Artículos SCI

Abstract

In this study, the potential of a bimetallic Metal-Organic Framework Zn-MIL53(Fe) for electro-Fenton catalysis was evaluated. After the material characterisation, its catalytic activity was validated in Fenton reaction to degrade a model organic pollutant: Rhodamine B. After that, the evaluation of Zn-MIL53(Fe) as electro-Fenton catalyst was performed and improved outcomes were reached by electro-Fenton regarding anodic oxidation. Then, electro-Fenton treatment optimisation was carried out using response surface methodology assays considering different catalyst dosages (7.2-43.2 mg), current intensities (5-45 mA) and treatment time (30-90 min) in a volume of 0.1 L. Under optimal conditions, a degradation rate over 90 % for Fluoxetine and Sulfamethoxazole in synthetic wastewater was achieved within 90 min, using graphite sheet as anode and nickel foam as cathode (25 mA), with a catalyst dosage of 43.2 mg in a volume of 0.1 L. Additionally, its application in the pathogen inactivation was evaluated using different gram-negative and gram-positive bacteria. Complete eliminations of both types of bacteria were reached in 5 min using the optimal conditions. In the end, Zn-MIL53(Fe) was proven as a reusable material, capable of performing 3 complete cycles of electro-Fenton treatment for both types of pollutants bacteria and pharmaceuticals, which makes it a promising candidate for more efficient wastewater treatment applications which involve the Fenton reaction.

Abstract

In this paper, visible light-activated phosphorus-doped TiO2 (P-TiO2) was used as a photoactive phase to prepare polymer composites for the degradation of the pesticide thiacloprid under direct sunlight irradiation. In particular, a monolithic composite aerogel, consisting of P-TiO2 embedded in syndiotactic polystyrene (PTsPS), and a composite polymer film, consisting of P-TiO2 immobilized on the surface of a Corona-pretreated polypropylene film (PT/PP), were prepared and characterized by XPS, TEM, XRD and N2 adsorption at-196 degrees C. The latter were then tested for the degradation of thiacloprid under solar irradiation. The best results were obtained using the PT/PP composite film, which allowed the total degradation of thiacloprid after 180 min of treatment. This performance remained almost unchanged even after several reuse cycles. The effect of pH and the concentration of bicarbonate (HCO3-), calcium (Ca2+), and chloride (Cl-) ions on the PT/PP film photocatalytic activity was also investigated. In addition, the photocatalytic activity of the PT/PP film remained high even in the presence of drinking water spiked with the target pollutant. Photocatalytic tests in the presence of scavenger molecules clarified that the hydroxyl radical is the main reactive oxygen species (ROS) responsible for the photodegradation mechanism of the target pollutant with P-TiO2, even if a possible role of superoxide cannot be excluded. Finally, DFT studies and ESI(+)-FT-ICR-MS analysis were conducted to formulate a hypothesis on the degradation pathway, identifying possible reaction intermediates.

Abstract

The thermal memory effect, TME, has been studied in Ni₅₅Fe₁₉Ga₂₆ shape memory alloys, fabricated as ribbons via melt-spinning and as pellets via arc-melting, to evaluate its dependence on the martensitic structure and the macrostructure of the samples. When the reverse martensitic transformation is interrupted, a kinetic delay in the subsequent complete transformation is only evident in the ribbon samples, where the 14M modulated structure is the dominant phase. In contrast, degradation of the modulated structure or the presence of the γ phase significantly reduces the observed TME. In such cases, the magnitude of the TME approaches the detection limits of commercial calorimeters, and only high-resolution calorimeter at very low heating rate (40 mK h⁻¹) can show the effect. Following the kinetic arrest and subsequent cooling, the reverse martensitic transformation was completed at several heating rates to confirm the athermal nature of the phenomenon.

