Search Results (428)

In this work, a dynamic polymer electrolyte membrane (PEM) fuel cell system is modelled in Modelica using the in-house developed, open-source library ThermoFluidStream. The focus lies on the fuel cell stack, the hydrogen fuel supply and the air supply. Additionally, the thermal management and the power electronics are considered in a simplified manner. Dynamic simulations are carried out for this system over an exemplary aircraft gate-to-gate mission. Simultaneously, a baseline control scheme is developed to provide the fuel cell with sufficient product gases in a suitable state regarding the temperature, pressure and relative humidity. The results indicate that the fuel cell system performs well with standard PI controllers. Only when strong dynamics occur, such as when going from taxi to take-off, does the control scheme show some weaknesses, as expected. This fuel cell system together with its control is a powerful baseline for future investigations. Full article

Salinity stress is one of the major obstacles to glycophytic crop production worldwide, including rice. It alters cellular metabolism, causing significant crop destruction that results in substantial reductions in yield. The overexpression of C₄ enzymes, such as phosphoenolpyruvate carboxykinase (PEPCK), at high levels in C₃ transgenic plants through genetic engineering can decrease oxidative stress while increasing photosynthetic capabilities. In this research, we evaluate the efficiency of transgenic rice plants (Oryza sativa L. cv. IR64) overexpressing PEPCK genes in mitigating salinity stress and increasing photosynthetic efficiency. The T1 transgenics showed increased levels of several biochemical factors, including ascorbate peroxidase (APX), catalase (CAT), proline, glutathione reductase (GR), and guaiacol peroxidase (GPX) activities. This was accompanied by reduced levels of malondialdehyde (MDA), hydrogen peroxide (H₂O₂), and electrolytic leakage, suggesting an effective antioxidant defense mechanism against the oxidative damage driven by salt stress. Photosynthetic parameters—such as chlorophyll content, net photosynthetic rate, intercellular CO₂ content, and stomatal conductance—were elevated in transgenic plants compared to control plants. The transgenics also exhibited superior agronomic characteristics. Our findings provide conclusive evidence of the PEPCK gene’s potential role in regulating salt stress response and tolerance in rice plants. Full article

This study investigates the enhancement of hydrogen production efficiency in water electrolysis through the application of external magnetic fields. A series of controlled experiments were conducted using four distinct electrode materials—stainless steel (SS), low-carbon steel (LCS), titanium (Ti), and platinum-plated titanium (Ti/Pt)—to identify the optimal configuration for maximizing gas output. The research evaluated the influence of electrolyte concentration (KOH), current density, and magnetic field intensity ranging from 0 to 1800 G. Our findings indicate that the application of a 200 G magnetic field leads to a notable 6% increase in the rate of gas production compared to non-magnetized conditions. Specifically, a magnetic field oriented parallel to the electrode plates outperformed a perpendicular orientation by approximately 5%, a phenomenon attributed to the Lorentz force facilitating ionic mass transfer and gas bubble detachment. Furthermore, the integration of ion-exchange and proton-exchange membranes (MC-3470 and N-117) effectively isolated the anodic and cathodic products, elevating hydrogen purity from 67.4% to approaching 100% without compromising electrolysis efficiency. These results demonstrate that the strategic coupling of moderate magnetic fields with optimized electrode configurations provides a promising pathway for improving the efficiency and cleanliness of hydrogen production, which is essential for its role as a sustainable energy carrier. Full article

