Knowledge Center
Find our whitepapers, assembly and FAQ videos, as well as literature using our equipment.
Understanding and managing pressure losses in tubing and electrochemical units is essential for ensuring optimal performance and reproducibility in electrochemical flow systems. We are often asked about best practices and design considerations regarding pressure drop. While the final configuration must be tailored to your specific application, this white paper provides guidance and insight to support more informed decision-making.
Flow battery R&D is much driven by optimisation of electrodes and flow cell geometry. In a standard lab type flow battery setup, it is only the electrical current and cell potential that is measured. Although these two parameters alone determine the overall performance, it is from an R&D perspective desired to understand which parts and components that contributes to the overall energy losses. This white paper focuses on the experimental possibilities for mapping these losses out.
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Assembly Tutorial for the X-Cell with 3 Compartments
In this video, we dive deep into the assembly of a 3-Compartment Electrolyser Cell designed specifically for CO2 Electrolysis.
How-to Video on Installing the Swagelok Fittings using Teflon Tape
Step-by-step guide on how to install Swagelok fittings to a flow body for your Redox Flow Battery or CO2 Electrolysis system.
How-to Video on Inserting the Thermometer Holder into your Cell
This video, we will guide you through the essential steps to insert a thermometer holder into a REDOX battery or electrolyser test cell.
Literature
A collection of published research that utilizes our cells/batteries in their experimental setups.
Electrochimica Acta, Volume 470, 1 December 2023, 143306
Leuaa, P., Kraglund, M. R., & Chatzichristodoulou, C. (2023). Decoupling of reaction overpotentials and ionic transport losses within 3D porous electrodes in zero-gap alkaline electrolysis cells. Electrochimica Acta, 470, 143306.
Designing more efficient and productive alkaline electrolysis (AE) cells requires the development of electrode microstructures that facilitate mass transport and reduce associated ionic transport losses within the electrodes. Here we propose a method, relying on a minimum of three reference electrodes, that allows to decouple the Galvani potential losses (GL) associated with ionic migration within each of the electrodes from the overall electrode overpotential. This provides additional insight along with the separation of the voltage losses within the anode, cathode, and separator that is also achieved during zero-gap operation at industrially relevant conditions. Different Nickel electrode structures have been investigated to assess the effect of thickness, surface area, and porosity on the GL within the electrodes. The GL in the anode are higher than in the cathode for the same electrode structure and decrease upon decreasing electrode thickness. Reducing the cathode thickness, while maintaining the same specific surface area, improves performance more compared to the anode. Moreover, electrodes with large pore diameter (0.43 mm) were observed to facilitate the oxygen evolution reaction (OER), whereas electrodes with small pore diameter (0.23 mm) and large surface area are beneficial for the hydrogen evolution reaction (HER). Overall, the proposed methodology provides vital information in guiding the microstructural optimization of electrodes for advanced alkaline electrolysis cells.
Advanced Energy & Sustainability Research, Volume 5, Issue 10, 01 July 2024
Almeida, R. G., De Silva, O., Delolo, F. G., Araujo, M. H., Maniam, S., & da Silva Júnior, E. N. (2024). The Use of the Mannich Reaction toward Amino‐Based Anthraquinone Applied in Aqueous Redox Flow Battery. Advanced Energy and Sustainability Research, 5(10), 2400118.
A water-soluble anthraquinone derived from alizarin, 3HAAQ, is introduced as the redox-active material in a negative potential electrolyte (anolyte) for aqueous redox flow batteries operating at pH 14. The synthesis of 3HAAQ is carried out using the Mannich reaction, which significantly improves the solubility of the new compound, an important factor for its use in RFB. Pairing with potassium ferri/ferrocyanide positive electrolyte, this flow battery exhibits an open-circuit voltage of 1.24 V and maintains nearly 80% of the theoretical capacity at 40 mA cm−2 current density.
Sustainable Energy Fuels, 2019, 3, 2399-2408
Bae, D., Faasse, G. M., Kanellos, G., & Smith, W. A. (2019). Unravelling the practical solar charging performance limits of redox flow batteries based on a single photon device system. Sustainable Energy & Fuels, 3(9), 2399-2408.
