Electrolysis System Research Articles

High‐Entropy Phosphide Catalyst‐Based Hybrid Electrolyzer: A Cost‐Effective and Mild‐Condition Approach for H2 Liberation from Methanol

AbstractMethanol as a hydrogen carrier provides a practical solution for H2 storage and transport, but traditional reforming faces challenges with low efficiency, CO2 emissions, and the need for specialized infrastructure. In this study, a reliable approach for fabricating low‐cost electrodes is presented by in situ growing high‐entropy phosphide nanoparticles on nickel foam (FeCoNiCuMnP/NF). This cost‐effective design is specifically engineered for alkaline methanol oxidation reactions (MOR), achieving a current density of 10 mA cm−2 at an applied voltage of only 1.32 V, while also demonstrating exceptional selectivity for formate products. Advanced Monte Carlo (ML‐MC) simulations identify copper as the predominant surface element and highlight phosphorus coordination as a key factor in enhancing catalytic activity. The field is advanced with a pioneering hybrid acid/alkali flow electrolyzer system, integrating FeCoNiCuMnP/NF anode and commercial RuIr/Ti cathode to enable indirect hydrogen liberation from methanol. This system requires an electrolytic voltage as low as 0.58 V to achieve a current density of 10 mA cm−2 and remains stable for hydrogen liberation over 300 h of operation. This achievement not only offers a highly efficient alternative to indirectly liberate H2 stored in methanol but also establishes a new benchmark for sustainable and economically viable H2 production.

Direct parallel electrosynthesis of high-value chemicals from atmospheric components on symmetry-breaking indium sites

To tackle significant environmental and energy challenges from increased greenhouse gas emissions in the atmosphere, we propose a method that synergistically combines cost-efficient integrated systems with parallel catalysis to produce high-value chemicals from CO2, NO, and other gases. We employed asymmetrically stretched InO5S with symmetry-breaking indium sites as a highly efficient trifunctional catalysts for NO reduction, CO2 reduction, and O2 reduction. Mechanistic studies reveal that the symmetry-breaking at indium sites substantially improves d-band center interactions and adsorption of intermediates, thereby enhancing trifunctional catalytic activity. Employed in a flow electrolysis system, the catalyst achieves continuous and flexible production of NH3, HCOO-, and H2O2, maintaining over 90% Faradaic efficiency at industrial scales. Notably, the parallel electrolysis device reported in this study effectively produces high-value products like NH4COOH directly from greenhouse gases in pure water, offering an economically efficient solution for small molecule synthesis and unique insights for the sustainable conversion of inexhaustible gases into valuable products. Therefore, this work possesses considerable potential for future practical applications in sustainable industrial processes.

Optimization of hydrogen production via electrocatalysis using NiCoMo-modified electrodes: An RSM approach

ABSTRACT The depletion of fossil fuels and the environmental impact of their combustion have increased the demand for sustainable energy alternatives, with hydrogen appearing as an appropriate option due to its clean energy potential. This study focuses on developing a laboratory-scale alkaline electrolysis system for hydrogen production. Platinum, known for its high catalytic activity and durability, was employed as the anode, while graphite was selected as the cathode for its cost-effectiveness. To enhance catalytic performance, the graphite electrodes were modified with nickel-cobalt-molybdenum (NiCoMo) using a galvanostatic method. The electrode voltage and molarity were chosen as independent variables to evaluate their effect on hydrogen production. Using the Design-Expert software, the optimal conditions were identified at 3 V and 1.5 mol/l, yielding 10.67 ml of hydrogen. The coefficient of determination (R2) values 98.81% for R2, 97.96% for adjusted R2, and 91.63% for predicted R2 indicate suitable model accuracy. The error margin between experimental and optimized results was only 1.7%, confirming the reliability of the method. This study highlights the potential of NiCoMo-modified electrodes to enhance hydrogen production efficiency. Future research could explore scaling up the system and integrating it with renewable energy sources, positioning this method as a viable pathway toward sustainable hydrogen production.

Development of compact electrolytic enrichment system for environmental tritium analysis.