Designing materials with superior corrosion resistance is critical for seawater electrolysis systems to achieve efficient and long-term stable hydrogen production. In the current study, CrAlN coatings were deposited on TA1 titanium substrates by reactive magnetron sputtering with nitrogen flow ratios ranging from 40%–70% to investigate the effect of nitrogen stoichiometry on corrosion behavior in simulated alkaline seawater (pH ≈ 14, chloride-containing). Microstructural characterization (Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), Grazing Incidence X-Ray Diffraction (GIXRD), Transmission Electron Microscopy (TEM), X-Ray Photoelectron Spectroscopy (XPS), Atomic Force Microscopy (AFM)) reveals that a 60% nitrogen ratio promotes grain refinement, improved CrN/AlN phase stoichiometry, and reduced oxygen-related defects, resulting in a dense columnar structure with minimized diffusion pathways. Electrochemical measurements show that this condition yields the lowest corrosion current density (0.297 μA·cm⁻²) and the highest polarization resistance (123.9 kΩ·cm²). Electrochemical impedance spectroscopy confirms enhanced charge transfer resistance and suppressed ionic transport at the coating/electrolyte interface. The results establish a clear correlation between nitrogen-controlled phase evolution, defect density, and passivation kinetics in highly alkaline chloride environments relevant to seawater electrolysis. This study targets the fabrication of protective coatings for alkaline seawater electrolysis via nitrogen flow ratio optimization. The optimized CrAlN coating achieves remarkably improved corrosion resistance compared with existing coatings, showing promising practical value for long-term stable seawater electrolysis. Full article

A ternary CdS–MoS₂–rGO photocathode was developed to enhance visible light-driven hydrogen evolution through interfacial heterostructure engineering. The composite was fabricated via a solution-based deposition method followed by thermal conversion, resulting in crystalline CdS and MoS₂ phases that were uniformly integrated within a conductive reduced graphene oxide (rGO) framework. Structural and surface analyses (XRD and XPS) confirmed the coexistence of Cd²⁺, Mo⁴⁺, and S²⁻ chemical states without detectable secondary phases. Photoelectrochemical measurements revealed that the ternary architecture significantly improves charge separation efficiency and interfacial charge-transfer kinetics compared to binary and single-component films. The CdS–MoS₂–rGO photocathode exhibited the highest photocurrent density, reduced charge-transfer resistance, and favorable Tafel slope under visible-light irradiation (0.25 sun, neutral electrolyte). Gas chromatography measurements verified that these electrochemical enhancements translate into increased hydrogen production rates, following the trend: CdS–MoS₂–rGO > CdS–rGO > MoS₂–rGO >> rGO. Applied bias photon-to-current efficiency (ABPE) analysis further confirmed improved photon utilization efficiency in the ternary system. The enhanced performance is attributed to synergistic integration of CdS (light harvesting), rGO (rapid electron transport), and MoS₂ (catalytic edge sites), which suppresses recombination and accelerates proton reduction kinetics. These findings demonstrate that rational multi-component heterostructure design is an effective strategy for improving hydrogen evolution rate under mild operating conditions. Full article

Electrolysis of water is a promising emission-free approach of hydrogen production, making water electrolyzers important for many renewable energy systems. Electrochemical electrodes enriched with nanocatalysts can significantly advance such technologies, but the use of nanomaterials, deployed as packed powders or painted films, is generally limited by durability and reusability challenges. To overcome these deficiencies, we have fabricated hierarchical hybrid electrode (HHE) monoliths comprising carpet-like arrays of multiwalled carbon nanotubes covalently bonded to porous reticulated carbon foams that are further functionalized with strongly attached nanocatalysts. This paper presents our investigation of HHE materials with CNT carpets and palladium nanoparticle (PdNP) catalysts in two key electrolysis reactions: hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Their performances in different electrolytes have been evaluated using cyclic voltammetry, linear sweep voltammetry and Tafel analysis. This architecture provided multi-faceted advantages, and the contribution of each nanocomponent in the monolith has been analyzed. The presence of Pd-NP in the HHE also improved the electrode’s tolerance to Cl⁻ ions, which is very promising for saline water electrolysis. These studies indicate that the HHE architecture of electrochemical electrodes can be a versatile and tunable option for future electrochemical systems relevant to renewable energy applications. Full article

