Alkaline metal-air batteries (AMABs) are of interest due to the potential for high energy density, which typically exceeds that of Li-ion batteries. In open systems such as metal-air batteries, however, performance must be assessed in terms of maximizing power or current density rather than the usual energy density metric. Cost and system performance are most strongly affected by these parameters because of their strong impact on cell count needed to achieve a given total power for an application. One of the key challenges of getting high-performance AMABs is to make a low-cost, durable membrane with high conductivity. This work describes the characterization of a KOH-loaded ion-conducting membrane with excellent conductivity and chemical stability for hydroxide ion conduction, which we refer to a ‘cross-linked, loaded alkaline membrane’ (CLAM). This CLAM membrane was developed in our lab from conserved polymer backbones modified with cationic moieties and cross-linking agents, leading to processible films that are effectively cross-linked hydrogels. The cross-linking process was carried out during film formation. This membrane can be used as a versatile electrolyte for the AMABs for 50% or higher relative humidity (RH). This membrane was used in several different kinds of metal-air batteries. High conductivity (exceeding 100 mS/cm) and high power and current density were experimentally observed in multiple different kinds of metal-air batteries and related devices. In addition to a survey of different uses of the membrane, this study focuses on the NMR characterization and rheology to identify the nature of crosslinking of the versatile electrolyte. The crosslinking time and theoretical degree of crosslinking were stochiometrically modified by diluting the imidazole crosslinker in the solution. This modification leads to the detection of broadening and downfield shifting of 1D proton NMR peaks with time, confirming the electron-withdrawing environment of the solution. Further study of crosslinking density was obtained via NMR diffusion and Rheology. Other membrane properties will be reported, including conductivity studies carried out over months under aggressive conditions to probe membrane durability.

Major improvements in the performance of aluminum-air batteries, based on improvement of the aluminum electrode polarization and limiting side reactions, are demonstrated. At high rates of discharge, cell performance is largely dictated by ohmic losses at the anode associated with the aluminum product layer. Turnover of this secondary passivation layer entails conversion of insoluble aluminum hydroxide to soluble aluminate ions. In cells employing the same air electrode and a polymer-based electrolyte, aluminum electrode behavior is systematically investigated as a function of hydroxide concentration, temperature, and electrolyte flow rate to identify optimum conditions and start-up protocols for battery discharge. Stannate addition and plating was explored as a path to inhibit Al corrosion and limit hydrogen evolution as a side reaction. The transient behavior of cells containing stannate in the electrolyte was studied to identify start-up conditions. Overall, this optimization enables a peak power density of 710 mW cm-2 in polarization experiments. Long-term constant current holds of the battery are also shown.

Serendipity struck our laboratory one day: a student attempting to make an air electrode for a metal air battery did some preliminary work using a gold electrode. He found the voltammetry that corresponds to a reversible 2-electron process, oxygen to peroxide. Over time, we were able to identify the source of the reaction, arising from some ‘dirt’—actually a possible ligand--from a student who had previously used the electrode. We were able to reproduce the excellent performance using this and similar ligands. The air electrode cycles with 95% efficiency and 40 mA/cm 2 in a symmetric cell. The student went on to form a company, Peroxygen Systems Inc., now Phase 2 Chemicals, for on-site peroxide production. That also led to efforts to create stable, high surface area versions of the catalyst. We have bonded ligand to carbon surfaces and can obtain ORR at similar potentials. After much trial and error, these efforts were also somewhat successful in producing peroxide redox catalyzed by organometallic complexes. We will describe the synthesis and testing of these materials. We then began to apply these catalysts along with a high-performance separator prepared in our labs, in several different rechargeable alkaline systems, including a Zn-peroxide battery and a ‘Peroxide Enabled Long-duration Electrochemical Energy Storage System’ (PELoDEES). In both cases, much higher efficiency is obtained relative to the corresponding four-electron ORR/OER systems, with particularly strong advantages on charging the cell. We will describe the testing of cells and, for PELoDEES, we show the advantageous technoeconomic properties of systems derived from this technology.

