In recent years, anion exchange membrane fuel cells (AEMFCs) have drawn more attention by showing high performance and potentially allowing catalysts based on more abundant materials. One frequently overlooked parameter in these systems is membranes permeability, often referred to as gas crossover. This undesirable phenomenon creates mixed potentials and also hotspots with temperatures high enough to cause membrane defects and pinholes. Therefore, it is important to investigate it quantitatively at conditions where a fuel cell often operates. In this study, hydrogen and oxygen crossover of several Aemion anion exchange membranes (AEMs) are measured with mass spectrometer (MS) at various relative humidities (RHs) and temperatures. The proton exchange membrane (PEM) Nafion is also investigated for a comparison. AEMs are generally less permeable to oxygen and hydrogen than PEM. The first-generation AEMs show a decreasing trend in permeability with RH, opposite to PEM. The second-generationAEMs are much less affected by RH levels. The measured oxygen crossover was two to six times lower compared to hydrogen crossover, depending on the membrane type and RH. The influence of membrane interface on crossover is evaluated to be higher for reinforced membranes, but overall smaller compared to the bulk contribution. Overall, AEMs show lower crossover than PEM, and from that perspective making them more suitable and a safer choice for fuel cell and electrolysis applications.

Anion Exchange Membrane Water Electrolysis offers technological advantages over Alkaline Electrolysis and Proton Exchange Membrane Water Electrolysis potentially lowering the cost of green hydrogen. It allows the utilization of platinum-group-metal-free (PGM-free) catalysts which, together with a less corrosive low concentration electrolyte, can result in more sluggish kinetics as well as increased cell resistances. Here we explain the effect of low KOH concentration on the performance of NiFe-based electrodes using a Transmission Line Model (TLM) and modified electrode design. By employing the catalyst coated membrane (CCM) method and using non-active titanium for PTL and flow fields, we could study the activity of the catalyst layer. A decreased concentration of KOH resulted in higher cell voltage and higher cell resistances at all current densities. Addition of a conductive material in the anode phase improved the catalyst utilization at all KOH concentrations. Moreover, the addition of conductive material partially mitigated the increase in the cell resistance. We also separated and evaluated the resistances in the electrode layer by ex-situ measurements and studied the effect of KOH concentration on the cell resistance using the TLM.

Anion exchange membrane water electrolysis (AEMWE) has been the focus of significant research as it combines the advantages of previous electrolysis technologies. One pressing problem is the use of potassium hydroxide (KOH) as the feed in AEMWE systems due to its role in performance degradation. Asymmetric operation is one way forward, but the transport of KOH within these systems has not been extensively studied. Herein, a comprehensive study of KOH transport via pH measurement in-operando is exhibited. We have shown that KOH crossover heavily impacts the AEMWE performance. Transport number of potassium ion (K+) is calculated, indicating that K+ significantly contributes to the current. Moreover, we have shown that different alkali cations behave differently under applied electric fields. These measurements shed light on apparent mass transport limitations when near-neutral anolyte is used. Thus, the importance of KOH transport is highlighted herein, and directly contributes to the understanding of AEMWE.