Abstract

This study investigates biomass-derived adsorbents in powder and bead forms for the efficient removal of methylene blue MB from wastewater. Activated biochar powders (ABC and ABCZ) were synthesized using H3PO4 and ZnCl2 as activators for the chemical treatment of Crataegus azarolus CAS seed waste, while polyaniline (PA) and sodium alginate (SG) were integrated to form two bead-shaped composites. Compared to ZnCl2, H3PO4 activation produced similar acidic site concentrations but resulted in improved mesoporosity and larger pore diameters. Untreated lignin-like ABC and PA-functionalized ABC were successfully encapsulated into uniform composite beads (ABC-SG and ABC-PA-SG) with negatively charged surfaces at neutral pH of solution as confirmed by FTIR, TGA, and pHpzc analyses. Adsorption efficiency depended on material composition, form, and texture. Encapsulation significantly enhanced MB adsorption capacity, with ABC-PA-SG beads achieving 821 mg/g, compared to 261 mg/g for ABC powder. While greater surface area improved MB adsorption in powders, PA incorporation in composite beads contributed to higher adsorption performance. Kinetic modeling showed that MB adsorption on ABC powder was governed by chemisorption and pores filling, while composite beads followed a physical interaction-driven process. Thermodynamic analysis confirmed that adsorption was spontaneous and endothermic. Statistical modeling and DFT calculations provided deeper insights into the adsorption mechanisms. it-it interactions dominated MB adsorption, with a horizontal molecular arrangement. ABC powders exhibited multi- layer pore filling on a heterogeneous surface, whereas adsorption on ABC-PA-SG beads followed a double-energy double-layer mechanism. This study provides integrated insights into biomass-derived composite beads adsorbents, highlighting their potential for sustainable wastewater treatment applications.

Abstract

Dye Sensitized Solar Cells (DSSCs) have recently gained renewed interest for their potential in indoor light harvesting and powering wireless devices. However, to fully exploit their potential, crucial aspects require further attention, in particular, the improvement of spectral compatibility and low-light harvesting mechanisms, as well as the development of efficient photoanodes through high-yield scalable methods. In this article, we propose the use of nanocomposite photoanodes integrating mesoporous TiO2 nanoparticles, ITO nanotubes (NT), and anatase TiO2 shells (ITO@TiO2 NT) prepared by step-by-step method relying on mild temperature conditions and avoiding toxic precursors. These photoanodes outperform previous attempts to implement low-dimensional ITO and ITO@TiO2 nanowires and nanotubes for outdoor light conversion, demonstrating a power conversion efficiency under low artificial light intensity of 24 % for at 0.014 mW cm-2, a 166 % increase compared to the conventional architectures. Advanced microstructural, optical, and electrochemical characterizations have revealed that the strong scattering effect of the light in the visible range coupled with enhanced charge collection at low-intensity illumination are the essential mechanisms responsible for such enhanced energy conversion. Remarkably, our devices retain up to 90 % of the normal incidence efficiency even under glancing illumination, while conventional reference devices retain only 30 %.

Abstract

Direct upgrading of biogas by CO2 methanation aims to produce a gas to be injected into the grid. Operating at moderate pressures favors thermodynamics, but catalyst surface and reaction mechanism under realistic conditions are not well investigated. We study the role of basic and metallic sites on performance and mechanism of clean biogas methanation (CO2/CH4=1/1 v/v) at 1, 5 and 7 bar. Ni/Mg/La/Al hydrotalcite-derived catalysts, with different Ni and La contents, are investigated combining tests and physico-chemical characterization, including quasi-in situ XPS at 7 bar, with CO2-adsorption and methanation DRIFTS at 1 and 7 bar, respectively. An optimized catalyst (6.5 wt% La, 35 wt% Ni) with 3-4 nm Ni0 and balanced basicity, achieves 96 LCH4*gcat- 1* h- 1 (300 degrees C, 7 bar). DRIFTS confirm catalysts activity experimental trend. Optimizing Ni and La results in higher consumption rates of formate intermediate and sufficient Ni0 sites for CO formation. Increasing pressure to 7 bar promotes CO and m-HCOO reactivity.

