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Giron Rodriguez et al. [ACS Sustainable Chem. Eng., 2023, 11, 1508] previously showed that radiation-grafted anion-exchange membranes containing N-benzyl-N-methylpiperidinium headgroups (MPIP-RG-AEM) are promising for use in CO2 electrolysis (cf. commercial and other RG-AEM types). For a more sustainable synthesis, MPIP-RG-AEMs have now been fabricated using a reduced 1.1 times excess of amine reagent (historically made using >5 times excess). A resulting RG-AEM promisingly had a bulk amination level that was comparable to those made with the traditional large excess. Unexpectedly, however, it had a significantly reduced water content, with two further batches showing that this observation was repeatable (and reproducible via measurements collected on a single batch using different techniques in different labs). The ionic conductivities of the RG-AEM made with a controlled 1.1 excess of amine were also lower, with higher activation energies. Terahertz time-domain spectroscopy measurements showed that the lower water uptake RG-AEMs, made with the 1.1 amine excess, contained smaller amounts of bulk water relative to bound water (a repeatable observation with different counter-anions). This lack of bulk water, yielding reduced water diffusion coefficients, led to a change in the water management when such RG-AEMs were tested in CO2 electrolysis cells, with significantly affected in situ performances. Small angle scattering data (X-ray and neutron) indicated that MPIP-RG-AEM fabrication with the 1.1 excess of amine reduced the size of the amorphous lamella domains on hydration, and this change is suspected to be the cause of the lower water uptakes and swelling. The finding that chemically similar AEMs can have significantly different hydration properties is potentially important to all ion-exchange membrane users and developers (beyond the CO2 electrolysis scope of this study). [ABSTRACT FROM AUTHOR]

Summary: Herein, we describe the incorporation of cerium oxide‐coated amine‐functionalized titania nanorods (CeO2‐ATiO2) as a bifunctional nanofiller in sulfonated poly(ether ether ketone) (SPEEK) as a cost‐effective and high‐performance proton exchange membrane (PEM) for PEM fuel cells (PEMFCs). Facile and effective functionalization of TiO2 was performed using amine‐containing organic moieties, followed by coating the ATiO2 nanorods with CeO2. A simple solution casting method was employed to incorporate CeO2‐ATiO2 into the SPEEK matrix with various weight ratio of 0.5%, 1%, 2%, 4%, or 6%. The successful incorporation of prepared nanofiller in the SPEEK membrane matrix was confirmed by structural and morphological studies such as Fourier transform infrared, X‐ray diffractometer, scanning electron microscopy, and atomic force microscope of the SPEEK/CeO2‐ATiO2 composite membranes. The presence of ATiO2 improved proton conductivity while CeO2 alleviated the chemical degradation of the membrane by scavenging free radicals. The proton conductivity of an SPEEK/CeO2‐ATiO2 (2 wt%) nanocomposite membrane at 60°C under 20% relative humidity (RH) was 17.06 mS cm−1 whereas that of a bare SPEEK membrane under the same conditions was only 4.53 mS cm−1. PEMFCs containing SPEEK/CeO2‐ATiO2 (2 wt%) nanocomposite membrane attained a maximum power density of 117 mW cm−2 at a load current density of 371 mA/cm2 at 60°C under 100% RH. In contrast, a PEMFC containing the bare SPEEK membrane delivered a power density of 91 mW cm−2 at a load current of 253 mA cm−2. A single cell open circuit voltage (OCV) test to examine the durability of membranes revealed that a PEMFC with an SPEEK/CeO2‐ATiO2 (2 wt%) membrane showed excellent stability with an OCV decay of 0.925 mV h−1 at 60°C under 30% RH, whereas that of a PEMFC with a bare SPEEK membrane was 3.437 mV h−1 under identical conditions. Based on the abovementioned results, it is found that the SPEEK/CeO2‐ATiO2 nanocomposite membranes overcome the durability issues of pristine SPEEK membranes and show enhanced electrochemical performance under a harsh PEMFC environment. Highlights: CeO2‐ATiO2 was utilized as a bifunctional filler to fabricate composite membrane.Integration of CeO2‐ATiO2 improved the proton conductivity of sulfonated poly(ether ether ketone) (SPEEK) under low relative humidity.Addition of CeO2‐ATiO2 to SPEEK resulted in improved physiochemical and thermomechanical properties.Optimized SPEEK/CeO2‐ATiO2 (2 wt%) exhibited improved proton exchange membrane fuel cell performance while retaining excellent durability compared to pristine SPEEK. [ABSTRACT FROM AUTHOR]

