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Industrially, petroleum naphtha reforming and steam cracking are two major multistep and energy-intensive sources for p-xylene production. Additionally, p-xylene is also produced by selective toluene disproportionation, heavy (C9) aromatics trans-alkylation and isomerization of xylenes. Rapidly changing market dynamics from fuels to petrochemicals coupled with growing petrochemicals demand has led to the further exploration of economical and highly p-xylene selective processes by using surplus low-value aromatics. Methylation of toluene with methanol has been envisaged as one such potential opportunity to produce p-xylene. For the purpose, significant efforts have been made in the past forty years to develop suitable shape selective zeolite catalysts and technologies to make toluene methylation a highly p-xylene selective process. Current paper briefly highlights various advancements in the toluene methylation process development and aims to provide an extensive review of several works put up in the past to design suitable catalysts, catalyst's limitations and developmental challenges for toluene methylation. Further, this paper provides an useful insight for two competing chemistries of toluene alkylation and side-by-side methanol reactions. Finally, motivated by competitive chemistry of methanol conversion reactions, existing catalytic limitations and novel synthesis opportunities in engineering shape selective zeolite catalysis, a way forward is proposed to arrive at a logical and futuristic catalyst design strategy for p-xylene production via toluene methylation. The proposed strategy is envisaged to offer low-to-moderate catalyst acidity, improved toluene methylation activity, high p-xylene selectivity and improved catalyst life which, otherwise, up till now have been the bottlenecks to develop distinctly economical toluene alkylation to p-xylene process. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Materials Engineering / Cailiao Gongcheng is the property of Journal of Materials Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The development of renewable and affordable energy is crucial for building a sustainable society. In this context, establishing a sustainable infrastructure for renewable energy requires the integration of energy storage, specifically use of renewable hydrogen. The hydrogen evolution reaction (HER) of electrochemical water splitting is a promising method for producing green hydrogen. Recently, two-dimensional nanomaterials have shown great promise in promoting the HER in terms of both fundamental research and practical applications due to their high specific surface areas and tunable electronic properties. Among them, molybdenum disulfide (MoS2), a non-noble metal catalyst, has emerged as a promising alternative to replace expensive platinum-based catalysts for the HER because MoS2 has a high inherent activity, low cost, and abundant reserves. At present, greatly improved activity and stability are urgently needed for MoS2 to enable wide deployment of water electrolysis devices. In this regard, efficient strategies for precisely modifying MoS2 are of interest. Herein, the progress made with MoS2 as an HER catalyst is reviewed, with a focus on modification strategies, including phase engineering, morphology design, defect engineering, heteroatom doping, and heterostructure construction. It is believed that these strategies will be helpful in designing and developing high-performance and low-cost MoS2-based catalysts by lowering the charge transfer barrier, increasing the active site density, and optimizing the surface hydrophilicity. In addition, the challenges of MoS2 electrocatalysts and perspectives for future research and development of these catalysts are discussed. [ABSTRACT FROM AUTHOR]

Use of oral agents to treat gestational diabetes mellitus remains controversial. Recent recommendations from the Society for Maternal-Fetal Medicine assert that metformin may be a safe first-line alternative to insulin for gestational diabetes mellitus treatment and preferable to glyburide. However, several issues should give pause to the widespread adoption of metformin use during pregnancy. Fetal concentrations of metformin are equal to maternal, and metformin can inhibit growth, suppress mitochondrial respiration, have epigenetic modifications on gene expression, mimic fetal nutrient restriction, and alter postnatal gluconeogenic responses. Because both the placenta and fetus express metformin transporters and exhibit high mitochondrial activity, these properties raise important questions about developmental programming of metabolic disease in offspring. Animal studies have demonstrated that prenatal metformin exposure results in adverse long-term outcomes on body weight and metabolism. Two recent clinical randomized controlled trials in women with gestational diabetes mellitus or polycystic ovary syndrome provide evidence that metformin exposure in utero may produce a metabolic phenotype that increases childhood weight or obesity. These developmental programming effects challenge the conclusion that metformin is equivalent to insulin. Although the Society for Maternal-Fetal Medicine statement endorsed metformin over glyburide if oral agents are used, there are few studies directly comparing the 2 agents and it is not clear that metformin alone is superior to glyburide. Moreover, it should be noted that prior clinical studies have dosed glyburide in a manner inconsistent with its pharmacokinetic properties, resulting in poor glycemic control and high rates of maternal hypoglycemia. We concur with the American Diabetes Association and American Congress of Obstetricians and Gynecologists, which recommend insulin as the preferred agent, but we believe that it is premature to embrace metformin as equivalent to insulin or superior to glyburide. Due to the uncertainty of the long-term metabolic risks of either metformin or glyburide, we call for carefully controlled studies that optimize oral medication dosing according to their pharmacodynamic and pharmacokinetic properties in pregnancy, appropriately target medications based on individual patterns of hyperglycemia, and follow the offspring long-term for metabolic risk. [ABSTRACT FROM AUTHOR]

