Frontiers of Chemical Science and Engineering最新文献

In photocatalytic studies, tetragonal bismuth vanadate (t-BiVO₄) is not promising due to its wide band gap. However, according to previous studies, the tetragonal phase is inevitable when the monoclinic bismuth vanadate (m-BiVO₄) is modified. Therefore, it is necessary to find ways to improve the photoresponse and photocatalytic ability of t-BiVO₄ under visible light. In this study, Yb³⁺ and Tm³⁺ co-doped BiVO₄ was synthesized by a simple hydrothermal method, and its microstructure, morphology and optical properties were characterized and analyzed by scanning electron microscope, transmission electron microscopy, Brunauer-Emmett-Teller, X-ray diffraction, Raman, X-ray photoelectron spectroscopy, diffuse reflectance spectra, photoluminescence, upconversion luminescence and other means. The results show that BiVO₄:Yb³⁺/Tm³⁺ (BVYT) has a high content of tetragonal phase (about 80%), showing the characteristics of t-BiVO₄. BVYT shows a higher separation efficiency of photogenerated carriers, its transient photocurrent response intensity increased by about 3 times, and the photocatalytic efficiency is significantly improved compare with the undoped m-BiVO₄. Under simulated sunlight, BVYT completely degraded methylene blue (MB) solution and rhodamine B solution in 45 and 90 min, respectively, and the reaction rate was significantly improved. BVYT also shows excellent photocatalytic ability under visible light, about 35% of MB solution was degraded within 45 min under visible light irradiation (> 420 nm), this is because Yb³⁺ effectively promotes the upconversion luminescence of Tm³⁺ in response to visible light, and the energy cycle mechanism of Yb-Tm-Tm is proposed. Consequently, BiVO₄ with high content of tetragonal phase has excellent photoactivity, even exceeding m-BiVO₄. This is a novel discovery in the field of photocatalysis, which provides a broader application prospect for BiVO₄ in photocatalysis.

Photocatalytic CO₂ reduction is a promising solution to simultaneously provide renewable chemical fuels and address the greenhouse effect. However, designing practical photocatalysts with advanced architectures remains challenging. Herein, we report the preparation of a novel CdIn₂S₄/TiO₂ binary heterojunction via an in situ solvothermal approach, which exhibits superior photocatalytic activity for sunlight-driven CO₂ reduction. The CdIn₂S₄/TiO₂ composites exhibit significantly enhanced photocatalytic performance for CO₂ reduction compared to unmodified TiO₂. Among them, the 3% CdIn₂S₄/TiO₂ composite has optimal CO and CH₄ evolution rates of 18.32 and 1.03 µmol·g⁻¹·h⁻¹, respectively. The yield of CO is 4.7 times higher than that of pristine TiO₂. This improved photocatalytic activity of the CdIn₂S₄/TiO₂ heterostructure can be attributed to its large surface area, extended light absorption range and high separation efficiency of photogenerated electron-hole pairs, which are supported by the results of photoluminescence spectroscopy and the photoelectrochemical measurements. Moreover, the photocatalytic mechanism based on the binary CdIn₂S₄/TiO₂ heterojunction is proposed and separation process of photogenerated electron-hole pairs is discussed. In brief, we aim to provide insights into the application of TiO₂ in energy conversion processes through the construction of heterogeneous junctions.

This perspective discusses three alternative techniques which complement conventional infrared spectroscopy for obtaining vibrational information about zeolite catalysts and adsorbed molecules: inelastic neutron scattering, infrared micro-spectroscopy, and two-dimensional infrared spectroscopy. The techniques are illustrated briefly and future prospects for their use discussed.

