Substitution of vanadium into earth-abundant maghemite iron oxide introduces cation vacancies that increase Li+ storage capacity concomitant with a positive shift in its electrochemical potential. Expressing vanadium ferrite (VFe2Ox) as an aerogel offers an opportunity to probe Li+ storage in this inherently defective spinel from highly disordered (X-ray amorphous) to nanocrystalline. To understand the redox sequence of the host cations, we use in situ X-ray absorption near-edge spectroscopy (XANES) obtained using an in-lab X-ray absorption spectrometer in concert with density functional theory calculations to uncover the quantum mechanical-level effects that underpin relevant energy-storage behaviors. The Fe K-edge spectra indicate that upon Li+ insertion, the change in Fe oxidation state occurs primarily at high voltage (average voltage ∼2.9 V), which is ∼0.7 V higher than the average voltage for γ-Fe2O3. Parallel computations using density functional theory show that tetrahedral V and octahedral Fe sites are reduced during lithiation and that the hybridization of Fe and V orbitals imposes a positive shift in voltage for Fe redox. Our combined experimental and computational investigation sheds light on how these complex materials store Li+ and increase cell voltage. These findings point toward future compositional alterations that may further improve their properties.

Much of the contemporary research on advanced desalination materials strives for high gravimetric capacity but ignores their applicability to engineered devices. Practical faradaic deionization of saline and brackish waters requires electrodes that are scalable beyond micrometer-thickness in order to achieve high areal capacity. To break the status quo approach to materials research at nanometric scales, we design and test three-dimensional architectures capable of melding materials properties with performance. Monolithic sponges that facilitate ionic and electronic conductivity within the architected electrode offer a path to rapid and energy-efficient desalination. Salt-templated synthesis of porous Ag and AgCl@Ag sponges yields millimeters-thick architected electrodes with full-cell capacity surpassing 40 mAh cm-2 (200 mAh cm-3), making them suitable for compact and portable desalination devices. This form factor comprises interconnected networks of micrometer-sized Ag particles that electron-wire the electrode volume, which greatly increases the specific surface area (260 cm2 g-1) and the extent of Ag/AgCl conversion compared with bulk commercial forms (e.g., silver mesh). Desalination tests performed in a rocking-chair, flow-through cell demonstrate NaCl-removal capacities of 78 mg g-1 (66 mg cm-2) at rates up to 2 mg g-1 min-1 (1.7 mg cm-2 min-1), removing 25% salt from 35 g L-1 NaCl. The low-voltage reaction of the Ag/AgCl conversion cell consumes as little as 0.02 Wh g-1 at 5 mA cm-2. In a 5 g L-1 influent concentration of NaCl, the Ag sponge cell provides single-stage, fit-for-purpose desalination, achieving 90% salt removal at a throughput productivity of 6.21 L m-2 h-1 with only 0.55 Wh L-1 energy consumption. When combined with multistage batch desalination, the single-membrane device can reduce saline water to potable levels at 6.4 Wh L-1.

In order to provide stability to natural energy sources such as solar and wind power, there has been a strong drive to improve the performance of electrochemical supercapacitor devices through the incorporation of novel electrode materials. Metal-organic frameworks represent one type of these materials that can increase the capacitance of these systems by enhancing the electric double layer formation mechanism with their vast surface area while also providing species that can participate in reversible redox reactions; however, further studies are necessary to fully understand these energy storage mechanisms so that they can be exploited to bolster device performance. Here, we demonstrate the first use of in situ nuclear magnetic resonance chemical shift imaging on an aqueous-based supercapacitor device that incorporates a metal-organic framework, zeolitic imidazolate 67 (ZIF-67), as the working electrode material. These measurements provide insight into the device's charge/discharge behavior. Most notably, we observe a downfield trend in the chemical shift of electrolyte near the ZIF-67 electrode during the device's first cycle that we have connected to the material's degradation, independently corroborating a previous study's findings with different experimental techniques. Furthermore, we show that once the device has been electrochemically conditioned, this process only occurs to a much smaller extent, and reversibility is displayed. These results highlight the ability of chemical shift imaging to detect chemical changes in these systems and weigh in on the viability of ZIF-67 in this application.

