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To develop high-performance anion exchange membranes (AEMs), the effect of the length of semi-fluoroalkyl pendants on physical and electrochemical properties of the resulting AEMs was investigated. A series of 2,5-dichlorobenzene monomers differing in semi-fluoroalkyl pendant length were synthesized and copolymerized with 2,2-bis(4-chlorophenyl)hexafluoropropane and piperidine functionalized 2,7-dichlorofluorene. The terpolymers provided bendable membranes by solution casting. The membranes with comparable ion exchange capacity (IEC = ca. 1.85 meq g−1) showed similar water uptake, while the hydroxide ion conductivity increased by 24% on increasing the pendant chain from 7 to 11 carbons. The maximum ion conductivity of 112 mS cm−1 (at 80 °C) was achieved for the membrane formulated with the C11 pendant. Cx-QPip-n membranes showed good alkaline stability; in particular, C11-QPip-1.86 retained 75% of the original conductivity after 1056 h under harsh alkaline conditions (8 M KOH at 80 °C). An alkaline water electrolysis cell assembled with the C11-QPip-1.86 membrane and with a PGM-free anode catalyst (Ni0.8Co0.2O) showed good performance (1.0 A cm−2 at 1.64 V) with high voltage efficiency (75%). The cell was durable for 1000 h with minor voltage change (28 μV h−1) under constant current density (1.0 A cm−2) operation. [ABSTRACT FROM AUTHOR]

Designing suitable anion exchange ionomers is critical to improving the performance and in situ durability of anion exchange membrane water electrolyzers (AEMWEs) as one of the promising devices for producing green hydrogen. Herein, highly gas‐permeable and dimensionally stable anion exchange ionomers (QC6xBA and QC6xPA) are developed, in which bulky cyclohexyl (C6) groups are introduced into the polymer backbones. QC650BA‐2.1 containing 50 mol% C6 composition shows 16.6 times higher H2 permeability and 22.3 times higher O2 permeability than that of QC60BA‐2.1 without C6 groups. Through‐plane swelling of QC650BA‐2.1 decreases to 12.5% from 31.1% (QC60BA‐2.1) while OH− conductivity slightly decreases (64.9 and 56.2 mS cm−1 for QC60BA‐2.1 and QC650BA‐2.1, respectively, at 30 °C). The water electrolysis cell using the highly gas permeable QC650BA‐2.1 ionomer and Ni0.8Co0.2O in the anode catalyst layer achieves two times higher performance (2.0 A cm−2 at 1.69 V, IR‐included) than those of the previous cell using in‐house ionomer (QPAF‐4‐2.0) (1.0 A cm−2 at 1.69 V, IR‐included). During 1000 h operation at 1.0 A cm−2, the QC650BA‐2.1 cell exhibits nearly constant cell voltage with a decay rate of 1.1 µV h−1 after the initial increase of the cell voltage, proving the effectiveness of the highly gas permeable and dimensionally stable ionomer in AEMWEs. [ABSTRACT FROM AUTHOR]

To investigate the effect of cross‐linking on partially fluorinated anion exchange membranes tethered with trimethylpropyl side chains (QPAF‐C3), styrene‐based cross‐linker is introduced into the precursor copolymers and then cross‐linked via free radical reaction. The one‐pot cross‐linking and quaternization reactions are successful as confirmed through nuclear magnetic resonance spectra. By solution casting, the resulting polymers provide flexible membranes (xQPAF‐C3‐VB) with 9.1–36.0% degree of cross‐linking. The cross‐linking results in smaller hydrophilic/hydrophobic phase‐separated morphology as confirmed by transmission electron microscopy images. The cross‐linking effect on the membrane properties is observed in the suppressed water uptake and decreased hydroxide ion conductivity. Among the cross‐linked membranes, xQPAF‐C3‐VB membranes with 17.4% degree of cross‐linking and 1.16 meq g−1 of ion exchange capacity exhibit the highest hydroxide ion conductivity (56 mS cm−1 at 30 °C) that is comparable to that of the pristine membrane (54 mS cm−1). The cross‐linking contributes to improving the thermomechanical properties with higher glass transition temperature. The cross‐linked xQPAF‐C3‐VB is applied to alkaline water electrolyzer to achieve high efficiency (74%) and reasonable performance (1.67 V at 1.0 A cm−2). [ABSTRACT FROM AUTHOR]

A 3D structural model for fuel cell catalysis systems is constructed, which consist primarily of Pt and CeO2 nanoparticles, to fit observed small angle X‐ray scattering (SAXS) patterns by using the reverse Monte–Carlo (RMC) method. The observed SAXS patterns are well reproduced by those of the simulations. Pore size distributions using the obtained structure models are compared with the Barrett–Joyner–Halenda (BJH) analysis for the nitrogen gas adsorption data, and the lower quartiles and medians of the pore diameters are reasonably consistent. In addition, analysis of the SAXS patterns indicates that the number of nanometer‐size Pt particles is much smaller than that of the introduced amount. This suggests that most Pt particles are not uniformly distributed in the catalysis system. [ABSTRACT FROM AUTHOR]

To evaluate the effect of the piperidinium structure on the properties of anion-exchange membranes, hydrophilic components containing five different piperidinium head groups were designed and combined with hydrophobic components (hexafluoroisopropylidene biphenylene groups) to obtain a series of target copolymers. The effect of CH3– and CF3– substituents was less on the mechanical properties of the copolymer membranes, and more prominent on the hydroxide-ion conductivity and chemical stability in the order of QBP-1 (no substituents) > QBP-2 (with methyl) > QBP-3 (with dimethyl) > QBP-4 (with trifluoromethyl), which was related to the extent of water uptake. QBM-2.7 with ammonium nitrogen at the terminal position of the side chains achieved the highest chemical stability (86% conductivity remaining after a 1000 h stability test in 8 M KOH at 80 °C). A QBM-2.7 membrane was applied to an alkaline water electrolysis cell, which exhibited high current efficiency (76%) and performance (1.62 V at 1.0 A cm−2) and was operable for 1000 h with minor changes in the cell performance. [ABSTRACT FROM AUTHOR]