Alkaline water electrolysis (AWE) is a pivotal technology for sustainable hydrogen production. However, hydrogen permeation through its membranes remains a critical concern, as excessive gas crossover can lead to the formation of explosive mixtures and pose severe safety hazards. While conventional measurement techniques, such as pressure drop and electrochemical methods, are suitable for porous membranes, they exhibit inherent limitations when applied to dense membranes such as anion exchange membranes. This study proposes a cross-flow measurement methodology applicable to all types of AWE membranes. Unlike traditional dead-end configurations, the cross-flow approach effectively mitigates impurity accumulation and maintains a continuous electrolyte flow parallel to the membrane surface. This configuration ensures uniform electrolyte distribution, minimizes local concentration and pressure fluctuations, and enhances measurement reliability and reproducibility relative to the conventional dead-end flow. Furthermore, the methodology ensures accurate and reproducible measurements, demonstrating enhanced detection capability for dense membranes with intrinsically low permeability by mitigating fouling and concentration polarization effects. These findings provide a robust framework for the development of high-performance membranes designed to suppress dissolved hydrogen permeability. Full article

One of the main challenges in hydrogen production via electrolysis is the reliable measurement of the electrical work supplied. In this work, a robust electronic data acquisition system was developed to obtain precise and accurate data to evaluate the electrical work. The electrolytic concentration and electrical work were the main variables in this study. The supplied electrical energy was analyzed under both constant and pulsed voltage conditions. The results reveal that hydrogen production depends on voltage amplitude, PWM, and electrolyte concentration. The applied voltage shows a slight positive correlation with hydrogen production. PWM influences hydrogen production in the range of 0 to 1 Hz, while no significant effect is observed at higher frequencies. Electrolyte concentration has a stronger influence on hydrogen production in the range of 0.125 to 0.25 M. The optimal operating conditions were identified at 0.375 M, 1 Hz and 6 VDC, and under these conditions the hydrogen production is 0.145 mL/s and the specific energy is 165 kWh/kg. Full article

Hydrogen production is gaining increasing importance as a key component of the transition toward carbon-neutral energy systems. In this study, the prediction of hydrogen generation in membraneless alkaline water electrolyzers (MAWEs) is investigated using deep-learning-based time-series modeling. A single-input modeling framework is adopted, where only the system current is used as the input variable. Experimental current signals obtained from long-duration tests conducted at electrolyte concentrations between 5 and 35 g KOH (7200 s per experiment) are employed as the model inputs, while mass-based hydrogen production (in grams) is used as the output variable. Two recurrent neural network architectures, namely Long Short-Term Memory (LSTM) and Gated Recurrent Unit (GRU), are implemented, and their predictive performance is comparatively evaluated using RMSE, MAE, and R² metrics. In addition to deep learning models, classical approaches including Linear Regression, ARIMA, and Naïve Forecast are also considered for comparison. The results show that both models are capable of accurately reproducing the hydrogen-production dynamics across the entire concentration range. In particular, the prediction accuracy improves notably at medium and high electrolyte concentrations, where the coefficient of determination (R²) approaches 0.98. The residual distributions remain narrow and symmetric around zero, indicating the absence of systematic estimation bias. The results also show that classical models can achieve comparable performance under stable operating conditions, while deep learning models provide advantages in capturing nonlinear and dynamic behavior. While LSTM and GRU exhibit comparable accuracy, each architecture provides complementary advantages under different operating conditions. These findings indicate that deep-learning-based time-series modeling constitutes a lightweight and reliable framework for prediction and control applications in MAWE systems. Overall, this study demonstrates the applicability of data-driven models for the dynamic characterization of membraneless water electrolysis. Full article