Metal-air batteries are energy storage devices that attract a lot of research interest due to their high energy density, that generally surpasses that of Li-ion batteries. Metal-air batteries can be used in a wide range of applications such as vehicles, stationary power and low power/long duration devices. A good amount of research has been devoted to developing and understanding the metal anode for both primary, and secondary metal-air batteries. However, the great variety of this type of battery makes very challenging to design the air electrode, a key component to obtain high performances. In our lab, we have been developing a mechanically rechargeable aluminum-air battery operating under alkaline conditions, and while the aluminum anode performance has been already optimized by determining best operating battery temperature, electrolyte concentration and flow rates, we are just starting to optimize the air-electrode in this working cell environment. Our battery is composed of an exchangeable Aluminum foil anode, a polymeric separator and the air electrode, which for these studies was a commercial Pt/C catalyst. KOH-based Electrolyte is recirculated through the aluminum side, while air, with and without humidification, is fed on the air side. Battery performance is determined by means of polarization curves, with the novelty of introducing a home-made flexible Hg/HgO reference electrode, which allows the separation of the individual contributions of the anode and cathode electrodes. In this work we study the effect that binder to catalyst ratio, PTFE addition and air relative humidity have on the battery performance.

Aluminum-air batteries (AABs) have been attracting increasing attention due to their high specific energy, relatively low cost, and scalability [1]. Moreover, high-performance AABs could enable critical applications such as electric vehicles including aerial travel and military applications [2]. Alleviating limitations in AABs must address multiple processes. Among them, adopting a zero-gap cell design – commonly used in proton exchange membrane (PEM) fuel cells and electrolyzers – may allow for significantly higher power densities, which are essential for high energy and power applications. Developing a zero-gap cell structure to improve battery performance requires thorough investigation of the principal components, i.e., electrodes, diffusion media, membranes/separators, electrolytes, and cell architecture. Especially for high-power applications, commercialization of AABs requires a thorough understanding of optimal cell conditions and architecture [3]. In this study, we investigated the effects of varying aluminum purities and oxidant quality on AAB performance. In our novel cell architecture, we demonstrate enhanced battery performance, achieving high power densities exceeding 1 W cm⁻² — an outcome not previously reported in the literature, to the best of our knowledge. Overall, this research provides valuable insights into the advancement of high-power AABs and their potential in critical applications. References Rani, B., et al., Aluminum–air batteries: current advances and promises with future directions. RSC Advances, 2024. 14 (25): p. 17628-17663. Dilshad, M., et al., Next-Generation Aluminum-Air Batteries: Integrating New Materials and Technologies for Superior Performance. ACS Applied Energy Materials, 2025. 8 (6): p. 3248-3275. Gaele, M. F. and T. M. Di Palma, Polymer Electrolytes for Al-Air Batteries: Current State and Future Perspectives. Energy & Fuels, 2022. 36 (21): p. 12875-12895. Figure 1

The aluminum-air battery presents itself as a device with great potential in the field of electrochemical energy storage and conversion. Its high theoretical energy density and abundant reactant supply make it an attractive candidate for research attention. The main issue facing the system is utilization loss due to the corrosive hydrogen evolution reaction that occurs at the anode in alkaline solutions. In recent years, advances have been made that have greatly reduced this reaction to improve aluminum utilization and corresponding system energy density. As improvements continue to develop on this front, an additional focus on system scale up and operation is critical. To complement energy density, a parallel focus on increased power output is necessary for practical system applications. Along with material selection and operating conditions, discharge protocols can be manipulated to maximize system performance. In this investigation, different pulse techniques will be studied to determine how they improve aluminum utilization and power output. Pre-discharge pulses of varied length and intensity will be used to influence tin deposition on the aluminum surface in stannate-containing electrolyte solutions. Intermittent pulses of low current during extended discharge will be used to promote homogeneous wear patterns and minimize localized corrosion effects. The study will primarily consist of full-cell experiments with support from three-electrode cell testing. Galvanostatic discharge and electrochemical impedance spectroscopy will be used as the primary mode of analysis along with polarization curves and surface imaging. In conjunction with optimal cell parameters, proper pulse discharge protocols have the potential to greatly improve aluminum-air battery performance.