This paper discusses the effect of a ZnGeN2 layer inserted into the wells of Type-I InGaN/GaN QWs LEDs on the electrical and optical properties by using the Silvaco TCAD Simulator. First, the new structure is compared to the standard type-I LED based on InGaN. We found that using ZnGeN2 layer in the In0.2Ga0.8N-QWs LED leads to wavelength extending from the blue to the red region. Next, we highlighted the effect of quantum well number and In-molar fraction in the wells of InxGa1-xN/ZnGeN2 type-II LEDs. As a result, increasing the number of wells from two to six QWs creates an extension of spontaneous emissions while keeping a low concentration of indium in the wells (x = 0.16) and improving the electrical and optical properties, as we found an improvement in light output power of 10.7% at 40Acm-2. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Materials Engineering / Cailiao Gongcheng is the property of Journal of Materials Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The catalytic volcano activity models are the quantified and visualized tools of the Sabatier principle for heterogeneous catalysis, which can depict the intrinsic activity optima and trends of a catalytic reaction as a function of the reaction descriptors, i.e., the bonding strengths of key reaction species. These models can be derived by microkinetic modeling and/or free energy changes in combination with the scaling relations among the reaction intermediates. Herein, we introduce the CatMath—an online platform for generating a variety of common and industrially important thermal + electrocatalysis. With the CatMath, users can request the volcano models for available reactions and analyze their materials of interests as potential catalysts. Besides, the CatMath provides the function of the online generation of Surface Pourbaix Diagram for surface state analysis under electrocatalytic conditions, which is an essential step before analyzing the activity of an electrocatalytic surface. All the model generation and analysis processes are realized by cloud computing via a user-friendly interface. [ABSTRACT FROM AUTHOR]

Due to unique and excellent properties, carbon nanotubes (CNTs) are expected to become the next-generation critical engineering mechanical and energy storage materials, which will play a key role as building blocks in aerospace, military equipment, communication sensing, and other cutting-edge fields. For practical application, the assembled macrostructures from individual CNTs are the common paradigms such as fibers or films. As the main representative, CNT films can not only retain the unique properties of their CNTs components, but also are more likely for mass-production than other macrostructures. Therefore, in this review, we focus on preparation of CNT films and discuss their emerging applications in the field of mechanical and electrochemical energy storage/conversion. Firstly, different preparation processes are systematically summarized. Then we introduce some typical strategies to improve their mechanical performances besides strengthening mechanism. Based on the progress of mass-production and performance optimization, we further discuss their potential utilization in mechanical and electrochemical energy storage/conversion devices. Finally, future perspectives for the development of CNT films in both production and application are proposed. We hope that this review will shed light on the preparation/assembly of CNT films and integrated application of excellent properties from individual to macroscopic dimensions. Moreover, the preparation and crossscale application paradigms of CNT films also offer a good model for other macroscopic ordered assemblies of one-dimensional nanomaterials. [ABSTRACT FROM AUTHOR]

