Aqueous Flow Research Articles

Miniaturize the Redox Flow Battery for Accelerated Materials Discovery and Development

Abstract Redox flow batteries are a promising technology for grid-scale energy storage. The aqueous organic redox flow battery is of particular interest for its potentially low material cost and sustainability. Developing novel organic active material for flow battery electrolytes typically entails molecular engineering toward desired properties, necessitating organic synthesis. In a research laboratory setting, the synthesis of specifically designed organic molecules featuring targeted functional groups is time and resources intensive. In the past, synthesizing materials required for battery testing has often required gram-scale production, presenting considerable constraints on the pace of novel organic material discovery. In this report, we introduce a miniaturized cell design that mandates only milligram-scale material synthesis while yielding testing outcomes equivalent or superior to those reported with other commercially available or homemade flow cells in the literature. The test results under various pH conditions validate the scale-down strategy to accelerate the flow battery material discovery and development using the newly designed mini cell. This approach offers researchers an efficient means to notably reduce the time and resource required to develop novel materials for flow batteries.

Flow field design and visualization for flow-through type aqueous organic redox flow batteries

Aqueous organic redox flow batteries (AORFBs), which exploit the reversible redox reactions of water-soluble organic electrolytes to store electricity, have emerged as a promising electrochemical energy storage technology. Organic electrolytes possess fast electron-transfer rates that are two or three orders of magnitude faster than those of their inorganic or organometallic counterparts; therefore, their performance at the electrode is limited by mass transport. Direct adoption of conventional cell stacks with flow fields designed for inorganic electrolytes may compromise AORFB performance owing to severe cell polarization. Here, we report the design of a flow field for flow-through type AORFBs based on three-dimensional multiphysics simulation, to realize the uniform distribution of electrolyte flow and flow enhancements within a porous electrode. The electrolyte flow is visualized by operando imaging. Our results show that multistep distributive flow channels at the inlet and point-contact blocks at the outlet are crucial geometrical merits of the flow field, significantly reducing local concentration overpotentials. The prototype pH-neutral TEMPTMA/MV cell at 1.5 M assembled with the optimized flow field exhibits a peak power density of 267.3 mW cm-2. The flow field design enables charging of the cell at current densities up to 300 mA cm-2, which is unachievable with the conventional serpentine flow field, where immediate voltage cutoff of the cell occurs. Our results highlight the importance of AORFB cell stack engineering and provide a method to visualize electrolyte flow, which will be appealing to the field of aqueous flow batteries.

Gradient Distribution of Zincophilic Sites for Stable Aqueous Zinc-Based Flow Batteries with High Capacity.

Current collectors, as reaction sites, play a crucial role ininfluencing various electrochemical performances in emerging cost-effective zinc-based flow batteries (Zn-based FBs). 3D carbon felts (CF) are commonly used but lack effectiveness in improving Zn metal plating/stripping. Here, a current collector with gravity-induced gradient copper nanoparticles (CF-G-Cu NPs) is developed, integrating gradient conductivity and zincophilicity to regulate Zn deposition and suppress side reactions. The CF-G-Cu NPs electrode modulates Zn nucleation and growth via the zincophilic Cu/CuZn5 alloy has been confirmed by density functional theory (DFT) calculations. Finite element simulation demonstrates the gradient internal structure effectively optimizes the local electric/current field distribution to regulate the Zn2+ flux, improving bottom-up plating behavior for Zn metal and mitigating top-surface dendrite growth. As a result, Zn-based asymmetrical FBs with CF-G-Cu NPs electrodes achieve an areal capacity of 30 mAhcm-2 over 640h with Coulombic efficiency of 99.5% at 40mAcm-2. The integrated Zn-Iodide FBs exhibit a competitive long-term lifespan of 2910h (5800 cycles) with low energy efficiency decay of 0.062% per cycle and high cumulative capacity of 112800 mAhcm-2 at a high current density of 100mAcm-2. This gradient distribution strategy offers a simple mode for developing Zn-based FB systems.

