Microporous electrodes (pores < 2 nm in width) can confine molecules into uniquely packed, charged volumes that exhibit characteristics different from molecules from a bulk solution interacting with an electrode surface. By using surface and electrochemical characterizations, we show the confinement of organic molecules in micropores can shift their redox potentials beyond the classical Nernstian regime, with a shift as large as 252 mV. We identify an excess contribution to the electrochemical potentials of ions that leads to the thermodynamic limit for these shifts and use continuum-scale simulations from a modified Donnan model to confirm this limit and derive deviations from it. Density functional theory simulations confirm that micropore confinement can change the mechanism of charge transfer. We find trends in behavior in micropore environments for organic and metalorganic molecules in aqueous solutions based on their electrophilicity, charge, core molecules, and molecular functionalizations (i.e. side chains). Finally, using micropore confinement on the high and low potential sides of an enclosed secondary battery to increase the open circuit voltage, we demonstrate an increase in average discharge cell voltage of 39% and a corresponding increase in discharge energy density of 36% by replacing macroporous electrodes with microporous electrodes.

Selective sodium removal from water sources is crucial for irrigation and other applications, yet challenging due to the abundance of sodium ions compared to essential minerals like calcium and magnesium. Capacitive deionization (CDI) is an emerging electrochemical technique for water treatment and desalination which uses a small electrical potential to adsorb ions in the double layers of microporous electrodes. Given the micropore size is of the same order of magnitude as hydrated ions, CDI offers potential for ion differentiation based on properties such as charge, radius, diffusion constant, and more. Herein, the development of monovalent selective CDI through surface modification of activated carbon cathodes with phosphoric acid groups is described. Cathode phosphorylation induces negative surface charges within the micropores, resulting in enhanced absorption of smaller sodium ions and no calcium uptake during CDI. By applying short, alternating charge-discharge cycles, this membraneless system achieves perfect monovalent cation selectivity with low energy consumption (as low as 0.28 kWh m-3), removing sodium from the water without reducing the calcium concentration.

A comprehensive study of stronger-binding complexing agents than MEP to increase coulombic and energy efficiency using a membraneless single-flow zinc–bromine battery with a multiphase electrolyte.

Developing large-scale storage of intermittent renewable energy to meet growing energy demands is a pressing current need. Multiphase single flow batteries are a promising solution for such grid-scale energy storage, demonstrating an affordable redox flow battery design that reduces both cell and balance of plant costs. However, their major limitation is the considerable variance in electrolyte conductivity under different battery flow conditions and electrolyte properties, with no current predictive model to comprehensively understand and optimize it. Here, we develop an analytical model for such emulsion electrolytes with a continuous aqueous-based phase and dispersed reactant-rich phase, which enables electrolyte resistance prediction. We show that a key mechanism affecting electrolyte conductivity is the formation of a sedimented layer along the flow channel, revealing the critical effect of non-aqueous phase sedimentation. Experimental validation using a zinc-bromine single flow battery demonstrates excellent agreement with theoretical results during both transient and steady operations, allowing extraction of challenging-to-measure parameters, such as the in-situ size of dispersed phase droplets. This foundational model is essential in minimizing power losses, improving electrolyte and cell designs, and holds broad applicability across diverse chemistries for single-flow batteries.

Capacitive deionization (CDI) is notable for its ability to perform low-energy desalination of brackish water and selective separation/recovery of salt and metal ions. However, redox side-reactions at porous carbon electrodes, such as the formation of weakly-acidic, oxygen-containing surface groups, limit ion electrosorption into double layers and electrode lifespan. In this study, we employ porous electrode theory to investigate the coupled effects of transport, electrosorption, redox reactions, and acid/base surface chemistry in practical flow through electrode (FTE) CDI cells, and we develop an efficient numerical solver that allows us to perform full-cell simulations over numerous charging/discharging cycles. We verify that our high fidelity model's predictions agree with analytical solutions in the limit of small voltage perturbations, and we demonstrate the significance of accurately capturing interplay between pH dynamics and surface chemistry. Our simulations demonstrate that anodic oxidation in FTE CDI is substantially inhomogeneous in space and in time, exhibiting cyclic protonation/ deprotonation of surface groups and traveling, shock-like pH fronts. Moreover, we uncover connections between microscopic behavior and macroscopic performance parameters, demonstrating that this theoretical and numerical approach may substantially benefit the practical design optimization of CDI cells.

