Search Results (8,532)

The work reports a facile synthesis of high thermally stable nanocrystalline anatase TiO₂ nanoparticles (NPs) doped with different atomic concentrations (0.5, 1.0, 3.0, and 6.0%) of Gd³⁺ and Nd³⁺ ions by a template-free and one-step solvothermal process, using titanium(IV) butoxide as a titanium precursor and dimethyl sulfoxide (DMSO) as a solvent. The structure and morphology of the Gd³⁺, Nd³⁺, and 0.5%Gd³⁺-0.5%Nd³⁺/doped TiO₂ NPs have been characterized by using various analytical techniques. The Gd³⁺/ and Nd³⁺/TiO₂ molar ratios were found to have a pronounced impact on the crystalline structure, size, and morphology of TiO₂ NPs. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) studies revealed the proper substitution of Ti⁴⁺ by Gd³⁺ and Nd³⁺ ions in the TiO₂ host lattice. The as-prepared Gd_x/TiO₂, Nd_x/TiO₂, and Gd_1.0/Nd_x/TiO₂ bimetallic NPs, x = 0.5, 1.0, 3.0, and 6%, have been investigated as electrocatalysts for hydrogen evolution reaction (HER) in 1.0 M KOH solution using a variety of electrochemical techniques. At any doping percentage, the Gd_1.0/Nd_x/TiO₂ bimetallic NPs showed higher HER catalytic performance than their corresponding counterparts, i.e., Gd_x/TiO₂ and Nd_x/TiO₂. Upon increasing the Nd content from 0.5 to 6.0%, the HER catalytic performance of the Gd_1.0/Nd_x/TiO₂ bimetallic NPs was generally enhanced. Among the studied materials, the bimetallic Gd_1.0/Nd_6.0/TiO₂ NPs emerged as the most promising catalyst with an onset potential of −22 mV vs. RHE, a Tafel slope of 109 mV dec⁻¹, and an exchange current density of 0.72 mA cm⁻². Such HER electrochemical kinetic parameters are close to those recorded by the commercial Pt/C (onset potential: −15 mV, Tafel slope: 106 mV dec⁻¹, and exchange current density: 0.80 mA cm⁻²), and also comparable with those measured by the most active electrocatalysts reported in the literature. The synergistic interaction of Gd and Nd is thought to be the major cause of the bimetallic catalyst’s activity. Full article

Cu/ZnO/Al₂O₃ catalysts are extensively utilized in methanol synthesis from CO and CO₂, which is a vital industrial process and a promising strategy for mitigating CO₂ emissions when renewable green hydrogen is employed. Despite the considerable efforts to study CO₂ hydrogenation over Cu/ZnO, understanding the structure of active sites on Cu/ZnO has remained a major challenge. We studied a series of Cu/ZnO catalysts with various Cu particle sizes and found a volcano-like pattern in methanol selectivity with respect to the Cu particle size. TEM, XPS, and TPD measurements demonstrated the migration of ZnO_x species onto the Cu particle surface and showed a correlation between the ZnO_x-Cu interface and methanol yield. The size of supported Cu particles affects the migration of Zn species onto Cu particle surfaces. Our study has thus explicated the role of the ZnO_x-Cu interface in catalyzing CO₂ hydrogenation to methanol. Full article

Extensive research has been conducted on platinum nanoparticles or clusters supported on zeolite for various catalytic applications, primarily due to the well-defined structure contained within the pore. The preparation and characterization of these particles have been thoroughly examined using advanced techniques such as X-ray absorption fine structures (XAFSs), both in situ and ex situ. In this study, we employed the Wavelet method to analyze the structure of platinum nanoparticles encapsulated within the supercage of a Y zeolite, where XAFS data were collected over a temperature range of 100 K to 423 K, both with and without hydrogen. The adsorption of hydrogen caused a relaxation in the structure of the platinum nanoparticles, thus leading to a decrease in the Pt–Pt distance and resulting in a lower Debye–Waller factor compared to bare nanoparticles. This structural change induced by hydrogen chemisorption aligns with the findings of the density functional theory (DFT) calculations for Pt₁₃ nanoparticles located in the supercage. The relaxation of the structure results in charge redistribution, thereby ultimately generating atomic hydrogen with a partial negative charge, which is crucial for catalytic processes. Full article

