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Ammonia electrosynthesis in a palladium membrane flow cell

Fertilizer granules

Ammonia (NH₃) is a crucial raw material for fertilizer production and a potential renewable, carbon-free energy storage solution. It is produced in the Haber-Bosch process using natural gas (CH4). During this process, natural gas is converted into hydrogen (H₂) and CO₂ by steam reforming. The Haber-Bosch process accounts for approximately 1-3% of global CO₂ emissions. This method requires stable energy supply and CAPEX intensive facilities, leading to highly centralized ammonia production. In contrast, alternative electrochemical pathways for ammonia production represent sustainable and decentralized solutions.

Electrochemical ammonia production is not a new process and is based on hydrogen electrolysis. In a subsequent step, hydrogen is used for catalytic nitrogen reduction. Experimentally, lithium and calcium have been used as electrocatalysts. Ammonia has been produced in continuous flow cells with efficiencies of up to 76%, as well as in other electrochemical cells. However, stable ammonia production in flow cells requires dry and purified hydrogen.

The primary issue with moist hydrogen is the excessive formation of lithium hydroxide (LiOH):

2 Li + 2 H₂O → 2 LiOH + H₂

However, water electrolysis could be completely eliminated if the protons (H+) generated from water oxidation were directly supplied to the lithium-coated cathode. This would further simplify systems and lower investment costs.

Researchers at Imperial College London followed exactly that approach. They coupled continuous water oxidation directly to lithium-mediated nitrogen reduction under non-aqueous conditions in a two-chamber flow cell. They recently published their results in the journal ACS Energy Letters.

The coupling was achieved through an electrically isolated, hydrogen-permeable palladium membrane between the chambers. On the anodic side (aqueous), water was oxidized at an iridium oxide-coated titanium anode to produce protons, meaning adsorbed H. This form of hydrogen permeated the palladium membrane. It then entered the dry, non-aqueous cathodic chamber, where N₂ was reduced on lithium.

Schematic palladium membrane ammonia synthesis

The palladium membrane was not integrated into the external circuit during nitrogen reduction. It simultaneously served as both a proton source and sink, made possible by its electrical conductivity and hydrogen permeability.

The scientists first validated proton transport through the palladium membrane while preventing water crossover through symmetric cell tests and ¹H-NMR isotopic exchange using water (H₂O) and deuterium oxide (D₂O, heavy water).

Real-time mass spectrometry of D₂O at the anode confirmed that deuterons supplied through the palladium membrane were incorporated into ammonia (ND₂H). This demonstrates that the protons in NH₃ originated from water oxidation and not solely from the ethanol used as well. It was evidence for linear charge transfer while maintaining negligible water transport.

As a control, an experiment was conducted using a Nafion™ membrane to demonstrate that membranes allowing water crossover prevented lithium-mediated ammonia synthesis. Nafion™ permits proton transfer while being permeable to water.

The researchers showed that the electrical conductivity of the palladium membrane enabled it to operate simultaneously as both an anode and a cathode. This allowed for continuous conversion of nitrogen and water into ammonia without producing molecular hydrogen as an intermediate. The Nafion™ control proved that the transport of protons while preventing water crossover allowed for lithium-mediated ammonia synthesis.

The necessity for pre-hydration of the membrane and the gradual increase in membrane potential during pulsed operation indicated that the kinetics of hydrogen transfer and membrane stability were key factors for performance. This was because the system was optimized for the neutral aqueous electrolyte with isotopic labeling. The researchers proposed ways to improve efficiency in their article, including the exploration of alternative hydrogen-permeable metals and alloys.

The presented membrane could find applications beyond ammonia synthesis, in other electrochemical transformations where anhydrous conditions and controlled proton release are required. These include CO₂ reduction and non-aqueous redox flow batteries.

For further research, the authors suggested:

  • Increase proton flow and reduce membrane transition resistance,
  • Test alternative hydrogen-permeable metals or alloys to reduce costs, and
  • Conduct pulse and idle protocols to monitor lithium loss.

At Frontis Energy, we are eager to see how individual monolithic palladium membranes will enter in the market. Continuous ammonia electrosynthesis represents a conceptual advancement towards simpler, more robust green fertilizer production and energy storage.

Ye et al. 2026, Continuous ammonia electrosynthesis from nitrogen and water in a monolithic Pd membrane-based flow cell, ACS Energy Letters, DOI: 10.1021/acsenergylett.5c03617

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Polyelectrolyte coatings for ion-exchange membranes in electrodialysis

Reverse electrodialysis water purification

Ion exchange membranes are key components for various electrochemical technologies in water treatment and energy storage, such as electrodialysis, membrane electrolysis, and flow batteries. These membranes are characterized by a high concentration of charged groups, which can be either cationic (positively charged) or anionic (negatively charged). The function of an ion exchange membrane is to facilitate the transport of counterions while limiting the loss of water and co-ions.

