Anion exchange and bipolar membrane fuel cells generate electrical energy directly from chemical fuels and have attracted considerable interests as alternate power sources for large market applications, such as transportation (hydrogen fuel cells) and unmanned vehicles (sodium borohydride fuel cells). Anion exchange membrane (AEM), generally composed of a polymer with covalently tethered ionic groups, is the central component of the fuel cell serving as the electrolyte, conducting hydroxide ions from cathode to anode, where fast ionic conduction is directly related to power output. However, AEMs currently used in fuel cells (H2 fuel cells and sodium borohydride fuel cells) exhibit ion poor transport properties at operation conditions of fuel cells, such as low hydroxide ion conductivities at 80 °C. Another concern with the use of AEMs in fuel cells is their stabilities in strong alkaline environment. AEMs suffer Hoffmann elimination, where the cation is cleaved and a direct nucleophilic (SN2) reaction where the cation is completely cleaved too.This dissertation targets on solving these two major obstacles for using AEMs as electrolytes in alkaline electrochemical energy storage and conversion. To solve the first problem, a triblock copolymer-based polymer (polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene, SEBS) has been developed to synthesize AEMs with high ion conductivities by engineering a phase-separated morphology. To address the second problem, novel cation groups such as imidazolium-based cation and phosphonium-based cation have been incorporated in AEMs. Also, by attaching a six-carbon alkyl spacer between polymer backbone and cation group, alkaline stability of such AEM has been investigated.Once the degradation mechanism of AEMs is well understood and AEMs with high ion conductivities have been developed, this dissertation focuses on developing such AEMs electrolyte for different electrochemical systems such as direct sodium borohydride fuel cells (DBFCs) and redox flow batteries (RFBs).Besides the concern of ionic conductivities and alkaline stabilities of AEMs in alkaline environment, another obstacle for the development of DBFC is the crossover of fuels and oxidants. We demonstrate a pH-gradient-enabled macroscale bipolar interface (PMBI) to effectively separate the anolyte and catholyte of the DBFC. The PMBI configuration enabled significantly enhanced performance in a DBFC as compared to either an all-anion-exchange or an all-cation-exchange configuration (330 mA/cm2 at 1.5 V and 630 mWpeak/cm2 at 1.0 V). The PMBI-type electrodes provide a new and fascinating design to engineer fuel-cell membrane electrode assemblies (MEAs). The bipolar-interface configuration also holds significant applicability in the field of water electrolysis, where the membrane could separate an acidic H2-evolution cathode (a very fast reaction) from an alkaline O2-evolution anode (possible on non-Pt-group metals) in a system wherein the benefits of the best electrodes of present acidic/alkaline water electrolyzers are combined.RFBs are promising candidates for large-scale energy storage systems, since the capacity, power and energy density parameters can be designed independently, which facilitates a convenient way of modification even after installation. AEMs play an important role as separators in some of RFBs where a degree of reactant isolation is required between the anolyte and catholyte compartments. A primary goal for membrane development in RFBs is to limit the diffusion of active species, while maintaining high oxidative stability in related species. A vanadium-cerium redox flow battery (V-Ce RFB) employing SEBS-based AEM as the separator yields an energy efficiency of 86% at a current density of 50 mA/cm2 with a 10% drop in capacity over 20 charge/discharge cycles. In contrast, a V-Ce RFB using Nafion®212 as the separator has an energy efficiency of 80% and a 40% drop in capacity over 20 charge/discharge cycles. The observed capacity fade is primarily due to cation intermixing between the anodic and cathodic compartments -- much better permselectivity has been obtained with the AEM separator. After 60 charge-discharge cycles (350 hours of operation), the ion exchange capacity and ionic conductivity of the AEM drops by about 20%. There has been no observed change in mechanical properties. The oxidative stability of the AEM has been evaluated ex situ by immersion in 1.5 M VO2+ + 3 M H2SO4 for 500 hours - the ionic conductivity remained constant over this timeframe.

This pioneering textbook on the topic provides a clear and well-structured description of the fundamental chemistry involved in these systems, as well as an excellent overview of the real-life practical applications. Prof. Holze is a well-known researcher and an experienced author who guides the reader with his didactic style, and readers can test their understanding with questions and answers throughout the text. Written mainly for advanced students in chemistry, physics, materials science, electrical engineering and mechanical engineering, this text is equally a valuable resource for scientists and engineers working in the field, both in academia and industry.