The new electrolytic enrichment system with compact glass cell was designed. Three (Ni-Fe-Ni) electrodes are used, and electrolysis is carried out at a rate of 2.45g per h with constant current density of 120mA per cm2. This enrichment system allows the enrichment for small, limited sample volumes (e.g. Tritiated Water (HTO) recovered from air). With an initial water volume of 100ml, the tritium enrichment factor of 7 within 2days and a detection limit of 0.12Bq per L can be obtained by Liquid Scintillation Counter (LSC) measurement for 1000minutes, which is better than the direct measurement with 50ml sample water using large vial. It is also possible to perform the high enrichment process. The initial sample volume of 700ml enriched for 12days by manual refilling yields a tritium enrichment factor of around 43 and detection limit of 0.02Bq per L for 1000minutes of LSC measurement.

An Analysis of the Conceptual and Functional Factors Affecting the Effectiveness of Proton-Exchange Membrane Water Electrolysis

Hydrogen has the potential to decarbonize the energy and industrial sectors in the future, mainly if it is generated by water electrolysis. The proton-exchange membrane water electrolysis (PEMWE) system is regarded as a propitious technology to produce green hydrogen from water using power supplied by renewable energy sources. It offers many benefits, such as high performance, high proton conductibility, quick response, compact size, and low working temperature. Many conceptual and functional parameters influence the effectiveness of PEM, including temperature, pressure of anode and cathode regions, water content and wideness of the layer, and cathode and anode exchange current density. In addition, the anodic half-reaction (known as the oxygen evolution reaction (OER)) and cathodic half-reaction (known as the hydrogen evolution reaction (HER)) perform an important function in the development of PEMWE. The current study aims to present these parameters and discuss their impacts on the performance of PEM. Also, the PEM efficiency is presented. The different methods used to enhance the scattering of OER electrocatalysts and minimize catalyst loading to minimize the price of PEMWE are also highlighted. Moreover, the alternative noble metals that could be used as electrocatalysts in HER and OER to minimize the cost of PEM are reviewed and presented.

Parameter Analysis of Anion Exchange Membrane Water Electrolysis System by Numerical Simulation

Anion exchange membrane electrolysis, which combines the advantages of both alkaline electrolysis and proton-exchange membrane electrolysis, is a promising technology to reduce the cost of hydrogen production. The present work focused on the study of the electrochemical phenomena of AEM electrolysis and the investigation of the key factors of the AEM hydrogen production system. The numerical model is established according to electrochemical reactions, polarization phenomena, and the power consumption of the balance of plant components of the system. The effects of operation parameters, including the temperature and hydrogen pressure of the electrolyzer, electrolyte concentration, and hydrogen supply pressure on the energy efficiency are studied. The basic electrochemical phenomena of AEM water electrolysis cells are analyzed by simulations of reversible potential and activation, and ohmic and concentration polarizations. The results reveal that increasing the operating temperature and hydrogen production pressure of the AEM electrolyzer has positive effects on the system’s efficiency. By conducting an optimization analysis of the electrolyzer temperature—which uses the heat energy generated by the electrochemical reaction of the electrolyzer to minimize the power consumption of the electrolyte pump and heater—the AEM system with an electrolyzer operating at 328 K and 30 bar can deliver hydrogen of pressure up to 200 bar under an energy efficiency of 56.4%.

Fluorine-Induced Lattice Oxygen Participation in 2D Layered Double Hydroxide/MXene Hybrids for Efficient Oxygen Evolution.

In oxygen evolution reaction (OER), the participation of lattice oxygen can break the limitation of adsorption evolution mechanism, but the activation of lattice oxygen remains a critical challenge. Herein, a surface fluorinated highly active 2D/2D FeNi layered double hydroxide/MXene (F-LDH/MX) is demonstrated, boosting OER with the enhanced lattice-oxygen-mediated path. The introduction of fluorine promotes the self-evolution of catalyst in an alkaline environment, even without an external current. It further accelerates the formation of active metal oxyhydroxides with abundant oxygen vacancies under the operating potential. The introduced oxygen vacancy activates the lattice oxygen, increasing the proportion of lattice oxygen mechanism in OER. Owing to the synergistic effects of the 2D/2D hierarchical structure and the modulated active surface, F-LDH/MX possesses excellent electrochemical performances, including a low overpotential of 251 mV at 10 mA cm-2, a low Tafel slope of 40.28 mV dec-1, and robust stability. The water electrolyzer system with F-LDH/MX as the anode offers the benchmark current density at a low cell voltage of 1.53 V, while the Zn-air battery with F-LDH/MX as the air electrode exhibits a higher power density of 75.43 mW cm-2. This study presents a promising strategy to design highly active electrocatalysts for energy conversion and storage.

