Topics in Catalysis最新文献

Iron is a crucial trace element in DNA synthesis, oxygen transport and various biological processes. However, iron overdose can result in health issues like liver damage and neurodegenerative disorders. The present study reports a green and eco-friendly route for biosynthesis of lead oxide nanoparticles using Bougainvillea flower extract. The structural and chemical composition of lead oxide was investigated by XRD and XPS methods, respectively. The average diameter size of lead oxide was ~ 400 nm. The lead oxide-modified glassy carbon electrode (GCE) was investigated for electrochemical sensing of iron (III) ions in aqueous solutions. The lead oxide electrodes show a nearly linear increase in peak current density with varying iron concentrations, indicating effective detection capabilities. The lead oxide displayed high sensitivity, selectivity and durability for detecting iron (III) ions with a detection limit of 8.22 mM in the linear detection range of 0-0.1 M. The results highlight oxide-based electrochemical sensors as a promising candidate for real-time detection and quantification of iron (III) ions in aqueous environments.

The selection of appropriate catalysts is critical for the efficient operation of hydrotreaters, due to the diverse types of reactions inherent to the process. In this study, various Type I and Type II sulfided NiMo/γ-Al₂O₃ hydrotreating catalysts were prepared using chelating agents and support modification, and the apparent activity differences were evaluated using step response experiments. The experiments were conducted in a trickle bed reactor at 300 °C and 120 barg using phenanthrene and carbazole as model compounds while the apparent activities were elucidated using dynamic reactor modelling. It was found that the addition of citric acid to the impregnation solution to chelate the Ni leads to an average 30% increase in the active site density for hydrogenation (HDA) and hydrodenitrogenation (HDN), without significantly affecting the reaction rate coefficients suggesting similar activity per active site. Phosphorus modification of the support, however, results in larger reaction rate coefficients for both hydrogenation of phenanthrene as well as adsorption and reaction coefficients for carbazole, resulting in more active catalysts both for HDA and HDN. This enhanced activity is accompanied by increased selectivity to HDN suggesting that catalysts exhibiting higher activity for HDA reactions are more susceptible to inhibition by organonitrogen compounds. In addition, dynamic activity testing indicated that catalysts with superior HDN activity attain their new steady state in the shortest time. Thus, the selection of catalysts for efficient hydrotreater operation necessitates activity testing under dynamic conditions to account for competing and inhibitory reactions, rather than relying solely on steady-state activity. Such an approach, allows for the elucidation of the differences in HDA and HDN activity, providing valuable insights to support the catalyst selection process.

Nepafenac (NPC) is a topical nonsteroidal anti-inflammatory drug used to treat postoperative eye pain and inflammation following cataract surgery. It is also effective against photophobia, intraocular pressure, hyperemia, and itching. However, NPC has side effects, such as dry eyes, eye itching, eyelid flaking or drooping, eye discharge, dizziness, nausea, hypersensitivity, and allergic conjunctivitis (eye allergy). Therefore, the detection of NPC in physiological and biological samples is of great importance. Rapid, inexpensive, and practical advanced analytical methods are required for routine analysis. To date, there have been very few studies on NPC analysis. In this study, a sensitive and reproducible electrochemical sensor was developed for the determination of NPC. Voltammetric measurements were carried out using paste electrodes modified with multi-walled carbon nanotubes (MWCNTs: MWCNT, MWCNT-NH₂, MWCNT-COOH) and polymer-based sensors using monomers (phenylalanine, lysine, glycine, and proline). Among these, MWCNT-NH₂ modified paste electrode (PE) and poly(glycine)-modified glassy carbon electrode (GCE) showed the highest sensitivity and were selected for detailed analysis. Electrochemical behavior and electrode mechanisms of NPC were studied using different voltammetric methods. The optimum signals were observed at pH 9.0 for MWCNT-NH₂PE and pH 10.0 for poly(glycine)/GCE in Britton–Robinson buffer. The linear detection range was 0.4–128.0 µM for MWCNT-NH₂ PE and 1.18–12.98 µM for poly(glycine)/GCE. The limit of detection values (LOD and LOQ) were calculated as 0.025 µM and 0.41 µM, respectively. This work presents an electrochemical method and a new generation sensor that is more sensitive, selective and easy to fabricate than existing analytical techniques for NPC detection.

Herein, the effects of precursor (urea, melamine, and dicyandiamide), calcination temperature, and Pt/Au loading on the photothermal carbon dioxide reduction performance of g-C₃N₄ catalyst were studied, and its physicochemical and photochemical properties were characterized. The results showed that the increase of calcination temperature stabilized the crystal structure but decreased the carbon dioxide adsorption and light absorption capacity. Urea-derived g-C₃N₄ calcined at 550 °C achieved CO and CH₄ yields of 1.42 and 0.21 µmol·g^-1·h^-1, respectively, which had the strongest photoelectron transfer capacity and catalytic efficiency. Through the surface plasmon effect, Pt and Au can effectively improve the light absorption property and charge transfer efficiency of g-C₃N₄ catalyst, thus effectively improving the catalytic performance. Pt loading (2 wt%) enhanced CH₄ selectivity to 64.4% (vs. 12.9% for pure g-C₃N₄), while Au loading (3 wt%) boosted CO production to 4.17 µmol·g^-1·h^-1, A higher noble metal loading ratio leads to a decline in catalytic performance, possibly due to the agglomeration of precious metal particles.

