Facile Synthesis of N-Doped Metal-Free Catalysts for Oxygen Reduction Reaction via a Self-Sacrificed Template Method Using Zinc Amino-Acid Complex.

Precisely controlled heteroatom-doped metal-free carbon catalysts are highly desirable for use in various renewable energy conversion and storage devices. Herein, we report a nitrogen-doped metal-free carbon catalyst for the oxygen reduction reaction (ORR) using a facile and cost-effective synthetic method. The obtained catalysts (NC-1100) were synthesized in two steps via an amino-acid complex coating and high-temperature carbonization. The various physical characteristics revealed that NC-1100 has a unique morphology, a controlled nitrogen bonding configuration, and a uniform pore distribution. The resulting catalyst shows excellent catalytic performance toward direct 4-electron oxygen reduction reaction (ORR) in an alkaline electrolyte, with a high onset potential of 0.95 V versus RHE and limiting current density (4.5 mA cm-2). Furthermore, the developed catalysts showed superior long-term operating stability and methanol durability compared to those of commercial Pt/C. This study provides a promising guideline for the development of next-generation electrocatalysts for fuel cells and wider applications.

Facile and Cost-effective Synthesis of CoP@N-doped Carbon with High Catalytic Performance for Electrochemical Hydrogen Evolution Reaction.

The manufacture of efficient and low-cost hydrogen evolution reaction (HER) catalysts is regarded as a critical solution to achieve carbon neutrality. Herein, we developed an economical method to synthesize a CoP-anchored N-doped carbon catalyst via one-step pyrolysis using inexpensive starting materials (cobalt ion salt, phytic acid, and glycine). The size of the CoP nanoparticles was controlled by adjusting the Co/P ratio of the catalysts. Nanoscale CoP particles with adequate exposure to active sites were uniformly anchored on the surface of the conductive nitrogen-doped carbon substrate, ensuring the rapid transfer of electrons and species. When Co/P=0.89, the as-made catalyst exhibited outstanding HER activity, with an extraordinarily low overpotential of 202 mV at 10 mA cm-2 and long-term stability.

A zeolite templating method for fabricating edge site-enriched N-doped carbon materials.

N-doped carbon materials have attracted considerable attention as highly functional materials because nitrogen doping distorts the carbon lattice, changes the charge density, and introduces additional defects. Among various positions of N atoms in N-doped carbon compounds, pyridinic-N, pyrrolic-N, and valley-N, which are doped at edge sites, exhibit specific electrocatalytic activities during the oxygen reduction reaction (ORR). However, it is difficult to selectively introduce these N atoms into a carbon matrix because the synthesis procedure typically includes high-temperature heat treatment. In this study, we applied a zeolite templating method to synthesize edge site-rich N-doped carbon materials. The sample fabricated using a zeolite template possessed high concentrations of pyridinic-N and valley-N atoms, demonstrating a significantly higher ORR catalytic activity than the sample synthesized without a zeolite template. Additional experiments conducted using various zeolites confirmed the positive effect of N-doped carbons on the ORR catalytic performance. This work demonstrated that the zeolite templating method not only increased the specific surface area and the number of active sites but also selectively created edge sites and improved the quality of the active sites.

Bottom-up Synthesis of Nanosheets at Various Interfaces.

Nanostructured materials with high aspect ratios have been widely studied for their unique properties. In particular, nanosheets have safety, dispersibility, and nanosized effects, and nanosheets with exceptionally small thicknesses exhibit unique properties. For non-exfoliable materials, the bottom-up nanosheet growth using various interfaces as templates have been investigated. This review article presents the synthesis of nanosheets at the interfaces and layered structure; it explains the features of each interface type, its advantages, and its uniqueness. The interfaces work as templates for nanosheet synthesis. We can easily use the liquid-liquid and gas-liquid interfaces as the templates; however, the thickness of nanosheets usually becomes thick because it allows materials to grow in thickness. The solid-gas and solid-liquid interfaces can prevent nanosheets from growing in thickness. However, the removal of template solids is required after the synthesis. The layered structures of various materials provide two-dimensional reaction fields between the layers. These methods have high versatility, and the nanosheets synthesized by these methods are thin. Finally, this review examines the key challenges and opportunities associated with scalable nanosheet synthesis methods for industrial production.