The demand for electronic devices that utilize lithium is steadily increasing in this rapidly advancing technological world. Obtaining high-purity lithium in an environmentally friendly way is challenging by using commercialized methods. Herein, we propose the first fuel cell system for continuous lithium-ion extraction using a lithium superionic conductor membrane and advanced electrode. The fuel cell system for extracting lithium-ion has demonstrated a twofold increase in the selectivity of Li+/Na+ while producing electricity. Our data show that the fuel cell with a titania-coated electrode achieves 95% lithium-ion purity while generating 10.23 Wh of energy per gram of lithium. Our investigation revealed that using atomic layer deposition improved the electrode's uniformity, stability, and electrocatalytic activity. After 2000 cycles determined by cyclic voltammetry, the electrode preserved its stability.

Desalination fuel cell (DFC) is an electrochemical cell driven by hydrogen-oxygen redox reactions to simultaneously generate electricity and desalted water. Methanol reforming (MR), although being a relatively well-established method for H-2 generation, produces CO2 and small amounts of CO. While the detrimental effect of CO on proton exchange membrane fuel cells has been extensively studied, the effect of CO on DFC performance has not yet been investigated. In this study, we introduce a novel integrated MR-DFC system and investigate its performance characteristics experimentally. Specifically, we examined the system's response to the presence of CO2 and CO in the MR outlet stream that is directly fed to the DFC inlet. Our findings reveal a decrease in the open-circuit voltage (OCV) and limiting current when utilizing the MR outlet as a feed, although the ohmic region remains intact and the desalination process is not affected significantly. Rotating disk electrode (RDE) tests were conducted to validate the observed reduction in the OCV. A stability test was conducted for 25 h, revealing that feeding the MR outlet to DFC initially provides a similar discharge current to that with pure H-2 feed, followed by certain degradation that was attributed to CO poisoning. Our study provides valuable insights into the performance of the integrated MR-DFC unit, advancing the development of this sustainable water-power system.

High specific surface area K-Fe/gamma-Al2O3 was synthesized via the reverse microemulsion method and tested for direct hydrogenation of CO2 to light hydrocarbons (lower paraffins and olefins). The effect of the synthesis method was investigated by several characterization techniques and via reaction tests, while using wet impregnation-synthesized catalysts as a reference. The reverse microemulsion method resulted in superior catalytic performance, ascribed to the enhanced specific surface area, enhanced active phase-support interaction and reducibility, and facile formation of the active Hagg iron carbide (chi-Fe5C2) phase. The maximum obtained CO2 conversion and selectivity to C2+ hydrocarbons were 56 % and 52 %, respectively, attaining 7.4 mmol g- 1 h- 1 space time yield at 10 bar and 375 degrees C. Characterization results revealed the formation of chi-Fe5C2 and Fe3O4 phases under reaction conditions. Compared to the impregnation method that resulted in the formation of Fe3O4 nanoparticles and Fe/Fe3O4 core-shell nanoparticles, the reverse microemulsion-synthesized catalyst comprised of a mixture of Fe3O4 and chi-Fe5C2 nanoparticles with a relatively uniform particle size distribution. The superior catalytic activity of the reverse microemulsion-synthesized catalyst can be elucidated by the promoted magnetite -* iron carbide transformation that results from the small initial nanoparticle size (below 10 nm).