The photoelectrocatalytic degradation and mineralization of sulfamethazine (SMT), a sulfonamide drug, were explored in aqueous solution. Working electrodes with TiO₂ coatings on Ti substrates (TiO₂/Ti) were used, which were produced by the dip coating method. TiO₂ film electrodes were analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD) following annealing at 500 °C for 1.5 h. To photoelectrochemically characterize them, photocurrents vs. applied potential curves were used. The photoelectrocatalytic efficiency (PEC) of the TiO₂/Ti electrodes regarding the oxidation of SMT has been assessed with reference to degradation and mineralization under different experimental conditions. The selected drug molecule was effectively degraded following the Langmuir–Hinshelwood (L-H) kinetic model. The degradation efficiency was shown to increase with increasing applied potential bias up to +1.5 V vs. Ag/AgCl. It was found to be more favorable in acidic environments compared to alkaline ones. A decrease in the destruction rate constant was recorded when the pH was increased from 3 to 5.6 (natural pH) and 9. The decomposition rate was shown to first increase and subsequently reach a saturation value at high concentrations of SMT, indicating that the degradation also depends on other parameters (e.g., the rate of the charge or the mass transfer on the electrode double layer). The results of the photoelectrocatalytic experiments were compared to those of electrochemical (EC) and photocatalytic (PC) degradation of SMT. A significant enhancement was recorded in the case of the PEC degradation, leading at +1.5 V to an increase of the apparent rate constants of degradation, k, and mineralization, k_TOC, of 153 and 298%, respectively, compared to the simple photocatalytic process. Full article

The deposition of nanostructured carbon particles on the surface of a catalyst (carburization) is routinely considered an inalienable and undesirable secondary process in Fischer–Tropsch synthesis. However, very little is known about the actual role of the nanocarbon particles and how they influence catalysis. This paper reports research on the influence of carbon deposition on the performance of a cobalt-based Fischer–Tropsch-synthesized catalyst in an industrial-scale fixed-bed reactor (length—6000 mm, inner diameter—16.5 mm). The comparison of the structure and catalytic performance of a pelletized cobalt catalyst with the same catalyst, which was preliminary carburized, is presented. Pellet pore structure, catalyst surface, cobalt cluster morphology and the main catalytic properties (CO conversion, C₅₊ hydrocarbon productivity and selectivity to C₅₊ hydrocarbons and CH₄ formation) were investigated. It is shown that the primary pre-carburization effect is a result of the physical blockage of the catalyst pore structure not followed by drastic changes in the cobalt cluster’s structure. Full article

The g-C₃N₄@ZnIn₂S₄ heterostructures were successfully synthesized through a combination of thermal annealing and hydrothermal methods. To enhance the photocatalytic hydrogen production performance and explore the interface between charge carriers, heterostructures of g-C₃N₄@ZnIn₂S₄ were fabricated using varying weights of g-C₃N₄ nanostructures under visible light irradiation. Remarkably, the photocatalytic hydrogen production efficiency of g-C₃N₄@ZnIn₂S₄ heterostructures with 0.01 g g-C₃N₄ nanostructures was significantly improved, showing approximately 228.6 and 2.58 times higher than that of g-C₃N₄ nanostructures and ZnIn₂S₄ nanostructures, respectively. This enhancement in photocatalytic performance is attributed to the effective utilization of visible light and the efficient separation of photogenerated electron-hole pairs facilitated by the heterojunction structures. Moreover, the reusability test validated the outstanding performance of g-C₃N₄@ZnIn₂S₄ heterostructures, as they maintained high photocatalytic hydrogen production even after undergoing eight cycles without any noticeable decrease in efficiency. This study offers a promising strategy for designing and synthesizing an environmentally friendly g-C₃N₄@ZnIn₂S₄ heterojunction with potential applications in photocatalytic hydrogen evolution. Full article

Agro-industrial activities generate large volumes of wastewater. When this wastewater is discharged to the environment without proper treatment, it represents a serious problem. Bioenergy production can be conducted using wastewater, but the presence of some recalcitrant compounds may require a pre-treatment step. Advanced oxidation processes (AOPs) were traditionally used to treat hazardous materials but have recently been applied in various bioenergy production processes. AOPs are highly competitive water/wastewater treatment technologies and their application in the bioenergy sector is increasing as a pre-treatment process. Despite the increasing interest in using AOPs to enhance biofuel production, there is a lack of comprehensive documentation on their integration into biofuel production operations. This critical review highlights the application of AOPs as pre-treatment for agro-industrial wastewater (AIW) to enhance bioenergy production. It was noted that AOP applications can reduce the COD, VS, TS and total polyphenols, resulting in an improvement in their biodegradability. Moreover, these processes help remove hemicellulose and lignin contents, increasing the production of biogas, biodiesel and bioethanol. Among the different AOPs presented in this work, wet air oxidation showed promise for pre-treating lignocellulosic biomass to produce various energy types, while sonolysis and ozonation proved effective as a biosolid pre-treatment. Ozonolysis, Fenton reagents and photocatalysis are commonly used to selectively remove phenolic compounds and colorants from organic effluents. The high energy requirements and chemicals reagents costs are identified as obstacles to the application of AOPs in bioenergy production. Further studies should investigate the integration of AOPs with other treatment processes to improve the cost-effectiveness. Full article