Two-dimensional transition metal dichalcogenides (TMDs) have gained attention as potent catalysts for the hydrogen evolution reaction (HER). The traditional trial-and-error methodology for catalyst development has proven inefficient due to its costly and time-intensive nature. To accelerate the catalyst development process, the Gibbs free energy of hydrogen adsorption (Δ G H ∗ ), computed using the density functional theory (DFT), is widely used as the paramount descriptor for evaluating and predicting HER catalyst performance. However, DFT calculations for Δ G H ∗ are time-consuming and thus pose a challenge for high-throughput screening. Herein, we devise a predictive model for Δ G H ∗ within transition metal-doped TMD systems using a machine learning (ML) framework. We calculate DFT Δ G H ∗ values for 150 TM-doped MX2 (CrS2, MoS2, WS2, MoSe2, and MoTe2) and apply various ML algorithms. We validate the universality of our model by constructing 15 new external test sets. The prediction results show a high correlation coefficient of R 2 = 0.92. Based on feature analysis, the three most important parameters are the number of valence electrons of the doped transition metal, the distance of the valence electrons of the doped transition metal, and the electronegativity of the doped transition metal. Our DFT-based ML model provides a useful guideline for the material development process through Δ G H ∗ prediction and facilitates the efficient design of transition metal dichalcogenide catalysts that exhibit superior HER activity. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented in response to an article about the new diagnostic criteria for the diagnosis of gestational diabetes mellitus.

Copyright of University Chemistry is the property of Peking University, College of Chemistry & Molecular Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Hybrid density functional theory calculations are used to investigate different mechanisms of the isomerization of n-butane to isobutane via intermediate formation of olefins. The monomolecular mechanism for isomerization of butene and isobutene is found to be prevalent, with a Gibbs free energy barrier of 155 kJ/mol at 400°C, compared to the bimolecular mechanism (190 kJ/mol) due to less favorable entropy for the latter. Hydrogen transfer reactions that convert olefins into alkanes (and vice versa) are also included in the investigations, and show a free energy barrier of 203 kJ/mol for conversion of isobutene to isobutane. Additionally, a methyl transfer mechanism is discussed as a possible pathway for formation of C3 and C5 side products, in comparison to the bimolecular mechanism; the highest barrier of the initial methyl transfer is calculated to be 227 kJ/mol. We discuss the influence of entropy and anharmonicity on all mechanisms, stating that through the uncertainties in computational methods when calculating these systems, the calculated reaction barriers are likely to be overestimated here. [ABSTRACT FROM AUTHOR]

It is significant to optimize geometric configuration of metal catalytic sites and boost their catalytic activity. Herein, we synthesized isolated single Zn-N4 sites on N-doped carbon (Zn-CN) by pyrolyzing zeolite imidazole framework-8 (ZIF-8) at different temperatures. For the reciprocal transformation between benzyl alcohol and benzaldehyde, the catalytic activities of Zn-CN catalysts exhibited a volcano-like trend as the pyrolysis temperatures increased. The optimal catalyst was Zn-CN-900, with outstanding catalytic activity exceeding commercial 20 wt.% Pd/C and 20 wt.% Pt/C, promising to substitute the noble metal-based catalysts. X-ray absorption near-edge structure (XANES) measurements and density functional theory (DFT) calculation revealed the gradual transformation from tetrahedral ZnN4 sites of ZIF-8 into planar ZnN4 sites above 700 °C, with the maximum planar ZnN4 sites in Zn-CN-900. The stronger adsorption between reactants and planar ZnN4 sites facilitated the activation of reactants compared with tetrahedral ZnN4 sites. This work will provide valuable insight into rational design of efficient catalysts by optimizing geometric configuration of catalytic sites. [ABSTRACT FROM AUTHOR]