Nickel-based catalysts are widely studied for water-gas shift (WGS), a key intermediate step in hydrogen production from carbon-based feedstocks. Their viability under practical conditions is limited at high temperatures when Ni aggregates and converts CO to methane, an undesirable side product. Because experimental and computational studies identify undercoordinated Ni step sites as most active toward CH 4 formation, we eliminate Ni step sites by atomically dispersing Ni into networked, nanoparticulate CeO 2 aerogels. The mesoporous catalyst with 2.5 atomic % Ni in CeO 2 is highly active for WGS, converting near-equilibrium levels of CO at 350°C, while no CH 4 is detected at the limit of detection (<2 parts per million). In contrast, supporting low weight percentages of Ni clusters or nanoparticles on CeO 2 aerogels leads to methanation. The CH 4 yield produced by the atomically dispersed Ni-substituted CeO 2 aerogel is over an order of magnitude lower than previously reported Ni-based catalysts claiming methane suppression, marking an important advance in the development of WGS catalysts.

Vanadium–iron oxides (VFe2Ox) exhibit promising Li+-storage properties when expressed in high-surface-area, disordered/defective forms such aerogels.1 We have also shown that the specific capacity for VFe2Ox can be further increased by compositional substitution with minority amounts of electro-inactive cations such as Al3+ and Zr4+.2 To deconvolve the relative contributions of V- and Fe-based redox and the effects of metal substitution, we turn to X-ray absorption spectroscopy (XAS) as performed with a bench-scale instrument. X-ray absorption near-edge spectroscopy (XANES) provides vital element-specific information on electronic properties and metal oxidation state, while extended absorption fine-structure spectroscopy (EXAFS) produces information on local bonding/coordination, even for amorphous/disordered materials. Using pouch cells designed specifically for the bench-scale spectrometer, we collect in situ spectra on VFe2Ox electrodes as they undergo electrochemical cycling between 2.0 and 3.8 V vs Li/Li+ in conventional nonaqueous electrolyte. We show that the first stages of Li+-insertion are accompanied by Fe3+/2+ redox, with V5+/4+ redox becoming active only at lower cell voltages (<2.5 V). Parallel DFT calculations on a representative spinel-type VFe2Ox structure confirms that V incorporates at tetrahedral sites. The combination of Fe/V tetrahedral occupation and vacancy-induced disorder also lowers the overall energy to open an electronic energy gap that establishes the Fe3+/2+-to-V5+/4+ redox sequence during lithiation, in confirmation of experimental XAS findings. The role of additional metal substitution is also assessed by parallel XAS measurements and DFT computation. 1. C. N. Chervin, J. S. Ko, B. W. Miller, L. Dudek, A. N. Mansour, M. D. Donakowski, T. Brintlinger, P. Gogotsi, S. Chattopadhyay, T. Shibata, J. F. Parker, B. P. Hahn, D. R. Rolison, and J. W. Long, J. Mater. Chem. A 3, 12059 (2015). 2. C. N. Chervin, R.H. DeBlock, J. F. Parker, B. M. Hudak, N. L. Skeele, J. S. Ko, D. R. Rolison, and J. W. Long, RSC Adv. 11, 14495 (2021).

Electrochemical approaches to water desalination show promise for processing brackish water, but continued progress relies on developing scalable electrode architectures with competitive capacity and uptake dynamics for ion capture. Binder-free, device-ready carbon nanofoam papers (CNFPs) are one such candidate, where intermingled nanoscale networks of conductive carbon and pores balance the transport of electrons and ions throughout the electrified interior. Microwave-assisted electroless deposition of conformal nanoscale manganese oxide (MnOx) at the CNFP surface amplifies the ion-capture capacity to technologically relevant levels via faradaic pseudocapacitance. We take advantage of the design flexibility of these electrode architectures to vary CNFP pore size (5 to >100 nm) and thickness (100-300 mu m), and then characterize the resulting MnOx@CNFP electrode series for their respective desalination performance in 20 mM NaCl using automated recirculatingbatch protocols. The combination of CNFP conductivity and facile ion/electrolyte transport through the pore network with the faradaic ion-capture capability of the MnOx coating enables effective desalination. Using 0.3 mm-thick electrodes and MnOx loadings over 16 mg cm(-2), we obtain desalination productivity of 6.8 L m(-2) at 4.4 L m(-2) h(-1) for 90 % salt removal at only 0.13 Wh L-1 energy consumption.