Integration of a solid oxide electrolysis system with solar thermal and electrical energy: A testing campaign for operation and control strategy definition

AbstractThe EU project PROMETEO has the scope of testing a 25 kW solid oxide electrolysis system integrated with a concentrated solar power plant via thermal energy storage in a relevant environment. Given the plant layout and the hydrogen demand characteristics, this work aims to identify how to operate the system effectively when renewable electricity is unavailable and how to modulate the load during hydrogen generation, thus defining the system's operation modes and control strategy. A 5 kWe stack has been tested at the FBK facility. The hot standby tests show that feeding a reducing gas at the negative electrode and air at the positive electrode, without polarizing the stack, effectively keeps the stack hot at 750°C and prevents degradation. Conversely, the electric protection approach leads to significant stack degradation (15% voltage drop in 200 h for one cluster). Regarding modulation of hydrogen generation, with low steam flowrates, the stack current and the flow rate of produced hydrogen mainly depend on the steam flow rate, while it is not affected by the stack temperature; conversely, with high steam flowrates, the current depends only on the stack temperature (from 25 A at 670°C to 65 A at 760°C). Based on the results, two hot standby modes and two load control strategies to be implemented and tested in the PROMETEO prototype are proposed.

Enhanced Adsorption Kinetics and Capacity of a Stable CeF3@Ni3N Heterostructure for Methanol Electro‐Reforming Coupled with Hydrogen Production

Alkaline methanol‐water electrolysis system is regarded as an appealing strategy for electro‐reforming methanol into formate and producing hydrogen with low energy‐consumption compared with alkaline water electrolysis. However, stability and selectivity under high current densities for practical application remain challenging. Herein, a CeF3@Ni3N nanosheets array anchored on carbon cloth (CeF3@Ni3N/CC) was fabricated. The gradual extrusion of F species from Ni(OH)2 lattices can stabilize hierarchical structure and construct abundant heterostructure interfaces. Moreover, CeF3 can modulate electron distribution of Ni3N, thus simultaneously enhancing the surface adsorption kinetics and capability of methanol and OH‐, which is conducive to enhanced methanol oxidation reaction (MOR) activity and selectivity. Therefore, bifunctional CeF3@Ni3N/CC exhibits low potential of 1.43 V at 500 mA cm‐2, along with high stability over 72 h and high faradaic efficiency (FEs) in MOR, as well as an overpotential of 76 mV to achieve 50 mA cm‐2 for hydrogen evolution reaction (HER). Furthermore, membrane‐free CeF3@Ni3N/CC||CeF3@Ni3N/CC cell for MOR||HER delivers high electrocatalytic activity, long‐term stability and FEs at high current density of 300 mA cm‐2. This study highlights the importance of optimizing surface adsorption behavior of active species, as well as rational design of highly efficient heterostructure electrocatalysts for methanol upgrading coupled with hydrogen production.

Enhanced Adsorption Kinetics and Capacity of a Stable CeF3@Ni3N Heterostructure for Methanol Electro-Reforming Coupled with Hydrogen Production.