Discovery of electrocatalysts composed of cheap transition metals are urgent to replace the traditional Pt/C catalyst used for oxygen reduction reaction (ORR). Herein, we synthesized Cu nanoparticles encapsulated with nitrogen-doped carbon (Cu@NC) as an excellent and durable catalyst for ORR. A systematic evaluation of the effect of Cu content, acid leaching and secondary heat treatment have been established with the help of half-cell studies. The morphological analysis revealed that Cu nanoparticles surrounded by thick nitrogen doped carbon layers and further, the acid leaching and subsequent pyrolysis, boosted the electrocatalytic performance. The optimized Cu@NC catalyst showed onset potential (potential corresponding to a current density of 0.10 mA cm-2) and half-wave potential of 0.97 V vs. RHE and 0.85 V vs. RHE, surpassing the state -of-the-art Pt/C catalyst. In addition, the Cu@NC catalyst exhibited outstanding durability, tolerance to carbon monoxide and methanol molecules. In the alkaline fuel cell, Cu@NC catalyst delivered 118 mW cm-2 peak power density in alkaline fuel cell operated with H2-O2, whereas Pt/C only delivered a peak power density of 97 mW cm-2 under ambient operating conditions. High ORR activity and better stability of Cu@ NC catalyst could be a potential alternative to Pt/C catalyst in alkaline fuel cells and metal-air cell cathodes.(c) 2022 Elsevier B.V. All rights reserved.

Capacitive deionization (CDI) is an emerging technology applied to brackish water desalination and ion selective separations. A typical CDI cell consists of two microporous carbon electrodes, where ions are stored in charged micropore via electrosorption into electric double layers. For typical feed waters containing mixtures of several cations and anions, some of which are polluting, models are needed to guide cell design for a target separation, given the complex electrosorption dynamics of each species. An emerging application for CDI is brackish water treatment for direct agricultural use, for which it is often important to selectively electrosorb monovalent Na+ cations over divalent Ca2+ and Mg2+ cations. Recently, it was demonstrated that utilizing constant-voltage CDI cell charging with sulfonated cathodes and short charging times enabled monovalent-selective separations. Here, we utilize a one-dimensional transient CDI model for a flow-through electrode CDI cell to elucidate the mechanisms enabling such separations. We report the discovery that an asymmetric CDI cell with a chemically functionalized cathode induces electric charges in the pristine anode at 0 V cell voltage, which has important implications for monovalent cation selectivity. Leveraging our mechanistic understanding, with our model we uncover a novel operational regime we term "capacitive ion exchange", where the concentration of one ion species increases while competing species concentration decreases. This regime enables resin-less exchange of monovalent cations for divalent cations, with chemical-free electrical regeneration.

The world faces a rising demand for potable water and electricity, while a lack of clean water and use of polluting electricity sources are major hazards1. Nowadays reverse osmosis (RO) is widely used for sea and brackish water desalination2, where RO consumes ~3-4 kWh/m3 for seawater desalination3. A new class of water treatment technologies is emerging that is distinguished from the classical methods by utilizing chemical energy to power both water treatment and electricity generation simultaneously from a single electrochemical cell. When using the hydrogen/oxygen redox couple, such a cell is termed a desalination fuel cell (DFC) which was introduced by our group in 20204. A DFC utilizes a fuel cell anode and cathode to catalyze the chemical-to-electrical energy conversion, as well as a cation and anion exchange membrane to desalinate the feedwater flowing through the cell. A device with a single feed channel (figure a) was able to produce up to 10 kWh/m3 while desalinating water with sea-water level salinity4. In order to for this nascent technology to become practical, scale-up strategies need to be proposed and demonstrated. In this work we show results from the first scaled DFC, where we utilize scaling rules associated with electrodialysis by increasing the number of membrane pairs to allow either two or three feed channels (Figure b). We find the three feed channel device was associated with high voltage loss in the ohmic region and lower limiting current (figure c), but the salt concentration behaved linearly as a function of the current density as expected (figure d). The main voltage losses are clearly emanated from the cathode and the anode sides as the membranes potential loss was proven to be insignificant5. We showed that implementing higher acid concentration in the catholyte and higher base concentration in the anolyte channels can significantly improve performance of the stack. Figure (e) shows results using three different anolyte and catholyte solutions, with highest open circuit voltage (OCV) and improved polarization performance for 0.5M HClO4 and 0.5M NaOH in the catholyte and the anolyte, respectively. We also investigated the feed flow rate impact on DFC polarization performance and salt removal. Overall, we show successful implementation of a scaled-up DFC. References: Mekonnen, M. M. & Hoekstra, A. Y. Sustainability: Four billion people facing severe water scarcity. Sci. Adv. 2, 1–7 (2016). Greenlee, L. F., Lawler, D. F., Freeman, B. D., Marrot, B. & Moulin, P. Reverse osmosis desalination: Water sources, technology, and today’s challenges. Water Research vol. 43 2317–2348 (2009). Al-Karaghouli, A. & Kazmerski, L. L. Energy consumption and water production cost of conventional and renewable-energy-powered desalination processes. Renewable and Sustainable Energy Reviews vol. 24 343–356 (2013). Atlas, I., Abu Khalla, S. & Suss, M. E. Thermodynamic Energy Efficiency of Electrochemical Systems Performing Simultaneous Water Desalination and Electricity Generation. J. Electrochem. Soc. 167, 134517 (2020). Abdalla, S., Khalla, S. A. & Suss, M. E. Voltage loss breakdown in desalination fuel cells. Electrochem. commun. 132, 107136 (2021). Figure 1