The efficiency of cation exchange membranes is affected by unwanted co-ion and water transport. The transport of hydroxide ions (OH−) through cation exchange membranes is of particular interest. Depending on the application, cation exchange membranes are designed either to selectively facilitate hydroxide transport or to minimize hydroxide loss. Therefore, improved ion exchange membranes must support such additional functionalities.

Researchers at Wageningen University have characterized ion exchange and water transport through both coated and uncoated cation exchange membranes. The scientists published their findings in the Journal of Membrane Science. In their study, they examined cation exchange membrane coating with polyelectrolytes made of polyallylamine and polystyrene sulfonic acid.

The researchers coated one side of commercial cation exchange membranes with double layers of these two polymers. They then studied ion and water transport in diffusion dialysis and electrodialysis. Diffusion dialysis involves passive ion transport driven by concentration gradients, while in electrodialysis, ion transport occurs actively and is powered by an applied current.

The coatings were evaluated for their selectivity for monovalent and divalent ions. This selectivity affects hydroxide transport and water permeability. Both are key factors for the efficiency of bipolar membrane electrodialysis, where solutions containing multivalent cations such as magnesium and calcium are treated.

Magnesium and calcium transport was significantly limited by the coatings, while sodium ion transport remained largely unaffected. This selectivity was attributed to the Donnan exclusion mechanism and differences in hydration shells, as multivalent ions have a higher resistance within the cation exchange membrane.

Orientation is crucial in this context. Coating alignment affected performance. Resistance increased in the direction of multivalent ion flow, which reduced the flow of magnesium ions. This finding is impotant for the design of devices for bipolar membrane electrodialysis.

Surprisingly, the coatings did not reduce water crossover. Denser layers remained the bottleneck. The hydroxide flow was somewhat higher in coated membranes exposed to extreme pH values. This was likely due to structural changes during the coating process.

The combination of a low-water-content cation exchange membrane with a coating could enable the direct use of untreated salt solutions in bipolar membrane electrodialysis. This would reduce pretreatment costs and improve sustainability. The Fuji CEM-12 proved to be a promising candidate for future designs with coatings.

Salt diffusion through uncoated cation exchange membranes was mainly determined by the type of anion, such as chloride, sulfate, or hydroxide. In addition, membrane properties, including water content and ionic charge density, had a significant influence. The ionic charge density determined the anion distribution within the cation exchange membranes.

In summary, the researchers coated various commercial cation exchange membranes multiple times on one side with polyelectrolytes. For uncoated cation exchange membranes, water permeability correlated well with  ionic membrane resistance. This correlation was due to both parameters being dependent on the water content of the membrane. Moreover, permeability for co-ions increased with a higher volume fraction of water in the membranes.

Osmotic water transport in cation exchange membranes was not affected by the multiple layers of polyallylamine and polystyrene sulfonic acid. The researchers recommended single layer coating of low-water-content cation exchange membranes to minimize the transport of hydroxides and problematic multivalent cations.

This work demonstrates that surface modification using polyelectrolyte layers can enhance the functionality of conventional membranes without significant trade-offs. Water transport remained a challenge but the ability to block multivalent ions while maintaining conductivity for sodium ions represented a major step toward more efficient and cost-effective dialysis systems.

At Frontis Energy, we are excited about the future application of multilayered membranes on an industrial scale.

Elozeiri et al. 2026, Water and co-ion transport across ion-exchange membranes coated with PAH/PSS polyelectrolyte multilayer in electrodialysis and diffusion dialysis, Journal of Membrane Science,741, 125072, DOI: 10.1016/j.memsci.2025.125072

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Transforming water systems with scalable membrane solutions

Fresh water from a faucet

In a world increasingly defined by the need for cleaner processes, sustainable production, and advanced materials, membrane technology has emerged as a key enabler across multiple industries from water purification and energy generation to chemical separation and bioprocessing. Its high selectivity, compact footprint, and low energy requirements make it indispensable in meeting both environmental and performance demands.

At the heart of membrane fabrication lies a well-established method known as non-solvent-induced phase separation. This technique involves casting a polymer solution into a thin layer and exposing it to a non-solvent, typically through immersion or vapor contact, which triggers phase separation, forming a porous matrix with fine-tuned filtration properties. Due to its simplicity and scalability, this method has become a mainstay in industrial membrane production, offering reliable performance across many applications.­

However, as industries demand more specialized and high-efficiency membranes, researchers are continuously pushing the boundaries of conventional fabrication techniques. One of the most promising advancements is the spray-modified non-solvent-induced phase separation method, which swaps immersion for targeted non-solvent spraying. This subtle yet powerful modification enables patterned surface architectures, improved permeability, and reduced fouling, all while maintaining the advantages of scalable continuous production. Such innovation is instrumental in tailoring membranes to meet the complex needs of modern filtration systems.

