Search Results (5,932)

The electrochemical reduction of CO₂ to ethanol represents a sustainable alternative to recycle CO₂ into a value-added product, yet achieving high selectivity and efficiency remains a challenge. This work explores Cu-based catalysts supported on SiO₂ and ZrO₂, with and without ZnO doping, for ethanol production in a continuous flow-cell system. Gas diffusion electrodes are fabricated using commercial catalysts with varying Cu loadings (5–10%) and ZnO contents (2–3.5%). Comprehensive characterization by XPS confirms the presence of Cu²⁺ and Zn²⁺ species, while SEM reveals that ZnO incorporation improves surface uniformity and aggregate distribution compared to undoped samples. Electrochemical tests demonstrate that 10% Cu on SiO₂ achieves a Faradaic efficiency of 96% for ethanol at −3 mA cm⁻², outperforming both doped catalysts and previously reported materials. However, efficiency declines at higher current densities, indicating a trade-off between selectivity and productivity. ZnO doping enhances C₂⁺ product formation but does not surpass the undoped catalyst in ethanol selectivity. These results underline the importance of catalyst composition, support interactions, and operating conditions, and point to further optimization of electrode architecture and cell configuration to sustain high ethanol yields under industrially relevant conditions. Full article

Drugs and drug candidate compounds commonly suffer from poor solubility and permeability. One promising strategy to mediate these drawbacks is use of novel solvents, such as deep eutectic compositions. The present research aims to determine the applicability of this approach for therapeutic metal complexes on the example of [Cu(Fur)₂(Phen)] (Fur = furoate-anion, Phen = 1,10-phenantroline) and [Cu(Fur)₂(Neoc)(H₂O)] (Fur = furoate-anion, Neoc = 2,9-dimetyl-1,10-phenanthroline) with molar weight of appx. 500 Da. Interaction of the metal complexes with the deep eutectic solvent (DES) reline was studied using electron paramagnetic resonance (EPR). Minimal inhibitory concentrations of the complexes dissolved in DES and dimethyl sulfoxide (DMSO) were determined and found to be equivalent in both solvents. That is, use of reline as a solvent did not alter the functional properties of the metal complexes. Changes in the transdermal permeation of the complexes in DMSO and DES were assessed using a Franz diffusion cell. It was discovered that depending on the structure of the complex, the permeability might either increase (from 15 to 30%) or decrease (from 13 to 8%) with changes in the solvent, and this can be used to develop dosing strategies. Therapeutic eutectogels were successfully produced by impregnating SiO₂ nanoparticles with the metal complex solution in DES, facilitating convenient topical application. Full article

Continuous excessive CO₂ emissions have a negative impact on the environment. In order to address the issue of CO₂ emission control, its conversion to some valuable commodities is the way forward in dealing with this issue. Additionally, the conversion of CO₂ to some valuable product such as methanol fuel will not only tackle the issue but also result in producing energy. Here, the co-precipitation method was used to synthesize Cu-ZnO bimetallic catalysts based on TiO₂ support to be applied for CO₂ conversion to methanol fuel. To elucidate the role of potassium (K) as a promoter, varied concentrations of K were added to parent Cu-ZnO/TiO₂ catalysts. A number of analytical techniques were used to scrutinize the physico-chemical properties of calcined Cu-ZnO/TiO₂ catalysts. The crystalline nature of TiO₂ catalyst support with high metal oxide dispersion were the major findings disclosed based on X-ray diffraction examinations. The combination of the mesoporous and microporous character of the K-promoted Cu-ZnO/TiO₂ catalysts was discovered using the N₂ adsorption–desorption technique. Similarly, N₂ adsorption–desorption studies also revealed surface defects by K-promotion. The creation of surface defects was also endorsed by X-ray photoelectron spectroscopy (XPS) by showing additional XPS peaks for O1s in higher binding energy (BE) regions. XPS also showed the oxidation states of K-promoted Cu-ZnO/TiO₂ catalysts as well as metal–support interactions. Activity results demonstrated the active profile of K-promoted Cu-ZnO/TiO₂ catalysts for methanol synthesis via CO₂ reduction in a liquid phase slurry reactor. The methanol synthesis rate was accelerated from 35 to 53 g.MeOH/kg.cat.h by incorporating of K to parent Cu-ZnO/TiO₂ catalysts at reaction temperature and pressure of 210 °C and 30 bar, respectively. Structure–activity investigations revealed a promoting role of K by facilitating Cu reduction as well metal–support interaction. The comparative study further revealed the importance of K promotion for the title reaction. Full article

