Search Results (106)

The development of high-performance adsorbent materials is crucial for any sorption-based energy conversion process. In such a context, composite sorbent materials, although promising in terms of performance and stability, are often challenging to shape into complex geometries. Additive manufacturing, also known as 3D printing, has emerged as a powerful technique for fabricating intricate structures with tailored properties. In this paper, an innovative three-dimensional structure, constituted by zeolite as filler and sulfonated polyether ether ketone as matrix, was obtained using additive manufacturing technology, which is mainly suitable for sorption-based energy conversion processes. The lattice structure was tailored in order to optimize the synthesis procedure and material stability. The complex three-dimensional lattice structure was obtained without a metal or plastic reinforcement support. The composite structure was evaluated to assess its structural integrity using morphological analysis. Furthermore, the adsorption/desorption capacity was evaluated using water-vapor adsorption isobars at 11 mbar at equilibrium in the temperature range 30–120 °C, confirming good adsorption/desorption capacity. Full article

This paper presents the results of an investigation into the catalytic activity and selectivity of rhodium-based catalysts supported on natural zeolite clinoptilolite from the Shankanai field (Kazakhstan) in the dehydrogenation of light alkanes from associated petroleum gas (APG). Three modifications of the catalyst have been studied: basic 1%Rh/HCpt, modified with tin 1%Rh/10%SnO/HCpt, and combined with additives of tin and potassium 1%Rh/10%SnO/5%K₂O/HCpt. It has been shown that the addition of tin contributes to increased thermal stability and a decreased coking rate, while the addition of potassium suppresses side reactions (cracking and isomerization), increasing the selectivity for olefins. The highest yield of olefins (~30%) is achieved with the 1%Rh/10%SnO/5%K₂O/HCpt catalyst in the presence of water vapor. Using scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM), improved distribution of active components and reduced catalyst deactivation have been confirmed. The obtained data demonstrate the potential of the developed systems for the efficient processing of APG and the selective synthesis of olefins. Full article

Over the last decade, polymeric carbon nitrides (PCNs) have received exponentially growing attention as metal-free photocatalytic platforms for green energy generation and environmental remediation. Although PCNs can be easily synthesized from abundant precursors in a powdered form, progress in the field of photoelectrochemical applications requires effective methods for the fabrication of PCN films endowed with suitable mechanical stability and modular chemico-physical properties. In this context, as a proof-of-concept, we report herein on a simple and versatile chemical vapor infiltration (CVI) strategy for one-step PCN growth on porous Ni foam substrates, starting from melamine as a precursor compound. Interestingly, tailoring the reaction temperature enabled to control the condensation degree of PCN films from melem/melon hybrids to melon-like materials, whereas the use of different precursor amounts directly affected the mass and morphology of the obtained deposits. Altogether, such features had a remarkable influence on PCN electrochemical performances towards the oxygen evolution reaction (OER), yielding, for the best performing systems, Tafel slopes as low as ≈65 mV/dec and photocurrent density values of ≈1 mA/cm² at 1.6 V vs. the reversible hydrogen electrode (RHE). Full article

The aim of this study is to investigate a green and efficient hydrothermal synthesis method for obtaining a high-purity MIL-100(Fe) metal–organic framework (MOF) without using hazardous HF acid or other toxic reagents. The influence of various synthesis conditions (reactant ratios and reaction times) and washing protocols on the MOF’s properties and crystallinity was investigated. Additionally, the adsorption capacities of the synthesized MIL-100(Fe) for hydrogen (H₂), carbon dioxide (CO₂), and water vapor were evaluated at different temperatures and pressures. By analyzing the adsorption behavior, this research study aims to assess the potential of this material for thermal or specific gas storage applications. MF-S1 synthesis, using less iron and water, produces the purest MIL-100(Fe), as confirmed by XRD and FTIR. MF-S1-W2, with additional washing, is ideal for gas adsorption due to its crystallinity, purity, and high surface area. It effectively stores hydrogen (0.25 wt.% at 5 °C), CO₂ (32.6 wt.% at 5 °C), and water vapor (47.5 wt.% at 30 °C). Full article

