid form membrane increased with SC value and reached 0.103 S/cm at 90 °C for SPAE 80. The methanol permeabilities ranged from 7.4 × 10 −7 to 2.2 × 10 −9 cm/s at 30 °C and were lower than those of other conventional sulfonated ionomer membranes, particularly commercial perfluorinated sulfonated ionomer (Nafion).

Abstract A novel acid–base blend membrane based on sulfonated poly(ether ether ketone) (SPEEK) and polysulfone bearing benzimidazole side groups has been synthesized, characterized, and evaluated in proton exchange membrane fuel cell (PEMFC). The benzimidazole group tethered to the polysulfone backbone acts as a medium through the basic nitrogen for transfer of protons between the sulfonic acid groups of SPEEK, supporting a Grotthuss-type mechanism in addition to the vehicle-type mechanism present among SPEEK. The blend membrane exhibits better performance in PEMFC at 90 and 100 °C compared to the pure SPEEK and Nafion 115 membranes. The polymers bearing pendant benzimidazole groups offer a promising strategy to develop new membranes that can operate at higher temperatures and low relative humidity.

Aligned nano-sponges accommodate only non-freezable water and facilitate efficient water retention in the membrane, even under low relative humidity conditions.

Solid electrolytes have attracted much attention due to their great prospects in a number of energy‐ and environment‐related applications including fuel cells. Fast ion transport and superior mechanical properties of solid electrolytes are both of critical significance for these devices to operate with high efficiency and long‐term stability. To address a common tradeoff relationship between ionic conductivity and mechanical properties, electrolyte membranes with proton‐conducting 2D channels and nacre‐inspired architecture are reported. An unprecedented combination of high proton conductivity (326 mS cm−1 at 80 °C) and superior mechanical properties (tensile strength of 250 MPa) are achieved due to the integration of exceptionally continuous 2D channels and nacre‐inspired brick‐and‐mortar architecture into one materials system. Moreover, the membrane exhibits higher power density than Nafion 212 membrane, but with a comparative weight of only ≈0.1, indicating potential savings in system weight and cost. Considering the extraordinary properties and independent tunability of ion conduction and mechanical properties, this bioinspired approach may pave the way for the design of next‐generation high‐performance solid electrolytes with nacre‐like architecture.