Building on this progress, a recent study conducted by the Catholic University Leuven in Belgium successfully adapted the spray-modified non-solvent-induced phase separation technique to a roll-to-roll, 12-inch pilot-scale platform. This represents a meaningful advancement from laboratory concept to industrial feasibility. The findings were recently published in the Membranes. Through strategic variations in polymer concentration, molecular weight, and the inclusion of hydrophilic additives such as polyethylene glycol and polyvinylpyrrolidone, researchers fabricated defect-free, uniformly patterned polysulfone ultrafiltration membranes with remarkable performance gains. Notably, these membranes delivered up to 350% higher water flux compared to traditional flat membranes, attributed to their deep surface patterns—reaching 825 µm—and a porous, finger-like internal structure that enhances throughput without sacrificing rejection efficiency.

Among the additives tested, polyethylene glycol emerged as the standout, yielding membranes with high pure water permeance (over 1000 Liters/m²/hour/bar) and consistent protein rejection levels (around 90%). These membranes also demonstrated excellent structural fidelity and homogeneity, which are critical for ensuring long-term durability and process reliability. The study further identified operational parameters, such as optimal casting speed, non-solvent spray rate, and solution viscosity control, as essential contributors to reproducible membrane quality and process scalability.

This leap from bench to pilot scale carries profound industrial implications. The ability to continuously produce high-flux, anti-fouling membranes with precise structural characteristics offers industries a robust and scalable filtration solution. Applications span from municipal and industrial wastewater treatment to biopharmaceutical production and food processing—sectors where membrane performance can directly influence both environmental outcomes and operational costs.

In essence, the optimized spray-modified non-solvent-induced phase separation approach does more than enhance membrane metrics; it embodies the transition from research novelty to commercial readiness. By bridging the gap between design and deployment, this work lays a foundational blueprint for mass-producing advanced membranes that are not only efficient, but also economically and environmentally viable. It is a compelling example of how thoughtful engineering and process innovation can move technologies from promising prototypes to real-world solutions, thus shaping the future of filtration in a world that urgently needs it.

Frontis Energy envisions a world transformed by sustainable membrane innovations, where clean water, resource efficiency, and resilient infrastructure are accessible to all.

Ilyas, et al., 2025, Pilot-scale polysulfone ultrafiltrationpPatterned membranes: phase-inversion parametric optimization on a roll-to-roll casting system, Membranes 15, 8, 228, DOI: 10.3390/membranes15080228

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Sulfonated clay and carbon nanotubes Nafion™-based proton exchange membranes

Toyota fuel cell concept car

The demand for sustainable energy has accelerated the development of electrochemical systems for energy conversion. This includes, in particular, proton exchange membrane fuel cells (PEMFCs). PEMFCs offer numerous advantages, including high energy density, low operating temperatures, fast start-up times, and compact design. These characteristics make them especially suitable for mobile and decentralized energy applications. The development of high-performance proton exchange membranes is crucial for the advancement of fuel cell technology, particularly under demanding operating conditions.

The central component, the proton exchange membrane, is characterized by high proton conductivity, excellent chemical and physical stability, low gas permeability, and adequate water uptake under a variety of conditions. Nafion™, a perfluorosulfonic acid (PFSA) ionomer, is considered the gold standard for proton exchange membranes due to its outstanding proton conductivity and chemical resistance.

However, its performance degrades significantly at elevated temperatures (>80 °C) and low relative humidity due to excessive water loss. These limitations restrict its applicability in next-generation high-temperature fuel cells. To overcome these limitations, extensive efforts have been made to develop PFSA-based composite membranes. For this purpose, inorganic or organic fillers such as silica, metal oxides, and carbon-based nanomaterials have been used. These additives aim to improve water retention, mechanical strength, and thermal stability.

Italian researchers from the University of Calabria have developed Nafion™ membranes reinforced with sulfonated clay and carbon nanotubes to address issues with water retention and proton transport. They recently published their results in the journal Materials for Renewable and Sustainable Energy. The hybrid fillers created a synergistic effect. The clay improved the hydrophilic properties, while carbon nanotubes enhanced the structural integrity and conductivity.

In tests with hydrogen fuel cells at 120 °C and 20% relative humidity—conditions that typically severely impair normal PFSA membranes—the new composition achieved a peak power of 443 mW/cm². This was four times that of Nafion™ membranes. This breakthrough suggested that integrating nanofillers could yield further improvements in durability and efficiency of proton exchange membranes. At the same time, the experiments paved the way for robust fuel cells in the automotive and stationary energy sectors, where such performance improvements are particularly needed.