Effect of Ga substitution with Al in ZSM-5 zeolite in methanethiol-to-hydrocarbon conversion.

The catalytic properties of conventional H-[Al]-ZSM-5 and gallium-substituted H-[Ga]-ZSM-5 were evaluated in the conversion of methanethiol to ethylene (CH3SH → 1/2C2H4 + H2S). Dimethyl sulfide (DMS), aromatics, and CH4 were formed as byproducts on the H-[Al]-ZSM-5 catalyst. The introduction of Ga into the ZSM-5 structure provided a high ethylene yield with relatively high selectivity for olefins. Based on the temperature-programmed desorption of NH3 and pyridine adsorption on zeolites, the strength of acid sites was decreased by introducing Ga into the ZSM-5 structure. Undesirable reactions seemed less likely to occur at weakly acidic sites. The suppression of the formation of dimethyl sulfide (CH3SH → 1/2C2H6S + 1/2H2S) and the sequential reaction of ethylene to produce aromatics provided a high yield of ethylene over H-[Ga]-ZSM-5.

Detection of alkali and alkaline earth metal ions using birefringence of hyperswollen lamellar phase.

Chemical sensors have targeted various substances. Most sensors electrically amplify signals. Here, we propose a visual detection system that uses a hyperswollen lamellar phase and detects targets in a solution without electric amplification. Amphiphiles with an oligo(ethylene glycol) chain can catch alkali and alkaline earth metal ions and amplify to macroscopic birefringence.

Solvent-Free Soft-Template Synthesis of Highly Ordered Mesoporous Carbons via Self-Assembly Promoted by Mg(NO3)2.

To improve the pore uniformity and volume of ordered mesoporous carbons produced by soft templating under solvent-free conditions, magnesium nitrate inorganic salt was incorporated into the precursors during the synthesis. The addition of magnesium nitrate in this procedure lowered the melting point of resorcinol, increased the diffusivity of the resorcinol-Pluronic F127 complex, and promoted self-assembly. The entry of Mg species into the core of the micelle of Pluronic F127 resulted in a modification of the pore structure resembling a channel-like hexagonal structure. In addition, the MgO in the pores effectively prevented the shrinkage of the mesopores under high-temperature conditions. Correspondingly, the uniformity and the mesopore volume of the mesoporous carbon obtained were also enhanced. Moreover, when used as electrodes, this ordered mesoporous carbon was able to significantly increase the capacity of electric double-layer capacitors. Thus, the current study proposes a novel method for regulating the structure and distribution of ordered mesoporous carbons.

Amorphous Aluminosilicate Nanosheets as Universal Precursors for the Synthesis of Diverse Zeolite Nanosheets for Polymer-Cracking Reactions.

Zeolites catalyze some reactions in their molecular-sized pores, but large molecules can react only on their external surface. Zeolite-nanosheets (NSs) have been developed as catalysts for large molecules. The previously reported methods to synthesize zeolite-NSs are specialized for each zeolite type. Here we propose a new method to synthesize various zeolite-NSs from the same amorphous aluminosilicate NSs (AAS-NSs) as a universal precursor. We successfully synthesized the unprecedented AAS-NSs in the hydrophilic space of the stable hyperswollen lyotropic lamellar (HL) phase. The four zeolite types could be obtained from the single-species AAS-NSs. These results imply that this method enables us to synthesize almost all types of zeolite-NSs. Moreover, the synthesized CHA-NSs have great potential for various applications because of their thickness and large external surface area.