Manganese dioxide has garnered significant attention as a promising catalyst for the oxygen reduction reaction (ORR) in alkaline media due to its excellent catalytic activity, low cost, durability, and scalability. Despite its promising catalytic activity, MnO2 suffers from limitations such as low conductivity, particle dissolution, and diminished mass transport properties, particularly in high-throughput environments. Researchers typically couple MnO2 with high conductivity and high surface area materials such as conductive carbon black to overcome these challenges. However, this method still presents challenges, such as diminished catalyst-carbon interactions and the loss of catalytic active sites by the surrounding of larger carbon particles. In this study, we present a two-step synthesis method, initially proposed for the application of MnO2 as supercapacitor materials1, for the improvement of MnO2 catalytic activity towards the ORR. This synthesis method was achieved using diazonium chemistry, which involves the direct chemical attachment of KJB carbon black with MnO2 via a phenyl group linkage site. This process was done so that the mass ratio of MnO2 and KJB was 50:50. The synthesized materials were characterized using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Energy Dispersive X-ray Spectroscopy (EDX) to confirm varying morphologies, particle sizes, and material compositions. X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) were utilized to analyze the phases and crystallinities of the materials. Each characterization step was done before and after the chemical attachment process to ensure the modifications were performed. The electrochemical activity of the materials was investigated using three-electrode cells to study the ORR activities and stabilities of the synthesized materials. Rotating disk electrode (RDE) and rotating ring-disk electrode (RRDE) data were employed to analyze kinetic current densities, the number of electrons transferred, and the hydrogen peroxide production rates. Furthermore, the catalyst materials were implemented into aluminum-air battery configurations where polarization curves, electrochemical impedance spectroscopy (EIS), and multistep chronoamperometry experiments were conducted to evaluate the performance of the modified MnO2 catalyst materials. Overall, implementing this process led to substantial increases in the catalytic activities morphologically dependent MnO2 particles towards the ORR and highlighted the significance of this research in advancing the understanding and application of MnO2 catalysts in energy conversion and storage technologies. [1] Ramirez-Castro, C., Crosnier, O., Athouël, L., Retoux, R., Bélanger, D., & Brousse, T. (2015). Electrochemical Performance of Carbon/MnO 2 Nanocomposites Prepared via Molecular Bridging as Supercapacitor Electrode Materials. Journal of The Electrochemical Society, 162(5), A5179–A5184.

Using the Washburn method, the wettability of microporous layer (MPL)-coated carbon-felt gas diffusion layers (GDLs) with liquids with different polarities were studied using process tensiometry. The Washburn approach allows us to study fluid uptake into the electrode pores through capillarity and the resulting liquid-solid internal contact angles. Interpretation using the Owens-Wendt analysis reveals the effects of varying proportions of hydrophobic poly(tetrafluoroethylene) (PTFE) and multi-walled carbon nanotubes (MWCNTs) in the MPL yielding solid-vapor surface energies. An optimal MPL contained a 10 wt% MWCNT/KJB carbon substrate and 10 wt% PTFE loading. This information was corroborated by evaluating these materials in anion exchange membrane fuel cells with simultaneous gas and aqueous electrolyte feed.

