Search Results (45)

Among the various renewable-powered pathways for green hydrogen production, solar photovoltaic (PV) technology represents a particularly promising option due to its environmental sustainability, widespread availability, and declining costs. However, the inherent intermittency of solar irradiance presents operational challenges for electrolyzers, particularly in terms of stability and efficiency. This study presents a MATLAB-based dynamic model of an off-grid, DC-coupled solar PV-Anion Exchange Membrane (AEM) electrolyzer system, with a specific focus on realistically estimating hydrogen output. The model incorporates thermal energy management strategies, including electrolyte pre-heating during startup, and accounts for performance degradation due to load cycling. The model is designed for a comprehensive analysis of hydrogen production by employing a 10-year time series of irradiance and ambient temperature profiles as inputs. The results are compared with two simplified scenarios: one that does not consider the equipment response time to variable supply and another that assumes a fixed start temperature to evaluate their impact on productivity. Furthermore, to limit the effects of degradation, the algorithm has been modified to allow the non-sequential activation of the stacks, resulting in an improvement of the single stack efficiency over the lifetime and a slight increase in overall hydrogen production. Full article

In bulk liquid or on solid surfaces, nanobubbles (NBs) are gaseous domains at the nanoscale. They stand out due to their extended (meta)stability and great potential for use in practical settings. However, due to the high energy cost of bubble generation, maintenance issues, membrane bio-fouling, and the small actual population of NBs, significant advancements in nanobubble engineering through traditional mechanical generation approaches have been impeded thus far. With the introduction of the electric field approach to NB creation, which is based on electrostrictive NB generation from an incoming population of “electro-fragmented” meso-to micro bubbles (i.e., with bubble size broken down by the applied electric field), when properly engineered with a convective-flow turbulence profile, there have been noticeable improvements in solid-state operation and energy efficiency, even allowing for solar-powered deployment. Here, these innovative methods were applied to a selection of upstream and downstream activities in the oil–water–fuels nexus: advancing core flood tests, oil–water separation, boosting the performance of produced-water treatment, and improving the thermodynamic cycle efficiency and carbon footprint of internal combustion engines. It was found that the application of electric field NBs results in a superior performance in these disparate operations from a variety of perspectives; for instance, ~20 and 7% drops in surface tension for CO₂- and air-NBs, respectively, a ~45% increase in core-flood yield for CO₂-NBs and 55% for oil–water separation efficiency for air-NBs, a rough doubling of magnesium- and calcium-carbonate formation in produced-water treatment via CO₂-NB addition, and air-NBs boosting diesel combustion efficiency by ~16%. This augurs well for NBs being a potent agent for sustainability in the oil and fuels sector (whether up-, mid-, or downstream), not least in terms of energy efficiency and environmental sustainability. Full article

Heterogeneous photocatalysis has emerged as a versatile and sustainable technology for the degradation of emerging contaminants in water. This review highlights recent advancements in photocatalysts design, including band gap engineering, heterojunction formation, and plasmonic enhancement to enable visible-light activation. Various reactor configurations, such as slurry, immobilized, annular, flat plate, and membrane-based systems, are examined in terms of their efficiency, scalability, and operational challenges. Hybrid systems combining photocatalysis with membrane filtration, adsorption, Fenton processes, and biological treatments demonstrate improved removal efficiency and broader applicability. Energy performance metrics such as quantum yield and electrical energy per order are discussed as essential tools for evaluating system feasibility. Special attention is given to solar-driven reactors and smart responsive materials, which enhance adaptability and sustainability. Additionally, artificial intelligence and machine learning approaches are explored as accelerators for catalyst discovery and process optimization. Altogether, these advances position photocatalysis as a key component in future water treatment strategies, particularly in decentralized and low-resource contexts. The integration of material innovation, system design, and data-driven optimization underlines the potential of photocatalysis to contribute to global efforts in environmental protection and sustainable development. Full article