The development of environment-friendly new Poly-adenosine diphosphate (ADP)-ribose Polymerase (PARP) inhibitors are highly essential because of their involvement in the survival of cancer cells. Therefore, a library of indazolyl-substituted-1,3,4-oxadiazoles known to inhibit PARP in cancer cells was synthesized by a green protocol. Furthermore, the cytotoxic effects of these compounds were evaluated in human MCF-7 breast cancer (BC) cells, which revealed that the compound 2-(3-bromo-4-nitrophenyl)-5-(1-methyl-1H-indazol-3-yl)-1,3,4-oxadiazole (8) inhibited viability with an IC₅₀ value of 1.57 µM. Since the oxadiazole structure was extensively used in medicinal chemistry applications, the reported environment-friendly protocol was superior to the conventional method. Further, computational mechanistic studies revealed that the oxadiazole ring formation occurred spontaneously when compared to the conventional method. Additionally, the in silico bioinformatic studies of oxadiazole binding towards PARP1 showed that compound 8 could bind to PARP1 with higher binding energy (BE) of −7.29 kcal/mol when compound to compound 5s (BE = −7.17 kcal/mol), a known PARP cleavage oxadiazole structure (2-(3,4-Dimethoxybenzyl)-5-(3-(2-fluoro-3-methylpyridin-4-yl)phenyl)-1,3,4-oxadiazole) indicative of the improvement in the optimization process. In conclusion, a newer indazolyl-oxadiazole compound is reported, which could serve as a lead in developing PARP inhibitors in BC cells. Full article

The aim of this work was to investigate a new, simple, one-pot combustion synthesis technique for creating sulphur-based CuS/ZnS p-n heterojunction nanocomposite photocatalysts. This study examined the photocatalytic activity and reusability of these nanocomposites in removing rhodamine B (RhB) dye under visible-light irradiation. Various methods of characterisation were employed to determine the properties of the materials, including particle morphology, crystalline phases, and bandgap energy. The intrinsic reaction parameters, such as catalyst loading, the pH level of the solution, and initial pollutant concentration, were varied to establish the optimal photodegradation conditions. The results showed that a binary CuS/ZnS catalyst with a 10 g L⁻¹ loading, at pH 5, degraded 97% of 5 ppm RhB dye after 270 min of visible light irradiation. Additionally, this composite catalyst exhibited excellent chemical stability and reusability, achieving 83% RhB dye removal after five recycling runs. Scavenger tests identified the photogenerated holes (h⁺) and superoxide free radicals (•O₂) as the primary reactive species responsible for degradation. This study provides valuable insight into the design of highly efficient nanomaterials for removing organic pollutants in wastewater, and a possible reaction mechanism is proposed. Full article

A one-pot hydrogenolysis/hydrogenation reaction of maltose to two moles of sorbitol has been carried out over different supported Cu catalysts in water at 180 °C and 40 bar of H₂. Only the catalysts supported on silicas were found to be effective in this reaction, giving up to 86% yield in the desired product while the bare supports and the catalysts supported on alumina or silica alumina gave messy reactions. The peculiar activity of the two Cu/Silica systems tested was ascribed to high metal dispersion and suitable polarity of the catalyst surface. In exposing metallic Cu particles on the surface, the reduced catalyst showed unusual stability in the presence of water as a solvent and could be reused several times without any treatment. Full article

Functionalized polyethylene-based nanocomposites were prepared by in situ polymerization of ethylene with modified or neat MCM-41 nanoparticles (NMCM-41). Two different synthetic approaches were investigated to improve the compatibility between the hydrophobic HDPE matrix and the hydrophilic NMCM-41: (i) incorporation of UA into the polymeric matrix by copolymerization with ethylene, promoted by the zirconocene catalyst under homogeneous conditions, in the presence of pristine NMCM-41; (ii) use of undecenoic acid (UA) as an interfacial agent to obtain decorated NMCM-41 to be used as nanofiller for the in situ ethylene polymerization, catalyzed by Cp₂ZrCl₂/MAO under supported conditions. The strong polar character of the carboxylic group is expected to either increase the hydrophilicity of the HDPE chains (strategy i) or interact with the NMCM-41 surface and provide an additional link to the polymeric chains via copolymerization of the vinyl group under supported conditions (strategy ii). Although metallocene catalysts have been shown to copolymerize olefins with functional monomers, the presence of oxygen-containing compounds in the reaction media strongly affects the polymerization activity as a result of the interaction of functional groups with the electrophilic active center of the catalyst. Thus, UA was pre-contacted with tri(isobutyl)aluminum (TIBA) prior to its use in the polymerization to reduce the deactivating character of the carboxylic acid groups towards the zirconocene catalyst. The influence of the UA presence on the polymerization behavior of the protection step is discussed, and the polymerization activities observed for the different approaches are compared. In addition, the thermal behavior and structural details of the resulting materials have been characterized. The impact of using neat or functionalized NMCM-41 on the final dispersion within the polymeric matrix is also analyzed, which is correlated with the mechanical performance exhibited by these HDPE_UA_NMCM-41 nanocomposites. Full article