Hydrogen production through water electrolysis has attracted renewed interest in converting low-carbon electricity into hydrogen in the last few years. The so-produced hydrogen can be used as a reagent for the chemical industry, as a fuel, or for long-term storage of excess renewable energies, contributing to reducing CO 2 emissions in many sectors. The most mature and commercially available technology developed for hydrogen production is alkaline water electrolysis (AWE), where nickel-based electrodes are exploited as an anode and cathode and are immersed in concentrated KOH electrolyte (5-6 M). Proton exchange membrane water electrolysis (PEMWE) is also a commercially available technology that exploits ion exchange membranes. Platinum and iridium are exploited as the cathode and anode catalysts and are deposited directly on the ion exchange membrane, while pure water is fed to the system. Replacing the current AWE diaphragms with ion exchange membranes can improve the performance in terms of cell resistance and gas crossover, similar to PEMWE. This relatively new technology, called anion exchange membrane water electrolysis (AEMWE), has recently gained good attention. The common feature among all the above-mentioned technologies is using a flow cell and a membrane within to separate the anode and cathode. The membrane is significant in terms of output power and capital costs of the system. In this presentation, the membrane function in water electrolysis flow cells will first be explained, together with the most significant parameters influencing the system's performance. Next, the main focus will be on AEMWE systems using sustainable flourin-free ion exchange membranes. The research questions will be answered: What is the ideal membrane? And how does membrane and membrane-electrode assembly (MEA) influence the AEMWE performance? Also, the results of a new study we have done in collaboration with Lund University will be shared. A newly synthesized membrane, the poly(fluorene phenylpropylammonium) (PdF-TMA) was proposed for high electrolyte concentration. The performance of AEMWE was compared with a case using a commercial benchmark membrane (AEMION TM ). Increasing the electrolyte concentration improved electrode kinetics but with different effects on the membranes. PdF-TMA was quite stable during operation as its resistance did not increase. On the other hand, the AEMION TM lost conductivity and stability when operated in 2 M KOH.

Anion-exchange-membrane water electrolysis (AEMWE) is a nascent green hydrogen production technology. Its main advantage lies in its ability to utilize non-platinum group metals (PGMs) as catalysts and PFSA-free polymer as a membrane, unlike proton-exchange-membrane water electrolysis (PEMWE). It is well-known that, unlike PEMWE, AEMWE suffers greatly from substituting the electrolytic feed solution with a solution of a lower pH (e.g., pure water). Literature has attributed the loss of performance to the lower reaction kinetics of both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) and the drastic loss of electrolyte conductivity, which is further exacerbated at higher current density [1]. Notably, it is shown that addition of salt to improve the conductivity of electrolyte does not always equate to a better performance over time, depending on the feed configuration, highlighting the importance of understanding mass transport during cell operation [2]. Therefore, to decouple the causes of the drastic losses of performance in-situ, we have developed a system capable of feeding vapor and liquid into AEMWE asymmetrically. The cell is constructed using a membrane electrode assembly (MEA) fabricated by the catalyst coated membrane (CCM) method, where platinum on carbon (Pt/C) and iridium oxide (IrOx) are coated directly on PiperION® anion exchange membranes. Moreover, we have studied hydroxide crossover both statically using an h-cell test and dynamically in an AEMWE cell. We have shown that, by utilizing various combinations of feeds, including humidified gas, pure water, or KOH, through both cathode and anode, it is possible to study cell performance and hydroxide transport under different conditions. Through which, we have elucidated the performance loss, the importance of hydroxide transport, and a strategy to overcome such losses, thus showing the possibility of advancing toward pure water and low-temperature vapor electrolysis. [1] Liu, Jiangjin, et al. "Elucidating the role of hydroxide electrolyte on anion-exchange-membrane water electrolyzer performance." Journal of the electrochemical society 168.5 (2021): 054522. [2] Rossi, Ruggero, Rachel Taylor, and Bruce E. Logan. "Increasing the electrolyte salinity to improve the performance of anion exchange membrane water electrolyzers." ACS Sustainable Chemistry & Engineering 11.23 (2023): 8573-8579. Figure 1. Schematic of the developed feeding system capable of feeding water vapor and liquid into the electrolyzer. Figure 1

