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Perovskite LaFeO3 nanofillers (0.1%) are incorporated into a quaternized poly(vinyl alcohol) (QPVA) matrix for use as hydroxide-conducting membranes in direct alkaline methanol fuel cells (DAMFCs). The as-synthesized LaFeO3 nanofillers are amorphous and functionalized with cetyltrimethylammonium bromide (CTAB) surfactant. The annealed LaFeO3 nanofillers are crystalline without CTAB. The QPVA/CTAB-coated LaFeO3 composite membrane shows a defect-free structure while the QPVA/annealed LaFeO3 film has voids at the interfaces between the soft polymer and rigid nanofillers. The QPVA/CTAB-coated LaFeO3 composite has lower methanol permeability and higher ionic conductivity than the pure QPVA and QPVA/annealed LaFeO3 films. We suggest that the CTAB-coated LaFeO3 provides three functions to the polymeric composite: increasing polymer free volume, ammonium group contributor, and plasticizer to enhance the interfacial compatibility. The composite containing CTAB-coated LaFeO3 results in superior cell performance. A maximum power density of 272 mW cm−2 is achieved, which is among the highest power outputs reported for DAMFCs in the literature.

Anion exchange membrane fuel cells have unique advantages and are thus gaining increasing attention. Poly(vinyl alcohol) (PVA) is one of the potential polymers for the development of anion exchange membranes. This review provides recent studies on PVA-based membranes as alternative anion exchange membranes for alkaline fuel cells. The development of anion exchange membranes in general, including the types, materials, and preparation of anion exchange membranes in the last years, are discussed. The performances and characteristics of recently reported PVA-based membranes are highlighted, including hydroxide conductivity, water uptake, swelling degree, tensile strength, and fuel permeabilities. Finally, some challenging issues and perspectives for the future study of anion exchange membranes are discussed.

Alkaline fuel cells enable the use of earth-abundant elements to replace Pt but are hindered by the sluggish kinetics of the hydrogen oxidation reaction (HOR) in alkaline media. Precious metal–free HOR electrocatalysts need to overcome two major challenges: their low intrinsic activity from too strong a hydrogen-binding energy and poor durability due to rapid passivation from metal oxide formation. Here, we designed a Ni-based electrocatalyst with a 2-nm nitrogen-doped carbon shell (Ni@CNₓ) that serves as a protection layer and significantly enhances HOR kinetics. A Ni@CNₓ anode, paired with a Co–Mn spinel cathode, exhibited a record peak power density of over 200 mW/cm² in a completely precious metal–free alkaline membrane fuel cell. Ni@CNₓ exhibited superior durability when compared to a Ni nanoparticle catalyst due to the enhanced oxidation resistance provided by the CNₓ layer. Density functional theory calculations suggest that graphitic carbon layers on the surface of the Ni nanoparticles lower the H binding energy to Ni, bringing it closer to the previously predicted value for optimal HOR activity, and single Ni atoms anchored to pyridinic or pyrrolic N defects of graphene can serve as the HOR active sites. The strategy described here marks a milestone in electrocatalyst design for low-cost hydrogen fuel cells and other energy technologies with completely precious metal–free electrocatalysts.

The development of active hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR) catalysts for use in anion exchange membrane fuel cells (AEMFCs), which are free from platinum group metals (PGMs), is expected to bring this technology one step closer to commercial applications. This paper reports our recent progress developing HOR Pt-free and PGM-free catalysts (Pd/CeO2 and NiCo/C, respectively), and ORR PGM-free Co3O4 for AEMFCs. The catalysts were prepared by different synthesis techniques and characterized by both physical-chemical and electrochemical methods. A hydrothermally synthesized Co3O4 + C composite ORR catalyst used in combination with Pt/C as HOR catalyst shows good H2/O2 AEMFC performance (peak power density of ~388 mW cm−2), while the same catalyst coupled with our flame spray pyrolysis synthesised Pd/CeO2 anode catalysts reaches peak power densities of ~309 mW cm−2. Changing the anode to nanostructured NiCo/C catalyst, the performance is significantly reduced. This study confirms previous conclusions, that is indeed possible to develop high performing AEMFCs free from Pt; however, the challenge to achieve completely PGM-free AEMFCs still remains.