In recent years, solar redox flow batteries have attracted attention as a possible integrated technology for simultaneous conversion and storage of solar energy. Unlike solar water splitting technologies which require at least 1.8 V for meaningful performance, a lesson learned from previous studies on solar redox flow batteries (SRFBs) is that even single-photon devices can demonstrate unbiased photo-charging owing to the flexibility of redox couple selection. Thus, in this paper, we present a theoretical model reflecting experimental parameters, such that we can highlight important parameters that merit the most attention in further studies towards the practical development of SRFBs. Importantly, the results clearly show how to choose an optimum combination of semiconductors and redox couples under unavoidable conditions that a practical system would encounter, including, but not limited to, optical loss by the electrolyte, overpotential, device architecture and chemical potentials.
University of Waterloo, 29 April 2024
Lee, K. M. (2024). Structurally Enhanced Electrodes for Redox Flow Batteries Produced via Electrospinning.
The vanadium redox flow battery is one of the most promising secondary batteries for energy storage system due to its design flexibility attributed to the large adjustable capacity of the storage tanks filled with electrolyte solution. However, the vanadium redox flow battery is not yet widely deployed owing to its low power density. This thesis describes the way of constructing the fibrous electrode with novel structure to overcome the flaw. (…)
Membranes 2024, 14(8), 177
Van Cauter, C. J., Li, Y., Van Herck, S., & Vankelecom, I. F. (2024). Stability and performance of commercial membranes in high-temperature organic flow batteries. Membranes, 14(8), 177.
Redox flow batteries (RFB) often operate at extreme pH conditions and may require cooling to prevent high temperatures. The stability of the battery membranes at these extreme pH-values at high temperatures is still largely unknown. In this paper, a systematic screening of the performance and stability of nine commercial membranes at pH 14 and pH ≤ 0 with temperatures up to 80 °C is conducted in an organic aqueous RFB. Swelling, area resistance, diffusion crossover, battery performance and membrane stability after 40–80 °C temperature treatment are shown, after which a recommendation is made for different user scenarios. The Aquivion E98-05 membrane performed best for both the Tiron/2,7-AQDS battery and the DHPS/Fe(CN)6 battery at 40 mA/cm2, with stable results after 1 week of storage at 80 °C. At 80 mA/cm2, E-620-PE performed best in the DHPS/Fe(CN)6 battery, while Sx-050DK performed best in the Tiron/2,7-AQDS battery.
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Santander, D., Whitley, S., Kim, J., & Bae, D. (2023). Analysis of temperature distribution in PV-integrated electrochemical flow cells. Materials Futures, 2(4), 045103.
Photovoltaic (PV)-integrated flow cells for electrochemical energy conversion and storage underwent a huge development. The advantages of this type of integrated flow cell system include the simultaneous storage of solar energy into chemicals that can be readily utilized for generating electricity. However, most studies overlook the practical challenges arising from the inherent heat exposure and consequent overheating of the reactor under the sun. This work aims to predict the temperature profiles across PV-integrated electrochemical flow cells under light exposure conditions by introducing a computational fluid dynamics–based method. Furthermore, we discuss the effects of the flow channel block architecture on the temperature profile to provide insights and guidelines for the effective remedy of overheating.
New Mexico Institute of Mining and Technology ProQuest Dissertations & Theses, 2025
Schiller, V. (2025). Analysis and Optimization of Low-Cost Herbicidal Diquat Dibromide for Grid-Scale Redox Flow Batteries (Master’s thesis, New Mexico Institute of Mining and Technology).
The modern energy landscape is shifting toward renewable sources like solar and wind, whose intermittent output necessitates effective energy storage systems. Redox flow batteries (RFBs) offer scalable solutions compared to lithium-ion batteries, yet improving their performance remains challenging. In this research, diquat dibromide (DQ(Br)2 ), a low-cost herbicide sold at $0.05/g, compared to a previously studied, synthetically modified derivative, dimethyl diquat ($13.78/g), is observed.