Nafion, a perfluorosulfonic acid (PFSA) polymer, is a vital electrolyte that extensively contributes to the commercialization of polymer electrolyte fuel cells (PEFCs). However, adopting Nafion in high-temperature (HT) PEFCs (HT-PEFCs) is still a great challenge. Herein, we present a potential additive (carbon nitride–gadolinium zirconium oxide (gC3N4–Gd2Zr2O7)) to simultaneously extend the power density and lifetime of Nafion in HT-PEFCs. Owing to the porous nature, radical-scavenging ability, and thermal stability of gC3N4–Gd2Zr2O7, the Nafion/gC3N4–Gd2Zr2O7 membrane exhibited high water uptake, oxidative stability, and thermomechanical stability compared to the unmodified Nafion membrane. At 100 °C under 30% RH, the maximum power density of Nafion/gC3N4–Gd2Zr2O7 was 504 mW cm−2 at a load current density of 804 mA cm−2, which is 1.9 and 2.3 fold higher than that of commercial Nafion-212 and pristine Nafion membranes. Moreover, Nafion/gC3N4–Gd2Zr2O7 displays an open-circuit voltage (OCV) decay of 0.1 mV h−1 during 515 h of continuous operation, which is significantly lower than that of the Nafion membrane during the 300 h durability operation (2.8 mV h−1). When increasing the operating temperature to 125 °C under 15% RH, the Nafion/gC3N4–Gd2Zr2O7 based PEFC largely outperforms the Nafion-212 and pristine Nafion-based PEFCs, achieving an output of 380 mW cm−2, one of the most competitive HT-PEFC power densities reported for Nafion-based membranes. Post durability tests further ensure the superior stability of Nafion/gC3N4–Gd2Zr2O7 during HT-PEFC operation. The present study provides deep insight into developing and understanding of advanced Nafion composite membranes applicable for HT-PEFCs. [ABSTRACT FROM AUTHOR]

Summary: In this work, sulfonated diblock copolymers (SDBCs) were prepared by polycondensation of sulfonated poly(ether‐ether‐ketone) (SPEEK) and hydrophobic oligomer, which were combined with sintered anatase titanium oxide (S‐An‐TiO2) to create a hybrid membrane for apply in proton exchange membrane fuel cells (PEMFCs) operating with low relative humidity (RH). Then, a series of composite membranes (SDBC/S‐An‐TiO2) were prepared by varying the wt% of S‐An‐TiO2 blended with SDBC. The results showed that appropriate quantity (ie, 15 wt%) of S‐An‐TiO2 can significantly improve the proton conductivity and physiochemical properties of prepared composite membrane, as well as the PEMFC performance and durability under 20% RH. The 1.5 wt% of SDBC/S‐An‐TiO2 offers high current output, power output, and durability values at 60°C under 20% RH, which are 0.207 A cm−2, 0.074 W cm−2 and over 90 hours, respectively. These results can be attributed to the good interfacial compatibility between S‐An‐TiO2 and SDBC. [ABSTRACT FROM AUTHOR]

Sulfonated poly (vinylidene fluoride-co-hexafluoropropylene) (SPVdF-HFP)/sulfonated graphene oxide (SGO) hybrid membrane was prepared via solution casting process. Incorporation of SGO nanosheets into SPVdF-HFP matrix increases the density of sulfonic acid moieties of hybrid membrane. This offer better water uptake, good proton conductivity, than pristine SPVdF-HFP membrane. Additionally, the complex structure generated between SGO and membrane chains helps to reduce methanol uptake and swelling ratio of the hybrid membrane. The formation of electrostatic interaction between membrane backbone and SGO skeleton helps the SPVdF-HFP/SGO to retained lower weight loss than SPVdF-HFP during TGA analysis. The presence of SGO nanosheets in membrane matrix is confirmed by morphological studies. The SPVdF-HFP/SGO membrane achieved maximum proton conductivity of 7.8 mS/cm at 70 °C and low methanol permeability of 2.567 × 10−7 cm2/s at 70 °C whereas the pristine SPVdF-HFP membrane exhibits 1.7 mS/cm and 3.105 × 10−7 cm2/s. From the obtained good results of hybrid membrane, we believe that the SPVdF-HFP/SGO would be a promising candidate for the application of DMFCs. [ABSTRACT FROM AUTHOR]