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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 improve the properties of quaternized QPAF‐4 copolymers as anion exchange membranes, compositing with hydrophilic Ta–TiO2 particles are investigated. Flexible QPAF‐4/Ta–TiO2 composite membranes are obtained using solution‐casting and die coating methods. Cross‐sectional scanning electron microscopy reveals that the die coating method produces a more homogenous and uniform distribution of Ta–TiO2 particles in the composite membranes than the solution‐casting method. The Ta‐TiO2 particles promotes the suppression of water absorbability and dimensional swelling of the composite membranes which is more pronounced in the die coated membranes. The Ta–TiO2 increase hydroxide ion conductivity to 116.9 mS cm−1 at 80 °C for the die‐coated membrane, surpassing that of the pristine QPAF‐4 membrane (92 mS cm−1). Ta–TiO2 with the composite membranes survive in 4 m KOH at 80 °C for 1000 h, maintaining 96–112 mS cm−1 (88–99% remaining) of initial conductivity. All composite membranes exhibit higher mechanical robustness (elongation of >200%), with the die‐coated composite membranes. The optimized die coated composite membrane is fabricated in an alkaline water electrolysis cell achieving 1.63 V at 1.0 A cm−2 (75.5% efficiency). [ABSTRACT FROM AUTHOR]

Alkaline‐stable, highly conductive anion exchange membranes (AEMs) are attentively expected solid polymer electrolytes that contribute to achieving high performance and durability for anion exchange membrane water electrolyzers (AEMWEs). The technical challenges of AEMs mainly stem from the degradation of the polymer backbones, side chains, and anchoring cationic groups. Herein, new and stable AEMs (QTAF) are designed using 3,3′′‐dichloro‐2′,5′‐bis(trifluoromethyl)‐1,1′:4′,1′′‐terphenyl (TFP) monomers as the hydrophobic component incorporated into the polyphenylene backbone and 3,3′‐(2,7‐dichloro‐9H‐fluorene‐9,9‐diyl)bis(N,N‐dimethylpropane‐1‐amine) (AF) monomers as the hydrophilic component. After tuning the copolymer composition, the highest hydroxide ion conductivity (168.7 mS cm−1 at 80 °C) is achieved with the QTAF‐3.0 membrane. The QTAF‐3.0 membrane survives in harsh alkaline conditions (8 M KOH solution, 80 °C), with high conductivity (75.8 mS cm−1) after 810 h. A water electrolysis cell with QTAF‐3.0 membrane and non‐noble Ni0.8Co0.2O anode catalyst operates stably at a constant current density (1.0 A cm−2) for 1000 h with a negligible voltage increase rate of 1.1 µV h−1 after the initial voltage increase. The water electrolysis performance of the post‐tested QTAF‐3.0 cell is 1.83 V, only a 6.4% increase from the initial performance at 2.0 A cm−2, suggesting the high potential of the QTAF‐3.0 membrane for practical AEMWE applications. [ABSTRACT FROM AUTHOR]