Search Results (462)

The widespread presence of bisphenol A (BPA), a persistent endocrine-disrupting pollutant, in aquatic environments poses significant ecological and health risks, necessitating its effective removal. However, conventional remediation technologies are often hampered by catalysts with narrow pH adaptability and poor stability. In this study, a novel catalyst, Zeolite-supported Cu₃Mn-layered double hydroxide (LDH), was fabricated using the co-precipitation method. The synthesized catalyst was applied to activate peroxymonosulfate (PMS), effectively enabling decomposition of BPA by advanced oxidation processes. The composite material was characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM), which confirmed the successful synthesis of the zeolite-supported Cu₃Mn-LDH. The catalyst exhibited high activity in both neutral and strongly alkaline environments, achieving complete degradation of 10 mg⋅L⁻¹ bisphenol A (BPA) within 40 min and a 98% total organic carbon (TOC) removal rate when both the PMS and catalyst were dosed at 0.15 g⋅L⁻¹. Singlet oxygen was detected as the primary reactive species responsible for BPA degradation, as verified by quenching experiments and EPR analysis, which also identified the presence of sulfate (SO₄^•−), hydroxyl (•OH), and superoxide (•O₂⁻) radicals. The catalyst exhibited excellent reusability, maintaining high catalytic efficiency over two consecutive cycles with minimal performance loss. Gas chromatography-mass spectrometry (GC-MS) analysis revealed five intermediate products, enabling the proposal of potential BPA degradation pathways. This work not only presents a novel synthetic approach for zeolite-supported LDH composites, but also offers a promising strategy for the efficient removal of BPA from aqueous systems through AOPs. Full article

The development of highly selective and sensitive gas sensors is essential for detecting toxic pollutants, such as carbon monoxide (CO), which pose severe health and environmental risks. In this work, the adsorption of CO molecules on Ni_6−xCu_x (x = 0–6) clusters supported on hexagonal boron nitride quantum dots with nitrogen vacancies (h-BN_VQDs) is explored through density functional theory (DFT) calculations. For this purpose, the stability of the metallic clusters supported on the boron nitride sheet was calculated, and the adsorption properties of the CO molecule on the Ni_6−xCu_x (x = 0–6)/h-BN_VQDs composite were determined. The results demonstrated a high binding energy between Ni_6−xCu_x (x = 0–6) clusters and the h-BN_VQDs sheets, suggesting that Ni-Cu clusters are highly stable on h-BN_VQDs sheets. For CO adsorption, adsorption energy and charge transfer calculations indicated that the Ni₆ and Ni_6−xCu_x (x = 2 and 3) clusters exhibit the strongest CO binding and highest charge transfer, suggesting them as good candidates for CO gas sensing. These findings provide theoretical insights into the rational design of bimetallic catalysts for gas-sensing applications. Full article

This study focused on creating a novel material by integrating ZnO and CuO nanoparticles into the structure of halloysite using a hydrothermal method. The formation of the nanocomposite was validated through X-ray diffraction and Raman analysis, which confirmed the presence of ZnO and CuO phases without compromising the structure of halloysite. Microscopic analysis revealed a well-distributed presence of metallic oxide nanoparticles within the nanotubular structure of halloysite, which adhered to both the outer and inner surfaces of the clay mineral. Optical characterization identified a substantial density of defects, which played a key role in improving the performance of the supported semiconductors. Furthermore, the narrow band gap at 3.02 eV promoted the mobility of photogenerated charges. Photocatalytic tests yielded promising results, demonstrating a synergistic effect between photocatalysis and adsorption processes that positively influenced the removal of ciprofloxacin from solutions. The material achieved up to 76% removal of the antibiotic within 120 min, utilizing a catalyst concentration of 0.5 g L⁻¹ with a pollutant concentration of 20 mg L⁻¹. In reuse experiments, the material exhibited high recyclability even after multiple reaction cycles. Halloysite-based nanocomposites represent a strategic advancement in environmental remediation technologies, contributing to the development of clean, effective, and reusable materials. Full article