Currently, the conversion of waste plastics into high-value products via catalytic pyrolysis enables the advancement of plastics’ open-loop recycling. However, enhancing selectivity remains a critical challenge. This study introduces a novel approach to catalytic pyrolysis, utilizing a combination of MCM-41 and modified gallium-based HZSM-5 catalysts, to achieve exceptional selectivity for aromatic liquid-phase products from linear low-density polyethylene. Firstly, to enhance the probability of dehydroaromatization optimization, the type and proportion of metal active sites within the HZSM-5 catalyst are fine-tuned, which would establish equilibrium with acid sites, resulting in a remarkable 15.72% increase in the selectivity of aromatic hydrocarbons. Secondly, to enhance the accessibility of volatiles to active sites, mesoporous MCM-41 with cracking capabilities is introduced. The doping ratio of MCM-41 is meticulously controlled to facilitate the diffusion of cracked volatiles to the active centers of modified gallium-based HZSM-5, enabling efficient reforming reactions. Experimental findings demonstrate that MCM-41 significantly enhances the dehydroaromatization activity of the modified gallium-based HZSM-5 catalyst. Under the influence of MCM-41:Zr₂Ga₃/HZSM-5 = 1:2 catalyst, the selectivity for aromatic hydrocarbons reaches an impressive 93.11%, with a notable 60.01% selectivity for benzene, toluene, ethylbenzene, and xylene. Lastly, this study proposes a plausible pathway for the generation of high-value aromatic hydrocarbons using the combined catalyst.

Unspecific peroxygenases exhibit high activity for the selective oxyfunctionalization of inert C(sp³)-H bonds using only H₂O₂ as a clean oxidant, while also exhibiting sensitivity to H₂O₂ concentration. CdS-based semiconductors are promising for the photosynthesis of H₂O₂ owing to their adequately negative potential for oxygen reduction reaction via a proton-coupled electron transfer process, however, they suffer from fast H₂O₂ decomposition on the surface of pristine CdS. Therefore, [Cp*Rh(bpy)H₂O]²⁺, a highly selective proton-coupled electron transfer catalyst, was anchored onto a supramolecular polymer-grafted CdS nanoflower to construct an efficient integrated photocatalyst for generating H₂O₂, mitigating the surface issue of pristine CdS, increasing light absorption, accelerating photonic carrier separation, and enhancing oxygen reduction reaction selectivity to H₂O₂. This photocatalyst promoted the light driven H₂O₂ generation rate up to 1345 µmol·L⁻¹·g⁻¹·h⁻¹, which was 2.4 times that of pristine CdS. The constructed heterojunction photocatalyst could supply H₂O₂ in situ for nonspecific peroxygenases to catalyze the C-H oxyfunctionalization of ethylbenzene, achieving a yield of 81% and an ee value of 99% under optimum conditions. A wide range of substrates were converted to the corresponding chiral alcohols using this photo-enzyme catalytic system, achieving the corresponding chiral alcohols in good yield (51%–88%) and excellent enantioselectivity (90%–99% ee).

Owing to its uncomplicated synthetic methodology and exorbitant market demand, malachite green is widely used in numerous industries, particularly as a fungicide in aquaculture. Considering its intrinsic toxicity and potential long-term health impacts, deployable and cost-effective strategies must be developed for eliminating water-soluble malachite green. In this study, chemically activated phosphogypsum, a byproduct of fertilizer production, was used to remove malachite green from an aqueous system. Due to its low cost and abundance, the use of phosphogypsum as a sorbent material may significantly reduce the cost of adsorption-based processes. Moreover, its structural durability allows efficient recycling without significant deformation during reactivation. However, untreated phosphogypsum exhibits minimal efficiency in adsorbing synthetic dyes due to its unfavorable surface chemistry. Our investigation revealed that Zn activation induced a noticeable increase in pore volume from 0.03 to 0.06 cm³·g⁻¹. A 60 mg·L⁻¹ sorbent dose, pH 7, 150 r·min⁻¹, and operational temperature of 30 °C produced 99% quantitative sorption efficiency. Response surface methodology and artificial neural network were used to optimize process parameters by validating experimental values. No detectable toxicity was observed in Escherichia coli when exposed to the treated water.