Solar-driven interfacial evaporation has emerged as a sustainable and highly efficient technology for seawater desalination, attracting considerable attention for its potential to address global water scarcity. However, challenges such as low evaporation rates and salt accumulation significantly hinder the performance and operational lifespan of evaporators. Here, we present an innovative Janus-structured evaporator featuring distinct operational mechanisms through the integration of a hydrophobic PVDF-HFP@PPy photothermal membrane and a hydrophilic PVA-CF@TA-Fe³⁺ hydrogel, coupled with a unidirectional flow configuration. Distinct from conventional Janus evaporators that depend on interfacial water transport through asymmetric layers, our design achieves two pivotal innovations: (1) the integration of a lateral fluid flow path with the Janus architecture to enable sustained brine replenishment and salt rejection and (2) the creation of dual vapor escape pathways (hydrophobic and hydrophilic layers) synergized with hydrogel-mediated water activation to elevate evaporation kinetics. Under 1 sun illumination, the evaporator achieves a maximum evaporation rate of 2.26 kg m⁻² h⁻¹ with a photothermal efficiency of 84.6%, in both unidirectional flow and suspension modes. Notably, the evaporation performance remains stable across a range of saline conditions, demonstrating remarkable resistance to salt accumulation. Even during continuous evaporation of highly saline water (10% brine), the evaporator maintains an evaporation rate of 2.10 kg m⁻² h⁻¹ without observable salt precipitation. The dual anti-salt strategies—enabled by the Janus structure and unidirectional flow design—underscore the evaporator’s capability for sustained high performance and long-term stability in saline environments. These findings provide valuable insights into the development of next-generation solar evaporators that deliver high performance, long-term stability, and robustness in saline and hypersaline environments. Full article

Hydrogen energy generation plays a crucial role in enhancing the utilization of clean energy at coastal stations with abundant wind and solar resources in Antarctica. In response to the reliable demand for the application of hydrogen fuel cells in standalone observation systems in Antarctica, in this research, a power supply scheme based on a proton exchange membrane fuel cell (PEMFC) is introduced. Transient models of the PEMFC are developed, and the optimum operational and environmental conditions are determined through experimental investigations conducted at low temperatures. Based on the findings, a PEMFC-based power supply system is designed, encompassing a fuel cell stack, a measurement and control system, and an operation cabin. A temperature-coordinated control system leveraging a BP neural network, fuzzy logic rules, and the fuzzy-based active disturbance rejection control (Fuzzy-ADRC) strategy are proposed to ensure that the temperature of the PEMFC and cabin can reach the optimal state rapidly and that the output voltage is stable. The results indicate that the stack temperature reaches the specified value more rapidly than with PID and ADRC control methods when the current loading and changes in the ambient temperature are considered, and the output voltage oscillation amplitude can be more effectively minimized. This research provides preliminary guidance for a reliable energy supply scheme for PEMFCs, especially in standalone observation systems in coastal locales. Full article

Ivermectin (IVM) is a pharmaceutical antiparasitic agent with a broad range of medicinal properties that are comparable in impact to those of penicillin and aspirin. The molecule’s structural composition includes functional groups that indicate the potential for photoreactivity. However, there is a paucity of information regarding its photostability, particularly in tropical regions where parasitic diseases and intense solar radiation intersect. It would be beneficial to investigate the chemical transformation of this compound in a variety of natural aqueous environments under different irradiation sources. This knowledge gap motivated this study. Therefore, the chemical alterations of IVM were investigated in various natural aqueous media when exposed to solar radiation (UVA-Vis). In particular, an evaluation of its photostability was conducted at wavelengths of 350 and 254.5 nm. It is noteworthy that photodegradation occurred primarily at 350 nm. Additionally, IVM demonstrated photohemolytic effects on human erythrocytes, indicating phototoxicity. This suggests the presence of photoinduced mechanisms by this drug for the generation of free radicals, including singlet oxygen (¹O₂, type II mechanism), superoxide anion, and hydroxyl radical (^.O₂ and ^.OH, type I mechanism). The latter would also entail the interaction of the IVM molecule with the membrane of human red blood cells, which would signify a considerable biological impact. Furthermore, through computational calculations, potential photoproducts formed during IVM irradiation were deduced, simulating experimental conditions. Our findings contribute to an enhanced comprehension of IVM’s behavior under solar exposure, particularly in tropical contexts. Additional research is imperative to address its emerging biological activity status and potential implications for biomedical applications. Full article