Oxygen reduction reactions (ORRs) are unanimously a key factor of system performances in bioelectrochemical systems (BESs), low-temperature fuel cells, and generally in several electrochemical platforms. Platinum (Pt)-based catalyst is the finest electrocatalyst for ORR in BESs; however, it is constrained by its low abundance, high price, and poor catalytic durability in an electrochemical setup for cathodic reaction kinetics. In recent years, significant efforts in trimming the metal-based catalyst up to nanoscale to cater high performance of ORR have been explored. Still, there are many opportunities to improve catalyst performance at cathode through proper selection of an efficient low-cost metal-based ORR catalyst. Molybdenum (Mo) with its multi-dimensional form as 2D and 3D layers and synergistic combination with other non-metals offers prospects of extraordinary performance as low-cost metal-based ORR catalyst over the Pt in delivering enhanced ORR potential. The present review throws light on current requirements of a sturdier catalyst material and thus provides a comprehensive review on the continuing efforts in exploring the possibility of Mo as a low-cost metal-based ORR catalyst. This literature analysis would enlighten the significance of ORR in BESs, followed by the electrochemistry of Mo-based cathodic catalyst, its underlying mechanism and performance limiting factors in the operation of ORR. Moreover, the extensive and systematic acumen in the context of Mo-based catalytic formulations for increased ORR potentials including nano-composite Mo-cathode catalyst; development of Mo-catalyst with varied configurations; carbon-supported Mo-catalyst; morphological changes; surface area modifications; and Mo-coupling with other transition metal and its derivatives were discussed in great detail to provide prospective application of Mo-based catalyst. Lastly, numerous opportunities and projections for future research in fabrication, juxtaposition, and implementation of Mo-based cathodic catalysts and consequent recommendations were discussed as conclusive remarks for bringing out the state-of-the-art review on this subject. [ABSTRACT FROM AUTHOR]

Copyright of Electronic Components & Materials is the property of Electronic Components & Materials and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Strain engineering is a useful strategy for modifying the catalytic activity of electrocatalysts. However, in-situ visual characterization of the strain effect on the catalytic activity at nanoscale remains a huge challenge. Herein, we performed in-situ electrochemical scanning tunneling microscopy (EC-STM) imaging measurements at the local strained regions of extruded single-crystal molybdenum dioxide (MoO2) sheets with combination of current noise analysis (n-EC-STM). The intensity-enhanced noise was observed at the local strained region compared to the unstrained regions in the same frame, which reveals the positive effect of compressive strain on the hydrogen evolution reaction (HER) activity of MoO2 provided that the intensity of noise is positively correlated with catalytic HER Faradic current. Therefore, we clearly "see" the strain-induced enhancement of HER activity of MoO2 at nanoscale by means of noise visualization. This work extends the visual characterization of strain engineering in electrocatalysis and related fields. [ABSTRACT FROM AUTHOR]

Herein, we designed and constructed a mesoporous LaAlOx via a solvent evaporation induced selfassembly protocol. The structure and physicochemical property of the corresponding NiMo supported catalyst was analyzed by a set of characterizations, and its catalytic activity was investigated for hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene. It has confirmed that the incorporation of La profoundly facilitate the generation of "Type II" NiMoS phase by weakening the interaction of MoeO eAl leakage and promoting the sulfidation of both Ni and Mo oxides as well as changing the morphology of Ni promoted MoS2 slabs, thereafter boosting the HDS performance substantially. The finding here may contribute to the fundamental understanding of structure-activity in ultra-deep desulfurization and inspire the advancement of highly-efficient HDS catalyst in future. [ABSTRACT FROM AUTHOR]