Dielectric materials with higher energy storage and electromagnetic (EM) energy conversion are in high demand to advance electronic devices, military stealth, and mitigate EM wave pollution. Existing dielectric materials for high‐energy‐storage electronics and dielectric loss electromagnetic wave absorbers are studied toward realizing these goals, each aligned with the current global grand challenges. Libraries of dielectric materials with desirable permittivity, dielectric loss, and/or dielectric breakdown strength potentially meeting the device requirements are reviewed here. Regardless, aimed at translating these into energy storage devices, the oft‐encountered shortcomings can be caused by either of two confluences: a) low permittivity, high dielectric loss, and low breakdown strength; b) low permittivity, low dielectric loss, and process complexity. Contextualizing these aspects and the overarching objectives of enabling high‐efficiency energy storage and EM energy conversion, recent advances in by‐design inorganic–organic hybrid materials are reviewed here, with a focus on design approaches, preparation methods, and characterization techniques. In light of their strengths and weaknesses, potential strategies to foster their commercial adoption are critically interrogated.

The share of electricity generated from renewable sources is growing rapidly, and thus grid-scale battery storage is becoming more prevalent. Aqueous redox flow batteries have the potential to provide safe and scalable energy storage, but the high cost of storage, particularly the membrane and balance of plant costs, has inhibited commercialization. The recently developed single-flow battery leveraging a multiphase electrolyte promises a low-cost system [1], as it is membraneless and uses only one tank and flow loop, but suffers from low Coulombic efficiency [1]. To unlock the potential of such a system, the interplay between interphase mass transport, multiphase flow phenomena, and battery performance must be unraveled. Here, we will compare our previously developed theoretical battery model derived from a boundary layer analysis [2,3] to results from a dedicated experimental program [4]. This led to several key findings, including that our battery operates in a regime characterized by a high Stanton number, and that our analytical solutions led to excellent predictions in various operational regimes when using the interphase mass transport coefficient as a single-valued fitting parameter [4]. In other regimes, such as at low electrolyte velocity, results indicate that gravity acting on the denser polybromide phase played a significant role, and progress towards incorporating gravitational effects into models will be discussed [4]. Figure 1 : Schematic of a discharging single-flow battery leveraging a multiphase flow electrolyte. The flow consists of a continuous, bromine-poor aqueous phase and dispersed, bromine-rich polybromide phase. Bromine in the polybromide phase is largely electrochemically inactive, thus such an electrolyte enables membraneless operation by limiting the crossover of bromine to the zinc anode. References: [1] Amit, L., Naar, D., Gloukhovski, R., la O', G.J. and Suss, M.E., 2021. “A Single-Flow Battery with Multiphase Flow”. ChemSusChem , 14(4), pp.1068-1073. [2] Ronen, R., Gat, A.D., Bazant, M.Z. and Suss, M.E., 2021. “Single-flow multiphase flow batteries: Theory”. Electrochimica Acta , 389, p.138554. [3] Kuperman, S., Ronen, R., Matia, Y., Zigelman, A., Suss, M.E. and Gat, A.D., 2022. “Modelling the fluid mechanics in single-flow batteries with an adjacent channel for improved reactant transport”. Flow , 2, E11. [4] Ronen, R., Gloukhovski, R. and Suss, M.E., 2022. “Single-flow multiphase flow batteries: Experiments”. Journal of Power Sources, 540, p.231567. Figure 1