The incorporation of sulfonated clay and carbon nanotubes not only improved the ion exchange capacity and hydrolytic stability but also critically modulated the water dynamics. The result was superior water retention and sustained proton diffusion, particularly at elevated temperatures. The significantly higher proton conductivity under low humidity conditions was a crucial factor for the operation of high-temperature fuel cells in the study presented.

This study successfully demonstrated the significant potential of sulfonated clay and carbon nanotubes to enhance the performance and durability of Nafion-based proton exchange membranes for fuel cell applications. The incorporation of the additives also increased the structural integrity of the membrane. Dynamic mechanical analysis showed a significant reinforcement effect from the inclusion of the additives, with a consistent increase in storage modulus and a shift of the glass transition temperature to higher temperatures. For the improved membrane, the glass transition temperature increased from 120 °C for conventional Nafion to approximately 150 °C.

Moreover, the nanocomposite membrane exhibited a remarkable conductivity of 42.3 mS/cm at low humidity. This represented a significant improvement compared to pure Nafion™.

In summary, the nanohybrid membrane consistently overcame significant limitations of conventional PFSA membranes, particularly their susceptibility to drying out and mechanical degradation under demanding operating conditions.

At Frontis Energy, we are convinced that the synergistic interplay of enhanced proton transport pathways, improved water retention, and superior thermomechanical stability makes this composite membrane a promising candidate for robust and efficient next-generation fuel cells.

Nicotera, et al. 2025 Enhanced electrochemical performance and thermomechanical stability of nafion/sulfonated clay-carbon nanotube nanocomposite membranes for high-performance fuel cells under challenging conditions. Materials for Renewable and Sustainable Energy 14, 48, DOI: 10.1007/s40243-025-00325-7.

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Advancing wastewater sustainability: Nafion-powered ammonium recovery

Wastewater treatment plant Bern

DOI: 10.13140/RG.2.2.25254.59202

With global population growth and the resulting increase in environmental stress, the need for sustainable wastewater treatment is becoming ever more urgent. Traditional methods focus on removing pollutants but often overlook the opportunity to recover valuable resources. One such resource is ammonium. This nitrogen-containing molecule promotes growth and is a key component of fertilizers. When mishandled, such as through over-fertilization, ammonium becomes one of the main contributors to nitrogen pollution.

A promising solution lies in bioelectrical systems. This umbrella term refers to innovative technologies that not only purify wastewater but also recover resources like ammonium. At the same time, bioelectrical systems generate clean energy such as electricity or biogas. The technology is based on galvanic cells, where the two cell chambers are often separated by a membrane. High-performance cation exchange membranes enable precise ion transport and system stability. The premium product among cation exchange membranes is Nafion, such as our Nafion 115 membrane.

At Frontis Energy, we have demonstrated that bioelectrochemical systems can remove ammonium from wastewater, offering an energy-efficient alternative to the energy-intensive Haber-Bosch process. To validate this concept, we developed microbiological electrolysis cells populated with microorganisms from oxygen-deprived marine sediments off the coast of Namibia. These sediments are naturally rich in ammonia and low in organic carbon, ideal conditions for microbes capable of anaerobic ammonium oxidation. For comparison, we also used conventional municipal wastewater to populate the electrodes.

Maintaining anoxic conditions was crucial to avoid nitrification, a process that transfers electrons directly to oxygen, bypassing the anode and resulting in energy loss and reduced hydrogen production. Instead, we regulated the anode potential between +150 mV and +550 mV, well below the redox potential required for water oxidation (+820 mV). This configuration enabled the oxidation of ammonium to nitrogen gas (N₂) at the anode, while hydrogen (H₂) or methane gas was produced at the cathode.

Central to this process is Nafion 115, a membrane made of perfluorosulfonic acid polymers (PFSA polymers). Its exceptional proton conductivity, chemical resistance, and mechanical robustness make it ideal for demanding wastewater environments. Nafion 115 acts like a selective gate, allowing ammonium ions (NH₄⁺) to migrate from the anode to the cathode while blocking competing ions and maintaining anoxic conditions. This selective transport, driven by electric field gradients and concentration differences, ensures efficient nutrient recovery and stable performance of the bioelectrical system.

A practical validation of this technology comes from our earlier report, in which researchers developed a two-chamber, anoxic bioelectrical reactor that continuously removed ammonium at a rate of about 5 g/m³/day. Their system converted over 97% of the ammonium directly into nitrogen gas. This transformation occurred without the formation of harmful byproducts like nitrite or NOx gases. Particularly impressive was the energy consumption, just 0.13 kWh per kilogram of nitrogen removed. That is a 35-fold reduction compared to conventional aeration, which typically requires around 5 kWh/kg.

These results highlight the transformative potential of bioelectrical systems. As mentioned earlier, significant energy is used to remove nitrogen from wastewater, only to make it available again via the Haber-Bosch process, accounting for 1–2% of global energy consumption. Bioelectrical systems offer a circular alternative: by coupling ammonium oxidation with hydrogen production, wastewater treatment plants could become net energy producers. The generated hydrogen and biogas can be used directly for electricity generation and ultimately to reduce greenhouse gas emissions.