The presence of waste tires on open fields or households creates an ideal breeding ground for disease-carrying vermin, threatening human well-being. There are various technologies studied for efficient use of waste tires, such as pyrolysis, which results in char, oil, and non-condensable gases. Tire pyrolytic oil (TPO) has been reported to be similar to commercial diesel fuel. The current hurdle for using TPO in commercial diesel engines is the available sulfur content (>1.0 wt%). The disadvantages of sulfur in liquid fuels are its ability to reduce the engine's life due to corrosion and the undesirable emission of SOx that subsequently damages public health and property. There is a rising need to develop efficient technologies for the desulfurization of such liquid fuels. Besides conventional hydrodesulfurization, other emerging technologies include adsorption, oxidation, photocatalytic degradation, and biological desulfurization. This paper reviews the status of pyrolysis of waste tires and desulfurization technologies for TPO. Implications: The nature of tires makes them extremely challenging to recycle due to the available chemically cross-linked polymer and, therefore, they are neither fusible nor soluble and, consequently, cannot be remolded into other shapes without serious degradation. The presence of tire waste on open fields or households creates an ideal breeding ground for disease-carrying vermin which pose a threat to humans. Also, disposal in landfills can lead to groundwater pollution by heavy metals and cause hazardous and uncontrolled fires. Owing to the growing environmental concerns, the exploration of economically viable and environmentally friendly techniques for the management of waste tires has been intensified in the recent past. Thermochemical routes such as combustion, gasification, and pyrolysis are important in the management of waste tires, reducing the environmental impacts of tire volarization, and allowing for the recovery of products. Given the depletion of fossil fuels and to meet the ever-growing demand for fuel energy, several initiatives to find alternative fuel sources are currently being taken. Fuel oil obtained from the pyrolysis of waste tires is becoming a promising alternative source of energy given its availability and higher heating value. Pyrolysis, an eco-friendly process, is the heating of matter in the absence of oxygen and is normally practiced for the thermochemical decomposition of different types of feedstock including biomass, coal, tires, and municipal solid waste. This paper reviews the current studies for pyrolysis of waste tires and multiple desulfurization technologies used for treating TPO globally. The detailed specification on operating conditions for the pyrolysis reactor in achieving desirable products in terms of composition and ratios are discussed. [ABSTRACT FROM AUTHOR]

Nitrides are of particular interest in energy applications given their suitability to photocatalytically generate H 2 from aqueous solutions. However, one of the drawbacks of nitrides is the decomposition they suffer when used in photoelectrochemical cells. Here, we report the improvement of the catalytic performance and chemical stability of a GaN electrode when it is decorated with Fe 2 O 3 particles compared with an undecorated electrode. Our results show a higher reaction rate in the Fe 2 O 3 /GaN electrode, and that photocorrosion marks take more than 20 times longer to appear on it. We also characterized the crystalline properties of the Fe 2 O 3 particles with transmission electron microscopy. The results show that the Fe 2 O 3 particles keep an epitaxial relationship with GaN that follows the Fe 2 O 3 [Formula: see text]GaN[Formula: see text] and Fe 2 O 3 [Formula: see text]GaN[Formula: see text] symmetry constraints. We also characterized an Fe 2 O 3 (thin film)/GaN electrode, however it did not present any catalytic improvement compared with a bare GaN electrode. The epitaxial relationship found between the Fe 2 O 3 thin film and GaN exhibited the Fe 2 O 3 [Formula: see text]GaN[Formula: see text] and Fe 2 O 3 [Formula: see text]GaN[Formula: see text] symmetry constraints.

The change in the coordination environment of the active sites of a fuel cell cathode catalyst provides a new modulation strategy for stimulating the catalyst's oxygen reduction reaction activity. The thermodynamic and electronic properties of the FeCoN5A and FeCoN6A catalyst structures with nonmetallic A-doped (A = B, N, O, P, and S) coordination were calculated and analyzed based on density functional theory. The modulation order of G⋆OH by different A-doped FeCo bimetal pairs (BMPs) was as follows: S > P > O > N/C > B. There was a dynamic distribution of charges in the coordination environment during the adsorption of OH, which resulted in inversely proportional relationship with the charge transfer between the adsorbate OH, active site, first coordination layer, and second coordination layer in turn. Descriptors of the orbital energy levels of neighboring nonmetal atoms were constructed based on the p-electron number and electronegativity of the doped nonmetal A. The change of the orbital energy levels of the first coordination atom during the adsorption process caused the structure to exhibit different adsorption energies. This study provides new insights on the non-metallic modulation of the M-N-C coordination environment to improve the oxygen reduction reaction activity. [ABSTRACT FROM AUTHOR]