Search

The purposive and rational construction of novel multicomponent composites is highly attractive in order to achieve outstanding electromagnetic wave absorption properties. Transition metal–carbon composites derived from metal–organic frameworks (MOFs) have received increasing attention in this field. In our work, copper and indium metals were directly embedded in the dual active sites of porphyrins consisting of a central ring (N–H) and a peripheral carboxyl group (COOH) by employing a facile solvothermal process to prepare the single-crystal material of CuIn-PMOFs with periodically arranged structures (C50H32CuInN5O8). Afterwards, copper indium/carbon nitrogen (CuIn/CN) composites were synthesized via only in situ pyrolysis of CuIn-PMOFs without further adjustment of the bimetallic ratios. Concretely, due to the improved impedance matching and increased dielectric loss, the CuIn/CN composites prepared at 600 °C (CuIn/CN-600) display a maximum reflection loss (RL) of −78.42 dB at 13.84 GHz with an effective absorption bandwidth (EAB) of about 5.92 GHz (12.08–18 GHz) at 1.92 mm. Therefore, our work delivers a convenient and advanced prototype for the design of controllable MOF-derived composites as exceptional microwave absorbers with high absorption and broad bandwidth. [ABSTRACT FROM AUTHOR]

Aqueous Zn-ion batteries (AZIBs) are attractive for next-generation renewable and secure energy storage systems due to their high safety and low cost. However, dendrite growth and side reactions of Zn metal anodes severely limit their practical applications. Moreover, polarization is an important but easily overlooked factor hampering the development of AZIBs. Herein, a zincophilic, hydrophilic, and thin (∼100 nm) SnO2 protective layer is reported to remodel the Zn anode/electrolyte interface via a simple spin-coating approach. The SnO2 layer effectively inhibits the growth of the dendrites, which prolongs the lifetime of Zn anodes to 3900 h. It also alleviates the side reactions and endows Zn‖Cu cells with a high Coulombic efficiency of 99.3% over 2000 cycles. Meanwhile, the SnO2 layer presents fast Zn deposition kinetics to ensure reversible Zn anodes at high current/capacity by decreasing electrochemical polarization and concentration polarization. Consequently, SnO2/Zn anodes exhibit a high cumulative capacity of 4.5 A h cm−2 at an ultrahigh current of 30 mA cm−2 with a low overpotential of 90 mV and even 3.2 A h cm−2 at a high capacity of 4 mA h cm−2 and high current of 8 mA cm−2. Prototype SnO2/Zn‖δ-MnO2 full cells also obtain higher capacities and capacity retention (96.9% after 500 cycles at 2C) than bare Zn. This work offers new insights for ensuring the reversibility and durability of Zn anodes with low polarization at high current/capacity and provides a promising way to promote the practical application of AZIBs. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) are highly promising as a novel class of drug delivery carriers; however, there are few reports about their application in nanoparticle-based formulations for dermal administration. In this work, we developed a novel kind of nanoparticular system based on zeolitic imidazolate framework-8 (ZIF-8) and polydopamine (PDA) modification for improving the dermal delivery of 5-fluorouracil (5-FU). The structures and properties of the prepared nanoparticles were characterized using a variety of analytical methods. Their ex vivo delivery performance in the skin was investigated using Franz cells, and the underlying mechanisms were studied via confocal laser scanning microscopy (CLSM) and hematoxylin-eosin (HE) experiments which were employed to probe the penetration pathway and the interaction between nanoparticles and the skin. The results revealed that both 5-FU@ZIF-8 and ZIF-8@5-FU@PDA had an enhancement effect on the deposition of 5-FU in the skin, and the surface coating of PDA could further reduce drug permeation across the skin, especially in the case of impaired skin, in comparison with the drug solution. The CLSM study using rhodamine 6G as the fluorescent probe to mimic 5-FU indicated that ZIF-8 and ZIF-8@PDA could deliver their payloads into the skin via two pathways, i.e., intercellular and follicular ones, and the follicular route was shown to be particularly important for ZIF-8@PDA, in which the drug and carrier were co-delivered into the skin as an intact particle. This study provides evidence for using ZIF-8 and PDA modification for skin-specific drug delivery and offers an effective avenue to develop novel nanoplatforms for dermal application to treat skin diseases. [ABSTRACT FROM AUTHOR]