This study evaluates the spatio-temporal variations in vegetation ecological quality (EQI) on the Tibetan Plateau (TP) from 2001 to 2020 by integrating net primary productivity (NPP) and fractional vegetation cover (FVC). The results show that annual EQI increased at 0.8 decade⁻¹, with 65.6% of areas exhibiting improvement, particularly in sparse grasslands and mixed forests. NPP and FVC rose by 5.4 g C m⁻² decade⁻¹ and 0.008 decade⁻¹, respectively, displaying southeast–northwest spatial gradients. Climate warming (0.18 °C decade⁻¹) and wetting (27.5 mm decade⁻¹) drove EQI trends, with temperature positively correlating with EQI in eastern forests (29% mixed forests) but negatively in southern grasslands. Atmospheric circulation further modulated EQI: enhanced zonal water vapor flux and monsoon indices (IVarea, EMI) significantly impacted 10–25% of areas. Despite persistent improvement trends (13.9% of TP), 5.9% of regions face sustained degradation risks, emphasizing the need for climate-adaptive vegetation management. This synthesis of ecological-climate coupling provides actionable insights for conservation on the warming TP. Full article

2-Methyl-2-cyclopentenone (MCP) is the main by-product of the newly developed heterogeneous catalysis process for producing crotonaldehyde, which serves as an important intermediate for drug synthesis. However, how to recover and purify MCP from the product mixture is not known. To decipher this, a computer-aided process based on the measured phase-equilibrium data was developed. The improved Rose–Williams equilibrium kettle was used to measure the vapor–liquid equilibrium data for MCP–crotonaldehyde and MCP–water. Surprisingly, MCP and water formed a minimum azeotrope, which aided its own recovery from its dilute solution. The mole fraction of MCP in the azeotrope was 9.1%, the mole fraction of water was 90.9%, and the azeotropic temperature was 96.8 °C. Equilibrium data from the two binary systems were correlated using the Wilson and NRTL activity coefficient models. The NRTL-RK model was selected to simulate the process for recovering and purifying MCP. A two-column process was developed and optimized in this study, and the aim of effectively utilizing the by-product MCP was achieved with this process. Full article

We prepared antimony metal films via electrodeposition, followed by the synthesis of Sb₂S₃ films through a chemical vapor phase reaction. Finally, an Sb₂O₃ film was deposited onto the Sb₂S₃ film using a chemical bath method, successfully constructing a heterojunction photocathode of Sb₂S₃/Sb₂O₃; the synthesized Sb₂S₃/Sb₂O₃ heterojunction is classified as a Type I heterostructure. The resulting Sb₂S₃/Sb₂O₃ heterojunction exhibited a photocurrent density of −0.056 mA cm⁻² at −0.15 V (vs. RHE), which is 1.40 times higher than that of Sb₂S₃ alone under simulated solar illumination. Additionally, the Sb₂S₃/Sb₂O₃ heterojunction demonstrated a lower carrier recombination rate and a faster charge transfer rate compared to Sb₂S₃, as evidenced by photoluminescence and electrochemical impedance spectroscopy tests. For these reasons, the Sb₂S₃/Sb₂O₃ heterojunction obtained a hydrogen precipitation rate of 0.163mL cm⁻² h⁻¹, which is twice the hydrogen precipitation rate of Sb₂S₃, under the condition of 60 min of light exposure. The significant enhancement in photoelectrochemical performance is attributed to the formation of the Sb₂S₃/Sb₂O₃ heterojunction, which improves both carrier separation and charge transfer efficiency. This heterojunction strategy holds promising potential for visible light-driven photoelectrochemical water splitting. Full article