International Journal of Hydrogen Energy, Volume 140, 20 June 2025, Pages 803-814
Prits, A. V., Maide, M., Väli, R., Nunes, A. A., Valk, P., Bērziņš, M., … & Nerut, J. (2025). Electrochemical characterisation of Raney nickel electrodes for alkaline water electrolysis: From laboratory to industrial scale. International Journal of Hydrogen Energy, 140, 803-814.
A Raney nickel electrode is characterised in various electrochemical measurement setups for alkaline electrolysis. Experiments are conducted with a typical laboratory-scale three-electrode setup, two different flow-cell setups and a 10-kW electrolysis stack of 17 cells. In addition to the cell geometry (electrode area ranging from 1 cm2 to 960 cm2), the varied measurement conditions include temperature (ranging from room temperature to 80 °C), pressure (from 1 atm to 16 atm), electrolyte concentration (from 0.1 M to 30 %wt KOH), and the level of Fe impurities in the electrolyte. It is demonstrated that with an appropriate setup and measurement conditions, it is possible to predict the performance of electrodes at an industrial scale by conducting laboratory-scale experiments.
Journal of Energy Storage, Volume 60, April 2023, 106503
Clemente, A., Cecilia, A., & Costa-Castelló, R. (2023). Online state of charge estimation for a vanadium redox flow battery with unequal flow rates. Journal of Energy Storage, 60, 106503.
This study presents an observer-based methodology to estimate, in real-time, the state of charge of a Vanadium redox flow battery. Different from the available results in the literature, this work presents a new estimator that distinguishes between the concentration in the tank and cell parts of the system. Moreover, it presents an estimation of the state of charge that can deal with both balanced and unbalanced situations. The model used for the observer design is a nonlinear electrochemical model. A nonlinear observer is proposed, designed and validated through simulation and in an experimental prototype.
Flow4U conference, Eindhoven University on April 9, 2024
Smith, K., Pinto, D. F., Hauser, J., & Faez, S. (2024). Designing an Open-Source Flow Battery Kit: Workshop Presentation Given at Flow4U Conference.
These slides were presented at the Flow4U conference held at Eindhoven University on April 9, 2024. They detail the early efforts of a project to develop an open-source flow battery for research and educational use. An online version of the slides, including videos, is available at this link. The project and documentation are still works in progress and should not be taken as instructions for building a battery or a cell for non-experts.
Membranes 2020, 10(6), 134
Merino-Garcia, I., Kotoka, F., Portugal, C. A., Crespo, J. G., & Velizarov, S. (2020). Characterization of poly (Acrylic) acid-modified heterogenous anion exchange membranes with improved monovalent permselectivity for RED. Membranes, 10(6), 134.
The performance of anion-exchange membranes (AEMs) in Reverse Electrodialysis is hampered by both presence of multivalent ions and fouling phenomena, thus leading to reduced net power density. Therefore, we propose a monolayer surface modification procedure to functionalize Ralex-AEMs with poly(acrylic) acid (PAA) in order to (i) render a monovalent permselectivity, and (ii) minimize organic fouling. Membrane surface modification was carried out by putting heterogeneous AEMs in contact with a PAA-based aqueous solution for 24 h. The resulting modified membranes were firstly characterized by contact angle, water uptake, ion exchange capacity, fixed charge density, and swelling degree measurements, whereas their electrochemical responses were evaluated through cyclic voltammetry. Besides, their membrane electro-resistance was also studied via electrochemical impedance spectroscopy analyses. Finally, membrane permselectivity and fouling behavior in the presence of humic acid were evaluated through mass transport experiments using model NaCl containing solutions. The use of modified PAA-AEMs resulted in a significantly enhanced monovalent permselectivity (sulfate rejection improved by >35%) and membrane hydrophilicity (contact angle decreased by >15%) in comparison with the behavior of unmodified Ralex-AEMs, without compromising the membrane electro-resistance after modification, thus demonstrating the technical feasibility of the proposed membrane modification procedure. This study may therefore provide a feasible way for achieving an improved Reverse Electrodialysis process efficiency.
Journal of Power Sources, Volume 644, 15 July 2025, 237045
Kim, J., Akhtar, T., Liu, Y., Smirnov, V., Kim, H., In, S., & Bae, D. A 25 Cm2 Single Si-Based Solar Redox Flow Battery with Aqueous Iodine-Bromine Redox Couples. Available at SSRN 5117940.