Coke-Resistant Ni/CeZrO2 Catalysts for Dry Reforming of Methane to Produce Hydrogen-Rich Syngas.

Dry reforming of methane was studied over high-ratio zirconia in ceria-zirconia-mixed oxide-supported Ni catalysts. The catalyst was synthesized using co-precipitation and impregnation methods. The effects of the catalyst support and Ni composition on the physicochemical characteristics and performance of the catalysts were investigated. Characterization of the physicochemical properties was conducted using X-ray diffraction (XRD), N2-physisorption, H2-TPR, and CO2-TPD. The results of the activity and stability evaluations of the synthesized catalysts over a period of 240 min at a temperature of 700 °C, atmospheric pressure, and WHSV of 60,000 mL g−1 h−1 showed that the 10%Ni/CeZrO2 catalyst exhibited the highest catalytic performance, with conversions of CH4 and CO2 up to 74% and 55%, respectively, being reached. The H2/CO ratio in the product was 1.4, which is higher than the stoichiometric ratio of 1, indicating a higher formation of H2. The spent catalysts showed minimal carbon deposition based on the thermo-gravimetry analysis, which was <0.01 gC/gcat, so carbon deposition could be neglected.

Design of Zr- and Al-Doped *BEA-Type Zeolite to Boost LDPE Cracking.

Nowadays, the increase in plastic waste is causing serious environmental problems. Catalytic cracking has been considered a promising candidate to solve these problems. Catalytic cracking has emerged as an attractive process that can produce valuable products from plastic wastes. Solid acid catalysts such as zeolites decompose the plastic waste at a lower temperature. The lower decomposition temperature may be desirable for practical use. Herein, we synthesized both Zr- and Al-incorporated Beta zeolite using amorphous ZrO2-SiO2. The optimized Zr content in the dry gel allowed the enhancement of Lewis acidity without a significant loss of Brønsted acidity. The enhancement of Lewis acidity was mainly due to Zr species incorporated into the zeolite framework. Thanks to the enhanced Lewis acidity without any significant loss of Brønsted acidity, higher polymer decomposition efficiency was achieved than a conventional Beta zeolite.

Thin ZIF-8 nanosheets synthesized in hydrophilic TRAPs.

The preparation method of nanosheets using hyperswollen lyotropic lamellar phases, the 'two-dimensional reactor in amphiphilic phases (TRAP) method', has successfully provided nanosheets of various non-layered materials. Previously reported examples started from a single hydrophobic or hydrophilic precursor and multiple hydrophobic precursors. Here, we propose a synthesis method of nanosheets of ZIF-8, zinc 2-methylimidazolate, with a sodalite-like framework. They grow up to a few nanometers of thickness and several hundred nanometers of width with neither aggregation nor impurities from multiple hydrophilic precursors in the stoichiometric ratio inside the hydrophilic TRAPs consisting of the amphiphile Brij L4. The thin nanosheets of ZIF-8 doped with Co2+ (Co-ZIF-8) synthesized by the same method maintained a high specific surface area after calcination. Therefore, the oxygen reduction reaction (ORR) activity of the calcined Co-ZIF-8 NSs for fuel cells becomes higher than that of the calcined conventional Co-ZIF-8 crystals.

Gyroid-Nanostructured All-Solid Polymer Films Combining High H+ Conductivity with Low H2 Permeability.

Gyroid-nanostructured all-solid polymer films with exceedingly high proton conductivity and low H2 gas permeability have been created via crosslinking polymerization of mixtures of a zwitterionic amphiphilic monomer and a polymerizable imide-type acid that co-organize into bicontinuous cubic liquid-crystalline phases. The gyroid nanostructures are visualized by reconstructing a 3D electron map from the synchrotron X-ray diffraction patterns. These films exhibit high proton conductivity of the order of 10-1 S cm-1 and extremely low H2 gas permeability of the order of 10-15 mol m m-2 s-1 Pa-1 . These properties can be ascribed to the presence of the ionic liquid-like layer along the gyroid minimal surface. Since these two characteristics are required for improving the performance of proton-exchange membrane fuel cells, the present membrane design represents a promising strategy for the development of advanced devices, pertinent to establishing sustainable energy sources.