Anion exchange membranes (AEMs) are polymer-based electrolyte solids that conduct anions (OH-, HCO3-, Cl-, et al.), with positively charged groups bound covalently to the polymer backbones. There has been a strong and growing worldwide interest in the use of anion exchange membranes for electrochemical energy conversion and storage systems. Anion exchange membrane fuel cells (AEMFCs) have been regarded as promising energy conversion devices for stationary and mobile applications due to their potential low cost. To realize high-performance AEMFCs, new polymeric membranes are needed that are highly conductive and chemically stable. Herein, cross-linked, multication side chain, and fluorene side chain AEMs based on poly(2,6-dimethyl-1,4-phenylene oxide)s (PPO) were synthesized. PPO was chosen as an AEM substrate because of its ease of functionalization at large scale and relatively good stability and membrane properties. To produce anion conductive and durable polymer electrolytes for alkaline fuel cell applications, a series of cross-linked quaternary ammonium functionalized poly(2,6-dimethyl-1,4-phenylene oxide)s with mass-based ion exchange capacities (IEC) ranging from 1.80 to 2.55 mmol/g were synthesized via thiol-ene click chemistry. From small angle X-ray scattering (SAXS), it was found that the cross-linked membranes developed micro-phase separation between the polar PPO backbone and the hydrophobic alkyl side chains. The ion conductivity, dimensional stability, and alkaline durability of the cross-linked membranes were evaluated. The hydroxide ion conductivity of the cross-linked samples reached 60 mS/cm in liquid water at room temperature. The chemical stabilities of the membranes were evaluated under severe, accelerated aging conditions and degradation was quantified by measuring ion conductivity changes during aging. The cross-linked membranes retained their relatively high ion conductivity and good mechanical properties both in 1 M and 4 M NaOH at 80 °C after 500 h. Attenuated total reflection (ATR) spectra were used to study the degradation pathways of the membranes, and it was discovered that [beta]-hydrogen (Hofmann) elimination was likely to be the major pathway for degradation in these membranes. Side-chain containing AEMs with one, two or three cations per side chain were designed and synthesized, enabling a study of how the degree of polymer backbone functionalization and arrangement of cations on the side chain impact AEM properties. A systematic study of anion exchange membranes (AEMs) with multiple cations per side chain site was conducted to demonstrate how this motif can boost both the conductivity and stability of poly(2,6-dimethyl-1,4-phenylene oxide)-based AEMs. The highest conductivity, up to 99 mS/cm at room temperature, was observed for a triple-cation side chain AEM with 5 or 6 methylene groups between cations. This conductivity was considerably higher than AEM samples based on benzyltrimethyl ammonium or benzyldimethylhexyl ammonium groups with only one cation per side chain site. In addition to high conductivity, the multication side chain AEMs showed good alkaline and dimensional stabilities. High retention of ion exchange capacity (IEC) (93% retention) and ionic conductivity (90% retention) were observed for the triple-cation side chain AEMs during degradation testing in 1 M NaOH at 80 °C for 500 h. Based on the high-performance triple-cation side chain AEM, a Pt-catalyzed fuel cell with a peak power density of 364 mW/cm2 was achieved at 60 °C under 100% related humidity. Anion-conductive copolymers, poly(2,6-dimethyl-1,4-phenylene oxide)s containing fluorene side chains with pendant alkyltrimethylammonium groups, were synthesized via Suzuki-Miyaura coupling of aryl bromides with fluorene-boronic acids. The quaternized copolymers produced ductile, transparent membranes which were soluble in dimethyl formamide, dimethyl sulfoxide and methanol at room temperature. The fluorene side chain-containing membranes showed considerably higher hydroxide ion conductivities, up to 176 mS/cm at 80 °C, compared to that of typical anion exchange membranes based on the benzyltrimethyl ammonium moiety. The results of titration and hydroxide ion conductivity measurements demonstrated excellent chemical stability of the fluorene side chain-containing anion exchange membranes (AEMs), even after 1000 h immersion in 1 M NaOH at 80 °C. The results of this study suggest a scalable route for the preparation of AEMs for practical alkaline fuel cell applications. A unique approach was employed to toughen AEMs by crosslinking the AEMs using commercial Jeffamine additives. Compared to the BTMA40 membrane, the 10% Jeffamine cross-linked membrane demonstrated significantly higher elongation at break. To be specific, the hydrated BTMA40 membrane showed a 51.7% elongation at break, while the 10% Jeffamine cross-linked membrane had a 166.8 % elongation at break. Clearly, the introducing of hydrophilic cross-linked network greatly enhanced the toughness of the AEMs. Overall, this thesis details a number of strategies for the large-scale production of PPO-based anion exchange membranes. These strategies will be useful in going forward in the design and deployment of hydroxide, bromide, bicarbonate, and chloride-conducting membranes for water purification and electrochemical technology.