Aluminum-air batteries are a promising next-generation technology due to their high energy density coupled with the abundance of aluminum and a well-established supply chain. One field that stands to particularly benefit from these greater capacities is aircraft electrification. Aviation applications pose a unique challenge in that the energy source for flight must provide a considerable upside relative to the weight it adds to the vehicle. Lithium-ion technology has been successfully implemented in drones for short flight times, but aluminum-air batteries have the potential to greatly extend the durations of these flights. While the energy density is where this chemistry has a unique competitive advantage, the power output presents a challenge. Although researchers have investigated lithium-ion battery discharge at high C-rates, most aluminum-air battery research has focused on maximizing utilization and energy density. For viable implementation in electric aircraft, focus must be placed on maximizing the power output of the aluminum-air chemistry with care to maintain the energy density that gives it its competitive advantage. At high power outputs, system performance is largely dictated by ohmic losses on the anode side associated with the aluminum product layer. Turnover of this secondary passivation layer is based on conversion of insoluble aluminum hydroxide to soluble aluminate ions, and this can be strongly influenced by several system parameters including electrolyte concentration, temperature, and flow rate. This investigation conducts a parametric analysis of these parameters with respect to their influence on resistance of the aluminum product film and its dissolution. The effects will primarily be studied using electrochemical impedance spectroscopy and polarization curves in conjunction with insight from Tafel analysis, surface imaging, and extended discharge testing. Both three-electrode and full-cell setups will be used for testing to allow for clear insight to surface-level processes and an idea of how the investigated factors scale up when implemented in a real system. Management of the aluminum product film is critical for achieving high power output, and this investigation will provide further insight to how key cell parameters influence the realization of this goal.

Fuel cells for Heavy Duty Vehicles (HDVs) offer easy scalability and the potential for critical reduction in CO2 emissions. During the drive cycles of HDVs, the fuel cells will operate over a range of temperatures, with increases while climbing up steep gradients. Operating temperatures above 90°C will be necessary, along with low relative humidity (RH) due to the need to avoid pressurization of gases. Therefore, Proton Exchange Membranes (PEMs) for HDV applications need to be suitable over this range of conditions, including functioning at high temperatures and low relative humidity. Moreover, the membranes should not swell extensively when more water is present. In this study, sulfonated poly (arylene ether sulfone) multiblock copolymers were modified with the incorporation of clusters of modified cerium oxide nanoparticles to form composites. These synthesized novel membranes approach operational proton conductivity requirements for HDV vehicles, with conductivity of 15mS/cm at 120°C and 25% relative humidity, remarkably avoiding the typical large decrease in conductivity observed below 70% RH in non-fluorinated PEMs. One purpose of this study is to understand the water, proton, and polymer interactions within these membranes. The cerium nanoparticles and sulfonamide clusters play a critical role in the membrane, affecting conductivity, and water transport, especially at high temperatures and low relative humidity, while also suppressing swelling of the membrane. Membrane proton conductivity is also strongly influenced by physical properties such as water uptake and dimensional swelling behavior, which is further impacted by polymer morphology. To probe the dynamics of the components, the diffusion coefficient and relaxation time of water in the membrane and the protonic conductivity of the membrane as functions of membrane water content are analyzed using nuclear magnetic resonance (NMR) measurements and water uptake measurements. Film property and morphology changes are evaluated using Transmission Electron Microscopy (TEM) and Small-Angle X-ray Scattering (SAXS). This study demonstrates the advantageous and non-linear benefits of closely packed acid clusters with cerium oxide composites on membrane functionality under HDV operating conditions.