Abstract

This Letter reports on the first cross-section measurements for the 94Sr(alpha, n)97Zr and 86Kr(alpha, n)89Sr reactions. In particular, our measurement of 94Sr(alpha, n)97Zr is the first weak r-process reaction cross section obtained using a radioactive ion beam. This experiment was enabled by the use of novel solid helium targets, comprised of silicon thin films with high helium incorporation obtained via a sputtering technique. Yield measurements were performed at center-of-mass energies of 10.4 and 9.0 MeV for the 86Kr(alpha, n)89Sr reaction, and 9.9 MeV for 94Sr(alpha, n)97Zr, extending into the respective Gamow energy windows for a temperature of 5 GK. Reactions were uniquely identified by prompt gamma rays detected in coincidence with heavy ions selected by a recoil mass spectrometer. The obtained cross sections are smaller than predicted for both reactions. In the case of 94Sr(alpha, n)97Zr, the reaction rate found here is lowered by an order of magnitude at temperatures below 5 GK, which is expected to impact the predicted abundance of ruthenium, a signature weak r-process element.

Abstract

Exploring synergistic interactions between nanomaterials that can enhance their collective properties in ways that individual components cannot achieve represents an avenue for advancing beyond the current state of the art. This approach is particularly relevant in the context of ABX(3) nanocrystals, where pursuing cooperation could help to overcome current challenges associated with light generation. Transparent photoluminescent coatings are developed by combining perovskite nanomaterials and porous scaffolds of high optical quality phosphor nanoparticles. Fine tuning of the spectral content of the emission is achieved with the photoexcitation wavelength, allowing the demonstration of white light emission with tunable hues.

Abstract

This article presents a reproducible and affordable methodology for fabricating organic nanowires (ONWs) and nanotrees (ONTs) as light-enhanced conductometric O2 sensors. This protocol is based on a solventless procedure for the formation of high-density arrays of nanowires and nanotrees on interdigitated electrodes. The synthesis combines physical vapour deposition for the self-assembled growth of free-phthalocyanine nanowires and soft plasma etching to prompt the nucleation sites on the as-grown ONWs to allow for the formation of nanotrees. Electrical conductivity in such low-dimensional electrodes was analysed in the context of density, length, and interconnection between nanowires and nanotrees. Furthermore, the electrodes were immersed in water to improve the nanowires' connectivity. The response of the nanotrees as conductometric O2 sensors was tested at different temperatures (from room temperature to 100 degrees C), demonstrating that the higher surface area exposed by the nanotrees, in comparison with that of their polycrystalline thin film counterparts, effectively enhances the doping effect of oxygen and increases the response of the ONT-based sensor. Both organic nanowires and nanotrees were used as model systems to study the augmented response of the sensors provided by illumination with white or monochromatic light to organic semiconducting systems. Interestingly, the otherwise negligible sensor response at room temperature can be activated (On/Off) under LED illumination, and no dependency on the illumination wavelength in the visible range was observed. Thus, under low-power LED illumination with white light, we show a response to O2 of 16% and 37% in resistivity for organic nanotrees at room temperature and 100 degrees C, respectively. These results open the path to developing room temperature long-lasting gas sensors based on one- and three-dimensional single-crystalline small-molecule nanowires.

Abstract

CO₂ hydrogenation with green hydrogen is a practical approach for the reduction of CO₂ emissions and the generation of high-value-added chemicals. Generally, product selectivity is affected by the associated reaction mechanisms, internal catalyst identity and structure, and external reaction conditions. Here we examine typical CO₂ hydrogenation reaction pathways, which can provide insight useful for the atomic-level design of catalysts. We discuss how catalyst chemical states, particle sizes, crystal facets, synergistic effects and unique structures can tune product selectivity. Different catalysts, such as Fe-, Co-, Ni-, Cu-, Ru-, Rh-, Pd-based and bifunctional structured catalysts, and their influence on CO₂ hydrogenation products (such as CO, methane, methanol, ethanol and light olefins) are discussed. Beyond catalyst design, emerging catalytic reaction engineering methods for assisting the tuning of product selectivity are also discussed. Future challenges and perspectives in this field are explored to inspire the design of next-generation selective CO₂ hydrogenation processes to facilitate the transition towards carbon neutrality.