Metal oxide nanomaterials have emerged as transformative materials in the quest to enhance the energy density and overall performance of lithium-ion batteries (LIBs) and solid-state batteries (SSBs). Their unique properties—including their large surface areas and short ion diffusion pathways—make them ideal for next-generation energy storage technologies. In LIBs, the high surface-to-volume ratio of metal oxide nanomaterials significantly enlarges the active interfacial area and shortens the lithium-ion diffusion paths, leading to an improved high-rate performance and enhanced energy density. Transition metal oxides (TMOs) such as nickel oxide (NiO), copper oxide (CuO), and zinc oxide (ZnO) have demonstrated significant theoretical capacities, while binary systems like NiCuO offer further improvements in cycling stability and energy output. Additionally, layered lithium-based TMOs, particularly those incorporating nickel, cobalt, and manganese, have shown remarkable promise in achieving high specific capacities and long-term stability. The synergistic integration of metal oxides with carbon-based nanostructures, such as carbon nanotubes (CNTs), enhances the electrical conductivity and structural durability further, leading to a superior electrochemical performance in LIBs. In SSBs, the use of oxide-based solid electrolytes like garnet-type Li₇La₃Zr₂O₁₂ (LLZO) and sulfide-based electrolytes has facilitated the development of high-energy-density systems with excellent ionic conductivity and chemical stability. However, challenges such as high interfacial resistance at the electrode–electrolyte interface persist. Strategies like the application of lithium niobate (LiNbO₃) coatings have been employed to enhance interfacial stability and maintain electrochemical integrity. Furthermore, two-dimensional (2D) metal oxide nanomaterials, owing to their high active surface areas and rapid ion transport, have demonstrated considerable potential to boost the performance of SSBs. Despite these advancements, several challenges remain. Morphological optimization of nanomaterials, improved interface engineering to reduce the interfacial resistance, and solutions to address dendrite formation and mechanical degradation are critical to achieving the full potential of these materials. Full article

This study examines the influence of sintering temperature on the structural and transport properties of GdBa₂Cu₃O₇ (Gd123) superconductors prepared from nano-sized precursors via the co-precipitation method. The metal-oxalate precursor (average particle size < 50 nm) was calcined at 900 °C for 12 h, and then the prepared pellets were sintered under an oxygen atmosphere in the range of 920–950 °C for 15 h. All samples showed metallic properties and a sharp superconducting transition. Critical temperatures T_C(R=0) were 94–95 K, with higher sintering temperatures steadily boosting critical current density. X-ray diffraction confirmed orthorhombic Gd123 as the dominant phase, with its phase fraction increasing from 92% to 99.8% as the sintering temperature increased. SEM micrographs showed large, densely packed grains, with higher sintering temperatures promoting improved grain connectivity and reduced porosity. The sample sintered at 950 °C exhibited the most favorable transport performance, attributed to enhanced intergranular coupling and the presence of nanoscale secondary phases acting as effective flux-pinning centers. Overall, these results demonstrate that careful control of sintering temperature can significantly optimize the microstructure and superconducting properties of Gd123 materials, supporting their advancement for practical electrical and magnetic applications. Full article

The coexistence of plastics and metal-based materials in aquatic systems introduces complex interfacial processes that influence pollutant speciation and mobility. This study investigates the role of polystyrene (PS) in promoting UV-induced dissolution of ZnO and Cu₂O in aqueous media, revealing a plastic-mediated pathway for metal ion mobilization. Post-use expanded PS fragments were co-dispersed with the oxides and irradiated at 254 nm for 24 h. Ion concentrations were quantified by ICP-MS, while PS morphology and chemistry were characterized by SEM, EDX, FTIR, Raman, and DSC. The presence of PS markedly enhanced metal release, bringing Zn²⁺ from 29.9 to 50.6 ppm and Cu²⁺ from 1.1 to 26.5 ppm under irradiation, compared to minimal dissolution in the dark. Spectroscopic analyses indicated negligible polymer degradation, suggesting that enhanced dissolution arises from interfacial photooxidation and associated redox/pH microgradients at the polymer–oxide boundary. These findings demonstrate that PS may serve as a catalytic interface that accelerates UV-driven dissolution of otherwise poorly soluble metal oxides. This mechanism expands current understanding of plastic–pollutant interactions and has implications for predicting metal bioavailability and designing strategies to mitigate pollutant release in sunlit marine and coastal environments. Full article