Solar redox flow battery (SRFB) technology offers a compelling strategy for the efficient conversion and storage of solar energy, mitigating the intermittency challenges associated with renewable energy sources. This study presents an experimental investigation into the performance of a 25 cm2 SRFB employing a single-junction silicon photo-device coupled with a neutral pH aqueous iodine-bromine redox couple. The iodine-bromine redox couple was selected through a preliminary screening process, considering its compatibility with the photovoltaic device’s current-voltage performance and desirable electrochemical properties. Experimental results demonstrate the successful integration of a 25 cm2 photoactive-area device with the SRFB system, showcasing efficient solar charging capabilities. The integrated SRFB presented in this study reaches a solar-to-chemical (STC) conversion efficiency of 9.54 %. Subsequent discharge of the stored chemical energy yielded a maximum solar-to-output electricity efficiency (SOEE) of 3.11 %, with an average efficiency of 2.44 % over a continuous 360-hour cycling period. Furthermore, the electrochemical characterisation of the iodine-bromine redox couple confirmed desirable reversibility and stability. These findings underscore the potential of neutral pH aqueous iodine-bromine redox couples for scalable and sustainable solar energy storage applications, providing valuable insights for the further scale-up of SRFB systems.
Solid State Ionics, Volume 410, July 2024, 116544
Thiam, B. G., El Magri, A., & Vaudreuil, S. (2024). Sulfonated 3D printed poly (ether ether ketone) membrane coated with polydopamine for application in vanadium redox flow batteries. Solid State Ionics, 410, 116544.
Ion exchange membranes used in Vanadium Redox Flow Batteries (VRFB) must combine high proton conductivity with low vanadium ion permeability, something of a hurdle since these two types of ions move mainly through the membrane’s hydrophilic regions. A novel approach to address this hurdle is by 3D printing sulfonated poly(ether ether ketone) membranes which are then coated with dopamine. 3D printing makes it possible to manufacture precise and regular structures, while sulfonation ensures the attachment of SO3H groups in well-structured spaces of the membrane, thus promoting the transport of protons. Coating the membrane with polydopamine reduce the permeation of vanadium ions while enhancing chemical stability of the membrane. The 3D-SPEEK/PDA membranes therefore exhibited good properties against Nafion211, Fap450 and conventional SPEEK membranes. Moreover, the optimal application of a PDA coating on the 3D-SPEEK support membrane yielded cell performance (CE: ∼100%) at 100 mA·cm−2 higher than the commercial membranes Nafion211 and Fap450 (CE: ∼ 94% and 98%, respectively), as well as conventional SPEEK (CE: ∼97%). Meanwhile, the single cell assembled with the 3D-printed membrane exhibits a lower self-discharge rate and a more robust cyclic stability, thus demonstrating the great prospects of this 3D-SPEEK/PDA membrane for use in VRFB applications.
Electrochimica Acta, Volume 494, 1 August 2024, 144481
Thiam, B. G., El Ansary, Y., Marbouh, M., El Magri, A., & Vaudreuil, S. (2024). A low-cost design approach to vanadium redox flow test cell. Electrochimica Acta, 494, 144481.
Vanadium redox flow batteries (VRFB) will be essential in maximizing the large-scale use of renewable energy after achieving technical maturity. But as the test cells needed to conduct VRFB research are very expensive, the cost factor can prevent participation of developing countries in critical research. To address such issue, this work presents a novel low-cost design for laboratory VRFB cell yielding good performances. This design relies on sturdy ultra-high molecular weight polyethylene (UHMWPE) end plates with flow channels to provide the strength needed to seal other components while properly distributing electrolyte. This simpler design uses a reduced number of components compared to traditional cells, thus resulting in easier manufacturing and assembly while keeping costs low. This novel design approach achieved performances that are comparable to a commercial VRFB test cell in various testing conditions, but at roughly a third of the cost. Performances have been further improved by 3D printing end plates with optimized flow channels, with the added benefit of avoiding the complexity and costs of computer numerical control (CNC) milling. This novel design approach can thus be useful to many researchers in developing countries for their VRFB test.