Designing high-performance nonprecious electrocatalysts to replace Pt for the oxygen reduction reaction (ORR) has been a key challenge for advancing fuel cell technologies. Here, we report a systematic study of 15 different AB₂O₄/C spinel nanoparticles with well-controlled octahedral morphology. The 3 most active ORR electrocatalysts were MnCo₂O₄/C, CoMn₂O₄/C, and CoFe₂O₄/C. CoMn₂O₄/C exhibited a half-wave potential of 0.89 V in 1 M KOH, equal to the benchmark activity of Pt/C, which was ascribed to charge transfer between Co and Mn, as evidenced by X-ray absorption spectroscopy. Scanning transmission electron microscopy (STEM) provided atomic-scale, spatially resolved images, and high-energy-resolution electron-loss near-edge structure (ELNES) enabled fingerprinting the local chemical environment around the active sites. The most active MnCo₂O₄/C was shown to have a unique Co-Mn core–shell structure. ELNES spectra indicate that the Co in the core is predominantly Co2.7+ while in the shell, it is mainly Co2+. Broader Mn ELNES spectra indicate less-ordered nearest oxygen neighbors. Co in the shell occupies mainly tetrahedral sites, which are likely candidates as the active sites for the ORR. Such microscopic-level investigation probes the heterogeneous electronic structure at the single-nanoparticle level, and may provide a more rational basis for the design of electrocatalysts for alkaline fuel cells.

This article presents a modeling and analysis approach for a hybrid photovoltaic wind turbine (PV-WT) hydrogen production system. This study uses the TRNSYS simulation platform to evaluate the system under coastal climate conditions in Perth, Australia. The system encapsulates an advanced alkaline electrolyzer (ELE) and an alkaline fuel cell (AFC). A comprehensive 4E (energy, exergy, economic, and environmental) assessment is conducted. The analysis is based on hourly dynamic simulations over a full year. Key performance metrics include hydrogen production, energy and exergy efficiencies, carbon emission reduction, levelized cost of energy (LCOE), and levelized cost of hydrogen (LCOH). The TRNSYS model is validated against the existing literature data. The results show that the system performance is highly sensitive to ambient conditions. A sensitivity analysis reveals an energy efficiency of 7.3% and an exergy efficiency of 5.2%. The system has an entropy generation of 6.22 kW/K and a sustainability index of 1.055. The hybrid PV-WT system generates 1898.426 MWh of renewable electricity annually. This quantity corresponds to 252.7 metric tons of hydrogen production per year. The validated model shows a stable LCOE of 0.102 USD/kWh, an LCOH of 4.94 USD/kg, an energy payback time (EPBT) of 5.61 years, and cut CO2 emissions of 55,777.13 tons. This research provides a thorough analysis for developing green hydrogen systems using hybrid renewables. This study also offers a robust prediction model, enabling further enhancements in hybrid renewable hydrogen production.

Anion exchange membranes (AEMs) find widespread applications as an electrolyte and/or electrode binder in fuel cells, electrodialysis stacks, flow and metal-air batteries, and electrolyzers. AEMs exhibit poor stability in alkaline media; their degradation is induced by the hydroxide ion, a potent nucleophile. We have used 2D NMR techniques to investigate polymer backbone stability (as opposed to cation stability) of the AEM in alkaline media. We report the mechanism behind a peculiar, often-observed phenomenon, wherein a demonstrably stable polysulfone backbone degrades rapidly in alkaline solutions upon derivatization with alkaline stable fixed cation groups. Using COSY and heteronuclear multiple quantum correlation spectroscopy (2D NMR), we unequivocally demonstrate that the added cation group triggers degradation of the polymer backbone in alkaline via quaternary carbon hydrolysis and ether hydrolysis, leading to rapid failure. This finding challenges the existing perception that having a stable cation moiety is sufficient to yield a stable AEM and emphasizes the importance of the often ignored issue of backbone stability.