Strontium (Sr) is an essential trace element that plays a critical role in bone health, calcium absorption, cardiovascular function, and nerve function. In this experiment, fresh-cut peaches were treated with different concentrations of strontium chloride (SrCl₂) to study the effects of SrCl₂ on the antioxidant system, endogenous nitric oxide (NO) metabolism, and endogenous hydrogen sulfide (H₂S) metabolism, aiming to investigate the regulatory mechanism of Sr on postharvest quality of horticultural products. The results showed that, compared with the control, 320 μM SrCl₂ significantly suppressed the respiration rate by 15.10% and delayed the respiratory peak by 2 days. Meanwhile, SrCl₂ treatment effectively inhibited the rise in electrolyte leakage (EL), color difference, and weight loss, and delayed the decline in fruit firmness. In addition, SrCl₂ treatment significantly up-regulated the gene expression levels and enzyme activities of the antioxidant system, the AsA-GSH cycle, NO, and H₂S metabolism, which reduced the loss of antioxidants, enhanced the ability of fruits to scavenge hydrogen peroxide (H₂O₂), hydroxyl radical (˙OH), and superoxide anion (O₂⁻˙), and lowered the malondialdehyde (MDA) content. It suggests that SrCl₂ treatment has a positive effect on maintaining the postharvest quality of fresh-cut peaches, which appears to be associated with increased endogenous production of NO and H₂S, thereby enhancing antioxidant system activity. Full article

Electrocatalytic seawater splitting is an ideal strategy for the large-scale production of green hydrogen. Compared to scarce freshwater, oceanic seawater electrolysis represents a game-changer for the hydrogen economy. Herein, we report a cost-effective one-step synthesis of binder-free, self-supported 3D nickel–manganese–cobalt (NiMnCo) coatings on titanium (Ti) substrates and evaluated their electrocatalytic performance for the hydrogen evolution reactions (HERs) in alkaline media (1.0 M KOH), simulated seawater (SSW, 1.0 M KOH + 0.5 M NaCl) and alkaline natural seawater (ASW, 1.0 M KOH + natural seawater). These ternary coatings were electrodeposited on Ti substrates using an electrochemical deposition method via a dynamic hydrogen bubble template (DHBT) technique. The optimized ternary NiMnCo/Ti-2 electrocatalyst exhibited an enhanced HER activity in both alkaline and seawater media, achieving an ultra-low overpotential of 29, 59 and 66 mV to reach the benchmark current density of 10 mA cm⁻² in SSW, ASW and 1.0 M KOH, respectively. This efficient 3D ternary NiMnCo/Ti-2 electrocatalyst demonstrated stable long-term performance at a constant potential of −0.23 V (vs. RHE) and a constant current density of 10 mA cm⁻² for 50 h without any significant degradation. Furthermore, it exhibited long-term stability in alkaline electrolyte and simulated seawater during multi-step chronopotentiometric testing at variable current densities from 20 mA cm⁻² to 100 mA cm⁻² for 18 h. This superior performance can be attributed to its unique intermetallic structure and multi-component composition, which provides good Cl⁻ resistance, electrochemical stability and synergistic effects among its constituents. Therefore, the optimized NiMnCo/Ti-2 electrocatalyst is a promising candidate for practical seawater electrolysis aiming at green hydrogen production. Full article

The rational design of cost-effective and highly active electrocatalysts for overall water splitting remains a critical challenge for sustainable hydrogen production. Herein, we report a two-dimensional reduced graphene oxide (rGO)-supported Mo₂S₃ nanohybrid catalyst with a tunable electronic structure engineered through interfacial coupling. The intimate integration of Mo₂S₃ nanoflakes with conductive rGO nanosheet facilitates rapid electron transport, enhanced active site exposure, and optimized adsorption energetics for reaction intermediates. Structural and spectroscopic analyses confirm strong electronic interaction between Mo₂S₃ and rGO, leading to modulated charge density distribution and improved intrinsic catalytic activity. Electrochemical evaluations reveal significantly reduced overpotentials for oxygen evolution reaction (OER) with 166 mV overpotential at 10 mA cm⁻² current density, along with favorable Tafel kinetics with 38.1 mV dec⁻¹ and long-term operational stability in alkaline electrolyte. The rGO-Mo₂S₃-2||Pt-C cell delivers 10 mA cm⁻² at 1.64 V, indicating efficient alkaline water splitting. The enhanced performance is attributed to synergistic effects arising from electronic modulation, enhanced active sites, and accelerated interfacial charge transfer. Full article