Alkaline methanol-water electrolysis system is regarded as an appealing strategy for electro-reforming methanol into formate and producing hydrogen with low energy-consumption compared with alkaline water electrolysis. However, stability and selectivity under high current densities for practical application remain challenging. Herein, a CeF3@Ni3N nanosheets array anchored on carbon cloth (CeF3@Ni3N/CC) was fabricated. The gradual extrusion of F species from Ni(OH)2 lattices can stabilize hierarchical structure and construct abundant heterostructure interfaces. Moreover, CeF3 can modulate electron distribution of Ni3N, thus simultaneously enhancing the surface adsorption kinetics and capability of methanol and OH-, which is conducive to enhanced methanol oxidation reaction (MOR) activity and selectivity. Therefore, bifunctional CeF3@Ni3N/CC exhibits low potential of 1.43 V at 500 mA cm-2, along with high stability over 72 h and high faradaic efficiency (FEs) in MOR, as well as an overpotential of 76 mV to achieve 50 mA cm-2 for hydrogen evolution reaction (HER). Furthermore, membrane-free CeF3@Ni3N/CC||CeF3@Ni3N/CC cell for MOR||HER delivers high electrocatalytic activity, long-term stability and FEs at high current density of 300 mA cm-2. This study highlights the importance of optimizing surface adsorption behavior of active species, as well as rational design of highly efficient heterostructure electrocatalysts for methanol upgrading coupled with hydrogen production.

Cryptosporidium parvum inactivation from short durations of treatment with ozonated water produced by an electrolytic generation system.

Cryptosporidium is a waterborne pathogen that causes diarrhea in vertebrates and humans (mainly C. hominis and C. parvum). Ozone (O3) is a powerful disinfectant due to its high oxidative characteristics, and it is used to inactivate microorganisms in drinking water. As an alternative to the gas dissolution system for producing ozone from oxygen, a simpler electrolytic ozone generation system has recently been developed. In the present study, the efficacy of the ozonated water produced by this system in inactivating Cryptosporidium parasites (C. parvum) was evaluated at different current intensities (which change the ozone concentrations) and short exposure times (15-60s). Oocyst viability and integrity was assessed using vital dye staining, excystation assays, and scanning electron microscopy (SEM). SEM data revealed that oocyst walls were damaged by exposure to ozone molecules even at low concentrations (< 0.01mg/l for 1min) (current intensity 0.2 A), but that the excystation assay could not differentiate between deformed oocysts (dead) and partially excysted oocysts (alive). Exposure to ozonated water produced with a low current intensity (0.3 A) for 15 and 120s resulted in the inactivation of 96.2% (CT value < 0.003) and 99.4% (CT value < 0.020) of the oocysts, respectively. Thus, it was estimated that a CT value more than 0.020 was required to inactivate > 99% of the C. parvum oocysts. These results suggested that the electrolytic ozone generation system may be more effective than gas dissolution ozone generation; however, further studies using additional approaches are needed to obtain clearer evidence.

Optimization of chemical engineering control for large-scale alkaline electrolysis systems based on renewable energy sources

In the context of renewable energy, dynamic control is crucial for large-scale alkaline water electrolysis systems. Under traditional Proportional-Integral-Derivative (PID) control, the system's temperature and impurity levels may exceed safe limits during sudden load changes, compromising system safety. Therefore, this study proposes a control strategy based on mathematical models of system temperature and impurities, including Model Predictive Control (MPC) for temperature and Optimal Curve Tracking (OCT) for impurities. The MPC controller offsets the disturbances in temperature caused by current fluctuations through state prediction, while the OCT controller ensures that impurity levels remain within safe limits. Real-time application of these control strategies is achieved through MATLAB-PLC communication, validating controller performance. Experimental results show that the MPC controller exhibits excellent dynamic response and stability in controlling the stack temperature, with a maximum temperature peak deviation of only 2.9 K and a temperature fluctuation range of 5.9 K. This represents a reduction of 1.6 K in peak deviation compared to traditional PID controllers and significantly decreases the temperature fluctuation range. The OCT controller also demonstrates good safety and stability in controlling hydrogen to oxygen (HTO) impurity levels, consistently maintaining the HTO content at the set upper limit of 1.5%, thereby expanding the safe operational range of the system and reducing the need for frequent adjustments to the system setpoints.

Enhanced Oxygen Evolution Reaction Performance of NiMoO4/Carbon Paper Electrocatalysts in Anion Exchange Membrane Water Electrolysis by Atmospheric-Pressure Plasma Jet Treatment.