Gas diffusion layers (GDLs) utilized within anion-exchange membrane fuel cells (AEMFCs) serve a pivotal role in the management of aqueous and gaseous species within the electrode structure, ultimately influencing the stability and performance of these systems. Typically, in static environments with only the supply of gaseous molecules, reaction kinetics and mass transport limitations are present at the anode and cathode catalyst layers due to the lack of aqueous reactant species needed for high-output cell operation. The introduction of constantly replenishing alkaline electrolyte helps mitigate these issues leading to more stable, long-term device usage. Although these configurations help diminish losses within the system, they also expedite the phenomenon known as electrode flooding. This phenomenon has been studied extensively in proton exchange membrane (PEM) fuel cells and is a function of the accumulation of molecular water species at active sites within the catalyst layer due to poor electrode hydrophobicity and fluid management. Using carbon felt GDLs helps increase electrode surface area and structural integrity in flow-type environments, but they have substantially less electrical conductivities compared to carbon paper GDLs. Microporous layers (MPLs) enhance electrical conductivity and the surface area of electrode structures. In a previous study, we were able to show that carbon composite MPLs coated on carbon-felt GDLs lead to decreases in charge transfer resistances of cathode electrodes and increased current densities within the operating voltage window of these systems[1]. To better understand the performance increases and what correlation these increases have with mass transfer rates within the electrode, further analysis of these structures is needed. However, characterization techniques like external wettability and permeability measurements can be unreliable due to the surficial rigidity and asymmetry of carbon felt GDL materials. Herein, to continue this investigation, we present a study applying state-of-the-art methodologies, previously outlined by researchers at Case Western University, to MPL coated carbon felt GDLs to determine mass transport parameters such as internal contact angles[2] due to capillary effects and absolute permeability[3] of these electrode structures. [1] Washington, B., Goenaga, G., & Zawodzinski, T. A. (2022, October). (Digital Presentation) Evaluating the Performance of Multi-Walled Carbon Nanotube Composite Microporous Layers Deposited on Carbon Felt Gas Diffusion Layers. In ECS Meeting Abstracts (No. 1, p. 15). IOP Publishing. [2] Gurau, V., Bluemle, M. J., de Castro, E. S., Tsou, Y. M., Mann, J. A., & Zawodzinski, T. A. (2006). Characterization of transport properties in gas diffusion layers for proton exchange membrane fuel cells. 1. Wettability (internal contact angle to water and surface energy of GDL fibers). Journal of Power Sources , 160 (2 SPEC. ISS.), 1156–1162. [3] Gurau, V., Bluemle, M. J., de Castro, E. S., Tsou, Y. M., Zawodzinski, T. A., & Mann, J. A. (2007). Characterization of transport properties in gas diffusion layers for proton exchange membrane fuel cells. 2. Absolute permeability. Journal of Power Sources , 165 (2), 793–802.

Previous studies on Polymer Electrolyte Membranes have shown that sulfonated polymers exhibit high thermal stability and mechanical properties. The proton conductivity of the sulfonated polymer is strongly dependent upon the degree of sulfonation, where it increases with increasing degree of sulfonation. Also, some observations suggest that densely packed sulfonate groups confer some advantages in allowing more mobile water and protons in the low water content range. In this study bisphenol-based polymers were modified by adding sulfone-amides to form a ball of sulfonates (BOS). Thin, ductile films of the membrane are fabricated by the solution casting method, which resulted in membranes with a thickness of approximately 50 mm. The synthesized copolymers and membranes are characterized by 1 H NMR, FT-IR, ion exchange capacity, water uptake, specific density and proton conductivity measurements. The water uptake and proton conductivity of the membranes are analyzed to determine the impact of varying degrees of sulfonation and side -chains groups within the modified Bisphenol based membranes. Conductivity was tested over a range of temperatures and relative humidity levels simulating potential operating conditions. Water sorption was tested over a range of relative humidity levels to gain an understanding of how relative humidity affects membrane hydration, which is one of the primary factors determining the rate of proton transport in the membrane. In addition, specific density was also measured as density offers insight into membrane hydration and polymer morphology and allows assessment of the mobility of the charge carriers. By studying membranes in this fashion, their performance can be objectively assessed in a controlled environment prior to testing in PEM fuel cells.

Deep eutectic solvents (DESs) have emerged as an alternative to both common organic solvents and ionic liquids (ILs). DESs share physicochemical properties with ILs such as low vapor pressure, high thermal stability, high viscosity while offering advantages such as low toxicity, lower cost, and ease of preparation. Moreover, DESs are attractive candidates for electrochemical applications due to their large voltage windows and solubility properties. DESs as a solvent class share a general composition of a hydrogen bond donor (HBD), typically a polyol, amide, or acid, and a hydrogen box acceptor (HBA), usually a quaternary ammonium or phosphonium salt. At a specific molar composition of a HBD and HBD, the DES forms a eutectic mixture resulting in a large melting point depression due to extensive hydrogen bonding between the components. Despite being widely studied, the use and subsequent characterization of DESs as solvents for aromatic phenols and related aromatics has only recently received attention. In this study we have investigated the solubility of a broad class of aromatic solutes as a function of DES composition and solute concentration using 1H, 13C, pulsed field gradient (PFG), and nuclear Overhauser effect (NOE) NMR. The degree to which homogenous mixtures versus heterogeneous and/or multi-phase systems are formed as a function of solute, temperature, and DES composition is examined. Two classes of DESs glyceline (glycerol + choline chloride) and ethaline (ethylene glycol + choline chloride) were investigated. As many as three distinct phases depending on the nature of the aromatic solute are observed by NMR. {1H-1H}-NOESY measurements show strong correlations between the choline chloride ammonium cation and the aryl protons with cation-pi interactions disrupting the hydrogen bonding network of the DES. We will discuss the implications for these systems as green solvents and comment on how clustering of solutes on the nanoscale may find use in catalysis and self-assembly.