Granulometric properties of alkali metal chloride salts in induction heating-based pulsed spray drier: CFD-assisted study and validation

ABSTRACT Spray drying is one of the most widely used unit operation for producing solid directly from liquid solution form in single stage. In conventional co-current or counter-current spray drying arrangements, obtaining alkali metal chloride salts with uniform monosized particles and narrow particle size distribution is challenging because of anisotropic thermal utilisation of gas phase in drying chamber and also because of the hygroscopic nature of these salts. In the present work, the conventional counter-current spray drying arrangement is modified through incorporation of induction heating and mechanical pulsating techniques in the spray drying chamber to enhance the thermal uniformity of gas phase in the drying chamber. Laser diffraction analysis is used for measuring initial droplet size distribution. Meanwhile, a computational fluid dynamics (CFD)-assisted empirical model has been developed to predict particle properties at specified operating parameters of induction heating-based pulsed spray drier (IHPSD). Sensitivity analysis shows that the granulometric properties of all alkali metal chloride salts obtained from IHPSD are most significantly affected by changes in top plate temperature (induction heating temperature), followed by aqueous feed flow rate, then followed by atomiser air flow rate and are least affected by reciprocation rate of pulsating assembly.

A highly water-soluble phenoxazine quaternary ammonium compound catholyte for pH-neutral aqueous organic redox flow batteries

The pH-neutral aqueous redox flow battery (ARFB) is one of the most attractive flow batteries due to its non-corrosiveness, low-cost, and wider electrochemical stability window compared to those with acidic or alkaline electrolytes. However, there are few families of organic redox-active molecules available as catholyte materials for pH-neutral ARFBs. Herein, through incorporation of quaternary ammonium moiety into the redox-active phenoxazine nucleus, an organic catholyte material, N, N, N-trimethyl-2-(10H-phenoxazin-10-yl) ethan-1-aminium chloride (NEt-POZ) is achieved for pH-neutral ARFBs. The NEt-POZ has a high redox potential of 0.79 V versus SHE and rapid redox kinetics (0.23 cm s−1) as well as high water-solubility (∼2.6 M in H2O). Paired with a methyl viologen (MV) anolyte in the pH-neutral aqueous electrolyte, a viologen-phenoxazine ARFB full cell is assembled, which shows an open circuit voltage of ∼1.23 V. However, the results of long-term cycling experiments indicate low Coulomb efficiency and rapid declining capacity of the NEt-POZ catholyte. The mechanism analysis unveils that the unstable doubly oxidized tri-cations (NEt-POZ3+) formed via the disproportionation of radical di-cations (NEt-POZ2+) in solution readily react with chloride anions to form poly-chlorinated derivatives, which precipitate from the catholyte due to their poor water solubility, leading to a rapid decrease in capacity. When there is no chloride present in the electrolyte solution, highly reactive NEt-POZ3+ cations can interact with other counter-anions (such as sulfate and carbonate ions) and even water to form complex adducts.

Meta-substituted thienoviologen with enhanced radical stability via π-π interaction modulation for neutral aqueous organic flow batteries

The aqueous organic redox flow batteries (AORFBs) are recognized as the most promising large-scale storage technology for long-duration energy storage (LDES). Although viologen derivatives are widely used as anolyte materials for AORFBs, their practical application is strongly limited by weak conjugation and unstable radicals. Here, we present a novel thienoviologen derivative, [(NPr)2SV]Cl4, achieved utilizing a meta-substitution approach based on the pristine viologen derivatives ( [(NPr)2V]Cl4). Compared to other ortho- and para-substitution methods, this strategy features a locked plane configuration (0.14°), effectively regulating π-π interactions and suppressing reactivity between radical and oxygen, which is confirmed via X-ray single-crystal structural analyses, spectroscopy techniques, molecular dynamics simulation accompanied by linear ion trap mass spectrometry experiments. Additionally, the meta-substituted [(NPr)2SV]Cl4 significantly improves water solubility (2.39 M), enhances aromaticity, and extends radical lifetime compared with para-substituted [(NPr)2TV]Cl4. Consequently, the cycling stability of the [(NPr)2SV]Cl4-based AORFB over 2500 cycles is 4.1 times higher than that of [(NPr)2TV]Cl4. Furthermore, the 0.5 M battery delivers an impressive 99.83% capacity retention during 200 cycles and a power density of 147 mW cm-2.