Halogenated benzaldehydes possess unique chemical properties that render them valuable in pharmaceutical synthesis, pesticide formulation, and dye production. However, thorough thermodynamic data for these compounds remain scarce. This study aims to fill this knowledge gap by investigating key physical properties of several halogenated benzaldehydes, namely 4-chlorobenzaldehyde, 4-bromobenzaldehyde, 2,3-dichlorobenzaldehyde, 2,4-dichlorobenzaldehyde, and 2,6-dichlorobenzaldehyde. The physical properties determined in this study include volatility, phase transitions, and water solubility, all of which are crucial for predicting the environmental fate of these compounds. The vapor pressures of both crystalline and liquid phases were measured using a reliable static method, allowing for the determination of standard molar enthalpies, entropies, and Gibbs energies of sublimation and vaporization, as well as their triple points. The melting temperature and molar enthalpy, along with the isobaric molar heat capacity of the crystalline phase, were assessed using differential scanning calorimetry. Water solubility was evaluated at 25 °C through the saturation shake-flask method, complemented by ultra-violet visible spectroscopy. By combining sublimation and solubility data, additional properties such as Gibbs energies of hydration and Henry’s law constants were derived. The experimental results were integrated into existing databases, enhancing the predictive models for properties including melting temperature, vapor pressure, solubility, Gibbs energy of hydration, and Henry’s constant. These findings significantly improve the environmental modeling capabilities, providing valuable insights into the mobility and fate of halogenated benzaldehydes in various environmental contexts. Full article

Hydrogen production via water splitting is a crucial strategy for addressing the global energy crisis and promoting sustainable energy solutions. This review systematically examines water-splitting mechanisms, with a focus on photocatalytic and electrochemical methods. It provides in-depth discussions on charge transfer, reaction kinetics, and key processes such as the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Various electrode synthesis techniques, including hydrothermal methods, chemical vapor deposition (CVD), pulsed laser deposition (PLD), and radio frequency sputtering (RF), are reviewed for their advantages and limitations. The role of carbon-based materials such as graphene, biochar, and graphitic carbon nitride (g-C₃N₄) in photocatalytic and photoelectrochemical (PEC) water splitting is also highlighted. Their exceptional conductivity, tunable band structures, and surface functionalities contribute to efficient charge separation and enhanced light absorption. Further, advancements in heterojunctions, doped systems, and hybrid composites are explored for their ability to improve photocatalytic and PEC performance by minimizing charge recombination, optimizing electronic structures, and increasing active sites for hydrogen and oxygen evolution reactions. Key challenges, including material stability, cost, scalability, and solar spectrum utilization, are critically analyzed, along with emerging strategies such as novel synthesis approaches and sustainable material development. By integrating water splitting mechanisms, electrode synthesis techniques, and advancements in carbon-based materials, this review provides a comprehensive perspective on sustainable hydrogen production, bridging previously isolated research domains. Full article

Transition metal sulfide (TMS)-based electrocatalysts have received considerable attention in the field of sustainable energy, especially for their high activity in the hydrogen evolution reaction (HER). This review summarizes how researchers have improved the performance of TMSs by adjusting their composition. This review introduces the research background of transition metal sulfides and clarifies the reaction mechanism of the HER and its performance evaluation indicators. Then, it elaborates on the general synthesis techniques for preparing TMS materials, including hydrothermal methods, electrochemical deposition, liquid-phase exfoliation, chemical vapor deposition, and other methods. Moreover, it discusses the realization of excellent electrocatalytic performance in the HER through doping, hole treatment, heterostructures, and multi-sulfides. Finally, this review summarizes the current challenges and future development opportunities of TMS materials in the field of water electrolysis for hydrogen production. Full article

