Catalysis Letters最新文献

This work introduces innovative Bi₂O₃-ZnO/TiO₂ (BZT) composite photocatalysts, developed via a simple electrospinning technique. The incorporation of Zn²⁺ and Bi³⁺ ions was confirmed through high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy (XPS). XPS analysis confirmed the presence of Zn and Bi elements on the surface of TiO₂ nanofibers, with oxidation states of + II and + III, respectively. The band gaps, estimated through the Kubelka–Munk function and ultraviolet-visible diffuse reflectance spectroscopy, decreased from 3.18 eV for pristine TiO₂ to 2.9 eV for the 1%Bi₂O₃-ZnO/TiO₂ (1BZT) composites, resulting in improved light-harvesting capabilities. Photocatalytic performance studies, particularly methylene blue degradation under visible light, revealed notable improvements for Bi₂O₃-ZnO/TiO₂ systems compared to ZnO/TiO₂ and TiO₂. The 1%Bi₂O₃-ZnO/TiO₂ heterostructure was found as efficient photocatalyst with 98% photodegradation of MB. The maximum rate constant, 0.0234 min^− 1, was observed for 1BZT nanofibers, which was 4.97 and 16.7 times greater than those of ZnO/TiO₂ and TiO₂, respectively. This enhancement highlights the synergistic effect between Zn²⁺ and Bi³⁺, alongside the enhanced visible light absorption by Bi³⁺, which collectively elevated the photocatalytic efficiency. The heterojunction formed among Bi³⁺, Zn²⁺, and Ti⁴⁺ significantly facilitated the separation of photogenerated charge carriers, which is essential for high photocatalytic efficiency. Quenching experiments confirmed the important roles in the photocatalytic degradation of MB were played by ^•OH and ^•O⁻ ₂ rather than the h⁺ radical under sun light. The 1%Bi₂O₃-ZnO/TiO₂ photocatalyst exhibited the highest level of activity and excellent reusability, retaining its photocatalytic performance over multiple cycles.

Graphical abstract

A sustainable and cost-effective alternative for environmental applications is the use of PGM-free catalysts, which are crucial for pollutant removal. This research employed the sol-gel method to synthesize stable and effective mesoporous CeCuO_x mixed oxide catalysts to facilitate the oxidation of CO and C₃H₆ emissions at lower temperatures. Additionally, pure CeO₂ and CuO were also synthesized for comparative analysis. Catalytic performance was considerably increased by doping CeO₂ with Cu, whereas pure CuO and CeO₂ showed modest activity. XRD, SEM, BET, XPS, Raman spectroscopy, H₂-TPR, and CO-TPD showed that increasing Ce content produced a consistent pore structure without aggregation. In contrast, higher Cu concentration resulted in bulk CuO production, which led to decreased catalytic performance. In particular, the production of isolated CuO_x species partly covered or clogged pores when the Cu level was above 20 wt%, which reduced the total number of effective sites for O₂ activation. Compared to other mixed and pure oxides, the ideal catalyst, Ce₇Cu₃Ox (T_{90, CO} = 178 °C), showed smaller particle size, higher specific surface area, and a larger lattice oxygen species and oxygen vacancies concentration. Additionally, it showed the best CO and C₃H₆ conversion due to its high Ce³⁺ concentration and interfacial active Cu species ratio. H₂-TPR and CO-TPD analyses demonstrated that Ce-Cu mixed oxides with optimal Ce/Cu ratios, particularly Ce₇Cu₃O_x and Ce₅Cu₅O_x, achieve enhanced reducibility and balanced CO adsorption, which are critical for maximizing catalytic reactivity. The catalytic activity exhibited the following sequence: Ce₇Cu₃O_x > Ce₅Cu₅O_x > Ce₉Cu₁O_x > Ce₃Cu₇O_x > Ce₁Cu₉O_x > CuO > CeO₂. This investigation offers a valuable perspective on the mechanisms of Ce-Cu interaction, which contributes to developing high-performance CeCuOx catalysts that are free of PGMs and operate under realistic reaction conditions.