Screening of Cation Exchange Membranes for an Anthraquinone‐Ferrocyanide Flow Battery

AbstractThe disodium salt of 9,10‐anthraquinone‐2,7‐disulphonic acid (2,7‐AQDS) is an interesting platform for developing anthraquinone derivative negolytes for aqueous organic flow batteries. Recently, ammonium sulphate supporting electrolytes have been considered for improved stability and solubility. This work advances the 2,7‐AQDS/ferrocyanide flow battery with an ammonium sulphate supporting electrolyte (pH 5) by studying the suitability of six commercially available cation exchange membranes: E‐620, NR‐212, FS‐930, F‐1075‐PK, F‐1850 and N‐115. Cell cycling under galvanostatic regime plus potential hold was performed to determine coulombic efficiency, energy efficiency and accessible capacity for each membrane as well as capacity fade rate for three selected membranes under extended operation. Cell cycling under galvanostatic control only was carried out to observe transient membrane behavior alongside accessible capacity and apparent capacity fade rate. It was found that the capacity set by the limiting negolyte is consistent with 1.5 electrons per 2,7‐AQDS molecule and that energy efficiency shows a simple direct relationship to membrane thickness, with one exception. Meanwhile, four membranes displayed similar apparent capacity fade rates at this laboratory scale irrespective of their thickness, with capacity loss explained in terms of crossover. The best overall performance was attained by the thinnest membranes, E‐620 and NR‐212.

Nanocellulose-based ion-selective membranes for an aqueous organic redox flow battery

Nanocellulose-based ion-selective membranes for an aqueous organic redox flow battery

Soft-hard zwitterionic additives for aqueous halide flow batteries.

Aqueous redox flow batteries with halide-based catholytes (where the halogen atom (X) is Br or I) are promising for sustainable grid energy storage. However, the formation of polyhalides during electrochemical charging and the associated phase separation into X2 limits the operable state of charge (SoC), results in vaporization and self-discharge inefficiencies, and spurs complete device failure1-3. Here we introduce soft-hard zwitterionic trappers (SH-ZITs) as complexing agents composed of a polyhalide-complexing 'soft' cationic motif and a water-soluble 'hard' anionic motif to enable homogeneous halide cycling. More than 300 structures were designed and 13 were characterized, showcasing the ability to complex polyhalides in homogeneous aqueous solution, to deter cation-exchange membrane crossover and to alter the electrochemical electrode mechanism. In flow battery cycling at a standard catholyte SoC of 66.6 per cent (stoichiometrically X3-), an average coulombic efficiency of more than 99.9 per cent at 40 milliamperes per square centimetre with no apparent decay was observed after more than 1,000 cycles over 2 months, with stability at elevated temperatures also demonstrated. Interestingly, SH-ZITs enable homogeneous cycling of the halide catholyte up to 90 per cent SoC at 2 moles per litre (47.7 ampere-hours per litre) for bromide, revealing previously unknown polyhalide regimes to be studied. Ultimately, SH-ZIT enables ultrahigh catholyte capacity utilization up to over 120 ampere-hours per litre at 80 per cent SoC with homogeneous cycling as well as the ability to pair with a zinc anode in a hybrid flow battery.

In Situ Molecular Reconfiguration of Pyrene Redox-Active Molecules for High-Performance Aqueous Organic Flow Batteries.

Aqueous organic flow batteries (AOFBs) hold great potential for large-scale energy storage, however, scalable, green, and economical synthetic methods for stable organic redox-active molecules (ORAMs) are still required for their practical applications. Herein, pyrene-based ORAMs are obtained via an in situ organic electrolysis strategy in a flow cell. It is revealed that the water attacking pyrenes restructured molecules to produce a variety of isomers and dimers during the electrolysis, which can be modulated by regulating the local electron cloud density and steric hindrance of pyrene precursors. As a result, the molecularly reconfigured pyrene-based catholytes, even without any further purification, achieved a high electrolyte utilization of ≈96% and volumetric capacity above 50AhL-1. Inspiringly, remarkable cell stability with almost no capacity decay for ≈70 days is achieved, benefiting from the robust aromatic structure of the pyrene cores. The insights into the in situ electrosynthesis of pyrene-based ORAMs provided in the work will provide guidance for designing ultra-stable ORAMs for AOFB applications.