The CO₂ hydrogenation process is thought to be one of the feasible methods for producing methanol fuel, which might be used to fulfill future energy demands. Improving the catalytic efficiency and understanding of the process are essential elements for the viability of CO₂ conversion routes. Here, a co-precipitation method was used to synthesize Ni-Cu bimetallic catalysts supported by chromium oxide (Cr₂O₃). To examine nickel (Ni)’s promoting role, the synthesized catalysts were incorporated with different concentrations of Ni. The N₂ adsorption–desorption isotherm exposed the mesoporous nature of Cr₂O₃-based Ni-Cu catalysts. A Fourier Transform Infrared (FTIR) spectroscopy investigation revealed the effective doping of Ni-Cu metal oxides on the surface of Cr₂O₃ by instigating an FTIR absorption band in the region associated with the FTIR absorption of metal oxides. The uniform morphology and homogenous, as well as highly dispersed, form of both Ni and Cu metal were recorded using a Field Emission Scanning Electron Microscope (FESEM) and X-ray Diffraction (XRD) techniques. The surface chemistry, metal–metal, and metal–support interactions of the Ni-Cu/Cr₂O₃ catalysts were disclosed via temperature program reduction (TPR) as well as X-ray photoelectron spectroscopy (XPS). The synergism between the Ni and Cu metals was revealed using both XPS and TPR techniques, which resulted in improving the catalytic profile of Ni-Cu/Cr₂O₃ catalysts. The activity data obtained by applying a slurry reactor demonstrated the active profile of Ni for CO₂ reduction to methanol in terms of the methanol synthesis rate. The promoting role of Ni was established by observing the progressing and linear increase in methanol selectivity by Ni enrichment to the Ni-Cu/Cr₂O₃ catalysts. Structure and activity studies recognized the promoting role of Ni by experiencing metal–metal and metal–support interactions with highly dispersed metal oxides over the Cr₂O₃ support in the current case. Full article

The most viable way to decarbonize aviation in the near term is through Sustainable Aviation Fuel (SAF), most of which is currently produced via the deoxygenation of fats, oils, and greases (FOG) followed by a separate isomerization step. Multifunctional zeolite-supported catalysts offer several advantages over existing formulations, such as enabling the use of waste FOG streams, performing their deoxygenation via decarboxylation/decarbonylation (deCO_x), and effecting the synthesis of SAF in one-pot. Previous work has shown that while supported Ni-Cu catalysts can afford excellent results in the conversion of waste FOG to fuel-like hydrocarbons via deCO_x, zeolitic materials represent promising supports in formulations employed for the synthesis of SAF. In this contribution, catalysts involving different zeolitic supports and the same Ni-Cu active phase were prepared, characterized, and tested in the conversion of brown grease to SAF to identify the carrier affording the best results. A Ni-Cu/ZSM-5 catalyst displayed the highest conversion and yield of SAF-like hydrocarbons relative to formulations supported on ZSM-22, SAPO-11, or SAPO-34 (these catalysts being referred to herein as NCZSM-5, NCZSM-22, NCSAPO-11, and NCSAPO-34). Full article