NaA zeolite (Si/Al = 1.00) has been commercially applied for capturing radioactive ⁹⁰Sr²⁺ because of its high surface charge density, effectively stabilizing the multivalent cation. However, owing to its narrow micropore opening (4.0 Å), large micron-sized crystallites, and bulkiness of hydrated Sr²⁺, the Sr²⁺ exchange over NaA has been limited by very slow kinetics. In this study, we synthesized nanocrystalline low-silica X by minimizing a water content in a synthesis gel and utilizing a methyl cellulose hydrogel as a crystal growth inhibitor. The resulting zeolite exhibited high crystallinity and Al-rich framework (Si/Al of approximately 1.00) with the sole presence of tetrahedral Al sites, which are capable of high Sr²⁺ uptake and ion selectivity. Meanwhile, the zeolite with a FAU topology has a much larger micropore opening size (7.4 Å) and a much smaller crystallite size (∼340 nm) than NaA, which enable significantly enhanced ionexchange kinetics. Compared to conventional NaA, the nanocrystalline low-silica X exhibited remarkably increased Sr²⁺-exchange kinetics (> 18-fold larger rate constant) in batch experiments. Although both the nanocrystalline low-silica X and NaA exhibited comparable Sr²⁺ capacities under equilibrated conditions, the former demonstrated a 5.5-fold larger breakthrough volume than NaA under dynamic conditions, attributed to its significantly faster Sr²⁺-exchange kinetics.

Higher alcohol synthesis directly from syngas is highly desirable as one of the efficient non-petroleum energy conversion routes. Co⁰–CoO catalysts showed great potential for this reaction, but the alcohol selectivity still needs to be improved and the crystal structure effect of CoO on catalytic behaviors lacks investigation. Here, a series of tetrahedrally coordinated CoO polymorphs were prepared by a thermal decomposition method, which consisted of wurtzite CoO and zinc blende CoO with varied contents. After diluting with SiO₂, the catalyst showed excellent performance for higher alcohol synthesis with ROH selectivity of 45.8% and higher alcohol distribution of 84.1 wt % under the CO conversion of 38.0%. With increasing the content of wurtzite CoO, the Co⁰/Co²⁺ ratio gradually increased in the spent catalysts, while the proportion of highly active hexagonal close packed cobalt in Co⁰ decreased, leading to first decreased then increased CO conversion. Moreover, the higher content of zinc blende CoO in fresh catalyst facilitated the retention of more Co²⁺ sites in spent catalysts, promoting the ROH selectivity but slightly decreasing the distribution of higher alcohols. The catalyst with 40% wurtzite CoO obtained the optimal performance with a space time yield toward higher alcohols of 7.9 mmol·g_cat⁻¹·h⁻¹.

There are many disadvantages such as small detection range and environmental restrictions on application conditions, when the single quantum dot powder or solution is used for fluorescent probe detection. In this paper, the blue fluorescent silicon quantum dots and green fluorescent carbon quantum dots were prepared, and their fluorescence color changes after mixing in different proportions were investigated under different pH conditions. When the two quantum dots were mixed with a concentration of 0.1 mg·mL⁻¹ and a mass ratio of 1:1, the fluorescence color change could be better displayed at a pH from 1 to 14. Meanwhile, the double quantum dots were prepared into two forms (ink and film), successfully realizing the device application of the fluorescent probe. The films and inkjet-printed labels were used to test the spoilage of food (pork, milk, etc.), and the color change data of the labels were collected during the spoilage test. These data were used for neural network training to predict the spoilage changes of foods.

Lower olefins, produced from syngas through Fischer-Tropsch synthesis, has been gaining worldwide attention as a non-petroleum route. However, the process demonstrates limited selectivity for target products. Herein, a hybrid catalyst system utilizing Fe-based catalyst and SAPO-34 was shown to enhance the selectivity toward lower olefins. A comprehensive study was conducted to examine the impact of various operating conditions on catalytic performance, such as space velocity, pressure, and temperature, as well as catalyst combinations, including loading pattern, and mass ratio of metal and zeolite. The findings indicated that the addition of SAPO-34 was beneficial for enhancing catalytic activity. Furthermore, compared with AlPO-34 zeolite, the strong-acid site on SAPO-34 was identified to crack the long-chain hydrocarbons, thus contributing to the lower olefin formation. Nevertheless, an excess of strong-acid sites was found to detrimentally impact the selectivity of lower olefins, attributed to the increased aromatization and polymerization of lower olefins. The detailed analysis of a hybrid catalyst in Fischer-Tropsch synthesis provides a practical strategy for improving lower olefins selectivity, and has broader implications for the application of hybrid catalyst in diverse catalytic systems.