Anion exchange membrane water electrolysis (AEMWE) is receiving tremendous attention by many researchers in the field of the electrochemistry as it shows the potential to make the electrolytic hydrogen production more cost-effective. This technological advance has been made possible by the progress in the polymer chemistry of anion exchange membranes (AEMs) [1]. These materials can conduct hydroxide anions without suffering from the chemical degradation induced by the hydroxide itself. Like alkaline water electrolysis (AWE), AEMWE can exploit low cost and abundant materials, for example nickel and its alloys, for plates and porous transport layers and as catalysts. Furthermore, catalyst coated membranes (CCMs) can be manufactured as in proton exchange membrane water electrolysis and higher current densities can be achieved compared to AWE [2]. However, nickel-based catalysts suffer from low mass activity as many other platinum-group metals-free (PGM-free) catalysts [3]. This downside could be mitigated by employing thick and high loading catalyst layers. However, as the catalyst is placed further from the membrane, the ohmic loss induced by the thickness of the electrode increases and reduces the utilization of the catalyst [4]. As the cost of PGM-free catalysts is orders of magnitude lower than traditional platinum and iridium catalysts, the fabrication of high loading catalyst seems a viable solution. Nevertheless, as the catalyst layer thickness continues to increase, the utilization of the catalyst decreases further and eventually it limits the performance improvement [3]. This applies especially to water or low concentration electrolyte fed systems, as concentrated KOH solution has been shown to greatly reduce catalyst layer ionic resistance [5]. Furthermore, mass transport issue can also play a significant role limiting performance as thick electrode have higher diffusion resistance. To explore the fabrication and electrochemical behavior of high loading anode electrodes, catalyst coated membranes (CCMs) were manufactured via decal transfer method [6]. RaneyTM Nickel mixed with Co3O4and RaneyTM Nickel served as the anode and cathode catalyst and the anode catalyst layer thickness was adjusted to control the loading. Low concentration electrolyte (0.1 KOH) was fed to the anode and the cathode was left dry. As expected, the cell voltage decreased increasing the catalyst loading. Notably, the performance was improved even when the catalyst loading increased from 6 to 12 mg/cm2. This work aims to study the performance limitations of high loading catalyst layer with PGM-free catalysts. It was found that even high catalyst loadings (12 mg/cm2) can deliver a sensible improvement of overall performance. We explain this with our systematic approach in this study. References [1] Henkensmeier, Dirk, Malikah Najibah, Corinna Harms, Jan Žitka, Jaromír Hnát, and Karel Bouzek. “Overview: State-of-the Art Commercial Membranes for Anion Exchange Membrane Water Electrolysis.” Journal of Electrochemical Energy Conversion and Storage 18, no. 2 (May 1, 2021): 024001. [2] Chen, Binyu, Peter Mardle, and Steven Holdcroft. “Probing the Effect of Ionomer Swelling on the Stability of Anion Exchange Membrane Water Electrolyzers.” Journal of Power Sources 550 (December 2022): 232134. [3] Damjanović, Ana Marija, Burak Koyutürk, Yan-Sheng Li, Davide Menga, Christian Eickes, Hany A. El-Sayed, Hubert A. Gasteiger, Tim-Patrick Fellinger, and Michele Piana. “Loading Impact of a PGM-Free Catalyst on the Mass Activity in Proton Exchange Membrane Fuel Cells.” Journal of The Electrochemical Society 168, no. 11 (November 1, 2021): 114518. [4] Bernt, Maximilian, Armin Siebel, and Hubert A. Gasteiger. “Analysis of Voltage Losses in PEM Water Electrolyzers with Low Platinum Group Metal Loadings.” Journal of The Electrochemical Society 165, no. 5 (2018): F305–14. [5] Liu, Jiangjin, Zhenye Kang, Dongguo Li, Magnolia Pak, Shaun M. Alia, Cy Fujimoto, Guido Bender, Yu Seung Kim, and Adam Z. Weber. “Elucidating the Role of Hydroxide Electrolyte on Anion-Exchange-Membrane Water Electrolyzer Performance.” Journal of The Electrochemical Society 168, no. 5 (May 1, 2021): 054522. [6] Rossini, Matteo, Burak Koyuturk, Björn Eriksson, Amirreza Khataee, Göran Lindbergh, and Ann Cornell. “Rational Design of Membrane Electrode Assembly for Anion Exchange Water Electrolysis.” ECS Meeting Abstracts MA2023-01, no. 36 (August 28, 2023): 2059–2059. Figure 1 Polarization curve of CCMs with different anode catalyst loadings. RaneyTM Nickel and CO3O4 are used in the anode. The cathode contains catalyst RaneyTM Nickel and Super PTM Carbon. The measurements are conducted at 60 °C feeding 0.1 M KOH to anode. Figure 1