With the right biofilms, well-controlled electrode potentials, and robust membranes like Nafion 115, ammonium can serve as a clean, resource-efficient alternative to water electrolysis. This underscores the potential of bioelectrical systems to build a circular water economy, where waste is treated as a resource.

This technology reflects Frontis Energy’s commitment to promoting clean, efficient, and circular solutions that turn ecological challenges into sustainable opportunities.

Siegert and Tan, 2019, Electric stimulation of ammonotrophic methanogenesis, Frontiers in Energy Research 7:17, DOI: 10.3389/fenrg.2019.00017

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Stability of anion exchange membranes for electrolysis

Electrolyzer in China

DOI: 10.13140/RG.2.2.13818.56004

Energy security and climate change are among the greatest challenges of our time. To reduce dependence on fossil fuels, renewable energy sources are emerging as key solutions for sustainable energy production. To this end, scalable solutions are essential for storing and transporting renewable energy. Hydrogen produced in water electrolyzers and reconverted into electricity in fuel cells can help balance the seasonal variability of renewable energy.

Fuel cells have the potential to significantly contribute to the decarbonization of the transport sector. Transport of people and goods accounts for almost one‑third of global greenhouse gas emissions. Despite this potential, the widespread adoption of modern fuel cells and electrolyzers remains limited due to high investment costs. This is mainly due to expensive noble‑metal catalysts and perfluorinated proton exchange membranes.

This challenge has sparked growing interest in anion exchange membranes. Under alkaline conditions, they offer several advantages:

  • Use of non‑noble metal catalysts thanks to non‑corrosive conditions
  • More sustainable membrane materials

However, there are hurdles to their introduction, particularly their short lifetime under alkaline conditions and oxidative stress. The formation of hydrogen peroxide and hydroxyl radicals under alkaline conditions is responsible for the accelerated degradation of polymer membranes. Investigation radical‑induced degradation of anion exchange membranes is therefore of central importance.

Hence, efficient radical generation in the laboratory is required. Current methods such as thermal decomposition or UV activation of hydrogen peroxide are inefficient and prone to side reactions, limiting their relevance to real operating conditions. Immersion in oxygen‑saturated alkaline solutions has provided useful insights, but cannot distinguish between natural membrane degradation and radical‑accelerated breakdown.

Radioactivity and electromagnetic pulse radiation allow precise control of radical formation but require expensive, specialized infrastructure. Affordable and practical solutions are needed to study radicals under realistic laboratory conditions.

Researchers from SINTEF in Norway and ETH Zurich have addressed this challenge. They introduced adapted photochemical methods to generate radicals and study their influence on the stability of anion exchange membranes independently of other degradation processes. The results were recently published in Membranes.

By irradiating aqueous potassium nitrite solutions or titanium oxide suspensions with UV light at 365 nm, hydroxyl radicals or a combination of hydroxyl and superoxide radicals were successfully generated. Tests on three commercial anion exchange membranes – PiperION®‑40 (PiperION), FM‑FAA‑3‑PK‑75 (Fumasep), and PNB‑R45 (Polynorbornene) – showed clear differences in durability. As expected, thinner, non‑reinforced membranes degraded faster than thicker, reinforced ones, likely due to the limited penetration depth of highly reactive radicals.

Both methods proved to be practical, affordable, and accessible tools for evaluating the stability of anion exchange membranes against radical attack. Photochemical radical generation was thus a viable way to study radical‑induced degradation under controlled conditions. The nitrite‑based approach selectively generated hydroxyl radicals, while titanium oxide suspensions produced both hydroxyl and superoxide radicals. Longer irradiation intensified membrane damage, clearly demonstrating the critical role of radicals in membrane decomposition. Experiments at pH 10 enabled differentiation between natural and radical‑driven causes.

Beyond laboratory use, both methods are also of industrial relevance. Combined with low‑cost laboratory equipment, they provide widely applicable and reproducible tools for evaluating commercial and prototype anion exchange membranes. By reducing costs and extending durability tests under realistic conditions, the development of robust anion exchange membranes for fuel cells and electrolyzers can be accelerated.

Frontis Energy is part of the mission to provide cost‑effective solutions for the development of efficient energy conversion technologies. In doing so, we strengthen the global transition to clean, resilient, and sustainable energy systems.