This research explores the synthesis of carboxymethyl cellulose (CMC) for the development of a cost-effective bioplastic film that can serve as a sustainable alternative to synthetic plastic. Replacing plastic packaging with CMC-based films offers a solution for mitigating environmental pollution, although the inherent hydrophilicity and low mechanical strength of CMC present significant challenges. To address these limitations, zinc oxide nanoparticles (ZnO NPs) were employed as a biocompatible and non-toxic reinforcement filler to improve CMC’s properties. A solution casting method which incorporated varying concentrations of ZnO NPs (0%, 5%, 10%, 15%, 20%, and 25%) into the CMC matrix allowed for the preparation of composite bioplastic films, the physicochemical properties of which were analyzed using scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. The results revealed that the ZnO NPs were well-integrated into the CMC matrix, thereby improving the film’s crystallinity, with a significant shift from amorphousness to the crystalline phase. The uniform dispersion of ZnO NPs and the development of hydrogen bonding between ZnO and the CMC matrix resulted in enhanced mechanical properties, with the film CZ₂₀ exhibiting the greatest tensile strength—15.12 ± 1.28 MPa. This film (CZ₂₀) was primarily discussed and compared with the control film in additional comparison graphs. Thermal stability, assessed via thermogravimetric analysis, improved with an increasing percentage of ZnO Nps, while a substantial decrease in water vapor permeability and oil permeability coefficients was observed. In addition, such water-related properties as water contact angle, moisture content, and moisture absorption were also markedly improved. Furthermore, biodegradability studies demonstrated that the films decomposed by 71.43% to 100% within 7 days under ambient conditions when buried in soil. Thus, CMC-based eco-friendly composite films have the clear potential to become viable replacements for conventional plastics in the packaging industry. Full article

The laser pyrolysis technique was used in the synthesis of magnetic iron oxide nanopowders in the presence of ethanol vapors as a sensitizer. This technique uses the energy from a continuous-wave CO₂ laser operating at a 9.25 μm wavelength, which is transferred to the reactive precursors via the excited ethanol molecules, inducing a rapid heating of the argon-entrained Fe(CO)₅ vapors in the presence of oxygen. For a parametric study, different samples were prepared by changing the percentages of sensitizer in the reactive mixture. Moreover, the raw samples were thermally treated at different temperatures and their morpho-structural and magnetic properties were investigated. The results indicated a high degree of crystallinity (mean ordered dimension) and enhanced magnetic properties when high percentages of ethanol vapors were employed. On the contrary, at low ethanol concentrations, due to a decrease in the reaction temperature, nanoparticles with a very low size were synthesized. The raw particles have a dimension in the range of 2.5 to 10 nm (XRD and TEM). Most of them exhibited superparamagnetic behavior at room temperature, with saturation magnetization values up to 60 emu/g. The crystalline phase detected in samples is mainly maghemite, with a decreased carbon presence (up to 8 at%). In addition to the expected Fe-OH on the particles surfaces, C (and O) bearing functional groups such as C-OH or C=O that act as a supplementary hydrophilic agent in water-based suspension were detected. Using the as-synthesized and thermally treated nanopowders, water suspensions without or with hydrophilic agents (CMCNa, L-Dopa, chitosan) were prepared by means of a horn ultrasonic homogenizer at 0.5 mg/mL concentrations. DLS analyzes revealed that some powder suspensions maintained stable agglomerates over time, with a mean size of 100 nm, pH values between 4.8 and 5.3, and zeta-potential values exceeding 40 mV. All tested agents greatly improved the stability of 250–450 °C thermally treated NPs, with L-Dopa and Chitosan inducing smaller hydrodynamic sizes. Full article