Graphical abstract

Aliphatic chiral secondary alcohols are important chiral intermediates widely used in the synthesis of drugs and fine chemicals. The whole cells of recombinant E. coli co-expressing alcohol dehydrogenase and glucose dehydrogenase were used to catalyze the asymmetric reduction of three fatty ketones without the addition of exogenous cofactors. The reaction medium and reaction conditions were systematically studied. As expected, the kinds of co-solvents, the molar ratio of glucose/substrate, temperature, pH and cell amount have important influence on the reaction. Under the optimal condition (glucose at 1.5 times substrate concentration, isopropanol at 2%, PBS (0.1 M, pH 8.0), and 45℃), the cells co-expressing both enzymes efficiently catalyzed the asymmetric reduction of three fatty ketones to the corresponding (S)-fatty alcohols. The conversion and ee value of the products were both greater than 99% after 8 h reaction at 1 M of substrate concentration, and the space-time yield was between 346 ~ 470 g/(L·d). All the products can be obtained on gram scale. The results indicated that this method has potential application value in the efficient and green synthesis of aliphatic chiral secondary alcohols.

Graphical Abstract

In this study, a three-dimensional WO₃/BiVO₄ heterojunction was synthesized via layer-by-layer spin-coating and blow-drying, followed by heat treatment in a hydrogen-argon atmosphere to produce the WO₃/H-BiVO₄ photoanode. The introduction of oxygen vacancies improved electron-hole separation efficiency, thereby enabling efficient water-splitting. X-ray photoelectron spectroscopy (XPS) analysis revealed that WO₃/H-BiVO₄ exhibited a lower reflectance infrared (RIR) value, signifying a higher concentration of surface oxygen vacancies compared to WO₃/BiVO₄. Photoelectrochemical measurements at 1.23 V vs. RHE demonstrated that WO₃/BiVO₄ achieved photocurrent densities and carrier densities 5-fold and 1.3-fold greater, respectively, than WO₃. Notably, WO₃/H-BiVO₄ exhibited further enhancements, with photocurrent densities and carrier densities 1.4-fold and 2.4-fold higher, respectively, than WO₃/BiVO₄. These findings underscore the critical role of heterojunction construction in boosting photocatalytic activity, while oxygen vacancy introduction further elevates photoelectric performance. Specifically, WO₃/H-BiVO₄ achieved a peak photocurrent density of 6.5 mA·cm^− 2 at 1.6 V vs. RHE, attributed to its superior photogenerated charge separation and surface charge transfer efficiency. This study highlights that rationally expanding interfacial contact and optimizing oxygen vacancy concentrations are effective strategies for enhancing photocatalytic performance. These insights provide a valuable framework for the design and development of highly efficient photocatalysts for water-splitting applications.

Graphical Abstract

Ethanol is regarded as a promising and green hydrogen donor due to its easy and large-scale production from abundant biomass resources. In this work, a nitrogen-doped carbon-encapsulated Co catalyst (Co@NC-800) was synthesized by a simple pyrolysis process and demonstrated promising activity in the hydrodeoxygenation of sulfoxides and pyridine N-oxides, producing sulfide and pyridine with good yields ranging from 80.3 to 99.0%. Moreover, the activity of the Co@NC-800 catalyst remained stable after 5 runs, indicating good stability.

Graphical Abstract

In this work we have synthesized few layered MoS₂ nanosheets and to boost the electrochemical hydrogen evolution reaction (HER) over as an electrocatalyst, in situ Ag nanoparticles are loaded uniformly on the sheets by using simple and one pot method of hydrothermal synthesis. The overpotential drop recorded in Ag/MoS₂ is almost double as compared to pristine MoS₂ which indicates that decoration of Ag has lowered the barrier energy of the HER reaction and increased the efficiency of catalyst. In turn, layered structure of MoS₂ provided the matrix for uniform loading of Ag nanoparticles. More importantly, lower Tafel value (74 mV/dec), lower charge transfer resistance and increased electric double layer capacitance in 10 wt% Ag/MoS₂ clearly implies the enhanced HER performance as well as robust stability owing to improved interface between Ag and MoS₂ along with increased exposed active sites. Therefore, this work explicitly focuses on the study of in situ loading of Ag over MoS₂ which provided more accessibility to the active sites to elevate the HER activity.