The potential use of nanoparticle organic hybrid materials (NOHM) as electrolytes in redox flow batteries is being explored. NOHMs are composite particles formed by polymers grafted (either ionically or covalently) onto surface-modified inorganic nanoparticles. Such structure has great potential to capture and carry nonpolar electroactive species.1 In this work, the protonation behavior, and the effect NOHM structures have on metal cation uptake is evaluated. Both NOHMs considered in this analysis comprise silica cores ionically grafted with polymer tails. The polymer tails correspond to polyethylimine for the NOHM-I-PEI, and to polyetheramine with a sulfonic acid linker for the NOHM-I-HPE. Cyclic voltammetry was used to investigate the interaction of the copper species as the concentration of the NOHM of interest increases (Figure 1). NOHM-I-PEI showed inhibition of the oxidation and reduction peaks as the NOHM concentration increased, suggesting the formation of the cuprammonium complex. The formation of this complex was also explored via acid-base titration and UV-Vis. On the other hand, the dynamics of neat and NOHM-based fluids was explored via NMR. DOSY was used to explore the diffusion coefficients of the pure polymers and the NOHMs. References 1. Y. Park, C. Petit, P. Han, and A. H. Alissa Park, RSC Adv., 4, 8723–8726 (2014). Figure 1

In this work a series of platinum group metal-free catalysts based on iron, cobalt, copper, nickel, silver and their bimetallic combinations are synthesized and their behavior for oxygen reduction in alkaline media is tested. A phthalocyanine-like ligand supported on carbon black serves as the nitrogen source and carbon support, respectively, for the catalysts. The as-prepared materials are thermally activated by pyrolysis at temperatures ranging from 600 degrees C to 1000 degrees C. Oxygen reduction reaction (ORR) activity and stability in 0.1 M KOH are tested by rotating ring disk electrode (RRDE) experiments. Several of the catalysts show ORR activities in the RRDE experiment that are superior to Pt, with Co, Co/Fe and Ag/Co being the best. All catalysts show remarkable stability, even when they are tested under air for 5000 RRDE cycles. RRDE experiments are also used to study the effect of catalyst loading and to determine reaction order. A thorough study of the catalyst performance in a single cell fuel cell test is conducted; exploring different methods to prepare the electrodes and the effects of catalyst loading, the catalyst-to-binder ratio and the removal of excess metal on the cell performance. Different methods of preparation of membrane electrode assemblies are also studied.

The reactivity of cobalt(II) complexes with molecular oxygen has long been a known and is a much-studied chemical mechanism. These interactions result in the formation of metal-dioxygen adducts that are responsible for numerous cobalt-catalyzed oxidations. In the case of 4-coordinate cobalt salen [Co(salen)] complexes, the formation of catalytically active, mononuclear, superoxo adducts in the presence of a secondary, N -donor ligands has been demonstrated [Co(salen)pyr-O 2 ]. In batch reactions, these adducts are known to readily oxidize para-substituted phenolic compounds resulting in benzoquinone in high yield. Para-phenolic model compounds have been used to demonstrate the potential use of cobalt Schiff base complexes in the oxidation of lignin biomass. This work investigates the redox behavior of the Co(salen)pyr-O 2­­ adduct as a potential recyclable electrocatalyst. Using traditional electrochemical techniques, the activity of the Co(salen)pyr-O 2 adduct is evaluated as it applies to the oxidation of the substrate syringyl alcohol (4-(hydroxymethyl)-2,6-dimethoxy-phenol) in acetonitrile. Typical EC’ electrochemical behavior is reported showing a near linear relationship between substrate concentration and peak current density (J p ) up to 200 mV s -1 . Electrochemical titration of catalytic amounts of Co(salen) with pyridine in the presence of excess oxygen and substrate indicate that the one-electron oxidation of Co(salen)pyr-O 2 H is reversible up to 2:1 pyridine to cobalt. However, both FTIR and EPR characterization of electrolysis experiments with Co(salen)pyr-O 2 in the presence of excess substrate show evidence for the deactivation and/or degradation of the catalyst system after the two-hour mark indicating possible poor ligand stability under reaction conditions. Acknowledgements We gratefully acknowledge the NSF EPSCoR program, TN-SCORE, for support of this work.