Photocatalytic reactions can sustainably utilize inexhaustible solar energy for environmental remediation and conversion of photon energy into chemical energy, and thereby show great potential in alleviating the environmental stress and energy crisis. In particular, the constructed heterojunction photocatalysts, typically represented by type II and direct Z-scheme systems, possess many advantages, including broad light spectrum harvesting, decreased recombination rate of photogenerated electron–hole pairs and spatially separated photoreaction active sites, which are critical for enhancing the photocatalytic performance. However, the two systems are often indistinguishable because of the similar band structures. This perspective summarizes the state-of-the-art characterization methods that have been used to precisely probe interfacial charge transfer in the heterojunctions for photocatalysis, including those for the investigation of surface reactions, surface photovoltage, free radical trapping, binding energy shift and photogenerated charge carrier dynamics, as well as theoretical calculations. Based on these results, type II and direct Z-scheme charge transfer mechanisms can be distinguished. The future challenges and prospects in developing such characterization techniques are also discussed. [ABSTRACT FROM AUTHOR]

As an eco-friendly and renewable energy source, hydrogen energy has attracted widespread attention. MoS2 nanomaterials are typical catalysts for the electrocatalytic hydrogen evolution reaction (HER), but their performances are limited by their poor conductivity and spontaneous agglomeration. Here, we prepared few-layer fluorine-free Ti3C2TX (T = O, OH) as a conductive substrate of MoS2 for HER catalysis, and the as-prepared hybrid catalyst exhibits high catalytic activity with a small overpotential of 139 mV at −10 mA cm−2, a Tafel slope of 78 mV dec−1, and a negligible decay after 3000 cycles at a scan rate of 100 mV s−1 in an acidic solution. The excellent performance in HER activity can be attributed to the improved electrical conductivity, increased O active sites and optimized 2D mass-transport channels of the unique few-layer fluorine-free structure. Interestingly, the few-layer fluorine-free Ti3C2TX/MoS2 catalyst also performs well under neutral and alkaline conditions. This work demonstrates that few-layer fluorine-free Ti3C2TX (T = O, OH) can be used as an excellent conductive substrate to further improve the HER performances of other nanoscale electrocatalysts. [ABSTRACT FROM AUTHOR]

La0.6Sr0.4Fe0.9Nb0.1O3−δ (LSFN) and La0.6Sr0.4Fe0.8Nb0.1Cu0.1O3−δ (LSFNCu) perovskite oxides are prepared as catalysts for C2H6 dehydrogenation. The partial substitution of Fe by Cu enhances the structural stability and significantly increases the formation of oxygen vacancies and also the oxidation states of the Fe cations. The performances of the catalysts are investigated from 650 to 750 °C in a fixed-bed reactor. The C2H6 conversion by LSFNCu is about 42% at 750 °C, which is obviously higher than that by LSFN (37.8%). Furthermore, a symmetrical protonic solid oxide fuel cell reactor with the configuration of LSFNCu/BZCYYb/LSFNCu is prepared to cogenerate ethylene and electricity from ethane. At 750 °C, the peak power density of the symmetrical cell reaches 90 mW cm−2 in C2H6. Meanwhile, C2H6 conversion is about 41.5% at OCV conditions and can be increased to 43.4% under a constant current of 200 mA cm−2. This indicates that the consumption of the formed H2 promotes the dehydrogenation reactions. The performance of the fuel cell reactor is essentially stable during the 40 h test, confirming that LSFNCu is an excellent coking resistant electrocatalyst for cogeneration of C2H4 and electricity from ethane. [ABSTRACT FROM AUTHOR]

Based on semi-interpenetrating polymer network (semi-IPN) hydrogel films, a multiple stimuli-responsive film system composed of poly(acrylic acid) (PAA) and N,N-diethyl acrylamide (DEA), designated as PAA–PDEA semi-IPN films, was realized on a glassy carbon (GC) electrode surface with a one-step polymerization method. Rutin (RT), an electroactive probe, displayed invertible pH-, thermo- and SO42− concentration–sensitive cyclic voltammogram (CV) behaviors in the film system. This multiply sensitive electrocatalysis of RT at the PAA–PDEA films was employed to further investigate the multiple stimuli-responsive ON–OFF behaviors of RT. The scanning electron microscopy (SEM) images and control experiments showed pH-sensitive ON–OFF properties of RT, which could be ascribed to the protonated/deprotonated carboxylic (–COOH) groups of the PAA component in different pH buffers and the properties of RT itself. However, the confirmation change or phase transition of the PDEA hydrogel film between the coil and globular states led to thermo- and SO42− concentration–sensitive ON–OFF properties. According to these results, a 3-input/3-output logic gate and a 2-to-1 encoder were constructed successfully. This present system was fabricated for the first time, which may offer numerous possibilities for the design of new electrochemical drug sensors, drug-mimicking release processes and other medical applications. Furthermore, it also can contribute to the development of biomolecular or molecular computing. [ABSTRACT FROM AUTHOR]