Non-CO2-emitting sources of renewable energy, such as solar and wind, have become quite popular in recent years, and their electricity generation cost at scale has become comparable with that of gas- and coal-fired power plants. However, their intermittent output makes the resultant electricity hard to dispatch in a reliable manner in the absence of grid-scale electrical energy storage (EES) technologies. Redox-flow batteries (RFBs) are promising devices for medium- to large-scale electric energy storage. They are safe, reliable, and portable, and are designed with decoupled power and energy modules, which makes it easy and cost-effective to scale their output to meet user demands. However, a significant challenge in RFBs is low RFB efficiency, one key reason for which is short-circuiting due to active ion species crossover through the membrane between the electrolyte solutions.This dissertation focuses on resolving this obstacle and addresses the aforementioned issues in two parts. The first part focuses on the use of the boundary element method to model ion transfer and Donnan exclusion phenomena in both anion and cation exchange membranes. The results guided the membrane fabrication for homogeneous, heterogeneous, and asymmetric membranes. The second part of the dissertation focuses on studying the mechanism of ion selectivity in AEMs, especially the Donnan exclusion effect. Once the mechanism of the ion selectivity of membranes was well understood, modified AEMs with high ion selectivity were developed and applied in the V-Ce ED-RFB and Ti-Ce ED-RFB. 79% energy efficiency (EE) was obtained after 100 charge/discharge cycles at 50 mA/cm2 in V-Ce ED-RFB. The highly selective AEMs mentioned above exhibited 0.4 % cation crossover over 1000 hours of operation. The ED-RFB showed 100% capacity retention over 1300 hours of charge/discharge cycles with 70% energy efficiency.

Electromembrane processes offer a multitude of applications, allowing for the recovery of water, other products, and energy. This book is a collection of contributions on recent advancements in electromembrane processes attained via experiments and/or models. The first paper is a comprehensive review article on the applications of electrodialysis for wastewater treatment, highlighting current status, technical challenges, and key points for future perspectives. The second paper focuses on ZSM-5 zeolite/PVA mixed matrix CEMs with high monovalent permselectivity for recovering either acid or Li+. The third paper regards direct numerical simulations of electroconvection in an electrodialysis dilute channel with forced flow under potentiodynamic and galvanodynamic regimes. The fourth paper investigates the reasons for the formation and properties of soliton-like charge waves in overlimiting conditions. The fifth paper focuses on the characterization of AEMs functionalized by surface modification via poly(acrylic) acid yielding monovalent permselectivity for reverse electrodialysis. In the sixth paper, CFD simulations of reverse electrodialysis systems are performed. The seventh paper proposes an integrated membrane process, including electrochemical intercalation–deintercalation, for the preparation of Li2CO3 from brine with a high Mg2+/Li+ mass ratio. Finally, the eighth paper is a perspective article devoted to the acid–base flow battery with monopolar and bipolar membranes.

The book is a comprehensive view of all electromembrane processes, including electromembrane processes for energy conversion - a currently very significant problem. The necessary theory and basic information needed for understanding the technology are explained in Part I. Materials used for ion-selective membranes and seoaration processes are described in Part II, and the applications for synthesis and energy conversion in Part III.

This book focuses on novel electrochemical materials particularly designed for specific energy applications. It presents the relationship between materials properties, state-of-the-art processing, and device performance and sheds light on the research, development, and deployment (RD&D) trend of emerging materials and technologies in this field. Features: Emphasizes electrochemical materials applied in PEM fuel cells and water splitting Summarizes anode, cathode, electrolyte, and additive materials developed for lithium-ion batteries and reviews other batteries, including lithium-air, lithium-sulfur, sodium- and potassium-ion batteries, and multivalent-ion batteries Discusses advanced carbon materials for supercapacitors Highlights catalyst design and development for CO2RR and fundamentals of proton facilitated reduction reactions With a cross-disciplinary approach, this work will be of interest to scientists and engineers across chemical engineering, mechanical engineering, materials science, chemistry, physics, and other disciplines working to advance electrochemical energy conversion and storage capabilities and applications.