This study presents a comprehensive characterization of monometallic (Co or Cu) and bimetallic (Co-Cu) catalysts supported on cerium oxide (CeO₂). XRD and TEM analyses revealed that crystallinity decreases after reduction and that metal dispersion is highly dependent on composition, with cobalt exhibiting greater dispersion than copper. The results confirmed a strong interaction between the metals and CeO₂, which alters the ceria structure and facilitates the reduction of the metal oxides. H₂-TPR and XPS data indicated that monometallic and the bimetallic 15Cu15Co catalysts achieved nearly complete reduction, whereas other bimetallic catalysts did not. Furthermore, CO chemisorption and H₂-TPD demonstrated that the hydrogen activation capacity correlates with the degree of catalyst reduction. Notably, bimetallic catalysts did not show enhanced hydrogen activation compared to their monometallic counterparts. This suggests that the dispersion and metal–support interaction are more critical factors for catalytic activity in this system than the formation of metal alloys. Although the furfural conversion was complete, the selectivity depended greatly on the catalyst composition. The 30Co_R catalyst was most selective for 1,5-pentanediol (38.4%), the 30Cu_R catalyst for 1,2-pentanediol (22.1%), and the bimetallic catalysts for THFA. Reutilising the 30Co_R catalyst after five catalytic cycles resulted in a gradual reduction in the selectivity of 1,5-pentanediol. Full article

Although Cu 3D structures are widely used in electrocatalytic practice, this electrode has not been studied enough in relation to the electrochemical transformation of CO₂ to C2 products. Cu foam samples were deposited from acidic solutions with varying concentrations of primary components (H₂SO₄, CuSO₄, and Cl⁻ ions) with the aim of determining the relationship between catalyst structure and activity/selectivity in producing C2 gaseous compounds during CO₂ electrochemical reduction. The deposited samples were characterized using SEM and electrochemical techniques, including Pb underpotential deposition (UPD), to determine the contribution of crystal facets. The most efficient electrodes were found to be those deposited in a solution without Cl⁻ additives. Their effectiveness was related to the shape and size of the crystallites forming the branches. These crystallites create a spatial structure that supports C-C coupling and C2 gaseous compound formation. The higher catalytic activity and selectivity of this electrode may also be related to its lower Cu(111) facet input to the overall facet distribution and its higher number of structural defects. Despite the higher electrochemically active surface area of samples deposited in the presence of Cl⁻ ions, their lower activity is related to structural characteristics that cause possible mass transfer limitations. Full article

Reppe’s ethynylation of formaldehyde uses coal-based acetylene to produce commercially valuable 1,4-butynediol with a silica-supported copper oxide-bismuth oxide catalyst. Cuprous acetylide (Cu₂C₂) is generally accepted to be the catalytically active phase, which is formed in situ from the CuO-Bi₂O₃/SiO₂ pre-catalyst under ethynylation conditions. The catalytic performance and stability of this sensitive Cu₂C₂ phase are evaluated by long-term experiments (up to 240 h) and by catalyst recycling (10 cycles of 22 h). Powder X-ray diffraction and Raman spectroscopy are found to be the best and the only applicable analytical tools for qualitative evaluation of Cu₂C₂’s crystallinity, purity, and morphology during in situ formation and for phase transformations during the ethynylation. They were continuously correlated with the catalytic performance (1,4-butynediol yield determined by gas chromatography). No catalyst deactivation was observed, indicating outstanding catalyst stability. Observed structural changes within the active Cu₂C₂ phase have obviously limited influence on the catalytic cycle and performance. Full article

Carbon dioxide is naturally present in the Earth’s atmosphere and plays a role in regulating and balancing the planet’s temperature. However, due to various human activities, the amount of carbon dioxide is increasing beyond safe limits, disrupting the Earth’s natural temperature regulation system. Today, CO₂ is the most prevalent greenhouse gas; as its concentration rises, significant climate change occurs. Therefore, there is a need to utilize anthropogenically released carbon dioxide in valuable fuels, such as formic acid (HCOOH). Single-atom catalysts are widely used, where a single metal atom is anchored on a surface to catalyze chemical reactions. In this study, we investigated the potential of Cu@Phosphorene as a single-atom catalyst (SAC) for CO₂ reduction using quantum chemical calculations. All computations for Cu@Phosphorene were performed using density functional theory (DFT). Mechanistic studies were conducted for both bimolecular and termolecular pathways. The bimolecular mechanism involves one CO₂ and one H₂ molecule adsorbing on the surface, while the termolecular mechanism involves two CO₂ molecules adsorbing first, followed by H₂. Results indicate that the termolecular mechanism is preferred for formic acid formation due to its lower activation energy. Further analysis included charge transfer assessment via NBO, and interactions between the substrate, phosphorene, and the Cu atom were confirmed using quantum theory of atoms in molecules (QTAIM) and non-covalent interactions (NCI) analysis. Ab initio molecular dynamics (AIMD) calculations examined the temperature stability of the catalytic complex. Overall, Cu@Phosphorene appears to be an effective catalyst for converting CO₂ to formic acid and remains stable at higher temperatures, supporting efforts to mitigate climate change. Full article