Redox flow batteries (RFBs) promise to fill a crucialmissing linkin the energy transition: inexpensive and widely deployable grid andindustrial-scale energy storage for intermittent renewable electricity.While numerous lab-scale and demonstration-scale RFBs have been delivered,widespread commercial deployment is still limited by high electrolyte,stack, and balance of plant capital costs. Increasing the power densityof RFBs is correlated with lower stack costs, primarily because thearea needed for expensive electrode and membrane components to reacha target power density is reduced. In the present contribution, wesummarize the areal power densities reported for lab-scale RFBs, criticallyevaluate major pathways employed for power optimization, and identifyopportunities for developing yet-higher power density systems.

The leading-edge of a substrate undergoing convective mass deposition is a region of significant local deposition rate compared to the mass deposition at the downstream Leveque concentration boundary layer. The local increase in mass deposition is due to an intrinsic topological transition at the leading edge, a transition that is usually in the chemistry or geometry of the target surface for deposition. We study two leading-edge cases for model convective electrodeposition: a flat and a corner/step transitions between the inert wall and active cathode. We find that mass deposition at the leading-edge is faster than at the boundary layer and is connected to the Pećlet number differently. Its rate is correlated with the transition length and decays downstream to match the deposition rate at the boundary layer.

Ion-selective water treatment is an important frontier in water research, as for many applications removing all ions indiscriminately leads to significant extra energy and downstream re-ionization costs. Capacitive deionization (CDI) is under intensive investigations for ion-selective treatment of polluted feedwaters [1]. CDI has the remarkable feature of being not only highly selective, but additionally dynamically tuneable to adjust, real-time, to varying feedwater composition and produced water targets [1]. However, we will show that to further develop CDI technologies to achieve desired separations, in feedwaters of several competing anions and cations, requires detailed numerical models. Such models couple ion transport theory to nanopore electrosorption, and often include pH dynamics. We here describe our recent work exploring the limits of ion-ion selectivity by capacitive deionization with inexpensive nanoporous carbon electrodes. We show how theory enabled us to achieve in the lab remarkable selectivity and a diverse set of separations, such as “perfect” divalent cation selectivity[2], monovalent ion selectivity[3], and removal of amphoteric pollutant species such as boric acid and nutrient species[4]. We show using strong-acid functionalized electrodes that the same two-electrode system can be used for either excellent divalent selectivity, or long-lasting monovalent ion selectivity, depending on cell operational parameters [2,3]. Our work furthers the argument that membraneless CDI, based on inexpensive and easily-scalable porous carbon electrodes, can address a wide variety of important applications in water treatment. References: [1] J.G. Gamaethiralalage, et al. “Recent advances in ion selectivity with capacitive deionization”, Energy & Environmental Science, 2021. [2] R. Uwayid, E.N. Guyes, A.N. Shocron, J. Gilron, M. Elimelech, M.E. Suss. “Perfect divalent cation selectivity with capacitive deionization”, Water Research, 2022. [3] E.N. Guyes, A. Shocron, Y. Chen, C. Diesendruck, M.E. Suss. “Long-lasting, monovalent selective capacitive deionization electrodes.” NPJ Clean Water, 2021. [4] A.N. Shocron, E.N. Guyes, H.H. Rijnaarts, P.M. Biesheuvel, M.E. Suss, J.E. Dykstra, “Electrochemical removal of amphoteric ions”, Proceedings of the National Academy of Sciences, 2021. Figure 1: From Ref. 3. CDI concept for treatment of water for direct use towards irrigation. a) Schematic of a CDI cell fed with water containing excessive Na+ which must be removed for direct use in irrigation. The cell is charged at an applied cell voltage Vch at or above 1 V and for a time tch significantly shorter than the time to reach equilibrium, teq . b) The cathode nanopore is functionalized with strong-acid sulfonic groups, which enhances the preferential storage of monovalent Na+ over divalent Ca2+ at short charging times. c) The treated water has significantly reduced sodium absorption ratio (SAR) and ionic conductivity, rendering it suitable for direct use in irrigation. Figure 1