Abstract

Research on the reutilization of crop residues has gained significant attention as a strategy for generating energy and high-value chemicals from renewable sources, while simultaneously reducing feedstock costs and mitigating environmental pollution. Crop residues have been effectively applied in lignocellulosic sulfate-reducing bioreactors (LSRBs) for the treatment of mining-influenced water. A comprehensive evaluation of the state-of-the-art in LSRBs reveals their potential for leveraging syntrophic aerobic-anaerobic interactions between sulfate-reducing bacteria and facultative species, alongside cellulolytic-fermentative microorganisms, to facilitate the pretreatment of lignocellulosic biomass for biorefinery applications. Key variables influencing the availability of enzymatic substrates and the activity of lignin-degrading enzymes are identified, along with strategies to enhance catalytic efficiency. Additionally, approaches to ensure the availability of trace elements and to control the production of toxic intermediates that may hinder treatment processes are elucidated. Prominent strategies include the application of microaeration and the use of co-substrates. An innovative aspect is the exploitation of metal sulfide precipitation to mitigate toxicity while preventing the sequestration of hydrogen peroxide - an essential substrate for enzymatic activity - by sulfides generated during the process. This review emphasizes the need for scientific advancements focused on optimizing the valorization of lignocellulosic residues. A particular focus is placed on advancing the understanding of lignin's anaerobic degradation mechanisms, especially in systems co-treating lignocellulosic waste and mining-influenced waters. Such advancements hold promise for enhancing the efficiency and sustainability of biorefinery operations.

Abstract

A joint theory-experimental study is presented of irregularly shaped nano-pores in amorphous silicon. STEM- ELLS spectra were measured for each pore. The observed helium 1 s 2- 1 s 2 p( 1 P ) excitation energies were found to be shifted from that of a free atom. The relation between the helium density in the pore and these energy shifts is explored and shown to be completely consistent with earlier studies of helium in its bulk condensed phases as well as encapsulated as bubbles in solid silicon. The density, pressure and depth of the pores, all key properties for applications, were determined. An alternative and novel method for determining the depth of the pores more accurately is presented.

Abstract

This study investigates the impact of cerium promotion on NiMgAl catalysts for methane dry reforming (DRM) at 750 degrees C. A series of NiMgAl-Ce oxides with varying cerium content NiMgAlCe-x (x: rate of substitution of aluminium by cerium) were synthesized via co-precipitation method, aiming to enhance catalytic activity through the incorporation of nickel into hydrotalcite structures and cerium promotion. The obtained systems calcined at 800 degrees C, reduced at 750 degrees C and used catalysts were characterized by ICP, BET, XRD, SEM, H2-TPR, TPO and O2-TG analysis. The results demonstrate that cerium content influences specific surface area, with higher cerium promoting increased surface area but hindering catalytic activity and improved carbon resistance of the catalysts.. Activity improved with reaction temperature, with NiMgAl achieving the highest conversion, with CH4 conversion dropping from 16% at 450 degrees C to 95.0% at 750 degrees C. Stability tests at 750 degrees C, revealed decreased activity in cerium-containing catalysts. On the other hand in the case of catalysts without prior reduction, the catalytic activity of NiMgAlCe-1 and NiMgAlCe-2 catalysts are better, however, the NiMgCe solid presents a total catalytic inertia. This result suggests that the presence of aluminium is bringing a Lewis acidity favours this reducibility suggesting an influence on redox behaviour. Carbon fibers formation was observed, but it did not significantly affect reactor performance.

Abstract

The first demonstration of plasma-flash sintering (PFS) is presented in this work. PFS is performed under a low-pressure atmosphere that consecutively generates plasma and flash events. It is shown, by using several combined characterization techniques, that PFS stabilizes metastable phases on the surface of the material, which may be partially, but not solely, attributed to the generation of oxygen vacancies, and induces the absorption of ionized species, if a reactive atmosphere is employed. Even though additional research is required to understand the fundamentals of PFS, it is evidenced its potential to be used as a material surface engineering tool, which may widen the technological capabilities of flash sintering.