On the way to exploring superior hydrogenation catalysts, Ir-based catalysts with a record catalytic activity (up to 40 h−1) for the hydrogenation of benzoic acid to cyclohexanecarboxylic acid under mild reaction conditions (85 °C, 0.1 MPa H2, in water) have been successfully developed. By excluding various factors, the experimental results showed that the main factor governing the activity discrepancy between the Ir-based catalysts is actually the dispersion stability of the supports (such as N-doped carbon, active carbon, SBA-15 and various metal oxides) in the reaction solution, rather than the interaction between the Ir active component and the supports. Combined with theoretical investigation from first principles, an activity volcano curve considering the competing adsorption between the reactants (H2) and solvent (H2O) for aqueous aromatic ring hydrogenation was presented for the first time. The high activity of Ir can be deduced by the proper discrepancy of dissociation energies or adsorption energies between H2 and H2O on the catalysts. This activity volcano curve provides guidance for further rational design of promising catalysts for benzoic acid or even aromatic ring hydrogenation under true reaction conditions for practical applications. [ABSTRACT FROM AUTHOR]

Ruthenium nanoparticles (2.6 nm) uniformly dispersed on a three-dimensional (3D) interconnected hierarchical porous N-doped carbon (Ru/NHPC) have been successfully developed, serving as a highly active and stable catalyst for the selective hydrogenation of aromatics under mild conditions. A novel “leavening” strategy, i.e. using biomass-derived α-cellulose as a carbon precursor and ammonium oxalate as both a nitrogen source and foaming agent, affords the NHPC material a large surface area (870 m2 g−1), an excellent hierarchical nanostructure which acts as a convenient mass transfer channel and a high ability in stabilizing and dispersing Ru nanoparticles. The Ru/NHPC catalyst exhibits a substantially enhanced activity for the hydrogenation of toluene (TOF up to 39 000 h−1) and quinoline (TOF up to 2858 h−1) in comparison with Ru/HPC (3D-hierarchical porous carbon without nitrogen doping) and Ru/AC (commercial activated carbon) under the same reaction conditions. Further investigations indicate that the 3D interconnected porous structure and N-doping contribute to the improved diffusion and mass transfer, homogeneous dispersion of ruthenium nanoparticles and high percentage of Ru0 (active sites), which results in considerable catalytic performance. This work offers great potential for the application of supported catalysts based on NHPC materials in fine chemical production with high activity. [ABSTRACT FROM AUTHOR]

The explosive growth of energy consumption demands highly efficient energy conversion and storage devices, whose innovation greatly depends on the development of advanced electrode materials and catalysts. Among those advanced materials explored, carbon materials have drawn much attention due to their excellent properties, such as high specific surface area and tunable porous structures. Challenges also come from global warming and environmental pollution, which leads to the requirement of sustainable carbon-rich precursors for carbon materials. Hence, the use of biomass for carbon materials features the concepts of green chemistry. This review summarizes the most advanced progress in biomass-derived carbons for use in fuel cells, electrocatalytic water splitting devices, supercapacitors and lithium-ion batteries. Several synthetic strategies for synthesizing biomass-derived carbons, including direct pyrolysis, hydrothermal carbonization, and ionothermal carbonization, have been reviewed, and the corresponding formation mechanisms and prospects are also discussed. This provides fundamental insight and offers important guidelines for the future design of biomass-derived carbons in specific energy applications. [ABSTRACT FROM AUTHOR]

Graphitic carbon nitride (g-C3N4) nanosheets with large aspect ratios were fabricated from bulk g-C3N4 through an efficient top-down approach of moderate disintegration–exfoliation using diluted H2SO4 as an “efficient knife”. By prior disintegration in a diluted H2SO4 solution, the exfoliation of bulk g-C3N4 was effectively accelerated. The as-prepared g-C3N4 nanosheets possess a two-dimensional (2D) thin-layer structure with seven-atom thickness, a large lateral size of about 1 μm, and a high specific surface area of 80 m2 g−1. Compared with the bulk precursor, the g-C3N4 nanosheets showed much higher efficiency of photogenerated charge transfer and separation, and consequently exhibited enhanced photocatalytic activity toward hydrogen evolution and pollutant decomposition under both full-sunlight and visible-light irradiation. [ABSTRACT FROM AUTHOR]