Lateral Growth of Uniformly Thin Gold Nanosheets Facilitated by Two-Dimensional Precursor Supply.

The nanosheets of highly symmetric materials with a face-centered cubic lattice such as gold have been synthesized by adsorbing the precursors on a flat surface, whose chemical specificity induces the anisotropy of growth rates. We have succeeded in the fabrication of gold nanosheets in a hydrophilic space inside highly separated bilayers, which work as two-dimensional hydrophilic reactors, in a hyperswollen lamellar liquid crystalline phase of an amphiphile solution. One of the physical properties, amphiphilicity, confines the ingredients therein. The nanosheets can only grow in the in-plane direction due to the inhibition of the out-of-plane growth rather than the anisotropy of growth rates probably. Thus, the synthesis can be accelerated; the particles can be completed within 15 min. As not relying on chemical specificity, silver nanosheets could also be synthesized in the same way. The suspension of gold and silver nanosheets without any amphiphiles could be obtained, and the solvent is replaceable. We found that the width of the obtained gold nanosheets is proportional to the Reynolds number of the solution because the area of the bilayer in the hyperswollen lamellar phase depends on shear stress. This implies that the areas of gold nanosheets depend on the areas of the bilayers, and it can be controlled by changing the Reynolds number. This method could be widely used to continuously obtain large-area nanosheets of various materials in a roll-to-roll manufacturing process.

The removal of 3-monochloropropane-1,2-diol ester and glycidyl ester from refined-bleached and deodorized palm oil using activated carbon.

Palm oil has fulfilled most of the oil needs in the food sector in the world. However, palm oil is indicated to contain small amounts of compounds that are harmful to humans, especially to infants. These toxic contaminants are 3-monochloropropanediol (3-MCPD) esters and glycidyl esters (GE), which are formed during the deodorization of palm oil at high temperatures. This study aims to reduce the 3-MCPD ester concentration in refined, bleached, and deodorized palm oil (RBDPO) through adsorption using activated carbon. The activated carbons were treated with heat and acid-washing using HCl at various concentrations and were characterized. The treatment altered the physicochemical characteristics of the activated carbon (surface area, pore volume, pHPZC, and CEC), resulting in the enhancement of its adsorption characteristics (adsorption capacity). The activated carbon treated with 2 N HCl (AC 2 N) was chosen as the proper adsorbent, due to better surface area, better pore volume, highest CEC value, and better positive charge in RBDPO. The 3-MCPD and GE adsorption capacity of AC 2 N was 1.48 mg g-1 and 29.68 mg g-1, respectively. The adsorption ability of pretreated activated carbon towards 3-MCPD esters was examined in a batch system at various adsorption temperatures. The 3-MCPD ester concentration in RBDPO was successfully reduced by up to 80% at 35 °C using the activated carbon treated with 2 N HCl solution. On the other hand, the activated carbon was able to reduce the other contaminant of GE in RBDPO up to 97% from the initial concentration of GE.

Thermal Molecular Motion Can Amplify Intermolecular Magnetic Interactions.

Against a sensible expectation that molecular mobility in fluids generally disrupts magnetic orderings that depend on intermolecular interactions, some molecular compounds with isolated electrons, which are called radicals, exhibit the increase of magnetic susceptibility in melting. Here we first propose a simple model to explain the thermomagnetic anomaly unique to fluids; the effect of the magnetic interactions in each of the contacts could be accumulated on each of the molecular spins as if the molecular motion amplified the first coordination number of each molecule hundredfold. The huge coordination number theoretically guarantees the retention of memory of interactions at equilibrium; molecules might be able to conserve the memory of molecular conformations, configurations, electric charges, energies as well as magnetic memory with each other.