Solyom, P.; Nauser, T.; Nemeth, T. Photochemical Methods to Study the Radical-Induced Degradation of Anion-Exchange Membranes. Membranes 2025, 15, 305. DOI: 10.3390/membranes15100305

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Advances in ammonium recovery with bioelectrical systems

DOI: 10.13140/RG.2.2.16014.22082

In recent decades, the focus of wastewater treatment has shifted from mere disposal to the recovery of valuable resources. This approach aims to harness energy and nutrients found in wastewater. Among emerging technologies are bioelectrical systems, which can recover not only energy and carbon but also valuable compounds like ammonium. Nitrogen bound in ammonium is a key component of fertilizers. Today, two-thirds of this resource are produced through the highly energy-intensive Haber-Bosch process using natural gas extracted from air. Fertilizer production significantly contributes to anthropogenic CO₂ emissions and, ultimately, to global warming.

Bioelectrical systems for ammonium recovery are classified into microbial fuel cells and microbial electrolysis cells. In both, electrogenic microorganisms oxidize organic matter in wastewater into carbon dioxide and protons. Exoelectrogens, also known as anode-respiring bacteria, use the anode as an electron acceptor instead of oxygen, thereby gaining energy for their metabolic processes.

By combining microbial activity with electrochemical processes, chemical reactions in wastewater treatment are catalyzed efficiently. This novel biocatalytic application still faces challenges in terms of optimization for practical use. At Frontis Energy, we have already demonstrated through a patented process that ammonium can be effectively removed from wastewater using bioelectrical systems. We are currently working on scaling this method for industrial deployment. However, a comprehensive understanding of the underlying processes and recovery mechanisms is still lacking.

A new study conducted by the Autonomous University of Barcelona investigated the development and optimization of bioelectrical systems aimed at recovering ammonium from wastewater in an energy-efficient and concentrated form. The findings were recently published in Bioelectrochemistry. Using a three-chamber configuration with a hydrophobic membrane, the researchers systematically examined the influence of different levels of electric current and ammonium concentrations on recovery efficiency. The system achieved its highest ammonium recovery rate of 55 g/m²/day at a current of 75 mA. Overall, a 97% removal of ammonium from a 0.3% solution was attained.

Notably, electrons flow from the anode to the cathode via an external circuit, where they react with an electron acceptor. In ammonium recovery systems, ammonium ions migrate from the anode to the cathode through a cation exchange membrane, driven by concentration gradients and the electric field, allowing them to accumulate in the cathode chamber.

While this ion transport mechanism supports efficient ammonium recovery, the researchers found that high-performance operation led to material wear at the cathode. This highlights the need to balance operational intensity with material durability. Consequently, the team explored different cathode materials and voltages. Stainless steel electrodes operated at 1.4 V yielded the best results, achieving a removal rate of 21 g/m²/day and a recovery rate of 17 g/m²/day, primarily due to enhanced cation migration resulting from higher current density.

Long-term experiments revealed that higher ammonium concentration in the anolyte significantly improves selective migration of ammonium ions through the cation exchange membrane, further boosting system performance. Operating at 1.4 V increased recovery efficiency and reduced energy consumption per gram of nitrogen—making the process more cost-effective and environmentally friendly.

These insights underscore the practical potential of bioelectrical systems as a pioneering solution for sustainable nitrogen recovery. By fine-tuning material selection, system design, and operational parameters, high ammonium removal and recovery rates can be achieved with minimal energy input.

From an industrial perspective, this study represents a scalable advance in resource recovery within existing wastewater treatment infrastructures. If scaled, the technology could reduce reliance on the energy-intensive Haber-Bosch process.

Since concentrated ammonium is a commercially viable product, its recovery reduces operational costs for wastewater treatment plants. If the scaled-up process maintains its long-term stability and low energy demand, these would be compelling arguments for adopting bioelectrical technologies as part of a circular economy.

At Frontis Energy, we see great potential in scaling this technology and making a meaningful contribution to sustainable wastewater treatment.

Ul, et al. 2025, Electrochemical and bioelectrochemical ammonium recovery from N-loaded streams using a hydrophobic membrane, Bioelectrochemistry, Volume 166, 109013, 10.1016/j.bioelechem.2025.109013.

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Improved membrane configurations for capacitive flow-electrode desalination

DOI: 10.13140/RG.2.2.19476.16002

With the growing global scarcity of drinking water, the demand for practical and energy-efficient desalination methods is on the rise. Among potential solutions are osmotic desalination methods like capacitive deionization and its advanced form, flow-electrode capacitive deionization (FCDI). Flow electrodes are streaming electrodes composed of conductive particles suspended in a liquid. When electrically charged, these particles behave like capacitors and gain capacitive properties.

In flow-electrode deionization, flowable carbon electrodes are combined with ion-exchange membranes. The use of membranes enables continuous and efficient desalination. Membranes induce a selective transport of charged ions, allowing oppositely charged ions (counterions) to pass while repelling similarly charged ions (co-ions). This selective ion transport is essential for targeted salt removal from the feed stream.