A Mini-Review on Gene Therapy in Glaucoma and Future Directions

Glaucoma is a group of optic neuropathies characterized by the degeneration of retinal ganglion cells and the loss of their axons in the optic nerve. The only approved therapies for the treatment of glaucoma are topical medications and surgical procedures aimed at lowering intraocular pressure. Gene therapy involves the insertion, removal, or modification of genetic material within cells to repair or compensate for the loss of a gene’s function. It describes a process or technology that enables the genetic modification of cells to produce a therapeutic effect. However, changing the genetic material alone does not extend the duration of overexpression of proteins that combat disease, nor does it facilitate the production of new proteins for this purpose. We reviewed the literature concerning the use of gene therapy in the treatment of glaucoma and explored the future directions that this innovation may offer. Three genes associated with glaucoma have been identified within these loci: myocilin/trabecular meshwork glucocorticoid response (TIGR) (GLC1A), optineurin (GLC1E), and WDR36 (GLC1G). Among these, the most extensively studied glaucoma gene is myocilin (a TM-inducible glucocorticoid response gene). Building on previous successes, researchers have begun to apply genetic therapeutic approaches to alleviate or reduce symptoms associated with ocular hypertension (OHT) and glaucoma-like optic neuropathy (GON). It is evident that several therapeutic strategies exist that modulate aqueous humor production and flow, thereby regulating intraocular pressure (IOP) and protecting retinal ganglion cells (RGCs) from apoptosis. With the emergence of gene therapy as a potentially viable approach to preserving vision, new methods for managing glaucoma may soon become available. Genomic therapy is a promising treatment option for glaucoma patients and has significant potential for widespread clinical application.

A Multielectron and High-Potential Spirobifluorene-Based Posolyte for Aqueous Redox Flow Batteries.

The rising energy demand driven by human activity has posed pressing challenges in embracing renewable energy, necessitating advances in energy storage technologies to maximize their utilization efficiency. Recent studies in aqueous organic redox flow batteries have focused primarily on the development of organic negative electrolytes, while the progress in organic positive electrolytes remains constrained by limitations in their redox potentials and effective electron concentrations. Herein, we report a spatially twisted chlorinated spirobifluorene ammonium salts (CSFAs), created through an unexpected green chlorination-protection pathway during the initial cycling in the flow battery cell, utilizing chloride ions from counterions in aqueous solution. The chlorinated, nonplanar spiral structure of CSFAs possesses a one-step four-electron transfer electrochemical property and offers exceptional resistance to nucleophilic attacks, exhibiting an unprecedented redox potential as high as 1.05 V (vs. SHE). A full redox flow battery based on CSFA-Cl (chloride ions as the counter ions) with 1.4 M electron concentration achieved an average coulombic efficiency exceeding 99.4 % and a capacity utilization reaching 95 % of the four-electron capacity for a stable cycling over 250 cycles (~22 days). The present work exemplifies the use of side reactions to develop new redox species, which can be extended to create more structurally versatile energy storage materials.

Ferroelectric frontiers: Navigating phase portraits, chaos, multistability and sensitivity in thin-film dynamics

This research includes the study of the non-linear dynamics of thin-film ferroelectric materials governed by an equation of wave dynamics within the material. This equation plays a key role in both physics and the study of aqueous flow. The work is planned as examining the symmetries group analysis drops, studying the dynamical system features through bifurcation phase portraits, and carrying dynamic phenomena in chaos theory. Diverse techniques are taken, such as Lyapunov exponent, 2D, and 3D phase portraits, Poincaré maps, time series analysis, and sensitivity to multistability under the different conditions of the initial state. In addition, the study involves using the extended hyperbolic function method to obtain the general analytical solutions via which various kinds of solitary wave solutions are produced including trigonometric and hyperbolic functions and periodic, bright, and singular soliton solutions. These solutions are followed by a list of constraint conditions in the form of equations. Visual data of 2D, 3D, and contour plots are presented, with parameters carefully set to reflect various scenarios. Sensitivity analysis is performed using alternative initial conditions, and stability analysis is demonstrated graphically. To fully grasp the dynamic features of these systems and accurately predict outcomes, it is essential to advance new technologies and methodologies that can further enhance our understanding and predictive capabilities in complex systems.