The selective dehydrogenation of ethanol to acetaldehyde is an efficient alternative to biomass valorization. Herein, a series of Cu catalysts supported on Silicalite-1 zeolites with tunable contents of surface silanols and the same Cu loading of 3 wt% were synthesized by an impregnation method. The parent Silicalite-1 supports and as-synthesized Cu/S-1 catalysts were characterized by N₂ adsorption, XRD, SEM, TEM, TGA, DRIFT, ²⁹Si MAS NMR, XPS, and TPR. The Cu dispersion and Cu species distribution of Cu/S-1 catalysts can be modulated by engineering the amount of silanol groups on the support. More silanols present on the surfaces of parent Silicalite-1 supports can promote the Cu dispersion, and lead to a higher Cu⁺/Cu⁰ molar ratio arising from strong interfacial interaction between Cu species and silanols on the Silicalite-1 support via the formation of Si-O-Cu bonds. Thus, higher catalytic activity is achieved. Full article

The production of biodiesel from microalgae presents a sustainable and renewable solution to the growing global energy demands, with catalysts playing a critical role in optimizing the transesterification process. This study examines the emerging catalysts and innovative techniques utilized in converting microalgal lipids into fatty acid methyl esters, emphasizing their impact on reaction efficiency, yield, and environmental sustainability. Sulfuric acid demonstrates excellent performance in in situ transesterification, while NaOH/zeolite achieves high biodiesel yields using ultrasound- and microwave-assisted methods. Metal oxides such as CuO, NiO, and MgO supported on zeolite, as well as ZnAl-layered double hydroxides (LDHs), further enhance reaction performance through their high activity and stability. Enzymatic catalysts, particularly immobilized lipases, provide a more environmentally friendly option, offering high yields (>90%) and the ability to operate under mild conditions. However, their high cost and limited reusability pose significant challenges. Ionic liquid catalysts, such as tetrabutylphosphonium carboxylate, streamline the process by eliminating the need for drying and lipid extraction, achieving yields as high as 98% from wet biomass. The key novelty of this work lies in its detailed focus on the use of ionic liquids and nanocatalysts in microalgae-based biodiesel production, which are often underrepresented in previous reviews that primarily discuss homogeneous and heterogeneous catalysts. Full article

This paper presents the research results on the synthesis of rhenium catalysts MTO, Re₂O₇/Al₂O₃, and M-Re₂O₇/Al₂O₃ (where M = Ni, Ag, Co, Cu) from rhenium compounds (ammonium perrhenate, perrhenic acid, nickel(II) perrhenate, cobalt(II) perrhenate, zinc perrhenate, silver perrhenate, and copper(II) perrhenate) derived from waste materials. Methyltrioxorhenium (MTO) was obtained from silver perrhenate with a yield of over 80%, whereas when using nickel(II), cobalt(II), and zinc perrhenates, the product was contaminated with tin compounds and the yield did not exceed 17%. The Re₂O₇/Al₂O₃ and M-Re₂O₇/Al₂O₃ catalysts were obtained from the above-mentioned rhenium compounds. Alumina obtained in a calcination process of aluminum nitrate nonahydrate was used as a support. The catalysts were characterized in terms of their chemical and phase composition and physicochemical properties. Catalytic activity in model reactions, such as cyclohexene epoxidation and hex-1-ene homometathesis, was also studied. MTO obtained from silver perrhenate showed >70% activity in the epoxidation reaction, thus surpassing commercial MTO (1.0 mol% MTO, room temperature, and reaction time—2 h). Ag-Re₂O₇/Al₂O₃, Cu-Re₂O₇/Al₂O₃, and H-Re₂O₇/Al₂O₃ catalysts were inactive, while Co-Re₂O₇/Al₂O₃ and Ni-Re₂O₇/Al₂O₃ showed low activity (<43%) in the hex-1-ene homometathesis reaction. Only Re₂O₇/Al₂O₃ catalysts achieved >70% activity in this reaction (2.5 wt% Re, room temperature, and reaction time—2 h). The results indicate the potential of using rhenium compounds derived from waste materials to synthesize active catalysts for chemical processes. Full article