Research advancements have improved membrane properties, associated ion selectivity, and the design of galvanic cells, leading to practical applications. For example, flow-electrode deionization was tested for industrial feasibility in a pilot plant in 2023. Performance optimization depends significantly on understanding how ion transport behaves with different membrane configurations. Ion-exchange membranes play a key role in controlling ion movement. Certain membrane arrangements, such as membrane “sandwiches” made of anion and cation exchange membranes, significantly accelerated desalination. While promising results were achieved with simple salt solutions like NaCl and KCl, mixtures of diverse ions, as found naturally in seawater, are more challenging.

Researchers from RWTH Aachen University recently investigated how different ion-exchange membrane arrangements affect selective ion removal from complex salt mixtures, such as those containing carbonate and sulfate ions, in flow-electrode deionization. Their findings were published in the journal Desalination. Two deionization modules with different membrane setups were analyzed. Membrane layers were tested with the cation membrane on the inside and the anion membrane on the outside, and vice versa. Both configurations delivered similar desalination performance, but the time to reach a stable state varied depending on the arrangement and the flow electrode’s buffering capacity.

The tested anion exchange membranes showed a higher affinity for sulfate ions than for carbonate ions, which delayed stabilization in some cases. Strategies like reducing electrode volume and steering specific ions along the electrode path helped reach the steady state more quickly. These findings underscore the importance of membrane selectivity, electrode properties, and system design in enhancing the performance of flow-electrode deionization, especially for mixed-ion water sources.

The effectiveness of the process depends not just on reaching a steady desalination state but also on managing ion selectivity and system adaptation. With saltwater containing multiple cations and anions, membrane arrangement alone is not enough to achieve the desired results. To tackle these challenges, strategies like membrane coatings or modifying electrode properties must be considered.

The researchers also addressed evaluation methods in their study. Interestingly, measuring conductivity alone is not sufficient to assess desalination performance. While it indicates total salt concentration, it does not reflect changes in salt composition. Therefore, more precise evaluation methods are needed to meet specific requirements.

These advances are crucial for optimizing flow-electrode deionization performance and meeting the growing demand for efficient, adaptable water treatment technologies. At Frontis Energy, we are excited to see how this groundbreaking technology will scale in the future.

Mankertz, Theis, Linnartz, Wessling, 2025, Membrane arrangement influences time to steady state in FCDI with multi-ionic salt solutions, Desalination, Volume 613, 118939, DOI: 10.1016/j.desal.2025.118939.

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Electrolytic water splitting for binders in building material

DOI: 10.13140/RG.2.2.23827.54564

The oceans are rich in magnesium resources, which that could be used in the production of construction materials. Sorel cement (magnesium cement), for example, can be used in interior building applications as an alternative to screed. Extracting magnesium from seawater traditionally requires a highly energy-intensive calcination process to isolate magnesium oxide (magnesia). The innovative method of electrolysis-controlled water splitting can bypass this process, significantly reducing CO₂ emissions.

To obtain the precursor of magnesia, magnesium hydroxide (Mg[OH]₂), an alkaline solution must be produced. While previous research has investigated electrochemical methods for hydroxide production, few studies have combined efficient alkali synthesis with the direct precipitation of magnesium hydroxide to make magnesia for low-carbon cement. This critical knowledge gap in optimizing energy and material efficiency has now been addressed.

A new study led by a research team at Columbia University used electrochemical water splitting at low voltages (1.6–2.0 V). Hydroxide ions (OH⁻) were generated from seawater through hydrogen production. This led to the direct precipitation of magnesium hydroxide. The findings were recently published in the journal Desalination. This new approach reduces energy intensity by 52–78%. Normally, the energy consumption per ton of MgO is 0.56 MWh. With the new method, carbon emissions per ton of magnesia can be reduced by up to 0.41 tons of CO₂.

To further improve production efficiency, the nanostructure of magnesium hydroxide was optimized using urea as a crosslinker. This enhanced its reactivity, porosity, and specific surface area. At an optimal urea concentration of 0.2 mol/L, magnesia particles exhibited excellent binding properties. The researchers attributed this to the sealing effects of rosette-shaped dypingite and rod-shaped nesquehonite. According to the authors, the formation of these minerals facilitates CO₂ incorporation and enhances carbonate hardening.

Advances in symmetric electrochemical systems, as demonstrated in this study, result in up to a 78% reduction in energy demand for the production of alkaline solutions. This gives these methods the potential to serve as viable alternatives to traditional processes. The further optimization of electrodes and electrolytes represents a pioneering approach to the carbon-neutral production of building materials and alkalis. Additionally, this method highlights how construction material manufacturing can efficiently lead to large-scale CO₂ mineralization. As a result, the greenhouse gas can be permanently removed from the atmosphere.

The industrial scaling of electrochemical alkali production can reduce operating costs, minimize environmental impact, and improve the properties of low-carbon building materials. The economic aspects of this manufacturing process are particularly noteworthy, as the demand for efficient binding materials continues to grow.