This study details the design, fabrication, and experimental validation of three unique alkaline electrolysers, each featuring a modified internal electrode-support geometry. Their performance was comprehensively assessed through polarisation curve analysis in individual, partial, and global configurations. The development followed the Advanced Product Quality Planning (APQP) methodology, employing pure nickel electrodes to ensure stability. The results demonstrate that specific geometric alterations directly influence electrochemical performance and overall efficiency. By operating three electrolysers simultaneously, the system achieved an overall efficiency of 42% and a maximum oxyhydrogen production rate of 10 L·min⁻¹, with minimal electrolyte carryover. This systematic work establishes essential design guidelines to advance the technology from Technology Readiness Level (TRL) 5 to TRL 6, facilitating the development of a reliable 5 kW hydrogen production system. Full article

This study develops and applies an integrated modeling framework to assess the solar-to-hydrogen-to-power potential across Romania’s five hydrogen ecosystems defined in the National Hydrogen Strategy. The methodology couples PVGIS-based photovoltaic yield simulations, based on hourly solar irradiation data and including system losses, with MHOGA-based electrolysis simulation, enabling a quantitative-energetic-environmental (Q-E-E) system-level assessment. A 1 MW photovoltaic plant was simulated under three mounting configurations (15° fixed tilt, optimal tilt, and solar tracking) and interfaced with alkaline (AEL) and proton exchange membrane electrolysers (PEMEL). Specific photovoltaic yields reach up to 360 kWh/m²_PV·year under tracking conditions, producing up to 7.5 kg/m²_PV·year (AEL) and 6.8 kg/m²_PV·year (PEMEL), expressed per unit of photovoltaic surface area to enable consistent comparison across the configurations considered. The modeled round-trip efficiency of the full solar–electricity–hydrogen–electricity chain is 38.32% for AEL and 34.57% for PEMEL. Life-cycle-based emission modeling yields 0.92 kg CO₂/kg H₂ (AEL) and 1.03 kg CO₂/kg H₂ (PEMEL), while avoided emissions exceed 250 g CO₂/kWh relative to grid intensity. Land-use modeling indicates area requirements between 9402 and 18,804 m²/MW, depending on the Ground Coverage Ratio. Results demonstrate that system configuration exerts a stronger influence than regional solar variability in determining hydrogen yield, highlighting the need for integrated techno-environmental optimization for large-scale deployment. Full article

Urea electrolysis has emerged as a promising alternative to conventional water electrolysis for hydrogen production, owing to low electrical energy consumption as well as organic wastewater. However, the practical implementation of this approach is primarily constrained by the lack of cost-effective and efficient electrocatalysts. Thus, the development of earth-abundant, non-precious metal-based bifunctional electrocatalysts toward both the hydrogen evolution reaction (HER) and the urea oxidation reaction (UOR) is of critical importance. In this context, nanostructured, reduced nickel-cobalt tungstate supported on Ni foam is fabricated as a binder-free, freestanding electrode via a two-step hydrothermal process followed by partial thermal reduction. By systematically tuning the precursor concentrations of Ni, Co, and W, the morphology and electronic structure of the material are effectively modulated. The introduction of oxygen vacancies through partial thermal reduction plays a key role in enhancing charge transport properties. The optimized NiCo@W_0.5/NF electrode exhibits a porous, flower-like architecture and demonstrates excellent bifunctional electrocatalytic activity toward both UOR and HER, accompanied by improved mass transport behavior. When employed as both the anode and cathode for overall urea electrolysis, NiCo@W_0.5/NF requires a low cell voltage of only 1.68 V to achieve a current density of 100 mA cm⁻² and delivers impressive operational stability in an optimized electrolyte composed of 3 M KOH and 0.33 M urea. These results indicate that NiCo@W_0.5/NF is a highly promising and efficient bifunctional electrode material for urea assisted hydrogen production. Full article