Single-atom catalysts (SACs) have emerged as highly promising catalytic materials for the hydrogen evolution reaction (HER), attributed to their maximal atomic utilization efficiency and unique electronic configurations. Many structure parameters can influence the catalytic performance of SACs for HER, and the intrinsic advantages of SACs for HER still need to be summarized. This review systematically summarizes recent advances in SACs for HER. It discusses various types of SACs (including those based on Pt, Co, Ru, Ni, Cu, and other metals) applied in HER, and elaborates the critical factors influencing catalytic performance—specifically, the supports, coordination environments, and synergistic effects of these SACs. Furthermore, current research challenges and future perspectives in this rapidly developing field are also outlined. Full article

Reducing atmospheric carbon dioxide is a critical global priority. This study investigates the influence of Cu-Ni nanoalloy loading on the CO₂ electroreduction efficiency in the context of mesoporous carbon supports. Current methods struggle when it comes to catalyst efficiency, selectivity, and longevity. By synthesizing copper–nickel nanoparticles through chemical reduction and depositing them on porous carbon, this research aimed to optimize catalyst loading and understand the structure–activity relationships. Catalyst performance was evaluated using chronoamperometry and linear sweep voltammetry (LSV). The results showed that 12 wt% catalyst loading achieved optimal CO₂ reduction, outperforming its 36 wt% counterpart by balancing the catalyst quantity. This study reveals that 12 wt% Cu-Ni loading provides a higher CO₂ reduction current density and greater long-term stability than 36 wt% loading, owing to better nanoparticle dispersion and reduced aggregation. Unlike previous Cu-Ni/mesoporous carbon studies, this work uniquely compares different loadings to directly correlate the structure, electrochemical performance, and catalyst durability. Full article

The oxidative degradation of anthocyanins in red wine was investigated under controlled conditions using hydroxyl radicals generated in the presence of Cu (II) as a catalyst. A full factorial experimental design with 23 replicates was used to evaluate the effects of hydrogen peroxide concentration, catalyst dosage, and reaction temperature on anthocyanin degradation over a fixed time. Statistical analysis (ANOVA and multiple regression) showed that all three variables and the main interactions significantly affected anthocyanin loss, with temperature identified as the most influential factor. The combined effects were described by a first-order polynomial model. The activation energies for degradation ranged from 56.62 kJ/mol (cyanidin-3-O-glucoside) to 40.58 kJ/mol (peonidin-3-O-glucoside acetate). Increasing the temperature from 30 °C to 40 °C accelerated the degradation kinetics, almost doubled the rate constants and shortened the half-life of the pigments. At 40 °C, the half-lives ranged from 62.3 min to 154.0 min, depending on the anthocyanin structure. These results contribute to a deeper understanding of the stability of anthocyanins in red wine under oxidative stress and provide insights into the chemical behavior of derived pigments. The results are of practical importance for both oenology and viticulture and support efforts to improve the color stability of wine and extend the shelf life of grape-based products. Full article