Hierarchically porous carbons (HPCs) show great potential in energy storage due to their high surface area as well as short ion transport path derived from the interconnected porous framework. However, most existing protocols highly rely on nanocasting and soft-templating, which usually make the use of specific raw materials and thus their industrial application unfeasible. It still remains a big challenge to build HPCs from crude biomass, which is abundant on the earth, through a simple one-pot approach. Inspired by leavening of bread, we design a strategy to fabricate HPCs with three-dimensional (3D) hierarchical pores consisting of macro, meso, and micropores. The “leavening method” is conducted simply by mixing the biomass with KHCO3 followed by elevated temperature treatment. Besides the well-defined hierarchical structure, the as-prepared HPCs also exhibit notably large specific areas (up to 1893 m2 g−1). It is noteworthy that this “leavening” strategy is widely applicable to most of the biomass derivatives and biomass, including glucose, cellulose, chitin, starch, rice straw, bamboo, etc. When evaluated as supercapacitor electrode materials in two-electrode test systems, the as-prepared HPCs exhibit an excellent electrochemical performance: a specific capacitance of 253 F g−1, with almost no capacitance loss after 10 000 cycles. [ABSTRACT FROM AUTHOR]

We report a novel, simple, and one-pot method for the synthesis of ultrafinely dispersed iron oxide based nanoparticles (NPs) embedded in a nitrogen doped carbon matrix (denoted as Fe2O3/Fe@CN). A well-designed iron oxide based hybrid that demonstrates high activity and excellent durability for the HER in alkaline solution has been reported for the first time. The catalyst displays a small Tafel slope of 114 mV per decade and good electrocatalytic stability for 30 000 seconds. Detailed electrochemical and physical studies indicate that the high HER activity of the hybrid catalyst results from the strong interaction between Fe-based NPs and N-doped graphitic carbon, and especially the synergistic effect of Fe and Fe2O3. [ABSTRACT FROM AUTHOR]

Due to their industrial indispensability, heterogeneous catalytic oxidation and hydrogenation continue to be topics of great interest in both experimental and theoretical studies. Graphitic carbon nitride (g-C3N4), due to its unique structure and thus excellent properties such as semiconductivity and nitrogen richness, is suitable to act as a metal-free catalyst or catalyst support for these two significant transformations. This critical review will summarize the recent significant advances achieved in the field of oxidation and hydrogenation realized by g-C3N4 based catalytic systems. The review covers the practical applications and brief mechanistic discussions in three broad catalytic cases, catalytic oxidation under light irradiation, catalytic oxidation without light illumination, and catalytic hydrogenation with g-C3N4 supporting metal nanoparticles. The state-of-the-art and future challenges of heterogeneous hydrogenation and oxidation by g-C3N4 based systems are also discussed. [ABSTRACT FROM AUTHOR]

In recent years, photocatalytic reactions have shown great potential in degrading organic pollutants because of their simple operation and no secondary pollution. Graphitic carbon nitride (g-C 3 N 4 ) is one of the most frequently used photocatalyst materials in the field of photocatalysis because it is a form of photocatalytic material with facile synthesis, no metal, visible light response, and strong stability. Enzyme-catalyzed degradation has received extensive attention due to its broad selectivity, high efficiency, and environmental friendliness. Horseradish peroxidase (HRP), one of several oxidoreductases utilized for pollutant degradation, has a wide range of applications due to its mild reaction conditions and high stability. Exploring efficient platforms for immobilizing g-C 3 N 4 and HRP to develop photo-enzyme-coupled catalysis is an attractive practical topic. The coupling effect of g-C 3 N 4 and HRP improves the carrier separation efficiency and generates more active species, which finally realize the solar-driven non-selective destruction of organic pollutants. We describe the alteration of g-C 3 N 4 and the immobilization of HRP in detail in this study, and we outline recent developments in the photo-enzyme coupling of g-C 3 N 4 and HRP., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (This journal is © The Royal Society of Chemistry.)

As living standards improve, obesity has become an increasingly serious health problem. Natural extracts from a wide range of sources are non-toxic and have significant potential as drugs for the prevention and treatment of obesity. We assessed 243 natural small molecules in a HepG2 fat accumulation model and found that epigoitrin (EP) from Radix isatidis reduced intracellular fat deposition, increased short-chain acyl CoA dehydrogenase (SCAD) activity, promoted glucose uptake and glycogen storage, increased ATP production and reduced glutathione (GSH) content, reduced reactive oxygen species (ROS), and enhanced superoxide dismutase (SOD) activity. In a murine high-fat diet model, the addition of EP to the high-fat diet significantly reduced fat deposition, increased glucose tolerance, improved insulin sensitivity, and increased energy expenditure. In conclusion, EP alleviated obesity caused by a high-fat diet and improved disorders of lipid and glucose metabolism.