Water-based drilling fluids (WBDFs) are widely used due to their economic and environmental advantages; however, shale hydration remains a major limitation. This study evaluates Fe₂O₃, CuO, ZnO, and MgO nanocrystalline metal oxides synthesized via co-precipitation as inorganic shale inhibitors for WBDFs. Comprehensive characterization confirmed phase-pure nanocrystalline oxides (17–38 nm) with high thermal stability. Performance tests revealed that MgO-based WBDF exhibited the lowest plastic viscosity (17 cP), the highest pH (≈10.0), and the strongest shale inhibition (6.1% swelling), while Fe₂O₃ provided superior filtration control (6.0 mL). CuO showed balanced rheology, whereas ZnO displayed comparatively weaker inhibition. Compared with commercial inhibitors (Amine NF and Glycol), MgO- and Fe₂O₃-based systems achieved comparable or improved performance with enhanced thermal and environmental robustness. These results demonstrate the potential of nanocrystalline metal oxides as sustainable additives for improving WBDF performance under high-pressure, high-temperature (HPHT) conditions. Full article

This investigation has yielded a remarkably efficient metallic catalyst. Copper (Cu), cobalt (Co), and nickel (Ni) nanoparticles were concurrently deposited onto micron-sized aluminum (µAl) through a displacement reaction, resulting in the formation of [nCu+nCo+nNi]/µAl composites. The interfacial layer of the nanocomposite facilitates the creation of efficient oxygen transport pathways, significantly augmenting thermal release. In the context of the ADN/AP oxidizer, the [nCu+nCo+nNi]/µAl configuration demonstrates a substantial synergistic catalytic effect, reducing its thermal decomposition temperature by an impressive 104.1 °C. Combustion experiments have corroborated that this composite markedly enhances flame intensity, combustion temperature, and the burning rate of the ADN/AP system. The underlying thermal-oxidative mechanism was elucidated through comprehensive thermal analysis of the composite both prior to and following a heat treatment at 1100 °C. Moreover, through an integration of thermal analysis and combustion experiments, the catalytic mechanism of [nCu+nCo+nNi]/µAl on the thermolysis of ADN/AP was elucidated, and a plausible reaction pathway under thermal stimulation was proposed (e.g., ${\mathrm{NH}}_4{\mathrm{ClO}}_4+{{\mathrm{NH}}_4\mathrm{N}({\mathrm{NO}}_2)}_2\stackrel{\mathrm{Cu},\mathrm{Co},\mathrm{Ni}}{\to }{\mathrm{N}}_2+{\mathrm{H}}_2\mathrm{O}+\mathrm{HCl}+{\mathrm{O}}_2+\left[\mathrm{O}\right]$). The developed nanocomposite significantly enhances the performance of oxidizers, presenting considerable potential for a wide array of applications in solid propellants. Full article

This work investigated the effects of gamma irradiation on the adsorption capacities of rice husk (RH) for the removal of Cu²⁺, Cr³⁺, and Zn²⁺ ions from aqueous solutions, with potential applications in wastewater remediation. RH samples were gamma-irradiated at doses up to 40 kGy and characterized using SEM-EDS, XRF, FTIR, XRD, and BET analyses. While morphological and textural changes remained subtle, FTIR and SEM-EDS confirmed the formation and intensification of oxygen-containing functional groups, including –OH, –COOH, and C=O, as well as increased exposure of silica (Si–O) on the surfaces, which substantially enhanced surface reactivity of RH toward metal ions. Batch adsorption experiments revealed that 40-kGy irradiated RH samples (RH-40) exhibited the highest removal efficiencies compared to non-irradiated and lower-dose samples (RH-0, RH-10, RH-20, and RH-30), specifically with improvements of 415% for Cu²⁺, 502% for Cr³⁺, and 663% for Zn²⁺ compared to RH-0, determined at the initial concentration of 10 mg/L. Kinetic studies also showed rapid adsorption within the first 10–15 min, dominated initially by boundary-layer diffusion, followed by chemisorption-driven equilibrium behavior. The pseudo-second-order (PSO) model provided an excellent fit for all metals (R² = 0.999), indicating maximum model-predicted kinetic capacities of 555.56 mg/g (Cu²⁺), 769.23 mg/g (Cr³⁺), and 434.78 mg/g (Zn²⁺). Langmuir isotherms also fitted well (R² = 0.941–0.995), with predicted monolayer capacities of 535.33 mg/g (Cu²⁺), 491.64 mg/g (Cr³⁺), and 318.88 mg/g (Zn²⁺). Freundlich modeling further indicated favorable heterogeneous adsorption, with K_F values of 42.614 (Zn²⁺), 20.443 (Cr³⁺), and 16.524 (Cu²⁺) and heterogeneity factors (n) greater than 1 for all metals. These overall results suggested that gamma irradiation substantially enhanced RH functionality that enabled fast and high-capacity heavy-metal adsorption through surface oxidation and carbon valorization. Gamma-irradiated RH, therefore, represented a promising, low-cost, and environmentally friendly biosorbent for wastewater treatment applications. Full article