Cover Photograph: Plasma-Flash Sintering (PFS) is performed under low-pressure atmosphere that consecutively generates plasma and flash events. This study shows that PFS stabilizes metastable phases on the surface of the material and enables absorption of ionized species generated in the plasma, giving this technique potential to be used as a surface engineering tool. Read more in the rapid communication in this issue,

Abstract

Metal-Organic frameworks (MOFs) are promising candidates for advanced photocatalytically active materials. These porous crystalline compounds have large active surface areas and structural tunability and are thus highly competitive with oxides, the well-established material class for photocatalysis. However, due to their complex organic and coordination chemistry composition, photophysical mechanisms involved in the photocatalytic processes in MOFs are still not well understood. Employing electron paramagnetic resonance (EPR) spectroscopy and time-resolved photoluminescence spectroscopy (trPL), the fundamental processes of electron and hole generation are investigated, as well as capture events that lead to the formation of various radical species in UiO-66, an archetypical MOF photocatalyst. A manifold of photoinduced electron spin centers is detected, which is subsequently analyzed and identified with the help of density-functional theory (DFT) calculations. Under UV illumination, the symmetry, g-tensors, and lifetimes of three distinct contributions are revealed: a surface O2-radical, a light-induced electron-hole pair, and a triplet exciton. Notably, the latter is found to emit (delayed) fluorescence. The findings provide new insights into the photoinduced charge transfer processes, which are the basis of photocatalytic activity in UiO-66. This sets the stage for further studies on photogenerated spin centers in this and similar MOF materials.

Abstract

One of the biggest players in the world economy is the naval industry, which mainly controls the merchandise transportation sector. Any issue with ships could represent millions of USD of loss and increases in the cost of goods for the population worldwide. Two main problems which this industry has fought are corrosion and biofouling. Lastly, the pollution of the sea has gained importance, and more strict policies have been applied regarding the use of certain products by this industry. One of these is paintings, which represented this industry's definitive solution to avoid the mentioned problems for a long time. This situation allowed to explore other solutions like PVD coatings through multifunctional coatings. Zirconium nitride has been demonstrated to be useful in resisting corrosion with reliable mechanical properties. However, this material does not possess antimicrobial action. The present study presents a nanostructured coating combining ZrN with Cu, which works as a biocide, contributing to the desired multifunctionality. The developed coating was obtained using a hybrid magnetron co-sputtering employing High-power impulse (HiPIMS) and direct current (DCMS) power sources under a reactive atmosphere. SEM, EDX, XRD and Raman spectroscopy were used to assess the physico-chemical properties of the coatings. Besides, depth-sensing nano-indentation explored the mechanical properties. The tribological performance was tested by a reciprocating tribometer under dry and wet (with 3.5 % w/w NaCl solution) contact conditions and employing a soda lime glass ball as a counterbody. The results showed that adding Cu to ZrN through this technology resulted in a limited hardness reduction from 19 (pure ZrN) to 14 GPa. Also, the chemical activation with NaOCl solution softens the obtained coating and, together with the saline solution, influences the wear resistance. However, the nanostructured coating has been demonstrated to be suitable for use under real conditions, without loss of its protection over the used substrate. It opens a new possibility of a solution for the naval industry.

Abstract

The development of highly efficient and selective catalysts for carbonylation reactions represents a significant challenge in catalysis. Single-atom catalysts (SACs) have postulated as promising candidates able to combine the strengths of both homogeneous and heterogeneous catalysts. In this paper, we review recent advances in tailoring solid supports for SACs to enhance their catalytic performance in carbonylation reactions. We first discuss the effect of supports on the hydroformylation reaction catalysed by SACs, followed by recent advances for methanol, ethanol, and dimethyl ether carbonylation reactions, focusing on the design of halide-free catalysts with improved activity and stability. Finally, oxidative carbonylation is discussed. Overall, this review highlights the importance of tailoring solid supports for SACs to achieve highly active and selective catalysts in carbonylation reactions, paving the way for future developments in sustainable catalysis.