Lithium-rich transition-metal chalcogenides such as Li2FeS2 exhibit reversible charge-storage reactions via anionic sites (e.g., O2–, S2–, or Se2–), supplementing well-established metal cation-sited redox reactions to increase the energy density of lithium-ion batteries by up to 100 percent.1 Despite these promising characteristics, the structure–property relationships that govern cation- and anion-coupled redox reactions in chalcogenides remain poorly understood. To date the synthesis of such compounds has also been limited to high-temperature, solid-state methods that generate difficult-to-process, large-particulate solids. As an alternative, we describe a redox-mediated, wet-chemical strategy to insert Li+ into pyrite FeS2 to ultimately form Li2FeS2. With this method, the pyrite precursor may be formed from a number of methods to achieve greater control over particle size and allows for facile elemental substitution of Fe or S sites prior to chemical lithiation. The electrochemical characteristics (cation/anion redox potential, Li+-insertion capacity, reversibility) of the resulting lithiated iron chalcogenides are correlated with their electronic and structural properties as derived by X-ray absorption spectroscopy, X-ray photoelectron spectroscopy, and Raman scattering. We compare experimental results to density functional theory (DFT) calculations of analogous model compounds. Deconvolving the relationship between electronic band structure and reversible Li+ charge-storage will inform the design of future alkali-rich chalcogenides that exploit simultaneous cation + anionic redox. 1. C.J. Hansen, J.J. Zak, A.J. Martinolich, N.H. Bashian, F. Kaboudvand, A. Van der Ven, B.C. Melot, J.N. Welker, and K.A. See, J. Am. Chem. Soc. 142 (2020) 6737–6749.

Sulfur-based batteries have emerged as a leading contender for next-generation energy storage owing to their high redox capacity and the global availability of elemental sulfur. Yet the electronically insulating nature of sulfur limits the applicability of this battery chemistry. Redox kinetics are enhanced by coating sulfur onto a conductive, porous carbon scaffold1 and atomically mixing with selenium.2 Electrochemical discharge of S/Se blends exhibit additional voltage plateaus compared to a pure S cathode and in-situ optical microscopy identifies a more direct reaction pathway with less active material dissolution.3 Lab scale in-operando X-ray absorption spectroscopy reveals shifts in the Se K-edge correlated with features in electrochemical charge-discharge profiles, providing critical insights on the redox mechanism in nanocomposites of sulfur and selenium. 1. Neale, Z.G.; Lefler, M.J.; Long, J.W.; Rolison, D.R.; Sassin, M.B.; Carter, R.; Freestanding Carbon Nanofoam Papers with Tunable Porosity as Lithium-Sulfur Battery Cathodes. Nanoscale, 2023, 15, 16924-16932. 2. Deblock, R.H.; Lefler, M..J.; Neale, Z.G.; Love, C.T.; Long, J.W.; Carter, R.; Optical and X-ray Absorption Interrogation of Selenium-based Re-dox in Li-SxSey batteries, Energy Advances, 2024, 2024, 3, 424-429. 3. Carter, R.; NewRingeisen, A.; Reed, D.; Atkinson, R.W.; Mukherjee, P.P.; Love, C.T.; Optical Microscopy Reveals the Ambient Sodium Sulfur Discharge Mechanism, ACS Sustainable Chem. Eng. 2021, 9, 1, 92–100.

Lithium-rich iron sulphide, Li2FeS2, exhibits reversible charge-storage via both cationic and anionic sites, storing nearly 400 mA h g-1, but its synthesis is limited to solid-state methods that result in large primary particles. We describe an alternate solution-based, redox-mediated method to lithiate pyrite FeS2, ultimately forming nanoscale Li2FeS2.

Freshwater, a resource critical to social and economic stability, can become temporarily inaccessible after natural disasters such as earthquakes and hurricanes. Transport of water to remote areas during emergencies is expensive and potentially dangerous. Production of fresh water from local brackish and saline resources requires compact, mobile and energy-efficient devices. Reverse-osmosis (RO) uses high-pressure pumps that make down-sizing to mobile scales challenging, while an alternative to RO, capacitive deionization (CDI) based on low-density, low-capacity carbon electrodes, necessitates large footprint devices that are better suited for stationary desalination. Faradaic deionization (FDI) based on the silver–silver chloride conversion reaction provides high-capacity desalination in smaller formfactors. The silver electrode, with a theoretical capacity of 238 mAh/g, is used to remove chloride ions but the low-dimensional architectures of sheet and mesh electrodes limit material utilization. We have developed architected silver and silver chloride sponges that demonstrate high salt removal capacity (80 mg/g, 68 mg/cm2) owing to their high-surface area porous structure. The three-dimensionally interconnected silver network facilitates electronic and ionic transport throughout the bulk of the sponge, enabling scaling to millimeters-thick electrodes. We investigate the design of compact multi-channel flow-cell devices using Ag/AgCl sponges toward practical desalination of brackish and saline waters.