We have developed a novel interdigitated flow field for polymer electrolyte membrane electrolyzers (proton exchange membrane water electrolysis cells) for ground and space applications1),2), which are supposed to work in a hybrid system with a low temperature Sabatier reactor for effective use of heat3),4). This design separates the oxygen and liquid water inside the anode of the cell. It dispenses with water circulators and external separators that use natural or centrifugal buoyancy. To date, we have developed a numerical model for optimizing cell structures. Finite element modeling (COMSOL Multiphysics) of water transport is three-dimensionally conducted for the anode porous transport layer coated with a hydrophobic microporous layer (MPL) (SIGRACET 29BC, SGL Carbon Inc.) assembled with the interdigitated flow field. The MPL can separate the evolved oxygen gas and pressurized liquid water owing to capillary pressure5). The electrochemical kinetic parameters for the model are determined using electrochemical impedance spectra. We model the current densities and the current ratio between the reactant liquid water and water vapor at the interface between the MPL and catalyst layer (CL)6). The model involves the fractional bubble coverage of the produced oxygen gas at the CL, as well as liquid water saturation and liquid water permeability in the MPL7). The vapor evaporating from the liquid water in the MPL is assumed to be mixed with the evolved oxygen for diffusive water transport. The volumetric evaporation rate was estimated from experimental data8). Acknowledgement This study is based on results obtained from a project, JPNP21014, commissioned by the New Energy and Industrial Technology Development (NEDO). References 1) Y. SONE, O.S. HERNANDEZ-MENDOZA, A. SHIMA, M. SATO, H. NAKAJIMA, and H. MATSUMOTO, Water Electrolysis by the Direct Water Supply to the Solid Polymer Electrolyte through the Interdigitated Structure of the Electrode, Electrochemistry, 89 (2021) 138–140. https://doi.org/10.5796/electrochemistry.20-00145. 2) H. NAKAJIMA, V. VEDIYAPPAN, H. MATSUMOTO, M. SATO, O.S. MENDOZA-HERNANDEZ, A. SHIMA, and Y. SONE, Water Transport Analysis in a Polymer Electrolyte Electrolysis Cell Comprised of Gas/Liquid Separating Interdigitated Flow Fields, Electrochemistry, 90 (2022) 017002. https://doi.org/10.5796/electrochemistry.21-00097 3) H. NAKAJIMA, A. SHIMA, M. INOUE, T. ABE, H. MATSUMOTO, O.S. MENDOZA-HERNANDEZ, and Y. SONE, Three-Dimensional Numerical Modeling of a Low-Temperature Sabatier Reactor for a Tandem System of CO2 Methanation and Polymer Electrolyte Membrane Water Electrolysis, Electrochemistry, 90 (2022) 22–00035. https://doi.org/10.5796/electrochemistry.22-00035 4) A. Shima, M. Sakurai, Y. Sone, H. Nakajima, M. Inoue, and T. Abe, Development of CO2 Reduction-Water Electrolysis Tandem Device as a Full-Scale Model, in: 52nd Int. Conf. Environ. Syst., 2023: ICES-2023-196. https://hdl.handle.net/2346/89622 5) H. Nakajima, S. Iwasaki, and T. Kitahara, Pore network modeling of a microporous layer for polymer electrolyte fuel cells under wet conditions, J. Power Sources, 560 (2023) 232677. https://doi.org/10.1016/j.jpowsour.2023.232677 6) H. Nakajima, H. Ekström, A. Shima, Y. Sone, and G. Lindbergh, Water Transport Modeling in a Microporous Layer for a Polymer Electrolyte Membrane Water Electrolyzer Having a Gas-Liquid Separating Interdigitated Flow Field, ECS Transactions, 112 (4) (2023) 273–281. https://doi.org/10.1149/11204.0273ecst 7) S. Kubota, H. Nakajima, M. Sato, A. Shima, M. Sakurai, and Y. Sone, Liquid Water Permeability in a Hydrophobic Microporous Layer for the Anode Interdigitated Flow Field of a Gas-Liquid Separating Polymer Electrolyte Membrane Water Electrolyzer, ECS Transactions, 112 (4) (2023) 207-214. https://doi.org/10.1149/11204.0207ecst 8) P. Wang, H. Nakajima, and T. Kitahara, Effect of Hydrophilic Layer in Double Microporous Layer Coated Gas Diffusion Layer on Performance of a Polymer Electrolyte Fuel Cell, J. Electrochem. Soc., 170 (2023) 124514. https://doi.org/10.1149/1945-7111/ad13da