A novel self-reactivated catalyst Pt-ThO 2 /C was prepared for the first time by selecting radioactive material ThO 2 as the catalytic additive to address the low activity and toxicity of the anode Pt/C catalyst in a direct ethanol fuel cell. The catalytic activity and resistance to CO poisoning of Pt-6.67 wt%ThO 2 /C were found to be superior to those of Pt/C-NaBH 4 in electrochemical workstation and single-cell tests. It is speculated that the exist of ThO 2 not only improves the catalytic activity via the synergistic effect of Pt and Th, but also produces a large amount of radiolysis products, OH radicals, due to 232 Th which oxidatively desorbs CO from Pt-CO ads and solves the CO poisoning problem., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

5-Hydroxymethylfurfural (HMF) is one of the most important platform molecules and could be transformed into a variety of fuel additives and high value-added chemicals. Multiple catalyst systems have been developed for the conversion of carbohydrates to HMF, but there are still unavoidable problems, including high temperature and pressure, difficult recovery of solvent, corrosion of equipment, poor catalyst circulation, etc. Herein, a new magnetic Fe 3 O 4 @SiO 2 @mSiO 2 -TaOPO 4 catalyst for the preparation of HMF from fructose in 2-pentanol was developed. The structures of the catalysts were characterized by FT-IR, TSM, EDS, SEM, XRD and VSM. The 2-pentanol solvent is not only conducive to the production of HMF, but also enables the reaction to be carried out at a lower pressure. The highest yield of HMF (85.4%) was obtained using 20 wt% catalyst under 10% substrate concentration (0.5 g of fructose) at 120 °C for 3 h. The catalysts can be easily separated by magnetism. The slight decrease in catalyst activity after 7 cycles was mainly due to the loss of catalyst during the cycle operation. Simultaneously, the total yield of HMF was 51.3% after scale-up to 15 g of fructose, showing the possible industrial application potential of this catalyst system., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Lithium-ion capacitors (LICs) have attracted intense attention due to their high energy/power densities and good stability. However, their performance is severely limited by the imbalance in reaction kinetics and electrochemical capacity between the faradaic battery-like anodes and non-faradic capacitive cathodes. Here, we propose an all alginate-derived LIC assembled with a three-dimensional porous orthorhombic phase Nb 2 O 5 /C hybrid as the anode, seaweed-derived carbon as the cathode and sodium alginate (SA) as the electrode binder. The increase in the rate performance of the anode and the capacity of the cathode efficiently mitigates the mismatch between the counter electrodes, and the SA binder provides facilitated access for Li ions to the surfaces of electrode materials. The all alginate-derived LIC exhibits high energy (143.9 W h kg -1 at 87.6 W kg -1 ) and power (17.5 kW kg -1 at 75.1 W h kg -1 ) densities with a superior cyclability (84.6% capacity retention after 3000 charge-discharge cycles), surpassing those of previous Nb 2 O 5 -based LICs. This work provides a novel design strategy for the electrodes of next-generation high-performance LICs., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Graphitic carbon nitride (g-C3N4) nanosheets with large aspect ratios were fabricated from bulk g-C3N4 through an efficient top-down approach of moderate disintegration-exfoliation using diluted H2SO4 as an "efficient knife". By prior disintegration in a diluted H2SO4 solution, the exfoliation of bulk g-C3N4 was effectively accelerated. The as-prepared g-C3N4 nanosheets possess a two-dimensional (2D) thin-layer structure with seven-atom thickness, a large lateral size of about 1 μm, and a high specific surface area of 80 m(2) g(-1). Compared with the bulk precursor, the g-C3N4 nanosheets showed much higher efficiency of photogenerated charge transfer and separation, and consequently exhibited enhanced photocatalytic activity toward hydrogen evolution and pollutant decomposition under both full-sunlight and visible-light irradiation.

Pd@N-doped carbon (Pd@CN) exhibited four and two times higher peak current density toward ethanol electrooxidation than Pd@active carbon and Pd@non-nitrogen carbon. Controlled experimental results indicated that the incorporation of nitrogen into the carbon matrix improved the percentage of Pd(0) and increased the binding energy of Pd in Pd@CN, and accordingly enhanced the catalytic activity.