_Rechargeable alkaline Ni–Zn batteries configured with Zn-sponge anodes provide an energy dense, safe alternative to Li-ion batteries for a wide range of risk-averse applications. Advanced cathodes that provide high rate and capacity performance are needed to match that of Zn sponge anodes. We show that aluminum-substituted nickel hydroxide, α-Ni0.9Al0.1(OH)2, expressed in a nanosheet morphology, can be directly deposited onto a flexible carbon nanofiber paper (CNP) using a rapid and scalable two-step microwave-assisted hydrothermal reaction. The architected electrode (α-Ni0.9Al0.1(OH)2@CNP) wires the energy-storing Ni to the carbon scaffold, resulting in high capacity and stable cycling in Ni–Zn cells, performance not obtained using conventional powder-composite cathodes. The growth reaction time and temperature influence mass loading, thickness, crystal structure, the ratio of interlayer “free”-to-lattice metal-coordinated “bound” nitrates, and electrochemical performance. The architected α-Ni0.9Al0.1(OH)2@CNP||Zn sponge alkaline cell provides unprecedented performance, delivering high discharge capacity, storage of >1.4 electrons per Ni, good rate capability, excellent capacity retention, and high mass loading. Architected electrodes that combine 3D electronic wiring and structured active material provide a pathway to energy dense, safe, rechargeable Ni–Zn batteries and offer approaches to improve the electrochemical performance of a broad class of layered materials for multiple battery chemistries.

Historic metallic zinc (Zn) anodes suffer from catastrophic dendritic growth and limited charge-discharge reversibility in alkaline electrolyte. To combat these issues, the Naval Research Laboratory pioneered a 3D-architected zinc “sponge” anode that distributes the electrochemical reaction thus decreasing local current density and suppressing shape change [1]. Fabrication methods to Zn sponges have evolved from lab-scale protocols with specialized materials to those that are scalable, rapid, and cost-effective. The latest generation of zinc sponge fabrication methods employ common pore-forming agents such as sodium chloride and calcium carbonate combined with chemical sintering and a simplified thermal treatment. These methods are adaptable to various form factors, including plates, cylinders, and discs and can be scaled to hundreds of square centimeters. We evaluate these new Zn sponges in electrochemical configurations including zinc–air, nickel–zinc, and silver–zinc to demonstrate their cycle life and specific power capabilities. [1] J. F. Parker, C. N. Chervin, E. S. Nelson, D. R. Rolison, and J.W. Long. Energy Environ. Sci. 7 (2014) 1117–1124.

Recently, we reported on the synthesis and performance of a cross-linked single-anion-conducting solid-state electrolyte (SSE) based on quaternized poly(dimethylaminomethylstyrene) (pDMAMS+) via initiated chemical vapor deposition (iCVD). In the homopolymer pDMAMS+-based SSE, the cross-linking occurs at the positively charged ammonium cation sites, hindering ion transport and conductivity. To improve ionic conductivity, we now report on a copolymer system, comprising DMAMS and divinylbenzene (DVB). Incorporating DVB moves the cross-links to the polymer backbone leaving the quaternary ammonium cation and its paired anion with maximal dynamic freedom. We evaluate the structure-transport relationships of a series of p[DVB-DMAMS] copolymers with varying DVB content using electrochemical impedance spectroscopy, nuclear magnetic resonance spectroscopy, and small- and wide-angle X-ray scattering. Our best composition containing 2.5 wt % DVB provides 1 mS cm-1 single-ion OH- conductivity under hydrated conditions, a significant improvement over the 0.01 mS cm-1 of the hydrated homopolymer pDMAMS+ SSE. All copolymer compositions support Zn-ZnO and Ag-Zn electrochemical reduction-oxidation (redox) chemistry, which demonstrates the feasibility of a Ag-Zn battery using an alkaline single-ion-conducting SSE. Galvanostatic cycling shows some transport of Ag through the polymer electrolyte, however the deleterious effects of Ag migration can be partially mitigated by transitioning from a two-dimensional (2D) planar electrode to a 3D sponge electrode. With these promising results, the foundation is laid for using single-anion-conducting SSEs within alkaline Zn batteries.