A new interdigitated flow field design for polymer electrolyte membrane electrolyzers has been developed for ground and space applications. It internally separates oxygen and liquid water, eliminating the water circulators to remove the bubbles and external gas-liquid separators with buoyancy. The capillary pressure in the hydrophobic microporous layer(MPL) of the anode porous transport layer enables the internal separation of oxygen gas and pressurized liquid water. A finite element model (COM-SOL Multiphysics) simulates water transport in the MPL. Electrochemical impedance spectra determine the electrochemical kinetic parameters for the model. The model accounts for the oxygen bubble coverage of the CL, liquid water saturation in the MPL, and the current ratio between liquid water and water vapor at the MPL-CL interface. The vapor from liquid water in the MPL mixes with oxygen for diffusion. The water evaporation rate based on liquid water saturation in the MPL is introduced.

Proton Exchange Membrane Fuel Cells (PEMFCs) are promising for heavy-duty vehicles (HDV) in the strive to make the transportation sector more sustainable. However, because of the small temperature gradient between the cell (typically run around 80°C) and the ambient temperature, these cells require a large cooling system. Raising the operating temperature to an intermediate temperature range (IT: 80 – 120 °C) would reduce the cooling system size required in HDVs and improve the tolerance towards contaminants, although higher temperature may accelerate degradation [1,2]. To be able to withstand IT operation, reinforcements and chemical modifications have been implemented in commercial PFSA polymers. Unfortunately, most of the data available for PEMFCs are referred to non-reinforced membranes and only few studies analysed the latter under realistic operating conditions. Among some possible issues regarding proton exchange membranes (PEMs), hydrogen crossover is an undesirable, but inevitable phenomenon. The membrane is not perfectly impermeable to hydrogen gas and this results in a safety concern, lower cell efficiency and can lead to faster cell degradation. This work investigates the influence of the reinforcement in a PEM on the hydrogen crossover. Specifically, Nafion HP (reinforced) and Nafion 211 (non-reinforced) are compared under different operating conditions. The purpose of the reinforcement is to improve thermo-mechanical stability, and its physical properties can differ from the rest of the membrane, which can influence hydrogen crossover. Using electrochemical methods, the hydrogen crossover is measured in-situ in a PEMFC with hydrogen on one side and inert gas on the other side. The measurements have been performed between 80 and 120 °C, at different cell relative humidity (RH) conditions (20-90 %) and multiple levels of pressure for both reinforced and non-reinforced membranes. Particular attention has been paid to the case in which the hydrogen side of the cell is more pressurized than the inert side, as this is most often the case in HDV applications. In such conditions, hydrogen permeation increases considerably as a result of the total pressure gradient over the membrane, although this factor is rarely considered in the literature [3]. By adapting the methodology established in our previous work [4], here the effects of the differential total pressure and hydrogen partial pressures are decoupled through a systematic dilution of the hydrogen gas stream. Special points are measured in which the hydrogen partial pressure is kept equal to the ambient case, while the total pressure on the hydrogen side is increased by adding the inert gas, as shown in Figure 1, plot I. Results show that the presence of a reinforcement affects the amount of hydrogen that crosses through the membrane, as seen in Figure 1. Moreover, among the different conditions tested, higher total pressures, especially on the hydrogen side of the cell, are affecting hydrogen crossover the most, while a more modest change is observed for different RH and cell temperatures. The observation that pressure is the most important factor for hydrogen crossover has noteworthy implications and should have an influence when deciding at which pressure the PEMFC is operated in transportation applications. Minimizing hydrogen crossover, while still ensuring adequate cell performance, should be a priority to improve the overall fuel consumption and the electric power obtained from the fuel cell. Figure 1: Hydrogen crossover due to concentration gradients and, in certain conditions, to a differential total pressure. Three different conditions are used to measure crossover, whose results are reported in the right figure: I) the total pressure on the hydrogen side is increased by diluting with inert gas, while the hydrogen partial pressure is kept constant, the inert side is unvaried; II) the total pressure is increased symmetrically on both sides, the hydrogen side is not diluted; III) the total pressure on the hydrogen side is increased and no dilution is employed. [1] Cullen et al., “New roads and challenges for fuel cells in heavy-duty transportation,” Nat. Energy, 2021, doi:10.1038/s41560-021-00775-z. [2] Akitomo et al., “Investigation of effects of high temperature and pressure on a polymer electrolyte fuel cell with polarization analysis and X-ray imaging of liquid water,” J. Power Sources, 2019, doi:10.1016/j.jpowsour.2019.04.115. [3] Kreitmeier et al., “Investigation of membrane degradation in polymer electrolyte fuel cells using local gas permeation analysis,” J. Power Sources, 2012, doi:10.1016/j.jpowsour.2012.03.071. [4] Butori et al., “The Effect of Oxygen Partial Pressure and Humidification in Proton Exchange Membrane Fuel Cells at Intermediate Temperature,” J. Power Sources, 2023, doi:10.1016/j.jpowsour.2023.232803. Figure 1