At Frontis Energy, we are committed to promoting sustainable and economically viable energy solutions. Research like this provides valuable insights and innovations to support such sustainable advancements.

Chu. Yang, Unluer, 2025, Energy-efficient calcination-free Mg cement recovered from desalination brine, Desalination, Volume 610, 118928, 10.1016/j.desal.2025.118928.

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From waste heat to ultrapure water: A new technology transforming renewable hydrogen

DOI: 10.13140/RG.2.2.36620.17281

Hydrogen (H₂), produced using renewable energy, has emerged as a possible alternative to fossil fuel. This versatile molecule can serve as an energy carrier, an efficient storage solution, and a sustainable feedstock for transportation, chemical processing, and energy systems worldwide.

Unlike fossil fuels, hydrogen produces no harmful emissions when used. It can be generated using electrolyzers running on renewable energy and abundant water as feedstock. It then becomes a renewable and sustainable energy source, reducing reliance on depleting fossil fuel reserves, helping combat climate change. Consequently, hydrogen production has become a key priority on the political agenda of numerous countries.

However, the water used in electrolyzers must be ultrapure in order to protect the electrodes of electrolyzers from poisoning and avoid chloride oxidation to chlorine. Abundant seawater adds several challenges when directly fed to electrolyzer plants for hydrogen production, making highly pure water, specifically ultrapure water, an expensive necessity. Ultrapure water is produced in a series of steps, including pretreatment to remove suspended solids and desalination to eliminate salts, organics, and colloidal particles. Polishing techniques such as deionization, degasification, and ultraviolet treatment are then used to achieve the required quality. Among these processes, desalination is particularly critical for removing most impurities.

Reverse osmosis, especially seawater reverse osmosis, is a widely used desalination technology but has notable drawbacks, such as requiring high-pressure operation (high energy consumption), intensive pretreatment, and producing concentrated brine, which can harm marine ecosystems when discharged. Membrane distillation has gained attention as an alternative for producing high-quality water and supporting recovery applications. It operates at lower temperatures and has the ability to utilize waste heat.

Membrane distillation is a thermal separation process where a vapor pressure difference across a hydrophobic membrane causes liquid particles to phase change and pass through as gas. Operating at ambient pressure and utilizing low-temperature heat sources (<90 °C), membrane distillation offers significant advantages. However, research on membrane distillation as a viable alternative to reverse osmosis for ultrapure water production remains limited, particularly in areas such as module design and techno-economic analysis.

A group of researchers at the Fraunhofer Institute for Solar Energy Systems (ISE) in Freiburg, Germany, has explored the potential of membrane distillation as a cost- and energy-efficient alternative to reverse osmosis for producing ultrapure water for proton exchange membrane (PEM) electrolyzers. The findings were recently published in the Desalination Journal. They introduced membrane distillation as a possible alternative to reverse osmosis for ultrapure water production. But here is the twist: the membrane distillation system ingeniously taps into waste heat from a 5 MW proton exchange membrane electrolyzer, transforming what would typically be an efficiency liability into an asset for sustainability. So far, their results are impressive—membrane distillation not only produces exceptional distillate (<3 μS/cm) but does so at a cost ranging from €2.33 to €2.85 per ton of distillate, compared to reverse osmosis’s €2.80 to €5.51. Using membrane distillation, seawater desalination could be 50% or more cheaper.

Economic analyses highlight that membrane distillation’s cost-effectiveness is driven by its low electrical energy requirements and optimized short-channel module design. Its impressive energy efficiency, enabled using low-grade thermal energy, establishes membrane distillation as a highly versatile and environmentally friendly solution that aligns seamlessly with the vision for renewable hydrogen production. This study positions membrane distillation as more than just an alternative to reverse osmosis: it is a smarter and greener approach to ultrapure water production.

Their findings have the potential to reshape the industrial approach to ultrapure water production. By demonstrating an efficient use of waste heat and providing a more economical solution, it offers industries a pathway to lower operational costs while advancing sustainability. This aligns particularly well with sectors striving for greener operations, such as renewable hydrogen production and other energy-intensive applications. Moreover, the adoption of membrane distillation could catalyze innovation in system design and integration, encouraging industries to optimize processes and reduce dependence on traditional, energy-intensive methods. This shift can contribute to broader sustainability goals and improve the economic feasibility of renewable energy initiatives.

At Frontis Energy, we are committed to advancing sustainable and green energy solutions by embracing innovative technologies like membrane distillation, bringing us closer to a sustainable future.

Schwantes et al. 2025 Thermally driven ultrapure water production for water electrolysis – A techno-economic analysis of membrane distillation, Desalination, Volume 608, 118848, DOI: 10.1016/j.desal.2025.118848.

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