In situ X-ray absorption spectroscopy and optical imaging confirm the role of selenium additives for enhancing power performance, increasing utilization, and suppressing undesirable side reactions in Li–sulphur batteries.

Designing electrodes and catalytic platforms as architectures in which the entire volume of the porous “reactor” is wired continuously in three dimensions for electron, ion, and molecular transport expands the reactive electrochemical and catalytic turf beyond the limited footprint imposed by a two-dimensional cross-section or a single three-phase boundary per supported nanoparticle. Amplifying the electron/ion/molecularly wired interfacial area by hundreds of square centimeters per cross-sectional square centimeter converts redox reactions that lose morphological control at high local current density into more uniformly reactive events that experience low local current density. Similar distributed arrangement of the reacting species in architected catalytic platforms imparts resilience of the supported catalyst. Aperiodic architectures such as foams and sponges effectively distribute the available reactive, electron/ion/molecularly wired interfaces while maintaining a co-continuous mapping of void and solid to facilitate ingress/egress of reactants and products. Examples from our work with electrode architectures show the power of controlling energy-storage reactions locally by distributing them within electron-wired high-surface interiors. The arrangement ensures that per area current remains low throughout the volume of the electrode, yet the electrified area sums to provide device-relevant current. The intimate interfacial contact we achieve for copper nanoparticles supported on ceria aerogels yields active, selective, and stable architected catalysts for preferential oxidation of carbon monoxide in hydrogen feedstreams.

A liquid electrolyte based on the addition of a sodium salt in glyme solvent is encapsulated within a polymer-modified mesoporous silica matrix enabling the fabrication of a pseudosolid, sodium-ion electrolyte. This ionogel electrolyte is stable in contact with sodium metal leading to low overpotentials for sodium metal plating/stripping along with high Na+ conductivity and > 4 V electrochemical stability window. Sodium-metal batteries with sodium vanadium fluorophosphate positive electrode achieve over 400 Wh kg(-1) at 0.5C.

Vanadium ferrite (VFe 2 O x ) is a defective spinel system that can incorporate substantial Li+ and exhibits a high charge–discharge rate, particularly when structured as a nanoscale aerogel.1 Cations such as Zr, Zn and Al,2 can readily enter the structure substitutionally and have strong, but differing effects on the charge-storage capacity of the material. These earth abundant, cost- effective constituent elements give this class of materials strong potential as future Li-ion battery cathodes but optimizing the stoichiometry for maximum capacity and stability will require understanding the redox sequence of the host cations (Fe, V) and role of intentional dopants. We use density functional theory calculations in concert with in situ and operando X-ray absorption near-edge spectroscopy (XANES) spectra obtained using an in-lab X-ray absorption spectrometer to uncover the quantum mechanical-level effects that underpin relevant energy- storage behaviors of doped and undoped VFe 2 O x . Our experimental V K-edge and Fe K-edge spectra indicate reduction of both species during discharge but cannot distinguish between tetrahedral and octahedral Fe redox sites or fully resolve the valency of each element as a function of state of charge. Using a hybrid form of density functional theory that accounts for the strong correlation present in 3d elements, we show that both V and Fe are indeed reduced, but that only tetrahedral Fe is redox active until fully converted to Fe 2+ . Furthermore, both octahedral and tetrahedral Fe 3+ are high spin configuration, but the 5μ B moments in the fully filled majority spin channel at each symmetry site are anti-aligned. This arrangement allows for easy exchange of electrons and facilitates conduction. We also calculate XANES spectra based on first principles calculations to be compared directly to those measured in the lab. This cross- check allows us to understand the effect of Al, Zr, and Zn dopants on the redox sequence and relate these results to site preference and capacity. Our combined experimental and calculational investigation sheds light on how these complex materials store Li ions and points toward future alterations that may further improve their properties.