With an increasing interest for green hydrogen as an important fuel for the global energy transition and as a raw material for green chemistry, extensive research efforts are currently devoted to increase the performance of water electrolysis technologies. In this frame work, Anion Exchange Water Electrolysis (AEMWE) has a strategic role promising to boost electrolytic hydrogen production without relying on scarce resources as AEMWE does not need Iridium or other Platinum group metals (PGM) catalysts, unlike Proton Exchange Membrane Water Electrolysis (PEMWE), to reach high power density [1]. In this work, the focus is on electrode optimization for dry cathode operation. Operating without a liquid feed on the cathode reduces the extent of the drying of hydrogen gas and simplifies the balance of the plant. However, water must be transported from the anode to the cathode where it is consumed by the hydrogen evolution reaction (HER) [2]. Also, ionic connection from the membrane to catalyst surface must be provided by the ionomer without a supporting electrolyte which is generally employed in AEMWE to improve performance [1]. Under these premises, it is clear that using high catalyst loading to compensate for the intrinsic low activity of Platinum group metals-free (PGM-free) catalysts will result in lower utilization of the catalyst layer as a function of the electrode thickness [3]. To study how transport limitations hinder cathode performance, we manufactured catalyst coated membranes (CCMs) via decal transfer method and varied the cathode catalyst loading thereby adjusting catalyst layer (CL) thickness. Raney TM Nickel served as the cathode catalyst and Super P TM Carbon as the conductive additive. It was found that increasing the catalyst loading between 0.65 mg/cm 2 and 1.65 mg/cm 2 greatly improved cell performance (Figure 1). However, cell voltage proved to be less sensitive to cathode loading for higher loadings. In fact, to reasonably improve the performance further, a loading of 4.55 mg/cm 2 was necessary. Noticeably, the high frequency resistance (HFR) was found to be independent of catalyst loading (i.e. CL thickness) due to the high electronic conductivity of the cathode CL with carbon additive. This works sheds light on how AEMWE performance are related to cathode catalyst loading when the cathode is dry operated. It is found that performance improvement is limited at high loading (above 1.65 mg/cm 2 ). This shows how the ionic conductivity of the electrode should be improved to mitigate the low mass activity of PGM-free catalyst. [1] Ayers, Katherine, Nemanja Danilovic, Ryan Ouimet, Marcelo Carmo, Bryan Pivovar, and Marius Bornstein. “Perspectives on Low-Temperature Electrolysis and Potential for Renewable Hydrogen at Scale.” Annual Review of Chemical and Biomolecular Engineering 10, no. 1 (June 7, 2019): 219–39. [2] Koch, Susanne, Joey Disch, Sophia K. Kilian, Yiyong Han, Lukas Metzler, Alessandro Tengattini, Lukas Helfen, Michael Schulz, Matthias Breitwieser, and Severin Vierrath. “Water Management in Anion-Exchange Membrane Water Electrolyzers under Dry Cathode Operation.” RSC Advances 12, no. 32 (2022): 20778–84. [3] Liu, Jiangjin, Zhenye Kang, Dongguo Li, Magnolia Pak, Shaun M. Alia, Cy Fujimoto, Guido Bender, Yu Seung Kim, and Adam Z. Weber. “Elucidating the Role of Hydroxide Electrolyte on Anion-Exchange-Membrane Water Electrolyzer Performance.” Journal of The Electrochemical Society 168, no. 5 (May 1, 2021): 054522. Figure 1 Polarization curve of CCMs with different cathode catalyst loading. The cathode contains 65 % catalyst (Raney TM Nickel), 10% ionomer and 25% Super P TM Carbon. NiFe nanoparticles are used in the anode with 5% ionomer (AP-1-HNN5-00-X). The measurements are conducted at 60 °C feeding 1 M KOH to anode. Figure 1