Bismuth nanosheets guided zinc deposition enabled long-life aqueous zinc-based flow batteries

The poor cycling durability and low Coulombic efficiency (CE) of zinc (Zn) anodes substantially restrict their further development, which should be attributed to the severe uneven plating and hydrogen evolution reaction (HER) across the repeated plating/stripping processes. Herein, bismuth nanosheets decorated graphite felt (BiNS/GF) is constructed for Zn anode via galvanic replacement reaction. BiNS/GF affords more robust Zn nucleation sites, lower Zn nucleation overpotential and higher HER overpotential to guide even and dense Zn deposition. In addition, a total internal reflection imaging method is employed to detect micro-bubbles generated by HER on the electrode surface, revealing that BiNS prevents the formation of micro-bubbles and thus avoids dead Zn caused by unstable Zn deposition. As a proof of concept, BiNS/GF exhibits an average CE of 99.2 % in 300 cycles and a peak power density of 295.2 mW cm−2 at a current density of 380 mA cm−2 in aqueous neutral zinc-iron flow batteries. Therefore, it is reasonably anticipated that the BiNS/GF may emerge as suitable electrode for other aqueous zinc-based flow batteries.

Chelation approach to long-lived and reversible chromium anolytes for aqueous flow batteries

Iron chromium flow battery (ICFB) has the advances of low cost, safety, and independent design of power and capacity, but is restricted by the deactivation of chromium anolytes. Here, a complex of diethylenetriaminepentaacetic acid with chromium ion (CrDTPA) is designed with minimum capacity loss rate and best cycling stability. DTPA is an octadentate ligand and chelates with chromium ions in a seven-coordinated manner. The coordination structure was studied by Nuclear Magnetic Resonance, Fourier transform infrared and UV–vis absorption spectra, and identified as a robust structure. CrDTPA has good electrochemical activity and reversibility with a redox potential of −1.145 V versus saturated calomel electrode. A novel iron chromium flow battery (NICFB) is designed by coupling CrDTPA anolytes and Fe(CN)6 catholytes. NICFB displays high energy conversion efficiency with coulombic efficiency of 99.0 % and energy efficiency of 82.2 % at 40 mA cm−2. Importantly, NICFB shows superior cycling stability without performance decay for 160 cycles, ranking the best among recently reported ICFBs. This chelation approach provides a simple and practical method to solve chromium anolytes deactivation and improve cycling stability.

Enrichment of secoiridoid glycosides from Gentiana rigescens extracts in amino acid-based deep eutectic solvents via macroporous resin adsorption

The simultaneous enrichment of the secoiridoid glycosides gentiopicroside, loganic acid, swertiamaroside, and sweroside from amino acid-based deep eutectic solvent (AADES) extracts of Gentiana rigescens roots and rhizomes was developed. To screen suitable resins, the performance and characterization of 11 widely used macroporous resins for the adsorption and desorption of target secoiridoid glycosides were considered. Compared with the other resins, the H103 resin was found to have greater adsorption and desorption capacities for gentiopicroside, loganic acid, swertiamaroside, and sweroside. Therefore, this resin was chosen as the best resin for secoiridoid glycosides enrichment. In a column packed with H103 resin, the dynamic adsorption and desorption factors for the target secoiridoid glycosides were investigated and optimized. After dynamic testing on the H103 packed column, the optimal operating conditions were determined as follows: a sample volume of 12 bed volumes (BVs) and a loading flow rate of 2 BV/h were used, the volume of deionized water used for the aqueous washing process was 8 BV, and the aqueous washing flow rate was 3 BV/h. Ethanol with a volume fraction of 10–90 % was used as the eluent in the ethanol desorption process with a gradient of 10 %. Each ethanol volume fraction was used for 2 BV, with a flow rate of 3 BV/h. The eluent fractions containing 40–80 % ethanol were collected, combined, and concentrated, followed by vacuum drying to obtain the final product. The purities of gentiopicroside, loganic acid, swertiamaroside, and sweroside in the final product were 58.11, 13.73, 3.86, and 2.77 %, respectively, with corresponding recovery rates of 74.09, 72.19, 77.50, and 76.45 %, respectively. Additionally, the reuse of AADES proved to be effective.