Abstract

Ethylene, as an important chemical raw material, could be produced through the coal-based acetylene hydrogenation route. Nickel-based catalysts demonstrate significant activity in the semihydrogenation reaction of acetylene, but they encounter challenges related to catalyst deactivation and overhydrogenation. Herein, the effect of Sn promoter on Ni/CeO2 catalysts has been comprehensively explored for acetylene semihydrogenation. The optimized Ni/8%Sn-CeO2 catalytic performance was significantly improved, with 100% acetylene conversion and 82.5% ethylene selectivity at 250 degrees C, and the catalyst maintained high catalyst performance within a 1000 min stability test. A series of characterization tests show that CeO2 modified by moderate Sn4+ doping is more conducive to modulating the charge structure and geometry of the Ni active center. Additionally, the in situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy and density functional theory results indicated that catalysts doped with Sn4+ facilitated more efficient desorption of ethylene from the catalyst surface compared to Ni/CeO2 catalysts, thus improving ethylene selectivity and yield. This study highlights an effective strategy for improving the catalytic performance of rare-earth-based catalysts through the incorporation of effective metal promoters.

Abstract

Poly(vinylidene fluoride) (PVDF) is a piezoelectric and thermoplastic material with great potential for additive manufacturing (AM) applications. Using barium titanate (BaTiO₃) as filler, PVDF-based composite materials were developed, characterized, and processed by AM material extrusion (MEX). The morphological features and phase transformations occurring throughout the processing of BaTiO₃-filled PVDF, from the compounding to the printed part, were analyzed. The morphology of the powder feedstock after dispersion in a high-energy ball mill changed from spheroidal to laminar and β-phase formation was favored. Microhardness gradually increased with the BaTiO₃ content, obtaining an enhancement of ~60% for a content of 25 vol%, and supported the good dispersion of the filler. A ~48% increase of the dielectric permittivity was also achieved. After extrusion, filaments with a filler content of 15 vol% showed a more stable diameter, as well as higher crystallinity and surface roughness, compared with those with lower BaTiO₃ contents. Material extrusion of filament and direct printing of pellets based on MEX were successfully used to obtain AM parts. Composite parts showed enhanced surface roughness, hydrophilicity, and flexural modulus (up to ~33% for the 7 vol% composite compared with the PVDF), thus leading to superior mechanical characteristics and potential biomedical applications.

Abstract

The direct conversion of carbon dioxide into hydrocarbons is a very desirable but difficult approach for achieving lower value-added olefins with minimal CO selectivity. In this effort, we report the direct conversion of CO2 into light olefins on a Cu/CeO2 hybrid catalyst mixed with SAPO-34 zeolite. The samples are characterized by N-2 sorption, XRD, TEM, SEM, NH3-TPD and H-2 -TPR. The results showed that the acidity of modified zeolite had decreased. The response surface methodology has been used to optimize the operating parameters (temperature and space velocity (SV)) of process. A high olefin selectivity of 70.4% has been obtained on CuCe/SAPO-34 at H-2/CO2 =3, 10 h, 382.46 degrees C, 17.33 L/g.h and 20 bar. The optimum operating conditions for multiple responses have also been achieved. The optimal values are T = 396.26 degrees C and SV = 5.80 L/g.h. Under these conditions, the predicted olefin and CO selectivity and CO2 conversion are 61.83%, 57.11% and 13.15%, respectively. Multiple optimization outputs are outstanding for obtaining the suitable operating conditions.