Increasing global water stress motivates a growing interest in seawater desalination by reverse osmosis. Boron is typically weakly removed by reverse osmosis membranes at seawater pH, necessitating expensive post-processes such as caustic agent dosing of the permeate followed by additional filtration steps. It has been previously demonstrated that membraneless capacitive deionization can enable chemical-free boron removal from reverse osmosis permeate, with basic design rules established. However, the level of boron electrosorption per cell charge was limited to similar to 0.5 mu mol/g, a level too low for practical applications. We here explore, both theoretically and experimentally, methods to enhance boron removal by capacitive deionization. We found that reversing the polarity of the applied voltage during the discharge step resulted in an order of magnitude increase in boron electrosorption to nearly 4 mu mol/g with promising energy consumption of 0.2 kW center dot h/m(3). The promise of these results is highlighted when compared with recently-developed boron electrosorption cells requiring bipolar membranes, which demonstrate similar boron removal of 4.35 mu mol/g but with much higher energy consumption of 18.3 kW center dot h/m(3) while incurring significant membrane costs. Overall, we demonstrate for the first time that membrane- and chemical-free electrochemical technologies can remove sufficient boron from RO permeate in a single pass, significantly enhancing its potential to provide energy- and cost-efficient boron removal.

Desalination has evolved into a viable alternative to fresh water supply, increasing water availability and decreasing scarcity1. Reverse osmosis (RO) is the most-widely used technology today for desalination, and requires significant electrical energy investment, about 4 kWh/m3 of treated water, when desalinating sea water2. In contrast to such conventional desalination systems which utilize energy, we will here dicsuss desalination fuel cells (DFCs), an emerging electrochemical desalination technology proposed by our group3. DFC’s utilize hydrogen gas to simultaneously desalinate water and produce electricity from a single cell. Thus, water can be desalinated without any external electrical supply required. The desalination fuel cell is based on continuous energy conversion from chemical to electrical, and thus is not cyclic as with capacitive deionization4. As with an ED cell, our cell consists of one anion and one cation exchange membrane which sandwich a desalination channel fed with feedwater. Unlike an ED cell, on the opposite side of the anion exchange membrane is a hydrogen anode and anolyte, while an oxygen cathode and catholyte are placed opposite to the CEM. During operation, the reductant present in the anolyte (hydrogen) and oxidant present in the catholyte (oxygen) react spontaneously at the anode and cathode surfaces, respectively, providing an electric current between the anode and cathode which can be delivered to a load. The half-reactions also give rise to a spontaneous ionic current through the cell, which drives ion removal from the desalination channel (Figures a,b). The cell was characterized by running it in two modes, with either near-neutral pH in all channels (H2|O2) (Figure a) or with a pH-gradient mode (H2+B|O2+A) (Figure b), which allowed for deep insight into cell performance and detailed characterizations (Figures c-f)5. The results show that our prototype can desalinate water effectively while generating electricity, it was also found that operation in H2+B|O2+A mode enabled improved DFC performance, higher OCV, and produced electricity of up to 10 kWh/m3 (Figure g)5. A detailed voltage breakdown, elucidating key sources of loss in the cell was also demonstrated adding quasi-reference electrodes in all flow channels of the cell. It was shown that voltage loss across ion exchange membranes was generally insignificant, but the cathode is generally the component associated with the largest voltage loss, largely due to Nernstian losses exacerbated by likely chloride poisoning of the cathode catalyst (Figure i)6. Chloride poisoning was studied in-situ, by flowing different catholytes through the cell, and ex-situ using an RRDE. We further synthesized and optimized custom, non-precious metal-based Fe/N/C catalyst for desalination fuel cell cathodes, and showed nearly equal catalytic performance to that of the Pt/C commercial cathode (Figure h)7. References: Kummu, M. et al. The world’s road to water scarcity: Shortage and stress in the 20th century and pathways towards sustainability. Rep. 6, 1–16 (2016). Malaeb, L. & Ayoub, G. M. Reverse osmosis technology for water treatment: State of the art review. Desalination 267, 1–8 (2011). Atlas, I., Abu Khalla, S. & Suss, M. E. Thermodynamic Energy Efficiency of Electrochemical Systems Performing Simultaneous Water Desalination and Electricity Generation. Electrochem. Soc. 167, 134517 (2020). Porada, S., Zhao, R., Van Der Wal, A., Presser, V. & Biesheuvel, P. M. Review on the science and technology of water desalination by capacitive deionization. Mater. Sci. 58, 1388–1442 (2013). Abu Khalla, S., Atlas, I. & Suss, M. E. Desalination fuel cells with high thermodynamic energy efficiency. Environmental Science & Technology. Accepted. Abdalla, S., Abu Khalla, S. & Suss, M. E. Voltage loss breakdown in desalination fuel cells. Electrochemistry Communications 107136 (2021). Asokan, A., Abu-Khalla, S., Abdalla, S. & Suss., M. E. Chloride-tolerant, inexpensive Fe/N/C catalysts exceed platinum catalysts for desalination fuel cell cathodes. ACS Applied Energy Materials. Submitted. Figure 1