Magnetically controllable random laser in ferromagnetic nematic liquid crystals.

This paper first reports random laser action in dye-doped ferromagnetic nematic liquid crystals, which act as a randomly distributed cavity. The random laser intensity of the ferromagnetic nematic liquid crystals can be controlled by a weak magnetic field (∼1 mT). Moreover, the magnetic switching of random laser is attributed to the direction and polarization dependent emission of light in the ferromagnetic nematic liquid crystals in an external magnetic field.

Thiol-functionalized magnetic carbon nanotubes for magnetic micro-solid phase extraction of sulfonamide antibiotics from milks and commercial chicken meat products.

Thiol-functionalized magnetic carbon nanotubes (TMCNTs) were employed as the sorbent in the magnetic micro-solid phase extraction (M-µ-SPE) of sulfonamide antibiotics (SAs) in water, milks and chicken meat products prior to high performance liquid chromatography-diode array detector (HPLC-DAD) analysis. The synthesized sorbent was characterized by several spectroscopic techniques. Optimum conditions were: 20 mg of TMCNTs at pH 4, 2 min extraction time, 10% addition of salt and 30 mL of sample volume. Under the optimized TMCNTs-M-µ-SPE and HPLC-DAD conditions, the method showed good linearity in the range of 0.1-500 µg L-1 (r2 ≥ 0.9950), low limits of detection (0.02-1.5 µg L-1), good analytes recovery (80.7-116.2%) and acceptable RSDs (0.3-7.7%, n = 15). The method was applied to tap water (1), milks (15) and commercial chicken meat products (35), SAs were detected in five chicken meat samples (3.0-25.7 µg L-1). The method is critically compared to those reported in the literature.

Dispersive liquid-liquid microextraction combined with dispersive solid-phase extraction for gas chromatography with mass spectrometry determination of polycyclic aromatic hydrocarbons in aqueous matrices.

This study describes a dispersive liquid-liquid microextraction combined with dispersive solid-phase extraction method based on phenyl-functionalized magnetic sorbent for the preconcentration of polycyclic aromatic hydrocarbons from environmental water, sugarcane juice, and tea samples prior to gas chromatography with mass spectrometry analysis. Several important parameters affecting the extraction efficiency were investigated thoroughly, including the mass of sorbent, type and volume of extraction solvent, extraction time, type of desorption solvent, desorption time, type and amount of salt-induced demulsifier, and sample volume. Under the optimized extraction and gas chromatography-mass spectrometric conditions, the method revealed good linearity (10-100000 ng/L) with coefficient of determination (R2 ) of ≥0.9951, low limits of detection (3-16 ng/L), high enrichment factors (61-239), and satisfactory analyte recoveries (86.3-109.1%) with the relative standard deviations < 10% (n = 5). The entire sample preparation procedure was simple, rapid and can be accomplished within 10 min. This method was applied (after pretreatment) to 30 selected samples, and the presence of studied analytes was quantified in 17 samples.

Molecular Mobility Effect on Magnetic Interactions in All-Organic Paramagnetic Liquid Crystal with Nitroxide Radical as a Hydrogen-Bonding Acceptor.

We synthesized new chiral all-organic liquid crystalline (LC) compounds with nitroxide (NO) and hydroxy (OH) groups, which form intermolecular hydrogen bonds between the NO and OH groups. The LC compounds show hexagonal columnar phases at room temperature, which solidify as LC glasses at low temperature. The experimental magnetic susceptibility of each of the compounds in the LC and isotropic phases is larger than that theoretically estimated on the simple assumption about the amount of the spins, whereas it accords with the theoretical one in the LC glass state. It is called magneto-LC effects. The difference between experimental and theoretical magnetic susceptibilities gradually increases as temperature increases through the LC glass state-to-LC phase transition. It suggests that molecular mobility is one of the origins of the magneto-LC effects.