Topics in Catalysis最新文献

We synthesized a bismuth-MOFs@CNTs (BiBTC@CNTs) catalyst using a microwave-assisted solvothermal method. The mass ratios of CNTs and BiBTC varied from 0 to 2, 5, and 10% (denoted as BiBTC@CNTs-x, x = 0 to 2, 5, and 10). The characteristics of the catalyst were determined by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and diffuse reflectance spectroscopy (UV-Vis DRS). The catalytic activity of the material was tested by photodegradation of rhodamine B. The structure of BiBTC@CNTs-x displayed a UU-200 and CNT structure with rod-shaped interweaving between the CNT fibers. The results indicated that BiBTC@CNTs-2 had the most significant ability to degrade RhB, achieving 98% degradation in 180 min. The increased separation of electron-hole pairs via a built-in electric field between CNT and BiBTC is responsible for the improved photocatalytic degradation of RhB, as observed in the XPS spectrum, transient photocurrent response, electrochemical impedance spectroscopy (EIS), and Mott-Schottky plots. In addition, the catalyst mass, dye concentration, pH of the medium, and radical scavengers were investigated. Furthermore, free radicals (O²⁻) and electrons (e-) played the primary and most influential role in the photocatalytic degradation of both dyes, with a minor contribution from the photogenerated holes (h+). Kinetic study of the dye degradation process followed a first-order kinetic model.

This study focused on the development of vanadium-based catalysts for formic acid production from glucose. The influence of different vanadium precursors on the catalytic activity of titania supported catalysts was contemplated and compared to the performance of commercial and synthesized unsupported V₂O₅. The obtained results reveal a successful deposition of multiple vanadium species on TiO₂ as confirmed by XRD, Raman, and UV-Vis measurements. Catalyst screening identifies V⁵⁺ species as main player indicating its important oxidizing potential. Afterwards, the key reaction conditions, as temperature, time, pressure and catalyst loading, were optimized as well as the state of the catalyst after the reaction characterized.

Enzymes have revolutionized conventional industrial catalysts as more efficient, eco-friendly, and sustainable substitutes that can be used in different biotechnological processes, food, and pharmaceutical industries. Yet, the enzymes from nature are engineered to make them adapt and enhance their durability in the industrial environment. One promising approach involves the combined use of multiple enzymes that catalyze highly selective and sequential reactions in a single reaction vessel. The multi-enzymatic biocatalytic systems, achieved through gene fusion, fusion proteins, DNA manipulation and bioconjugation, protein engineering, or attachment to solid support materials for immobilization, such as protein-polymer, silica, metal organic framework, Carbon nanotubes or graphene based hybrids, have found widespread utility across various sectors, including the food industry, wastewater treatment, drug delivery, biosensors and methanol production. Enzyme conjugation enables the creation of novel enzymes with improved kinetics and synergistic effects. Researchers can evolve fusion proteins by fusion enzymes which can evolve novel catalytic activities in Biotechnological processes. These engineered enzymes can contribute in synthetic Biology in construction of synthetic system for various applications. Enzyme conjugation helps in metabolic engineering by optimization of pathways. Researchers can develop pathways for production of Bio-sensors, pharmaceuticals, biofuels and other valuable industrial products. This review comprehensively explores the techniques and applications of enzyme conjugation, highlighting its pivotal role in advancing the field of bio-catalysis.

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In this study, iron oxide nanofins (Fe₂O₃ NFs) were synthesized using Elaeocarpus hygrophilus leaves extract and decorated on graphitic carbon nitride (gCN) substrate to form the Fe₂O₃/gCN composite, as a photocatalytic candidate to degrade Rhodamine B (RhB) and produce hydrogen peroxide (H₂O₂). The morphological, structural, electrochemical, and optical properties of Fe₂O₃/gCN were determined via analytical methods, including scanning electron microscopy, energy dispersive X-ray, scanning electron microscopy field emission, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, photoluminescence spectroscopy, ultraviolet–visible diffuse reflectance spectroscopy (UV-DRS), electrochemical impedance spectroscopy, and photocurrent repones. As a result, the band gap of Fe₂O₃/gCN was determined to be 2.79 eV through UV-DRS and Kubelka–Munk function, which is lower than that of pure gCN (2.82 eV). Such phenomenon provides an RhB photodegradation efficiency of 99.23% within 120 min at pH 4, as well as an H₂O₂ concentration of 4237.03 μM/g h under visible light radiation, over the 1.0Fe₂O₃/gCN sample. Further insights elucidate that ⋅O₂^– plays an important part in the photocatalysis, contributing to light-driven RhB degradation and H₂O₂ production. The catalytic performance of 1.0Fe₂O₃/gCN was also maintained after 4 consecutive cycles, which indicates a high potential for environmental remediation and cleaner production processes using light as the driving force.

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The oxygen reduction reaction (ORR), occurred at cathodes in fuel cells, eco-friendly energy-conversion system, requires efficient electrocatalysts to overcome sluggish reaction kinetics. In this work, to enhance the ORR performance by decreasing potentials, we developed carbonized zeolite-imidazolate frameworks (ZIF) containing Co atoms (Co–C). The final product is produced by two-step process including (i) the formation of ZIF with Co species, and (ii) carbonization of the ZIF using high temperature treatment. Morphological characterizations revealed that the Co–C has polygon-shaped ZIF-based materials with metallic Co particles wrapped by layered carbon structures. The amount of Co atoms is found to be ~ 4 wt%, possessing a large surface area of 718 m²/g. X-ray photoelectron spectroscopy measurements further supported the formation of sp² carbon structures with N-doping. The Co–C products exhibit an efficient electrocatalytic ORR performance in alkaline media, with their onset and half-wave potentials as of 0.97 and 0.86 V, comparable to those of Pt/C. Furthermore, Co–C shows the excellent cyclic durability and stability against for methanol poisoning. Collectively, this system including Co-based active species on ZIF networks provides a promise route for the development of efficient ORR electrocatalysts.