Graphical Abstract

The selective epoxy product of limonene, specifically 1, 2-limonene epoxide, serves as a crucial intermediate with diverse applications. However, achieving high conversion rates and selectivity in selective epoxidation reactions presents significant challenges. In this study, the bimetallic metal-organic framework (MOF) material was synthesized via a hydrothermal method, which was designated as Zr₂Co₈-MOF-BTC-H. The incorporation of zirconium (Zr) markedly alters both the morphology and structure of the bimetallic Zr₂Co₈-MOF-BTC-H catalytic material. Notably, there were pronounced changes in the binding energies of the bimetallic elements within the Zr₂Co₈-MOF-BTC-H framework, which suggests that cobalt (Co) and Zr coexist within the coordination structure and exhibit substantial interactions. Compared to single-metal MOF materials, the acidity of the bimetallic Zr₂Co₈-MOF-BTC-H was significantly enhanced, thereby facilitating the selective epoxidation of limonene. Under optimal reaction conditions, epoxidation conversion achieved 91.8%, while selectivity for epoxy compounds reached 88.6%. Furthermore, after five cycles of use, there was no significant decline in activity for the Zr₂Co₈-MOF-BTC-H material, indicative of its remarkable recyclable stability.

This research paper examines the performance of strontium (Sr) promoted nickel (Ni) catalysts supported on magnesium oxide (MgO) in the dry reforming of methane (DRM) into syngas. The characterization of these catalysts is carried out using a range of analytical techniques, including measurements of surface area and porosity, thermogravimetric analysis (TGA), X-ray diffraction (XRD), transmission electron microscopy (TEM), hydrogen temperature-programmed reduction (H₂-TPR), temperature-programmed oxidation (TPO) and desorption (TPD) studies. The concentration of active sites, as well as the presence of acid and basic sites on the catalyst surface, are the primary factors influencing the catalytic activity of the 5Ni + xSr-MgO catalysts (where x = 1, 2, 3, and 4 wt%). Ni, supported over MgO, has few active sites and lacks a strong basic site, which results in minimum catalytic activity. Adding 1–4 wt% Sr over 5Ni-MgO induces the formation of higher concentrations of active sites and an increased population of strong basic sites. At 3 wt% Sr loading, concentration of active sits, strong basic sites, and strong acid sites are optimum which can activate CH₄ and CO₂ timely for DRM rather than coke deposition. So, 5Ni + 3Sr-MgO achieved 58.4% CH₄ conversion (with H₂/CO ratio 1.1) at 700 ^°C and ~ 82% CH₄ conversion at 750 ^°C. This study offers insights for turning a cheap catalyst system (5Ni-MgO) into a high-performance catalyst by optimum loading of Sr promotor.

Graphical abstract

Catalytic transfer hydrogenation (CTH) of α,β-unsaturated aldehydes to α,β-unsaturated alcohols over metal oxide catalysts is of potential for industrial application. Herein, we have developed a Ni/f-Al₂O₃ catalyst comprising atomically dispersed Ni^δ+ (2 < δ < 3) species on porous leaf-like Al₂O₃, over which a > 97% yield of furfuryl alcohol (FOL) from CTH of furfural (FFR) is obtained with a turnover frequency (TOF) of 216 h^− 1. Most importantly, the catalyst can be recycled at least 6 times without obvious loss of activity. Its superior catalytic performance can be attributed to the abundant and stable Ni^δ+-type acid-base pairs on the surface of Ni/f-Al₂O₃.

In this study, a heterogeneous catalyst was designed by comprising dodecatungstophosphoric acid and SBA-16 by wet impregnation method. It is characterized by different physiochemical techniques BET, EDX, TGA, FT-IR, ²⁹Si NMR spectroscopy, and TEM. The chemicals shift of the Si–O–Si peaks in the ²⁹Si NMR suggesting strong interaction between the active species and support. Its catalytic activity showed significant performance in the production of butyl levulinate, a promising fuel blend candidate via esterification of levulinic acid with n-butanol (93% conversion and 99% selectivity), following second order kinetic reaction with an activation energy 64 kJ/mol. Characterization of the recycled catalyst shows intact properties and reusability for up to three consecutive cycles. The present catalyst is superior to the previously reported ones with an outstanding turnover number (3571) and turnover frequency (595 h⁻¹). The industrial applicability of the catalyst was demonstrated by the esterification of different bio-based acids with minimal environmental impact.

Graphical Abstract