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The urgent demand for high-performance and sustainable energy storage solutions necessitates the development of advanced electrolytes with superior electrochemical properties. Hybrid lithium electrolytes, which integrate the advantages of inorganic and organic ionic conductors, have emerged as promising candidates for next-generation energy storage devices. This review presents a comprehensive bibliometric analysis of 1569 research articles from 2019 to 2024, sourced from Scopus and Web of Science (WOS) databases, highlighting the rising research focus on hybrid electrolytes. Key material properties such as wide electrochemical windows, thermal and chemical stability, low toxicity, and reduced volatility are critical for enhancing battery performance. The discussion encompasses recent advancements in solid-state, polymer, and hybrid electrolytes, emphasizing their role in improving energy density, cycling stability, and safety. Furthermore, this study examines the challenges associated with hybrid electrolytes, including ionic conductivity limitations, interfacial compatibility, and scalability for industrial applications. The integration of novel materials such as NASICON-type ceramics, perovskites, sulfides, and garnet-based electrolytes is explored for their potential to revolutionize lithium-ion battery technologies. By bridging the gap between fundamental research and practical implementation, this review provides insights into the future directions of hybrid electrolytes, paving the way for more efficient and sustainable energy storage systems.

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In this study, Fe₂O₃/TiO₂ nanocomposite was synthesized via a hydrothermal method and evaluated for its dual functionality in visible-light-driven photocatalytic dye degradation and electrochemical nitrite sensing. Structural, optical, and morphological characterizations confirmed the formation of a well-defined heterojunction with improved charge separation and visible light absorption. The nanocomposite demonstrated enhanced photocatalytic performance, achieving 100% degradation of methylene blue (MB) within 120 minutes under visible light. Kinetic studies confirmed pseudo-first-order behavior with an increased rate constant compared to individual TiO₂ and Fe₂O₃ components. Furthermore, the Fe₂O₃/TiO₂ modified glassy carbon electrode exhibited excellent electrocatalytic activity for nitrite detection, achieving a low detection limit of 1.4 µM with a linear response over a wide concentration range. These findings highlight the potential of Fe₂O₃/TiO₂ nanocomposites as multifunctional materials for environmental remediation and chemical sensing applications.

Graphical Abstract

Single-atom catalysts (SACs) offer a promise of providing unique properties, superior selectivity, and maximum atomic efficiency compared to traditional nanoparticle catalysts. However, their stability under reaction conditions remains a critical challenge. This study examines the reactivity and structural evolution of a thermally stable (~ 700 K) model Rh/Fe₃O₄(001) SAC, where Rh is substituted into the surface layer. Previously, we demonstrated that water formation via the Mars-van Krevelen mechanism during formic acid conversion destabilizes in-surface octahedral Rh, yielding active Rh adatoms and clusters that dynamically re-incorporate into the Fe₃O₄ lattice at 700 K. Here, we follow the evolution of the catalyst structure and changes in the CO and CO₂ formation kinetics during multiple formic acid conversion cycles. Temperature-programmed reaction spectroscopy (TPRS) cycles to 700 K reveal that small Rh clusters formed during the first several cycles can re-incorporate into the Fe₃O₄(001) lattice. Over subsequent cycles, larger nanoparticles eventually form and persist. These effects are further accelerated when annealing is limited to only 550 K. Changes in the CO₂ formation/desorption temperature in TPRS reveal that the activity for formic acid dehydrogenation increases progressively from single atoms to clusters and nanoparticles. This study provides fundamental insights into the dynamic behavior and performance of SACs during catalytic reactions.

Series of nickel catalysts, supported on γ-alumina and promoted with different Ce loading (1–5%), have been studied in conventional and sorption-enhanced CO₂ methanation reaction. In addition, a detailed kinetic water adsorption study has been performed on commercial zeolite (13X, 4 A, 3 A). The decrease in adsorption capacity is observed for all zeolites with increasing temperature. The highest water adsorption capacity is observed for the 13X zeolite for all investigated temperatures (100–350 °C). However, the 13X zeolite showed loss of 50% of its capacity after 100 adsorption/desorption cycles while the 4 A and 3 A zeolites are almost unchanged. The catalyst characterization results indicate that upon addition of a small amount of ceria, dispersion of the Ni catalyst is improved as well as CO₂ conversion in conventional methanation. The catalyst that showed best performance was further tested for sorption-enhanced methanation, where water sorbents (13X, 4 A, 3 A) are mixed with catalysts. All the tests performed in presence of zeolites showed an increase in CO₂ conversion compared to those carried out in their absence. In addition, a 34% increase in CO₂ conversion was observed when increasing the H₂/CO₂ ratio to 8 for the system with 13X zeolite. This indicates the enhancement effect when water is removed from the reaction.

Water availability and quality are worldwide issues due to limited resources and contamination stemming from human activities. Different contaminants, including organic and inorganic compounds and microorganisms, threaten surface and groundwater resources. Organic pollutants include pesticides, detergents, pharmaceuticals, cosmetics, organic dyes, etc. Among the organic pollutants, synthetic dyes are one of the serious environmental threats to human and aquatic life. Methyl orange (MO) is a widely used artificial dye in different applications, including paper, leather, textiles, gasoline, food additives, and the pharmaceutical industry. Therefore, monitoring MO in environmental samples like wastewater, groundwater, and food products is crucial. Here, Prussian blue (PB) thin-layer modified ITO electrodes were fabricated and utilized to monitor MO in wastewater samples. SEM and XRD were used to characterize the morphology of the fabricated electrodes. The effect of the PB layer was investigated, and it was found that the use of PB/ITO deposited at 20 cycles depicts the highest current response. Effects of MO concentration, scan rate, and pH on the electrochemical response were investigated. The modified electrode was very sensitive, detecting as little as 5.7 nmol L⁻¹ while working effectively with concentrations from 100 to 10 µmol L⁻¹. The modified electrode showed the capability to monitor MO in groundwater samples.