Several sepiolite-based catalysts have been prepared and investigated for pyrolytic H₂ production from a post-consumer mixture of residual plastics. The experimental installation involved a two-stage reaction system: first, the plastic mixture was thermally pyrolyzed at 500 ºC; then, the generated volatiles were reformed by increasing the temperature to 700 ºC and 800 ºC in the presence of the sepiolite-based catalysts. The real mixture came from non-separate waste collection streams and contained post-consumer polypropylene (rigid and film), expanded polystyrene, high-impact polystyrene, and polyethylene. The results demonstrated that the two-stage pyrolysis technique using sepiolite-based catalysts successfully generated hydrogen. The effects of the type of polymer, temperature, and catalyst were analyzed. The higher production of hydrogen (27.2 mmol H₂/g) was obtained when the mixture of plastic waste was pyrolyzed and then the volatiles were reformed at 800 °C with the SN5-800 12 nickel-modified sepiolite. Additionally, the generation of hydrogen also increased after acidifying natural sepiolite (from 18.2 mmol H₂/g plastic for natural sepiolite to 26.4 mmol H₂/g for acidified sepiolite at 800 ºC with a plastic/catalyst ratio of 1:2). Finally, the carbon deposited in the catalysts was examined. Approximately, only 20% of the carbon that was deposited in the sepiolite-based catalysts was filamentous carbon; the majority was amorphous carbon.

The results have therefore shown that it is possible to obtain a hydrogen-rich gas from the reforming of the pyrolysis vapors of a mixture of plastic waste using a low-cost catalyst based on nickel-modified sepiolite.

Presently, the creation of metal nanoparticles (NPs) using plant extracts has rapidly gained an appealing aspect in the realm of modern nanobiotechnology, with substantial merits over traditional techniques. In this context, cadmium oxide (CdO) NPs have been created utilizing a bio-inspired green synthetic approach using Citrus limetta peel extract. The active organic biomolecules within the peel extract functioned as reductants and stabilizers for NPs, resulting in pure CdO NPs. The structural, chemical, optical, and topological traits were evaluated utilizing XRD, FTIR, FESEM, EDX, HRTEM, UVDRS, and PL analyses. The synthesized CdO NPs are about 54 nm in size with a quasi-spherical morphology. The computed band gap of NPs was 2.59 eV, which validated the cubic phase formation of CdO NPs. The photocatalytic studies of the as-fabricated CdO NPs were investigated through Rhodamine B (RhB) dye degradation via H₂O₂-assisted AOP under sunlight. The effect of H₂O₂, photocatalyst loading, RhB dye concentration, contact time, scavengers, and recyclability study was also investigated in detail to demonstrate the functionality of the photocatalyst. Approximately 85% of the dye was decomposed within 60 min, revealing its excellent photocatalytic performance of CdO NPs. Therefore, the research outcomes thus offer that the CdO NPs may have a substantial potential for ecological remediation through a photocatalytic approach.

A new ZnO/MXene material was made using a simple hydrothermal method and heat treatment for measuring glucose without enzymes in sports drinks and human blood samples. The best ZnO/MXene-300 material, made at 150 °C and heated at 300 °C, had a large surface area of 152 m2/g, high current density of 1.12 mA/cm2, and low activation energy of 32.6 kJ/mol for glucose oxidation. The sensor could measure a wide range of glucose levels (0.01-12 mM) with a low detection limit (0.005 µM), worked well in the presence of other substances, remained stable (93.6% after 7 days), and gave consistent results (RSD of 3.2%). The material was tested by measuring glucose in sports drinks and blood samples, with measured values close to the actual values (96.4–104.5%) and high precision (RSDs of 2.8% and 3.8%). These results show that ZnO/MXene materials are promising for making sensitive and stable glucose sensors that don’t need enzymes.

Catalysts are essential for accelerating chemical reactions without altering the reaction itself. They can be homogeneous or heterogeneous, with heterogeneous catalysts being more recognized due to their lower energy consumption and cost-effectiveness. Biocatalysts, such as enzymes, are highly selective and efficient. The performance of catalysts is influenced by factors such as ideal porosity, pore width, surface area, and promoters like rare earth metals, alkaline, and alkaline earth metals. The effectiveness of multivalent metals as homogeneous or heterogeneous catalysts depends on a variety of variables, including coexistence, pH, formulation, and others. Currently, Fe-based catalysts, such as magnetite, olivine, and ilmenite, have gained interest due to their lower cost, higher reactivity, and stability. Metal-organic frameworks have gained interest as catalyst supports due to their high porosity, higher surface area, and ability to alter the size and shape of pores. The growing global population has led to environmental pollution and energy crises, necessitating the need for clean, renewable energy sources. This review focuses on the potential and utility of sustainable green catalysts like nanocatalysts and biochar-based catalysts for the efficient and sustainable production of biofuels. In addition, the usage of metal oxides, heteropoly acids, and aluminuminosilicate catalysts for wastewater remediation is also discussed in this review.