NiMoO4 was grown on carbon paper (CP) by a hydrothermal method. A rapid and high-temperature atmospheric-pressure plasma jet (APPJ) process was used to generate more oxygen-deficient NiMoO4 on the CP surface to serve as an electrode material for the oxygen evolution reaction (OER). After 60 s of APPJ treatment, the overpotential of the electrode at 100 mA/cm2 decreased to 790 mV and that at 10 mA/cm2 decreased to 368 mV. Additionally, the charge transfer resistance decreased from 2.8 to 1.2 Ω, indicating that APPJ treatment effectively reduced the electrode overpotential and impedance. The effect of NiMoO4/CP/APPJ-60 s on the anion exchange membrane water electrolysis (AEMWE) system was also tested. At a system temperature of 70 °C and current density of 100 mA/cm2, the energy efficiency reached 95.1%, and the specific energy consumption decreased from 4.02 to 3.83 kWh/m3. These results demonstrate that the APPJ-treated NiMoO4/CP electrode can effectively enhance the OER performance in water electrolysis and improve the energy efficiency of the AEMWE system. This approach shows promise in replacing precious metal electrodes, thereby potentially reducing the cost and providing an environmentally friendly alternative.

Intermittent polarity inversion of stainless-steel paired electrodes for efficient and durable water electrolysis

Designing robust and cost-effective catalysts through straightforward and replicable techniques is crucial for advancing water electrolysis. In this study, we introduce a dynamic polarization control method for the continuous activation of stainless steel (SS) substrates to achieve high water-splitting performance and durability. By applying periodic inverted current density during high-current–density operation (0.5 or 1 A cm−2) on bare SS adopted as both cathode and anode substrates, a NiFe-based oxide structure favorable for the hydrogen evolution reaction is formed at the cathode, while a Fe-incorporated NiOOH structure with high efficacy for the oxygen evolution reaction develops at the anode. Implemented in an anion exchange membrane water electrolysis system, this inverted polarization approach applied for the SS paired electrolyzer system successfully maintains a cell voltage of approximately 1.9 V for 500 h at a current density of 1 A cm−2 using bare SS for both electrodes.

Tantalum-induced reconstruction of nickel sulfide for enhanced bifunctional water splitting: Separate activation of the lattice oxygen oxidation and hydrogen spillover

Designing highly active and stable bifunctional catalysts for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) under alkaline conditions is crucial for sustainable overall water splitting. Herein, we present a targeted reconstruction of Ni3S2 by introducing tantalum, achieving remarkable overall water splitting performance through the separate activation of the lattice oxygen mechanism and hydrogen spillover. Electrochemical Mass Spectrometry and in-situ Raman spectroscopy reveal that tantalum induces Ni3S2 to reconstruct into nickel hydroxide during OER, thereby enhancing catalytic activity via the activation of the lattice oxygen mechanism. In the corresponding HER, tantalum promotes the reconstruction of Ni3S2 into oxysulfide, facilitates hydrogen spillover, and acts as an anchor to shorten the spillover distance, improving the HER catalytic performance, as verified by the kinetic isotope effect and theoretical calculations. Therefore, the catalyst-based anion exchange membrane water electrolyzer system achieves a current density of 1 A cm−2 at just 1.97 V, maintaining continuous operation for 500 h. This study offers new insights into the design of bifunctional catalysts, advancing the development of efficient and robust overall water splitting catalysts.

Biomass-Driven Polygeneration Coupled to Power-to-X: An Energy and Economic Comparison Between On-Site Electric Vehicle Charging and Hydrogen Production