Background: The issue of renewable energy (RE) source intermittency, such as wind and solar, along with the geographically uneven distribution of the global RE potential, makes it imperative to establish an energy transport medium to balance the energy demand and supply areas. A promising energy vector to address this situation is hydrogen, which is considered a clean energy carrier for various mobile and portable applications. Unfortunately, at standard pressure and temperature, its energy content per volume is very low (0.01 kJ/L). This necessitates alternative storage technologies to achieve reasonable capacities and enable economically viable long-distance transportation. Among the hydrogen storage technologies using chemical methods, liquid organic hydrogen carrier (LOHC) systems are considered a promising solution. They can be easily managed under ambient conditions, the H₂ storage/release processes are carbon-free, and the carrier liquid is reusable. However, the evolution of the proposals from the carrier liquid type and catalyst elemental composition point of view is scarcely studied, considering that both are critical in the performance of the system (operational parameters, kinetic of the reactions, gravimetric hydrogen content, and others) and impact in the final cost of the technology deployed. The latter is due to the use of the Pt group elements (PGEs) in the catalyst that, for example, have a high demand in the hydrogen production sector, particularly for polymer electrolyte membrane (PEM) water electrolysis. With that in mind, our objective was to examine the evolution and the focus of the research in recent years related to proposals of LOHCs and catalysts for hydrogenation and dehydrogenation reactions in LOHC systems which can be useful in defining routes/strategies for new participants interested in becoming involved in the development of this technology. Data sources: For this systematic review, we searched the SCOPUS database and forward and backward citations for studies published in the database between January 2011 and December 2022. Eligibility criteria: The criteria include articles which assessed or studied the effect of the type of catalyst, type of organic liquid, reactor design(s)/configuration(s), and modification of the reactor operational parameters, among others, over the performance of the LOHC system (de/hydrogenation reaction(s)). Data extraction and analysis: The relevant data from each reviewed study were collected and organized into a pre-designed table on an Excel spreadsheet, categorized by reference, year, carrier organic liquid, reaction (hydrogenation and/or dehydrogenation), investigated catalyst, and primary catalyst element. For processing the data obtained from the selected scientific publications, the data analysis software Orbit Intellixir was employed. Results: For the study, 233 studies were included. For the liquid carrier side, benzyltoluene and carbazole dominate the research strategies. Meanwhile, platinum (Pt) and palladium (Pd) are the most employed catalysts for dehydrogenation reactions, while ruthenium (Ru) is preferred for hydrogenation reactions. Conclusions: From the investigated liquid carrier, those based on benzyltoluene and carbazole together account for over 50% of the total scientific publications. Proposals based on indole, biphenyl, cyclohexane, and cyclohexyl could be considered to be emerging within the time considered in this review, and, therefore, should be monitored for their evolution. A great activity was detected in the development of catalysts oriented toward the dehydrogenation reaction, because this reaction requires high temperatures and presents slow H₂ release kinetics, conditioning the success of the implementation of the technology. Finally, from the perspective of the catalyst composition (monometallic and/or bimetallic), it was identified that, for the dehydrogenation reaction, the most used elements are platinum (Pt) and palladium (Pd), while, for the hydrogenation reaction, ruthenium (Ru) widely leads its use in the different catalyst designs. Therefore, the near-term initiatives driving progress in this field are expected to focus on the development of new or improved catalysts for the dehydrogenation reaction of organic liquids based on benzyltoluene and carbazole. Full article

Currently, due to the increasing impact of anthropogenic factors and changes in solar activity, the temperature on Earth is rising, posing a threat to biodiversity. Lichens are among the most sensitive organisms to climate change. Elevated ambient temperatures can have a significant impact on lichens, resulting in more frequent and intense drying events that can impede metabolic activity. It has been suggested that the possession of a diverse sterol composition may contribute to the tolerance of lichens to adverse temperatures and other biotic and abiotic stresses. The major sterol found in lichens is ergosterol (ERG); however, the regulation of the ERG biosynthetic pathway, specifically the step of epoxidation of squalene to 2,3-oxidosqualene catalyzed by squalene epoxidase during stress, has not been extensively studied. In this study, we used lichen Lobaria pulmonaria as a model species that is well known to be sensitive to air pollution and habitat loss. Using in silico analysis, we identified cDNAs encoding squalene epoxidase from L. pulmonaria, designating them as LpSQE1 for the mycobiont and SrSQE1 for the photobiont Symbiochloris reticulata. Our results showed that compared with a control kept at room temperature (+20 °C), mild temperatures (+4 °C and +30 °C) did not affect the physiology of L. pulmonaria, assessed by changes in membrane integrity, respiration rates, and PSII activity. An extreme negative temperature (−20 °C) noticeably inhibited respiration but did not affect membrane stability. In contrast, treating lichen with a high positive temperature (+40 °C) significantly reduced all physiological parameters. Quantitative PCR analysis revealed that exposing thalli to −20 °C, +4 °C, +30 °C, and +40 °C stimulated the expression levels of LpSQE1 and SrSQE1 and led to a significant upregulation of Hsps. These data provide new information regarding the roles of sterols and Hsps in the response of lichens to climate change. Full article