Pd2+-coordinated polybenzimidazole membranes with fast and selective ion transport for alkaline aqueous organic redox flow battery

The advancement of aqueous organic redox-flow batteries (AORFBs) is impeded by the lack of efficient, low-resistance, and highly selective ion-conducting membranes (ICMs). Although polybenzimidazole (PBI) is one of the most promising low-cost non-fluorinated ion-conducting membranes, it remains challenging to design stable PBI membranes with fast and selective ion transport channels. Here, we engineer the chemical structure of PBI and regulate the ion transport channels to prepare highly conductive and selective Pd2+-coordinated membranes with grafting and crosslinking structures. In this design, the positively charged quaternary ammonium groups on the side chain improve the conductivity of OH−, while the continuous cross-linked network formed by ionic bonds between quaternary ammonium groups and deprotonated imidazole groups significantly enhances the membrane's mechanical properties. Furthermore, the coordination of Pd2+ with PBI and plasticization of PBI chain by trifluoroacetate anions expand the molecular free volume while inducing local contraction. Consequently, the QPBI-xPBI-Pd membrane enables fast charge carrier transport and suppresses the diffusion of active substances. The AORFBs assembled with the QPBI-10PBI-Pd membranes exhibit high coulombic efficiency (99.6 %) and energy efficiency (77.67 %) at 100 mA cm−2, maintaining excellent stability for 500 cycles. This study provides an innovative strategy to design high-performance PBI membranes for RFBs, thereby advancing the viability of RFBs in the realm of large-scale energy storage technologies.

Can We Simplify Liposome Manufacturing Using a Complex DoE Approach?

Microfluidic liposome production presents a streamlined pathway for expediting the translation of liposomal formulations from the laboratory setting to clinical applications. Using this production method, resultant liposome characteristics can be tuned through the control of both the formulation parameters (including the lipids and solvents used) and production parameters (including the production speed and mixing ratio). Therefore, the aim of this study was to investigate the relationship between not only total flow rate (TFR), the fraction of the aqueous flow rate over the organic flow rate (flow rate ratio (FRR)), and the lipid concentration, but also the solvent selection, aqueous buffer, and production temperature. To achieve this, we used temperature, applying a design of experiment (DoE) combined with machine learning. This study demonstrated that liposome size and polydispersity were influenced by manipulation of not only the total flow rate and flow rate ratio but also through the lipids, lipid concentration, and solvent selection, such that liposome attributes can be in-process controlled, and all factors should be considered within a manufacturing process as impacting on liposome critical quality attributes.

Air-stable naphthalene derivative-based electrolytes for sustainable aqueous flow batteries

Air-stable naphthalene derivative-based electrolytes for sustainable aqueous flow batteries

Aqueous colloid flow batteries with nano Prussian blue

Flow battery is a safe and scalable energy storage technology in effectively utilizing clean power and mitigating carbon emissions from fossil fuel consumption. In the present work, we demonstrate an aqueous colloid flow battery (ACFB) with well-dispersed colloids based on nano-sized Prussian blue (PB) cubes, aiming at expanding the chosen area of various nano redox materials and lowering the cost of chemicals. Taking advantage of the two redox pairs of PB, the developed all-PB cell employing a low-cost dialysis membrane with the synthesized PB on both sides displays an open-circuit voltage (OCV) of 0.74 V. Moreover, when paired with an organic tetra pyridine macrocycle the cell with PB as positive electrolyte exhibits an OCV of 1.33 V and a capacity fade rate of 0.039 %/cycle (0.8 %/day). Redox-active colloids exhibit enduring physicochemical stability, with no evident structural or morphological changes after extensive cycling, highlighting their potential for cost-effective and reliable ACFB energy storage.