Abstract

Active and sustainable food packaging materials were prepared through solvent casting, by blending tea waste (TW) extract rich in bioactive molecules with a neat polylactide (PLA) polymeric matrix. The optimization of tea waste extraction using a response surface methodology allowed achieving efficient yield and high phenolic content, which significantly enhanced the antioxidant properties of the resulting bioplastics. TW extract incorporation into PLA films increased UV-blocking capability, while keeping the oxygen permeability performance. Mechanical testing revealed improved ductility and toughness in TW extract-containing films compared to pure polylactide film, ascribed to the plasticizing effect of TW polyphenols. Food packaging assays showed effective moisture retention, comparable to low-density polyethylene (LDPE) plastics, antioxidant activity, and excellent bacteria barrier properties allowing the use for food packaging applications. Moreover, migration tests and detection of non-intentionally added substances (NIAS) allowed to establish the safety and regulatory compliance of these bioplastics.

Abstract

Microplastics fibers shed from washing synthetic textiles are released directly into the waters and make up 35% of primary microplastics discharged to the aquatic environment. While filtration devices and regulations are in development, safe disposal methods remain absent. Herein, we investigate catalytic hydrothermal carbonization (HTC) as a means of integrating this waste (0.28 million tons of microfibers per year) into the circular economy by catalytic upcycling to carbon nanomaterials. Herein, we show that cotton and polyester can be converted to filamentous solid carbon nanostructures using a Fe-Ni catalyst during HTC. Results revealed the conversion of microfibers into amorphous and graphitic carbon structures, including carbon nano- tubes from a cotton/polyethylene terephthalate (PET) mixture. HTC at 200 degrees C and 22 bar pressure produced graphitic carbon in all samples, demonstrating that mixed microfiber wastes can be valorized to provide potentially valuable carbon structures by modifying reaction parameters and catalyst formulation.

Abstract

The endeavor of sustainable chemistry has led to significant advancements in green methodologies aimed at minimizing environmental impact while maximizing efficiency. Herein, a straightforward synthesis of benzimidazoles by reductive coupling of o-dinitroarenes with aldehydes is reported for the first time in aqueous media while using a non-noble metal catalyst. This work demonstrates that the combination of nitrogen and phosphorous ligands in the synthesis of supported heteroatom-incorporated Co nanoparticles is crucial for obtaining the desired benzimidazoles. The process achieves >99 % conversion, >99 % chemoselectivity and stability for the reduction of dinitroarenes using water as the solvent and hydrogen as the reductant under mild reaction conditions. The robustness of the catalyst has been investigated using several advanced techniques such as HRTEM, HAADF-STEM, XEDS, EELS, and NAP-XPS. In fact, we have shown that the introduction of N and P dopants prevents metal leaching and the sintering of the cobalt nanoparticles. Finally, to explore the general catalytic performance, a wide range of substituted dinitroarenes and benzaldehydes were evaluated, yielding benzimidazoles with competitive and scalable results, including MBIB (94 % yield), which is a compound of pharmaceutical interest.

Abstract

This work shows the synthesis and characterization of the Zn2-xGeO4-GeO2:(x)Mn2+ (x = 0.10, 0.25, and 0.50 at.%) films using the Ultrasonic Spray Pyrolysis (USP) technique. These films were deposited at 500 degrees C and heat treated at 800 degrees C for 13 h. X-ray diffraction (XRD) measurements showed the rhombohedral and hexagonal phases of Zn2-xGeO4 (78.8 %) and GeO2 (21.2 %), respectively. SEM micrographs exhibited the surface morphology of these films. The STEM and HAADF show Ge, Zn, and O atomic layers. In addition, XPS was carried out to observe the oxidation states of Mn2+ (75.4 %) and Mn3+ (24.6 %) for the films doped with Mn ions (0.10 at.%). Incorporating manganese ions into the Zn2-xGeO4-GeO2 host lattice generated an extremely green emission, exciting at 250 nm. The photoluminescence and persistence luminescence properties were studied in accordance with the manganese doping concentration. For photoluminescence, it was found that the optimal doping percentage was 0.25 at.%, and for persistence luminescence, it was 0.10 at.% Mn with lambda(ex) = 250 nm. Quantum efficiency measurements gave a result of 100 %. In addition, preliminary CL measurements were exhibited.