Lichens are symbiotic organisms that effectively survive in harsh environments, including arid regions. Maintaining viability with an almost complete loss of water and the rapid restoration of metabolism during rehydration distinguishes lichens from most eukaryotic organisms. The lichen Xanthoria parietina is known to have high stress tolerance, possessing diverse defense mechanisms, including the presence of the bright-orange pigment parietin. While several studies have demonstrated the photoprotective and antioxidant properties of this anthraquinone, the role of parietin in the tolerance of lichens to desiccation is not clear yet. Thalli, which are exposed to solar radiation and become bright orange, may require enhanced desiccation tolerance. Here, we showed differences in the anatomy of naturally pale and bright-orange thalli of X. parietina and visualized parietin crystals on the surface of the upper cortex. Parietin was extracted from bright-orange thalli by acetone rinsing and quantified using HPLC. Although acetone rinsing did not affect PSII activity, thalli without parietin had higher levels of lipid peroxidation and a lower membrane stability index in response to desiccation. Furthermore, highly pigmented thalli possess thicker cell walls and, according to thermogravimetric analysis, higher water-holding capacities than pale thalli. Thus, parietin may play a role in desiccation tolerance by stabilizing mycobiont membranes, providing an antioxidative defense, and changing the morphology of the upper cortex of X. parietina. Full article

The increasing demand for efficient wastewater treatment technologies, driven by global population growth and industrialisation, highlights the necessity for advanced, reliable solutions. This study investigated the efficacy of a slurry photocatalytic membrane reactor (PMR) for the advanced removal of organic pollutants, quantified via chemical oxygen demand (COD), under natural and simulated solar light irradiation. Employing two variants of iron-doped titania as photocatalysts and a polysulfone-based polymeric membrane for the separation process, the investigation showcased COD removal efficiencies ranging from 66–85% under simulated solar light to 52–81% under natural sunlight over a 7 h irradiation period. The overall PMR system demonstrated COD removal efficiencies of 84–95%. The results confirmed the enhanced photocatalytic activity afforded by iron doping and establish solar-powered slurry PMRs as an effective, low-energy, and environmentally friendly alternative for the advanced treatment of municipal wastewater, with the research providing valuable insights into sustainable water management practices. Full article

The diatom lipidome actively regulates photosynthesis and displays a high degree of plasticity in response to a light environment, either directly as structural modifications of thylakoid membranes and protein–pigment complexes, or indirectly via photoprotection mechanisms that dissipate excess light energy. This acclimation is crucial to maintaining primary production in marine systems, particularly in polar environments, due to the large temporal variations in both the intensity and wavelength distributions of downwelling solar irradiance. This study investigated the hypothesis that Arctic marine diatoms uniquely modify their lipidome, including their concentration and type of pigments, in response to wavelength-specific light quality in their environment. We postulate that Arctic-adapted diatoms can adapt to regulate their lipidome to maintain growth in response to the extreme variability in photosynthetically active radiation. This was tested by comparing the untargeted lipidomic profiles, pigmentation, specific growth rates and carbon assimilation of the Arctic diatom Porosira glacialis vs. the temperate species Coscinodiscus radiatus during exponential growth under red, blue and white light. Here, we found that the chromatic wavelength influenced lipidome remodeling and growth in each strain, with P. glacialis showing effective utilization of red light coupled with increased inclusion of primary light-harvesting pigments and polar lipid classes. These results indicate a unique photoadaptation strategy that enables Arctic diatoms like P. glacialis to capitalize on a wide chromatic growth range and demonstrates the importance of active lipid regulation in the Arctic light environment. Full article

Tandem photoelectrochemical cells (PECs) are devices useful for water splitting (WS) with the production of oxygen at the photoanode (PA) and hydrogen at the photocathode (PC) by adsorbing more than 75% of the solar irradiation; a portion of the UV/Vis direct solar irradiation is captured by the PA and a diffused or transmitted IR/Vis portion by the PC. Herein, Ti-doped hematite (PA) and CuO (PC) were employed as abundant and non-critical raw semiconductors characterised by proper band gap and band edge banding for the photoelectrochemical WS and absorption of sunlight. The investigation of inexpensive PEC was focused on the scalability of an active area from 0.25 cm² to 40 cm² with a rectangular or square shape. For the first time, this study introduces the novel concept of a glass electrode membrane assembly (GEMA), which was developed with an ionomeric glue to improve the interfacial contact between the membrane and photoelectrodes. On a large scale, the electron–hole recombination and the non-optimal photoelectrodes/electrolyte interface were optimized by inserting a glass support at the photocathode and drilled fluorine tin oxide (FTO) at the photoanode to ensure the flow of reagents and products. Rectangular 40 cm² PEC showed a larger maximum enthalpy efficiency of 0.6% compared to the square PEC, which had a value of 0.37% at a low bias-assisted voltage (−0.6 V). Furthermore, throughput efficiency reached a maximum value of 1.2% and 0.8%, demonstrating either an important effect of the PEC geometries or a non-significant variation of the photocurrent within the scalability. Full article

