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In this study, novel perovskite-type oxygen transport membranes were designed and synthesised by a scalable reverse co-precipitation. The substitution of Cu2+ and Zn2+ for partial Fe3+ in La0.7Ca0.3Co0.3Fe0.7O3–δ led to the generation of additional oxygen vacancies, an expansion in crystal volume for enhanced oxygen ion transport, and the formation of holes fostering higher concentrations of electronic conducting carriers, thereby improving oxygen permeability. The membrane’s [Detail] ...
Download coverA functional hybrid nano-hydroxyapatite (carboxymethyl cellulose-phytic acid-n-HA, CMC-PA-n-HA) was prepared by adding CMC and PA. The results of Fourier transformation infrared spectra, X-ray diffraction, thermal gravimetric analysis and dispersion experiments indicated that the addition of CMC and PA affected the morphology, crystallinity and crystal size of hybrid n-HA, and CMC endowed hybrid n-HA with excellent dispersion. Scanning electron microscope results showed that CMC-PA-n-HA nanoparticle could be uniformly dispersed in chitosan (CS) matrix to obtain composite membrane by casting technology, so that the highest tensile strength of CMC-PA-n-HA/CS composite membrane was 69.64% and 144.45% higher than that of CS membrane and n-HA/CS composite membrane, respectively. Contact angle test showed that CMC-PA-n-HA effectively improved hydrophilicity of the CS membrane. The simulated body fluid immersion results indicated that the CMC-PA-n-HA/CS composite membrane not only exhibited good degradability but also promoted bone-like apatite deposition. The cell proliferation experiments proved that the introduction of PA made the composite membrane have better cell adhesion and proliferation ability. Antibacterial tests demonstrated that PA could effectively improve the antibacterial properties of the composite membrane, which is expected to be applied as guide bone tissue regeneration membrane.
In this study, perovskite-type La0.7Ca0.3Co0.3Fe0.6M0.1O3–δ (M = Cu, Zn) powders were synthesized using a scalable reverse co-precipitation method, presenting them as novel materials for oxygen transport membranes. The comprehensive study covered various aspects including oxygen permeability, crystal structure, conductivity, morphology, CO2 tolerance, and long-term regenerative durability with a focus on phase structure and composition. The membrane La0.7Ca0.3Co0.3Fe0.6Zn0.1O3–δ exhibited high oxygen permeation fluxes, reaching up to 0.88 and 0.64 mL·min−1·cm−2 under air/He and air/CO2 gradients at 1173 K, respectively. After 1600 h of CO2 exposure, the perovskite structure remained intact, showcasing superior CO2 resistance. A combination of first principles simulations and experimental measurements was employed to deepen the understanding of Cu/Zn substitution effects on the structure, oxygen vacancy formation, and transport behavior of the membranes. These findings underscore the potential of this highly CO2-tolerant membrane for applications in high-temperature oxygen separation. The enhanced insights into the oxygen transport mechanism contribute to the advancement of next-generation membrane materials.
The scalable production of high grade activated carbon from abundant coal for supercapacitors application is an efficient way to achieve high value-added utilization of coal sources. However, this technology is challenging due to lack of comprehensive understanding on the mechanism of activation process and effect of external factors. In this paper, the effect of activating temperature and time on the specific capacitance of coal-based activated carbon prepared by H2O steam activation was studied using the response surface method. Under optimal conditions, coal-based activated carbon exhibits the largest specific capacitance of 194.35 F·g–1, thanks to the appropriate pore/surface structure and defect degree. Density functional theory calculations explain in detail the mechanism of contraction of aromatic rings and overflow of H2 and CO during the activation. Meanwhile, oxygen-containing functional groups are introduced, contributing to the pseudocapacitance property of coal-based activated carbon. This mechanism of reactions between aromatic carbon and H2O vapor provides understanding on the role of water during coal processing at the molecular level, offering great potential to regulate product distribution and predict rate of pore generation. This insight would contribute to the advancement of other coal processing technology such as gasification.