We will present a nascent technology which desalinates water and produces net electricity simultaneously from a single electrochemical cell, driven by the hydrogen/oxygen redox couple [1]. The cell combines hardware of PEM fuel cells, alkaline fuel cells and electrodialysis cells, and thus we term this device a "desalination fuel cell" [2]. We will describe both the operating principle and lab-scale cell results, as well as our development of the fundamental thermodynamics to predict the maximum available electricity production from our cell during its combined chemical reaction-separation process [2]. Our recent advances will be described, including the development of chloride-tolerant non-platinum group metal ORR catalysts [3], achievement of >95% thermodynamic energy efficiency [4], and establishment of system scaling rules. This technology promises to extend the concept of the hydrogen economy to water purification, and we will discuss the outlook on this technology and potential application areas. References: [1] Suss ME, Zhang Y, Atlas I, Gendel Y, Ruck EB, Presser V. Emerging, hydrogen-driven electrochemical water purification. Electrochemistry Communications. 2022 [2] Atlas I, Khalla SA, Suss ME. Thermodynamic energy efficiency of electrochemical systems performing simultaneous water desalination and electricity generation. Journal of The Electrochemical Society. 2020. [3] Asokan A, Abu-Khalla S, Abdalla S, Suss ME. Chloride-Tolerant, Inexpensive Fe/N/C Catalysts for Desalination Fuel Cell Cathodes. ACS Applied Energy Materials. 2022. [4] Abu Khalla S, Atlas I, Litster S, Suss ME. Desalination Fuel Cells with High Thermodynamic Energy Efficiency. Environmental science & technology. 2021. Figure 1: Schematic of a desalination fuel cell, which utilizes chemical energy to desalinate water and produce electricity simultaneously. The cell is driven by the hydrogen-oxygen redox couple. Figure 1

Clean technologies, which utilize or generate clean energy rather than fossil fuel-based energy, are under intense development to aid in addressing climate change. Current water desalination technologies are a growing user of fossil fuel-derived electricity. A recently developed technology, termed the desalination fuel cell (DFC), can address this issue by instead using hydrogen gas to drive both feedwater desalination and green electricity generation simultaneously in a single cell. The main bottleneck is the use of Pt-based catalysts, which leads to high device costs and catalyst surface poisoning due to chloride ions (Cl-) present in the feedwater. We here propose and demonstrate the first use of non-platinum group metal (non-PGM) catalysts toward DFCs. We synthesized a Fe/N/C based catalyst which demonstrated effective and Cl- tolerant oxygen reduction reaction ex situ and while used as a DFC cathode. The synthesis temperature and the metal concentrations were optimized using rotating disk electrode measurements, with an onset potential of up to 0.84 V vs RHE, on par with that of commercial Pt/C catalysts in a Cl- environment. When using the optimized Fe/N/C catalyst as a cathode in a prototype DFC, open circuit voltage was significantly improved relative to Pt/C, and measured cell voltage and desalination performance versus current density were nearly equivalent. Overall, these results show that non-PGM catalysts maintain or improve cell performance while significantly reducing cell costs, improving greatly the outlook for this nascent technology.