The growing amount of space debris in geocentricorbit poses a significant threat to the future of space operations. To mitigate this problem, current international guidelines state that a satellite should be able to deorbit or insert into a graveyard orbit within 25 years from the end of its operational life. In this context, drag-enhancing devices such as drag sails are currently an active field of research and development because of their ability to make a spacecraft decay from low Earth orbit without the need for any on-board propellant. Drag sails, conceptually similar to solar sails, are thin membranes deployed by a spacecraft at the end of its operational life to increase the area-to-mass ratio and, consequently, atmospheric drag. To be effectively exploited, a drag sail should maximize the surface area exposed to atmospheric particle flow. However, this would require a fully functional three-axis stabilization system, which may either be unavailable or non-functional on an orbiting satellite after years of space operations. To simplify the deorbiting phase, in this paper we propose to use a spin-deployed and spin-stabilized drag sail, which represents a reasonable compromise between simplicity of implementation and deorbiting performance in terms of total decay time. In fact, a spinning drag sail could take advantage of centrifugal force to unfold and of gyroscopic stiffness to maintain an inertially fixed axis of rotation. Numerical simulations accounting for the main perturbation effects quantify the effectiveness of the proposed device compared with an optimal configuration (i.e., a three-axis stabilized drag sail) and a tumbling drag sail. Full article

Photocatalysis has emerged as a promising technology for the removal of emerging contaminants such as antibiotics from water. Fixing photocatalytic materials on polymers to prepare applicable membranes is a feasible method for applying photocatalysis. This study explored the preparation of composite PAN-TiO₂ and PAN-TiO₂-rGO (PAN-rGTi) photocatalytic membranes by combining TiO₂, TiO₂-reduced graphene oxide (rGO) and polyacrylonitrile (PAN) using electrospinning. Characterization through SEM and EDS analysis confirms the composite membrane’s microstructure and elemental composition. The electrospun PAN-TiO₂ and PAN-rGTi composite membranes exhibit a stable and efficient photocatalytic performance in degrading sulfamethoxazole (SMX) and enrofloxacin (ENR), two typical antibiotics commonly found in water bodies. Photocatalytic degradation experiments under simulated solar light reveal the superior performance of the composite photocatalytic membranes compared to PAN alone, with a notable increase in the reaction rate constants of PAN-TiO₂ (1.8 to 2.2 times for SMX and 3.2 to 4.0 times for ENR) and even higher enhancements for PAN-rGTi (2.8 to 3.0 times for SMX and 5.4 to 6.5 times for ENR) compared to PAN alone. Despite minor decreases (from 97.6% to 90.4%) in activity over five cycles, the photocatalytic composite membranes remain effective, showcasing their stability and recyclability. This study highlights the potential application of PAN-TiO₂ and PAN-rGTi composite membranes as sustainable and effective materials for removing emerging contaminants from water. Further exploration should focus on optimizing materials for specific emerging contaminants and improving their application feasibility for wastewater and water treatment and water purification in water bodies. Full article

This study presents a relatively low-cost method for modifying TiO₂-based materials for photocatalytic bacterial inactivation. The photocatalytic inactivation of Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus epidermidis) bacteria using modified sulphated TiO₂ was studied. The modification focused on the reduction of TiO₂ by ammonia agents and hydrogen at 400–450 °C. The results showed a high impact of sulphate species on the inactivation of E. coli. The presence of these species generated acid sites on TiO₂, which shifted the pH of the reacted titania slurry solution to lower values, around 4.6. At such a low pH, TiO₂ was positively charged. The ammonia solution caused the removal of sulphate species from TiO₂. On the other hand, hydrogen and ammonia molecules accelerated the removal of sulphur species from TiO₂, as did heating it to 450 °C. Total inactivation of E. coli was obtained within 30 min of simulated solar light irradiation on TiO₂ heat-treated at 400 °C in an atmosphere of Ar or NH₃. The S. epidermidis strain was more resistant to photocatalytic oxidation. The contact of these bacteria with the active titania surface is important, but a higher oxidation force is necessary to destroy their cell membrane walls because of their thicker cell wall than E. coli. Therefore, the ability of a photocatalyst to produce ROS (reactive oxidative species) will determine its ability to inactivate S. epidermidis. An additional advantage of the studies presented is the inactivation of bacteria after a relatively short irradiation time (30 min), which does not often happen with photocatalysts not modified with noble metals. The modification methods presented represent a robust and inexpensive alternative to photocatalytic inactivation of bacteria. Full article