Manganese (Mn) is a crucial micronutrient for plants. The impaired function of the oxygen-evolving complex in Photosystem II (PSII) due to Mn deficiency is believed to result in the overproduction of reactive oxygen species and the induction of an enzymatic antioxidant system. In our study, we investigated the effects of progressive Mn deficiency (the difference in Mn content between the needles of control and Mn-deficient plants increased from 17-fold at the beginning of the experiment to 59-fold at the end) on the activities of superoxide dismutase (SOD), catalase, ascorbate peroxidase, and guaiacol peroxidase in the roots and needles of Scots pine seedlings. We found that the soluble protein content in plant organs under Mn deficiency was maintained at a level comparable to that of the control. Regardless of the severity of Mn deficiency, the needles of the Mn-deficient plants presented twofold lower SOD activity than the needles of the control plants. These differences were observed even when Mn deficiency did not negatively affect plant growth. Additionally, the total SOD activity in the needles of both plant groups was determined solely by the activity of the Cu/Zn-containing SOD isozymes. Compared with the control plants, Mn deficiency did not result in an increase in any of the studied H₂O₂-degrading enzymes in the needles of the seedlings. In contrast, the needles of the Mn-deficient plants presented a lower level of guaiacol peroxidase activity. Despite the inhibition of root growth, Mn deficiency led to changes in the balance of the enzymatic antioxidant system in plant roots. The data obtained suggest that the lack of activation of SOD and other antioxidant enzymes in Scots pine seedlings against the background of progressive Mn deficiency is due to the reduced ability of PSII to generate ROS under these conditions. Full article

This study aimed to determine the nutrient use efficiency of the yacon potato under NPK fertilization at different rates. The experiment followed a randomized block design with four replications and a split-plot arrangement. The main plots consisted of three fertilization levels (60%, 100%, and 140% of the reference dose—50:80:60 kg ha⁻¹ of NPK), with subplots to data collection intervals, performed every 30 days, for a total of 7 collections, generating 21 treatments. The dry biomass of whole plants and tuberous roots was determined. Samples were taken to determine the content of N, P, K, Ca, Mg, Cu, Fe, Mn, and Zn. The biological utilization coefficient (BUC) was calculated by dividing the mean values of dry biomass in kilograms of plant parts by the kilogram of nutrient found in that biomass. The application of 100% of the reference dose led to the highest use efficiency of P, K, Ca, and Mg, and intermediate efficiency for N in yacon tuberous roots and total biomass production throughout the cycle, provides a significant contribution to fertilization planning for this crop. The amount applied which was 100% of the reference dose was 17, 80, and 20 kg ha⁻¹ of N, P₂O₅, and K₂O, respectively, at planting, supplemented with 33 and 40 kg ha⁻¹ of N and K₂O as topdressing. Full article