As an important technology in fine chemical production, the selective hydrogenation of α,β-unsaturated aldehydes has attracted much attention in recent years. In the process of α,β-unsaturated aldehyde hydrogenation, a conjugated system is formed between >C=C< and >C=O, leading to hydrogenation at both ends of the conjugated system, which competes with each other and results in more complex products. Therefore, improving the reaction selectivity is also difficult in industrial fields. Recently, many researchers have reported that surface-active sites on catalysts play a crucial role in α,β-unsaturated aldehyde hydrogenation. This review attempts to summarize recent advances in understanding the effects of surface-active sites (SASs) over metal catalysts for enhancing the process of hydrogenation. The construction strategies and roles of SASs for hydrogenation catalysts are summarized. Particular attention has been given to the adsorption configuration and transformation mechanism of α,β-unsaturated aldehydes on catalysts, which contributes to understanding the relationship between SASs and hydrogenation activity. In addition, recent advances in metal-supported catalysts for the selective hydrogenation of α,β-unsaturated aldehydes to understand the role of SASs in hydrogenation are briefly reviewed. Finally, the opportunities and challenges will be highlighted for the future development of the precise construction of SASs.
Reducing the production costs of clean energy carriers such as hydrogen through scalable water electrolysis is a potential solution for advancing the hydrogen economy. Among the various material candidates, our group demonstrated transition-metal-based materials with tunable electronic characteristics, various phases, and earth-abundance. Herein, electrochemical water oxidation using Cu2Se–V2O5 as a non-precious metallic electrocatalyst via a hydrothermal approach is reported. The water-splitting performance of all the fabricated electrocatalysts was evaluated after direct growth on a stainless-steel substrate. The electrochemically tuned Cu2Se–V2O5 catalyst exhibited a reduced overpotential of 128 mV and provided a reduced Tafel slope of 57 mV·dec–1 to meet the maximum current density of 250 mA·cm–2. The optimized strategy for interfacial coupling of the fabricated Cu2Se–V2O5 catalyst resulted in a porous structure with accessible active sites, which enabled adsorption of the intermediates and afforded an effective charge transfer rate for promoting the oxygen evolution reaction. Furthermore, the combined effect of the catalyst components provided long-term stability for over 110 h in an alkaline solution, which makes the catalyst promising for large-scale practical applications. The aforementioned advantages of the composite catalyst overcome the limitations of low conductivity, agglomeration, and poor stability of the pure catalysts (Cu2Se and V2O5).
The fabrication of heterojunction catalysts is an effective strategy to enhance charge separation efficiency, thus boosting the performance of photocatalysts. This work presents the synthesis and investigation of a novel KNbO3/Bi4O5Br2 heterostructure catalyst for photocatalytic N2–to–NH3 conversion under light illumination. While morphology analysis revealed KNbO3 microcubes embedded within Bi4O5Br2 nanosheets, the composite exhibited no significant improvement in specific surface area or optical property compared to Bi4O5Br2 due to the relatively wide band gap and low surface area of KNbO3. The main contribution lies in the enhanced separation efficiency of photogenerated electrons and holes. Besides, the band structure analysis suggests that KNbO3 and Bi4O5Br2 exhibit suitable band potentials to form a type II heterojunction. Benefiting from the higher Fermi level of KNbO3 than Bi4O5Br2, the electron drift at the contact region thus occurs and leads to the formation of a built-in electric field with the direction from KNbO3 to Bi4O5Br2, accelerating electron migration and improving the operational efficiency of the photocatalysts. Consequently, the KNbO3/Bi4O5Br2 catalyst shows an increased photoactivity, achieving an NH3 generation rate 1.78 and 1.58 times those of KNbO3 and Bi4O5Br2, respectively. This work may offer valuable insights for the design and synthesis of heterojunction composite photocatalysts.