The present work describes the synthesis, characterization, and photomineralization activity of synthesized Ce_1−xZn_xO_2−x solid solution catalysts allowing the degradation of diclofenac as a model of anti-inflammatory medicines in water. The oxygen-deficient photocatalyst Ce_1−xZn_xO_2−x (CeZnx), produced by mixing ZnO and CeO₂, is characterized for its crystallographic parameters, specific surface area, and morphology. Photomineralization activity determination using TOC analysis shows efficient diclofenac photo-oxidation under sunlight. Moreover, the results indicate that the coexistence of Zn²⁺ and Ce⁴⁺ and the oxygen vacancies rate in CeZnx solid solution are key factors for strong drug mineralization. Ultimately, CeZn0.1, which is one of the photocatalysts synthesized in the present work, represents a cheap and efficient reagent for organic matter photomineralization in wastewater. Full article

At present, passive NO_x adsorbers (PNAs) represent one of the most effective technologies for addressing NO_x emissions from diesel engines during cold-start periods. Conventional PNAs, which primarily consist of noble metals (such as Pt, Pd, and Ag) loaded on metal oxides or zeolites, share the common drawback of high production costs. Consequently, developing low-cost PNAs with outstanding NO_x storage performance remains a significant challenge. In this study, a series of CuxBa5Ce adsorbents were synthesized using the impregnation method, and a monolithic adsorbent was employed to evaluate NO_x storage and release performance. Techniques such as XRD, UV-Vis DRs, H₂-TPR, XPS, and in situ DRIFTs confirmed the crucial roles of Cu and Ba in NO_x storage and release. Specifically, the incorporation of Cu into CeO₂ enhanced NO_x storage performance. Moreover, in the Cu3Ba5Ce adsorbent, the addition of Ba not only introduced new storage sites and altered the stability of NO_x adsorption species but also helped prevent the aggregation of CuO, thereby prolonging the complete NO_x storage duration and satisfying desorption temperature requirements. The Cu3Ba5Ce adsorbent exhibited the most favorable NO_x storage performance, including a complete NO_x storage time of 135 s and a NO_x storage efficiency exceeding 50% at 80 °C over a 10 min period. While PNAs loaded with noble metals, such as Pd/CeO₂ and Pt/CeO₂, exhibited NO_x storage efficiencies below 50% after adsorbing for 5 min at 80 °C. Therefore, this research offered a crucial strategy for developing non-noble-metal-loaded, Ce-based PNAs. Full article

Novel tungsten-modified mixed-valence tin oxides (Sn₃O₄) with two oxidation numbers, such as Sn²⁺ and Sn⁴⁺, were successfully prepared by the cetyltrimethylammonium bromide (CTAB)-assisted solvothermal method in one-step using tin (II) chloride dihydrate and sodium tungstate (IV) dihydrate as the precursors for dye degradation of methyl orange (MO) under visible light irradiation. The synthesized materials were characterized by various techniques to investigate the surface/structural morphology and the optical property. The presence of tungsten and the optimized amount of CTAB in the preparation method were favorable for the photocatalytic dye degradation reaction. In particular, when 0.03 of CTAB was added to W-modified Sn₃O₄ (W-Sn₃O₄@CTAB) and its concentration was 0.6 mg/mL, 10 mg/L of MO could be decolorized almost completely in 40 min, with the apparent reaction rate constant of 0.0496 min⁻¹. The improvement of photocatalytic activity for this proposed W-Sn₃O₄ results from increased reduction power, enhanced separation of electron–hole pairs, extended visible light absorption range, and optimized band structure by CTAB additive. The radical trapping experiments showed that the main reactive species during the photocatalytic reaction are superoxide ions. The developed photocatalysts may contribute to the development of environmental improvement technology. Full article

Operando diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) is combined with online mass spectrometry (MS) to help to resolve a long-standing debate concerning the active phase of RuO₂ supported on rutile TiO₂ (RuO₂@TiO₂) during the CO oxidation reaction. DRIFTS has been demonstrated to serve as a versatile probe molecule to elucidate the active phase of RuO₂@TiO₂ under various reaction conditions. Fully oxidized and fully reduced catalysts serve to provide reference DRIFT spectra, based on which the operando CO spectra acquired during CO oxidation under various reaction conditions are interpreted. Partially reduced RuO₂@TiO₂ was identified as the most active catalyst in the CO oxidation reaction. This is independent of the reaction conditions being reducing or oxidizing and whether the starting catalyst is the fully oxidized RuO₂@TiO₂ or the partially reduced RuO₂@TiO₂. Full article