This study introduces a hybrid optimization method to enhance the melting characteristics and weld bead morphology of flux-cored wire hardfacing with exothermic addition into the core filler. The Taguchi Design of Experiments (L9 orthogonal array) was used to analyze the effects of key conditions on multiple melting characteristics. The hybrid Taguchi-GRA-PCA effectively identified the best parameter combination, resulting in a significant improvement in overall melting performance. The impact of welding modes on weld bead parameters and melting characteristics was examined. It was determined that the optimal amount of the exothermic addition CuO-Al introduced into the flux-cored wire filler should be a medium level (EA = 28 wt.%). Results showed that wire feed speed WFS and EA had the greatest effect on MOR and DR, while EA and CTWD mainly influenced SF and De. It has been determined that the content of the exothermic additive has a significant impact on the melting process of filler materials, affecting the melting characteristics and weld bead morphology. It has been found that the melting characteristics of deposition rate and spattering factor can be used to optimize welding modes and characterize most output parameters of the welding/surfacing process. Full article

This study evaluated the surface functionalization of a non-equiatomic TiZrNbTaMo high-entropy alloy (HEA) by micro-arc oxidation (MAO) in Cu-rich electrolytes to tailor its performance for biomedical implants. The Cu content was varied, and the resulting coatings were investigated for their morphology, phase constitution, chemical structure, wettability, and cytocompatibility. X-ray diffraction (XRD) measurements of the substrate indicated a body-centered cubic (BCC) matrix with minor HCP features, while the MAO-treated samples depicted amorphous halo with sparse reflections assignable to CaCO₃, CaO, and CaPO₄. Chemical spectroscopic analyses identified the presence of stable oxides (TiO₂, ZrO₂, Nb₂O₅, Ta₂O₅, MoO₃) and the successful incorporation of bioactive elements (Ca, P, Mg) together with traces of Cu, mainly as Cu₂O. MAO treatment increased surface roughness and rendered a hydrophilic behavior, which are features typically favorable to osseointegration process. In vitro cytotoxic assays with MC3T3-E1 cells (24 h) showed that Cu addition did not induce harmful effects, maintaining or improving cell viability and adhesion compared to the controls. Collectively, MAO in Cu-rich electrolyte yielded porous, bioactive, and Cu-incorporated oxide coatings on TiZrNbTaMo HEA, preserving cytocompatibility and supporting their potential for biomedical applications like orthopedic implants and bone-fixation devices. Full article

The use of e-fuels, such as methanol (MeOH), is considered an alternative for the reduction of carbon emissions. MeOH can be produced from captured CO₂ and green H₂, with the exothermic (equilibrium-limited) reaction favoured at low temperatures and high pressures. However, CO₂ is a very stable molecule and requires high temperature (>200 °C) to overcome the slow activation kinetics. In this study, MeOH was synthesized from CO₂ and H₂ in a packed-bed membrane reactor (PBMR) using a commercial Cu/ZnO/Al₂O₃ catalyst and a tubular-supported, water-selective composite alumina–carbon molecular sieve membrane (Al-CMSM) immersed in the catalytic bed. A mixture of H₂/CO₂ (3/1) was fed into both sides of the membrane to increase the driving force of the gases produced by the reaction. The effect of the temperature of reaction (200, 220, and 240 °C), pressure difference (0 and 3 bar), and the sweep gas/reacting gas ratio (SW = 1, 3, 5) in the CO₂ conversion and products yield was studied. For comparison, the reactions were also carried out in a packed-bed reactor (PBR) configuration where the tubular membrane was replaced by a metallic tube of the same size. CO₂ conversion and MeOH yield are much higher in PBMR than in PBR configuration, showing the benefit of using the water-selective membrane. In PBMR, MeOH yield increases with SW and slightly decreases with the temperature, overcoming the limitation imposed by the thermodynamics. Full article

The catalytic combustion of toluene over cryptomelane and Cu-doped cryptomelane catalysts was investigated to evaluate the effect of copper incorporation on catalytic performance. It was found that a small addition of Cu into the cryptomelane framework resulted in a notable decrease in the temperature of 90% toluene conversion. To elucidate the structure–activity relationship, the catalysts were comprehensively characterized using XRD, FTIR, SEM-EDS, N₂ physisorption, XRF, XPS, O₂-TPD, and H₂-TPR techniques. The results revealed that Cu doping modifies the physicochemical properties of cryptomelane, most importantly the share of lattice and surface oxygen species, enhancing redox behavior and oxygen mobility, which in turn improves catalytic activity. For the lowest dose of Cu, both the temperatures of 50 and 90% conversion were found to be lowest among investigated catalyst series: 180 and 195 °C, respectively. These findings highlight the potential of Cu-doped cryptomelane as an efficient catalyst for the abatement of volatile organic compounds. Full article