Sodium-ion storage technologies are promising candidates for large-scale grid systems due to the abundance and low cost of sodium. However, compared to well-understood lithium-ion storage mechanisms, sodium-ion storage remains relatively unexplored. Herein, we systematically determine the sodium-ion storage properties of anatase titanium dioxide (TiO 2 (A)). During the initial sodiation process, a thin surface layer (~3 to 5 nm) of crystalline TiO 2 (A) becomes amorphous but still undergoes Ti 4+ /Ti 3+ redox reactions. A model explaining the role of the amorphous layer and the dependence of the specific capacity on the size of TiO 2 (A) nanoparticles is proposed. Amorphous nanoparticles of ~10 nm seem to be optimum in terms of achieving high specific capacity, on the order of 200 mAh g −1 , at high charge/discharge rates. Kinetic studies of TiO 2 (A) nanoparticles indicate that sodium-ion storage is due to a surface-redox mechanism that is not dependent on nanoparticle size in contrast to the lithiation of TiO 2 (A) which is a diffusion-limited intercalation process. The surface-redox properties of TiO 2 (A) result in excellent rate capability, cycling stability and low overpotentials. Moreover, tailoring the surface-redox mechanism enables thick electrodes of TiO 2 (A) to retain high rate properties, and represents a promising direction for high-power sodium-ion storage.

Potable water is an essential supply for humanitarian missions worldwide, yet delivering pre-purified water to remote locations is challenging, dangerous, and expensive. Therefore, it is desirable to develop and deploy on-site and portable desalination/water-purification equipment that draws on local water sources. Present reverse-osmosis systems effectively desalinate seawater, but are energy and time-intensive, require regular maintenance due to membrane fouling, and suffer from poor scalability. Capacitive deionization (CDI) technology provides energy-efficient desalination of brackish waters, but its use remains limited by low-capacity carbon-only electrodes that rely on double-layer ion storage. Transitioning to electrodes that also incorporate Faradaic ion-capturing materials with substantively higher storage capacity expands the efficacy and applicability of CDI. As one example, NRL-developed porous carbon nanofoam (CNF) architectures infiltrated with electrolessly deposited nanometric MnO 2 demonstrate 6-fold increase in sodium-ion adsorption capacity compared to bare-carbon CNFs, while solvothermally deposited BiOCl renders a high-capacity chloride-ion adsorption electrode. The tunability of CNFs as an electrode scaffolding affords the opportunity to balance ion-storage capacity and electrolyte transport for optimized desalination performance. Lessons of electrode architecture extend to NRL silver “sponge” electrodes that provide high capacity for chloride, fast uptake dynamics, and opportunities for various flow configurations. Continued progress in bench-top level flow-cells with high-capacity faradaic materials will demonstrate the promise of this technology en route to development of larger-scale prototype desalination devices.

Electrochemical desalination is presently a popular topic in the scientific literature as a response to global challenges with production of potable water. Many of these reports focus on materials/electrode properties for ion capture yet fail to account for other factors that impact practical device performance. For example, gravimetric ion-storage capacity is commonly reported while areal and volumetric capacities may be more important for desalination cell performance. Furthermore, the dynamic fluid mechanics of flow-cell devices require deliberately engineered electrodes in contrast to their static-electrolyte analogs for energy-storage devices (batteries or supercapacitors). To break from the academic status quo, we have designed a computer-controlled batch-process system to investigate desalination performance of practical electrode materials and architectures. This system allows continuous desalination to high degrees of salt removal on a laboratory scale without the need to use large-footprint electrodes. We demonstrate the characteristics of materials-based vs. system-based desalination metrics using NRL-pioneered electrodes — MnOx-decorated carbon nanofoam paper (MnOx@CNFP)1 — relatives of which are effective for faradaic desalination via Na+ capture.2 Scalable and freestanding CNFP electrodes possess three-dimensionally interconnected pore structures with tunable porosities to facilitate ion transport,3 while the interior surfaces of the CNFP (>200 m2 g–1 in mesopores and macropores) are readily functionalized with nanoscale MnOx by self-limiting electroless deposition.1 We investigate the effect of MnOx@CNFP pore structure and electrode thickness on practical desalination performance, and demonstrate the importance of reporting throughput (L/m2/h) and energy consumption (Wh/L) to better validate new electrode materials and architectures in flow-cell desalination devices. E. Fischer, K. A. Pettigrew, D. R. Rolison, R. M. Stroud, and J. W. Long, Nano Lett., 2007, 7, 281–286. Hand and R. D. Cusick, Environ. Sci. Technol., 2017, 51, 20, 12027–12034. C. Lytle, J. M. Wallace, M. B. Sassin, A. J. Barrow, J. W. Long, J. L. Dysart, C. H Renninger, M. P. Saunders, N. L. Brandell, and D. R. Rolison, Energy Environ. Sci., 2011, 4, 1913–1925.