The use of haloaluminate room temperature molten salts has potential for interesting battery chemistries. This is particularly true for acidic (excess Lewis acid, e.g. AlCl 3 , over the organic chloride salts) compositions. In that case, Al is readily plated and stripped, as we discussed some time ago. 1 A particularly interesting battery combination arises when the aluminum negative electrode is paired with the evolution of the halogen from the acidic melt. In that case, maximum redox active species concentration is achieved and maximum voltage can be obtained since the entire electrochemical window is utilized. However, several issues with chlorine evolution are known. First, in an acidic melt chlorination of imidazolium cations occurs. This can be partly mitigated by appropriate modification of the cation. A second problem is the somewhat sluggish catalysis of chlorine evolution observed on carbon surfaces. In this work, we report results of efforts to improve on the latter aspect. Specifically, we describe the catalysis of chlorine evolution by catalytically active surfaces. In particular, we show significant enhancements in onset potential for chlorine evolution using supported Ru catalysts. In Figure 1, we compare the chlorine evolution voltammetry in 1.5:1.0 AlCl 3 :EMIC on bare glassy carbon to that observed on the same electrode coated with a sample of 60 wt% Ru on multiwalled nanotubes (prepared in-house). The onset of chlorine evolution occurs on the order of 300 mV less positive with the supported Ru catalysts. We have deposited the Ru on various carbon structures to explore the applicability of this catalyst system for batteries and flow batteries. Studies of the same reaction on Pt electrodes show that the supported Ru nanoparticles have similar activity to that of Pt for this reaction. In addition, similar results were also obtained for bromine evolution. In that case, the lower volatility of the product allowed us to readily observe the bromine oxidation on the reverse scan. This reaction is substantially more reversible on these catalyzed surfaces. Figure 1: Voltammetry of 60%Ru on MWNT on glassy carbon compared to that of the bare glassy carbon electrode. Figure 1

The sluggish oxygen reduction reaction (ORR) in both proton exchange membrane and anion exchange membrane fuel cells, imposes the need for a catalyst to increase the reaction rate and overall cell efficiency. Pt, due to its high catalytic activity and relative stability, is currently the most used ORR catalyst. However, as a precious metal, Pt is expensive and a limited resource, greatly impacting the fuel cell’s cost and, as a consequence limiting its mass commercialization. An advantage of alkaline fuel cells (AFCs) over proton exchange membrane fuel cells (PEMFCs) is that non-precious metals catalysts (NPMC) that are not very efficient for the ORR in acidic environment present higher catalytic activity and stability in alkaline media, even comparable to Pt. Synthesis of NPMCs is often inspired by natural systems. Enzymes, such as laccase, are very efficient ORR catalysts and are known to reduce oxygen at approximately 1.2 V vs. the reversible hydrogen electrode (RHE) under mild pH conditions. We have synthesized a series of pyrolyzed NPMCs based on Cu, Co, Fe and their bimetallic combinations, and a phthalocyanine-like ligand supported on a carbon black. The as prepared catalysts are then pyrolyzed at temperatures ranging from 600 oC to 1000 oC. Various methods were used to optimize the catalysts activity; we evaluated the impact of different solvents during synthesis and removal of excess metal after pyrolysis. Catalyst ORR activity and stability in 0.1 M KOH were tested by rotating ring disk electrode (RRDE) experiment. Half wave potentials, number of electrons transferred and reaction rate were also calculated. The bimetallic catalysts based on CoFe and CuFe surpassed the ORR activity of commercial Pt/C, reaching half wave potentials E1/2of 0.832 V and 0.815 V respectively, compared to 0.808 V vs. RHE of Pt/C. See figure 1. The samples were characterized using scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), and x-ray powder diffraction (XRD). RRDE experiments were used to study the effect of catalyst loading, to determine the reaction order and catalyst stability. Ongoing experiments study the performance of the catalysts on a single cell using various anion exchange membranes. Figure 1. RDE plots for Cu, Co, Fe based catalysts and their comparison to commercial 30% Pt/C. Acknowledgments We gratefully acknowledge the support of this work by the NSF-funded TN-SCORE program, NSF EPS-1004083, under Thrust 2. References: X. Li, B. N. Popov, T. Kawahara, H. Yanagi. J. Power Sources 196 (2011) 1717-1722. H. Peng, F. Liu, X. Liu, S. Liao, C. You, X. Tian, H. Nan, F. Luo, H. Song, Z. Fu and P. Huang. ACS Catalysis 4 (2014) 3797−3805. Figure 1