A separator-electrode assembly (SEA) made of wood-based cellulose nanofibers (CNF) and Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) was fabricated by a facile spray-coating process. ...

The crystal structure of the title compound, [Ni3(C8H4O4)3(C3H7NO)4], is a two-dimensional coordination network formed by trinuclear linear Ni3(tp)3(DMF)4 units (tp = terephthalate = benzene-1,4-dicarboxylate and DMF = dimethylformamide) displaying a characteristic coordination mode of acetate groups in polynuclear metal–organic compounds. Individual trinuclear units are connected through tp anions in a triangular network that forms layers. One of the DMF ligands points outwards and provides interactions with equivalent planes above and below, leaving the second ligand in a structural void much larger than the DMF molecule, which shows positional disorder. Parallel planes are connected mainly through weak C—H...O, H...H and H...C interactions between DMF molecules, as shown by Hirshfeld surface analysis.

The crystal structure of the title compound, [Ni3(C8H4O4)3(C3H7NO)4], is a two-dimensional coordination network formed by trinuclear linear Ni3(tp)3(DMF)4 units (tp = terephthalate = benzene-1,4-di­carboxyl­ate and DMF = di­methyl­formamide) displaying a characteristic coordination mode of acetate groups in polynuclear metal–organic compounds. Individual trinuclear units are connected through tp anions in a triangular network that forms layers. One of the DMF ligands points outwards and provides inter­actions with equivalent planes above and below, leaving the second ligand in a structural void much larger than the DMF mol­ecule, which shows positional disorder. Parallel planes are connected mainly through weak C—H⋯O, H⋯H and H⋯C inter­actions between DMF mol­ecules, as shown by Hirshfeld surface analysis.

The crystal structure of the title compound, [Ni3(C8H4O4)3(C3H7NO)4], is a two-dimensional coordination network formed by trinuclear linear Ni3(tp)3(DMF)4 units (tp = terephthalate = benzene-1,4-di-carboxyl-ate and DMF = di-methyl-formamide) displaying a characteristic coordination mode of acetate groups in polynuclear metal-organic compounds. Individual trinuclear units are connected through tp anions in a triangular network that forms layers. One of the DMF ligands points outwards and provides inter-actions with equivalent planes above and below, leaving the second ligand in a structural void much larger than the DMF mol-ecule, which shows positional disorder. Parallel planes are connected mainly through weak C-H⋯O, H⋯H and H⋯C inter-actions between DMF mol-ecules, as shown by Hirshfeld surface analysis.

The crystal structure of the title compound, [Ni-3(C8H4O4)(3)(C3H7NO)(4)], is a two-dimensional coordination network formed by trinuclear linear Ni-3(tp)(3)(DMF)(4) units (tp = terephthalate = benzene-1,4-dicarboxylate and DMF = dimethyl-formamide) displaying a characteristic coordination mode of acetate groups in polynuclear metal-organic compounds. Individual trinuclear units are connected through tp anions in a triangular network that forms layers. One of the DMF ligands points outwards and provides interactions with equivalent planes above and below, leaving the second ligand in a structural void much larger than the DMF molecule, which shows positional disorder. Parallel planes are connected mainly through weak C-H center dot center dot center dot O, H center dot center dot center dot H and H center dot center dot center dot C interactions between DMF molecules, as shown by Hirshfeld surface analysis.