Abstract

In this study, the feasibility of preparing quinary equimolar high-entropy oxides within the Co–Cu–Fe–Mg–Mn–Ni–O system was explored using the reactive flash sintering (RFS) technique. Various compositions were tested using this technique under atmosphere pressure, leading to the formation of two primary phases: rock-salt and spinel. Conversely, a new high-entropy oxide was produced as a single-phase material with the composition (Co_0.2,Cu_0.2,Mg_0.2,Mn_0.2,Ni_0.2)O when RFS experiments were conducted in nitrogen atmosphere. The reducing conditions achieved in nitrogen enabled the incorporation of cations with oxidation states different from +2 into the rock-salt lattice, emphasizing the critical role of the processing atmosphere, whether inert or oxidizing, in the formation of high-entropy oxides. The electrical characterization of this material was obtained via impedance spectroscopy, exhibiting a homogeneous response attributed to electronic conduction with a temperature dependence characteristic of disordered systems. 

Abstract

Gel polymer electrolytes (GPEs) are regarded as a promising alternative to conventional electrolytes, combining the advantages of solid and liquid electrolytes. Leveraging the abundance and eco-friendliness of cellulose-based materials, GPEs were produced using methyl cellulose and incorporating various doping agents, either an ionic liquid (1-Butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide [Pyr14][TFSI]), its polymeric ionic liquid analogue (Poly(diallyldimethylammonium bis(trifluoromethylsulfonyl)imide) [PDADMA][TFSI]), or an anionically charged backbone polymeric ionic liquid (lithium poly[(4-styrenesulfonyl)(trifluoromethyl(S-trifluoromethylsulfonylimino) sulfonyl) imide] LiP[STFSI]). The ion dynamics and molecular interactions within the GPEs were thoroughly analyzed using Attenuated Total Reflectance Fourier-Transform Infrared Spectroscopy (ATR-FTIR), Heteronuclear Overhauser Enhancement Spectroscopy (HOESY), and Pulsed-Field Gradient Nuclear Magnetic Resonance Diffusion (PFG-NMR). Li+ transference numbers (tLi+) were successfully calculated. Our study found that by combining slow-diffusing polymeric ionic liquids (PILs) with fast-diffusing lithium salt, we were able to achieve transference numbers comparable to those of liquid electrolytes, especially with the anionic PIL, LiP[STFSI]. This research highlights the influence of the polymer ' s nature on lithium-ion transport within GPEs. Additionally, micro supercapacitor (MSC) devices assembled with these GPEs exhibited capacitive behavior. These findings suggest that further optimization of GPE composition could significantly improve their performance, thereby positioning them for application in sustainable and efficient energy storage systems.

Abstract

Efficient hydrogen generation from water-splitting is widely acknowledged as a priority route to promote the hydrogen economy. Anion exchange membrane water electrolyzers (AEMWE) offer multiple advantages in improving performance and minimizing the cost limitations of current electrolysis technologies. However, the persistence of issues related to the limited electrocatalytic activity of such materials and their poor stability under operating conditions makes developing highly active, stable, platinum-group-metal-free electrocatalysts for oxygen evolution reaction (OER) necessary. We report the development of Prussian blue analogues (PBA)-derived NiFe-based electrocatalysts through a mild aqueous phase precipitation method, followed by thermal stabilization and phosphorus doping. The formation of the NiFe-PBA-precursor with a framework nanocubic Ni(II)[Fe(III)(CN)₆]_2/3 structure was confirmed by X-ray diffraction, scanning electron microscopy, and inductively coupled plasma analysis. The NiFe-PBA-precursor was subjected to thermal stabilization and phosphorus doping to provide the material with enhanced OER catalytic activity and stability. The existence of OER active sites based on NiFe and NiFeP has been revealed by transmission electron microscopy, X-ray photoelectron spectroscopy, and electrochemical characterization in a three-electrode cell configuration in a 1 M KOH electrolyte. NiFe-PBA and NiFeP-PBA were assembled at the anode side of an AEMWE, resulting in an excellent electrochemical performance both in terms of current density at 2.0 V using 1 M KOH (1.21 A cm⁻²) and durability, outperforming the benchmark catalyst.