The power-to-X strategy for passenger car applications offers a viable solution for using the surplus electrical power from renewable energy sources instead of exporting it to the grid. The innovative system proposed in this study allocates surplus electrical power from a building-integrated biomass-based Combined Cooling Heating and Power (CCHP) system to on-site applications and evaluates the energetic and economic benefits. The system comprises two key components: a 50 kW electric vehicle (EV) charging station for EVs and a 50 kW alkaline electrolyzer system for on-site hydrogen production, which is later dispensed to fuel cell electric vehicles (FCEVs). The primary goal is to decrease the surplus of electricity exports while simultaneously encouraging sustainable transportation. The system’s economic viability is assessed through two scenarios of fuel (e.g., biomass) supply costs (e.g., with and without fuel market costs) and compared to the conventional approach of exporting the excess power. The key findings of this work include a substantial reduction in surplus electricity exports, with only 3.7% allocated for EV charging and 31.5% for hydrogen production. The simple payback period (SPB) is notably reduced, enhancing economic viability. Sensitivity analysis identifies the optimal hydrogen system, featuring a 120 kW electrolyzer and a 37 kg daily hydrogen demand. The results underscore the importance of prioritizing self-consumed energy over exports to the national grid, thereby supporting integrated renewable energy solutions that enhance local energy utilization and promote sustainable transportation initiatives.

Cobalt-based Molecular Electrocatalyst-Mediated Green Hydrogen Generation: A Potential Pathway for Decarbonising Steel Industry

Amid the climate change crisis, researchers are investigating the transformative potential of green hydrogen produced by renewable energy electrolysis to decarbonize the steel sector, a significant contributor to global carbon emissions. It aims to lower the carbon footprint of the steel industry by showcasing green hydrogen's potential as a cleaner substitute for traditional fossil fuels in the production process. Despite its potential, issues such as high costs, restricted availability, and infrastructural alterations must be addressed. Cobalt-based synthetic catalysts, especially cobaloximes, are being considered as a key electrocatalytic component for hydrogen production via water-splitting. Cobaloximes, noted for their efficiency and stability in catalysing hydrogen evolution, have made considerable advances in the field of molecular catalysis. Recently, advanced immobilisation procedures have appreciably enhanced their overall catalytic output and application. This article discusses several electrolyser technologies, such as proton exchange membrane (PEM) and alkaline electrolysis, highlighting the benefits of multi-stacked electrolyser systems for boosting hydrogen generation efficiency. These encouraging results are vital for unravelling a durable catalytic material that can be scaled up without much financial stringency. In light of the global climate pledges, the document concludes that green hydrogen might provide 24% of the world's energy needs by 2050, resulting in a considerable reduction in CO2 emissions.

Dual-objective Optimization of Solar Driven Alkaline Electrolyzer System for On-Site Hydrogen Production and Storage: Current and Future Scenarios

Dual-objective Optimization of Solar Driven Alkaline Electrolyzer System for On-Site Hydrogen Production and Storage: Current and Future Scenarios

Integrated solar-powered freeze desalination and water electrolysis system with energy recovery and storage for sustainable agriculture in desert environments

Integrated solar-powered freeze desalination and water electrolysis system with energy recovery and storage for sustainable agriculture in desert environments

Photovoltaic to electrolysis off-grid green hydrogen production with DC–DC conversion

Green hydrogen (H2), being the product of water electrolysis powered by renewable energy sources, is expected to be an energetic vector of major importance toward a more sustainable energy mix. In this context, photovoltaic (PV) -based H2 production is a key element, where power electronics technologies are critical to enable its development. In off-grid applications, designing DC–DC power electronics converters with high efficiency and high power density is really important since it can impact significantly the global performance of the H2 production system. In this work, a two-stage DC–DC power conversion system composed by an unregulated DCX converter and a regulated partial power converter is considered to increase the H2 production system efficiency. The DCX converter works in open-loop at resonant frequency with a high DC–DC conversion ratio. A partial power converter (PPC), which regulates only a fraction of the total power between its input and output terminals, represents a improvement in PV-to-H2 direct conversion, particularly since the PV panels do not require regulation from zero to nominal voltage, and in this work, is introduced for regulation of the DCX-based system, by optimizing the PV produced power through a maximum power point tracking (MPPT) algorithm along with the current control of the electrolyzer. A comparison with state-of-the-art converters show an important improvement of the proposed DCX with PPC regulated system. Compared to the solution with classical interleaved-buck pre-regulator, significant improvements in terms of efficiency for the whole range of operation are obtained, up to 2.5% higher with the proposed system. Experimental evaluation of the proposed PPC and DCX two stage converter for PV-powered electrolysis system is provided, validating its feasibility and interest for off-grid green hydrogen production application.