Carboxylated cellulose nanofibers, prepared by TEMPO-mediated oxidation (TOCN), were processed into asymmetric mesoporous membranes using a facile paper-making approach and investigated as lithium ion battery separators. Membranes made of TOCN with sodium carboxylate groups (TOCN-COO-Na+) showed capacity fading after a few cycles of charging and discharging. On the other hand, its protonated counterpart (TOCN-COOH) showed highly improved electrochemical and cycling stability, displaying 94.5% of discharge capacity maintained after 100 cycles at 1 C rate of charging and discharging. The asymmetric surface porosity of the membranes must be considered when assembling a battery cell as it influences the rate capabilities of the battery. The wood-based TOCN-membranes have a good potential as an ecofriendly alternative to conventional fossil fuel-derived separators without adverse side effects.

Anion exchange membrane fuel cells (AEMFC) or hydroxide exchange membrane fuel cells (HEMFC) are emerging as possible alternatives to proton exchange membrane fuels cells [1]. The alkaline environment in these fuel cells make possible the use of platinum free catalysts since the oxygen reduction is more easily catalysed. In addition, the higher pH is less corrosive towards the stainless steel bipolar plates. Thereby, AEMFC has potential to be produced at a lower cost. However, further research is still needed to improve cell components and to commercialize the technology. The polymeric material is a very important part in AEMFC, and new polymers are continuously being developed to improve the fuel cells [1-3]. The polymer electrolyte membranes have to be impermeable to gases and need to have a high hydroxide conductivity. If used as ionomers in the electrodes, high hydroxide conductivity, low swelling and a good interaction with the catalyst powder are desirable. During operation water is produced at the anode and consumed at the cathode meaning that the water will affect the polymer performance and, so electrochemical out-put. Further, the water balance across the cell is dependent on the membrane properties [4]. Thus, for better understanding of these materials, they have to be evaluated in a real fuel cell set-up. In this study the performance of novel poly(phenylene oxide) (PPO)-based polymer electrolytes with quaternary amines is evaluated. These materials have been synthesized to avoid hydroxide degradation of the backbone by attaching the quaternary amine at the end of a longer side-chain. Distancing it from the polymer backbone results in steric hindering of hydroxide attack. The chain structures compared in this study are shown in figure 1. Their polymer backbone remains the same, but the side-chains altered to have varying length or a different quaternary amine group. These materials have previously shown very promising properties in ex-situ tests at 80 °C. Among these, high conductivity for fully humidified membranes, over 100 mS cm-1, and high stability up to 200 h in 1 M NaOH with very low loss of ion-exchange capacity were measured [3]. Figure 1 -The polymeric backbone investigated is shown in a), and the three side chains that replaces the R in the backbone are shown in b), c) and d). Membrane electrode assemblies (MEAs) are prepared using the PPO-based membranes and in house made electrodes using Tokuyama AS-4 ionomer and Pt/C catalyst prepared on the gas diffusion layer. The ion-exchange of the membranes synthesized in bromide form was performed in carbon dioxide free environment prior to MEA preparation. The investigation focuses on electrochemical measurements of the cell, including in-cell gas crossover, cell resistance and fuel cell performance. Among other methods polarization curves, cyclic voltammograms and impedance spectra are used for cell characterization. In addition the water production and flux across the MEA is measured using humidity sensors. References: [1] B. Britton and S. Holdcroft, J. Electrochem. Soc., vol. 163, issue 5, pp. F353-F358, 2016. [2] J. R. Varcoe, et al., Energy Environ. Sci., vol. 7, pp. 3135–3191, 2014. [3] H.-S. Dang and P. Jannasch, Macromolecules, vol. 48, pp. 5742–5751, 2015. [4] T.J. Omasta, et al. J. Power sources, xxx, pp 1-9, In press 2017 Figure 1