The incineration technology of kitchen waste is one of the effective technologies to achieve the resource utilization of municipal solid waste. Pyrolysis is an important stage of incineration. Indole is a rich initial product in the pyrolysis process of kitchen waste, and the presence of H2O has a significant impact on the decomposition of indole to form NOx precursors. Therefore, this study uses density functional theory method to study the effect of H2O on the thermal decomposition of indole to produce NH3, HNCO, and HCN. When H2O participates in the reaction, it can provide oxidative groups to generate a new product HNCO, which is different from the previous findings by indole pyrolysis without the presence of H2O. Meanwhile, this study theoretically proves that NH3 is easier to form than HCN. This is consistent with the phenomenon that NH3 release is higher than HCN release in pyrolysis experiment. In addition, compared with the individual pyrolysis of indole, the participation of H2O reduces the energy barriers for the formation of NH3 and HCN during indole pyrolysis, thereby promoting the formation of NH3 and HCN.
Particle segregation and mixing behavior play a crucial role in industrial processes. This study investigates the saturated jetsam fraction, which indicates the maximum capacity of flotsam to entrain jetsam, in an initially separated binary fluidized bed with particle size differences. According to the value of saturated jetsam fraction, three distinct regimes—segregation, mixing, and an intermediate regime—are identified. Moreover, intriguing relationships between the saturated jetsam fraction and superficial gas velocity are observed, exhibiting monotonic trends in both the segregation and mixing regimes, while a unique volcano-shaped curve in the intermediate regime. Additionally, a comprehensive entrainment model based on two-fluid model elucidates the observed phenomena, emphasizing the significance of mixing behavior in fluidized layer on the saturated jetsam fraction. This work offers potential insights for evaluating segregation in industrial applications.
The advent of antiproliferative drug-eluting vascular stents can dramatically reduce in-stent restenosis via inhibiting the hyperproliferation of vascular smooth muscle cells. However, the antiproliferative drugs also restrain the repair of the injured endothelial layer, which in turn leads to the very later in-stent restenosis. Evidence points that competent endothelium plays a critical role in guaranteeing the long-term patency via maintaining vascular homeostasis. Boosting the regeneration of endothelium on the implanted vascular stents could be rendered as a promising strategy to reduce stent implantation complications. In this regard, bioactive zinc(II) metal-organic framework modified with endothelial cell-targeting Arg-Glu-Asp-Val peptide was embedded in poly(lactide-co-caprolactone) to serve as a functional coating on the surface of titanium substrate, which can promote the proliferation and migration of endothelial cells. The in vitro cell experiments revealed that the zinc(II) metal-organic framework embedded in the polymer coating was able to modulate the behaviors of endothelial cells owing to the bioactive effects of zinc ion and peptide. Our results confirmed that zinc(II) metal-organic framework eluting coating represented a new possibility for promoting the repair of the damaged endothelium with potential clinical implications in vascular-related biomaterials and tissue engineering applications.
Under optimal process conditions, pyrolysis of polyolefins can yield ca. 90 wt % of liquid product, i.e., combination of light oil fraction and heavier wax. In this work, the experimental findings reported in a selected group of publications concerning the non-catalytic pyrolysis of polyolefins were collected, reviewed, and compared with the ones obtained in a continuously operated bench-scale pyrolysis reactor. Optimized process parameters were used for the pyrolysis of waste and virgin counterparts of high-density polyethylene, low-density polyethylene, polypropylene and a defined mixture of those (i.e., 25:25:50 wt %, respectively). To mitigate temperature drops and enhance heat transfer, an increased feed intake is employed to create a hot melt plastic pool. With 1.5 g·min–1 feed intake, 1.1 L·min–1 nitrogen flow rate, and a moderate pyrolysis temperature of 450 °C, the formation of light hydrocarbons was favored, while wax formation was limited for polypropylene-rich mixtures. Pyrolysis of virgin plastics yielded more liquid (maximum 73.3 wt %) than that of waste plastics (maximum 66 wt %). Blending polyethylenes with polypropylene favored the production of liquids and increased the formation of gasoline-range hydrocarbons. Gas products were mainly composed of C3 hydrocarbons, and no hydrogen production was detected due to moderate pyrolysis temperature.