Currently, there is a rush to develop green polymeric films such as biodegradable chitosan (CH) films to control and prevent plastic pollution from degrading the environment. This study reports a novel and sustainable green approach to the development of CH films using lemon juice (LJ) and lemon peel extract (LPE), the latter to dilute the LJ. The LPE was also utilized for the synthesis of ZnFe₂O₄ nanoparticles (NPs), adding to this work’s novelty. The crystalline size of the ZnFe₂O₄ NPs was computed to be ~16 nm. The introduction of 1% and 2% ZnFe₂O₄ NPs improved not only the mechanical properties of the films, but also their barrier properties and water solubility (WS). The tensile strength increased from 0.641 MPa to 0.835 MPa when 2% NPs were incorporated, which is almost 1.30 times greater; the NPs also enhanced the surface strength by 2.66 times, which was demonstrated by the puncture strength. The introduction of NPs occupied the vacant spaces and improved the barrier capabilities of the CH film by reducing the water vapor permeability (WVP) value from 8.752 ± 0.015 for bare CH films to 6.299 ± 0.009 for 2% NP-containing CH films. Overall, the introduction of ZnFe₂O₄ NPs boosted the mechanical and barrier properties of the CH films, and offers a promising method for developing sustainable, eco-friendly, and biodegradable polymeric films for potential packaging and medical applications to contribute to circular economic efforts. Full article

In this work, the simple fabrication of a new superhydrophobic magnetic sponge based on CNTs, NiFe₂O₄ nanoparticles, and PDMS was investigated. CNTs were synthesized by chemical vapor deposition (CVD) on a nickel ferrite catalyst supported on aluminum oxide (NiFe₂O₄/Al₂O₃). The synthesis of nickel ferrite (NiFe) was accomplished using the sol–gel method, yielding magnetic nanoparticles (43 Am²kg⁻¹, coercivity of 93 Oe, 21–29 nm). A new superhydrophobic magnetic PU/CNT/NiFe₂O₄/PDMS sponge was fabricated using a polyurethane (PU) sponge, CNTs, NiFe₂O₄ nanoparticles, and polydimethylsiloxane (PDMS) through the immersion coating method. The new PU/CNT/NiFe₂O₄/PDMS sponge exhibits excellent superhydrophobic/oleophilic/mechanical properties and water repellency (water absorption rate of 0.4%) while having good absorption of oil, olive oil, and organic liquids of different densities (absorption capacity of 21.38 to 44.83 g/g), excellent separation efficiency (up to 99.81%), the ability to be reused for removing oil and organic solvents for more than 10 cycles, and easy control and separation from water using a magnet. The new PU/CNT/NiFe₂O₄/PDMS sponge is a promising candidate as a reusable sorbent for collecting oil and organic pollutants and can also be used as a hydrophobic filter due to its excellent mechanical properties. Full article

Pore engineering is commonly used to alter the properties of metal–organic frameworks. This is achieved by incorporating different linker molecules (L) into the structure, generating isoreticular frameworks. CPO-27, also named MOF-74, is a prototypical material for this approach, offering the potential to modify the size of its one-dimensional pore channels and the hydrophobicity of pore walls using various linker ligands during synthesis. Thermal activation of these materials yields accessible open metal sites (i.e., under-coordinated metal centers) at the pore walls, thus acting as strong primary binding sites for guest molecules, including water. We study the effect of the pore size and linker hydrophobicity within a series of Ni²⁺-based isoreticular frameworks (i.e., Ni₂L, L = dhtp, dhip, dondc, bpp, bpm, tpp), analyzing their water sorption behavior and the water interactions in the confined pore space. For this purpose, we apply water vapor sorption analysis and Fourier transform infrared spectroscopy. In addition, defect degrees of all compounds are determined by thermogravimetric analysis and solution ¹H nuclear magnetic resonance spectroscopy. We find that larger defect degrees affect the preferential sorption sites in Ni₂dhtp, while no such indication is found for the other materials in our study. Instead, strong evidence is found for the formation of water bridges/chains between coordinating water molecules, as previously observed for hydrophobic porous carbons and mesoporous silica. This suggests similar sorption energies for additional water molecules in materials with larger pore sizes after saturation of the primary binding sites, resulting in more bulk-like water arrangements. Consequently, the sorption mechanism is driven by classical pore condensation through H-bonding anchor sites instead of sorption at discrete sites. Full article