In recent years there has been a marked increased interest in alkaline based energy storage and conversion systems such as anion exchange membrane fuel cells and metal air batteries. Both technologies rely on the reduction and/or evolution of oxygen. The slow kinetics of the oxygen reduction (ORR) and evolution reactions (OER) in alkaline environments necessitate the use of electro catalysts to increase the reaction rate and increase cell efficiency. Precious metals are most commonly used due to their high activities and relative stabilities. There has been an extensive search for non-precious metal catalysts (NPMCs) that demonstrate comparable activity and stability for ORR and OER in alkaline environments, but at lower costs. Among the families of materials studied are precious metals, transition metal oxides, transition metal minerals (perovskites, spinels, pyrochlores, etc.), and organometallic complexes. The latter is the focus of this work. Organometallic NPMCs are generally synthesized by pyrolysis of a combination of metal salts, a nitrogen source (macromolecules or reactive gas) and a carbon support. State of the art NPMCs are based on Fe and Co and are synthesized in elaborate multi-step processes combining high temperature treatment (900oC to 1050oC) with acid wash or reactive gas (NH3) pyrolysis1. These catalysts have proven to have good ORR activity but limited durability. In this study we report the synthesis and characterization of a new class of NPMCs for ORR and OER based on organometallic complexes of nickel (Ni) and bimetallic complexes of nickel with cobalt (Co), copper (Cu), or iron (Fe). The complexes comprised of metals immobilized by ligands, covalently attached to a carbon black, yielding a phthalocyanine-like molecule. The as-synthesized catalysts show low catalytic activity for the oxygen reduction reaction when compared to Pt. However, after a one step pyrolysis at 700oC in inert atmosphere, the activity of catalysts was found to improve dramatically. The NiFe bimetallic catalyst had an onset potential of 1.03V vs. RHE (measured at 50µA/cm2). The as-synthesized catalysts generally demonstrate decent activity for the oxygen evolution reaction, vastly surpassing platinum. The activity was also found to increase after pyrolysis. The samples were characterized using fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), thermo gravimetric analysis – mass spectrometry (TGA-MS) and x-ray powder diffraction (XRD). RRDE experiments were used to study the effect of catalyst loading, oxygen concentration, to determine the ORR reaction order, and catalyst stability. Optimization methods to enhance the catalytic performance will also be described. In situ testing of catalysts in Zinc-air batteries was conducted and the cell performance was compared to precious metals and perovskites. Acknowledgements: We would like to thank the EPSCORE program for providing funding for this work. Figure 1: RDE voltammogram of Ni TrPc catalysts for ORR and OER compared to platinum (25µg Pt/cm2) References: X. Li, B. N. Popov, T. Kawahara, H. Yanagi. J. Power Sources 196 (2011) 1717-1722 Figure 1