Hydrogen fuel cell (FC) technologies are being worked on as a possible replacement for fossil fuels because they produce a lot of energy and do not pollute the air. In FC, ion-exchange membranes (IEMs) are the vital components for ion transport between two porous electrodes. However, the high production cost of commercialized membranes limits their benefits. Various research has focused on cellulose-based membranes such as IEM with high proton conductivity, and mechanical, chemical, and thermal stabilities to replace the high cost of synthetic polymer materials. In this review, we focus on and explain the recent progress (from 2018 to 2022) of cellulose-containing hybrid membranes as cation exchange membranes (CEM) and anion exchange membranes (AEM) for proton exchange membrane fuel cells (PEMFC) and alkaline fuel cells (AFC). In this account, we focused primarily on the effect of cellulose materials in various membranes on the functional properties of various polymer membranes. The development of hybrid membranes with cellulose for PEMFC and AFC has been classified based on the combination of other polymers and materials. For PEMFC, the sections are associated with cellulose with Nafion, polyaryletherketone, various polymeric materials, ionic liquid, inorganic fillers, and natural materials. Moreover, the cellulose-containing AEM for AFC has been summarized in detail. Furthermore, this review explains the significance of cellulose and cellulose derivative-modified membranes during fuel cell performance. Notably, this review shows the vital information needed to improve the ion exchange membrane in PEMFC and AFC technologies.

Anion exchange ionomer (AEI) binders are critical to the performance of alkaline electrochemical devices (i.e., fuel cells, electrolyzers, and batteries), as they facilitate ion transport, provide structural integrity, and improve the overall performance and lifespan of these devices. These binders not only ensure ion transport but also provide mechanical stability to the electrode materials. Recently, there has been significant progress in designing AEIs that are more compatible with existing electrode materials and electrolytes. This review summarizes the different types of AEI binders, focusing on their chemical structure, functionalization, conductivity, and how they affect the performance of alkaline fuel cells, specifically, anion exchange membrane fuel cells (AEMFCs). It also discusses how factors like functional groups, polymer backbone and side-chain flexibility, and ion exchange capacity balance conductivity, mechanical strength, and water uptake (WU). Recent advances in material design, such as polymer blends, composites, and crosslinked ionomers, as well as electrode setup, such as asymmetric ionomer electrodes, are explored as methods for improving stability and ion transport. The main challenges facing AEIs, including water management, alkaline degradation, phase separation, mechanical robustness, and long-term durability, are discussed along with strategies for overcoming them. Finally, we outline future research directions for developing scalable, economical solutions and integrating these binders with new electrode materials to help improve the performance and stability of next-generation AEMFCs.

A series of novel blended anion exchange membranes (AEMs) were prepared with hyperbranched brominated poly(arylene ether sulfone) (Br-HB-PAES) and linear chloromethylated poly(phenylene oxide) (CM-PPO). The as-prepared blended membranes were fabricated with different weight ratios of Br-HB-PAES to CM-PPO, and the quaternization reaction for introducing the ionic functional group was performed by triethylamine. The Q-PAES/PPO-XY (quaternized-PAES/PPO-XY) blended membranes promoted the ion channel formation as the strong hydrogen bonds interconnecting the two polymers were maintained, and showed an improved hydroxide conductivity with excellent thermal behavior. In particular, the Q-PAES/PPO-55 membrane showed a very high hydroxide ion conductivity (90.9 mS cm−1) compared to the pristine Q-HB-PAES membrane (32.8 mS cm−1), a result supported by the morphology of the membrane as determined by the AFM analysis. In addition, the rigid hyperbranched structure showed a suppressed swelling ratio of 17.9–24.9% despite an excessive water uptake of 33.2–50.3% at 90 °C, and demonstrated a remarkable alkaline stability under 2.0 M KOH conditions over 1000 h.