FeCo alloy/N,S dual-doped carbon composite as a high-performance bifunctional catalyst in an advanced rechargeable zinc-air battery

The rational design and development of cost-effective,high-performance,and stable bifunctional oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)electrocatalysts are essential for rechargeable zinc-air batteries.Herein,a novel FeCo composite composed of alloy nanoparticles embedded in an N,S dual-doped carbon matrix(FeCo/NSC)was prepared via one-step carbonization of amphiphilic dodecanethiol-metal salts wrapped in carbon nitride(C₃N₄).The compact combination of dual metalalloys and dual-doped carbon endowed the composite with the active sites for the ORR and OER,achieving efficient electrical transmission and highly efficient bifunctional catalytic performance.The obtained FeCo-1/NSC catalyst exhibited excellent electrocatalytic activity with a half-wave potential of 0.82 V(vs.RHE)for the ORR and a low overpotential of 0.325 V at 10 mA cm^-2 for the OER.The liquid Zn-air battery with FeCo-1/NSC as an air electrode displayed excellent charge-discharge performance,high power density,and robust charge-discharge stability for 150 h compared to the 20%Pt/C+RuO₂ counterpart.Furthermore,the FeCo-1/NSC-based flexible solid-state Zn-air battery exhibited a higher power density and good charge-discharge stability over 10 h of operation.Thus,a promising strategy for bifunctional electrocatalyst development as part of rechargeable and wearable Zn-air batteries was provided.     

Highly diastereoselective desymmetrizations of cyclo(Pro,Pro): an enantioselective strategy toward phakellstatin and phakellin

[reaction: see text] Monoenolates of C(2)-symmetric, proline-derived piperazine-2,5-diones were generated and trapped with a variety of electrophiles to produce, in a highly diastereoselective fashion, functionalized diketopiperazines (DKPs). These reactions provide the basis for an asymmetric, desymmetrization strategy toward the marine alkaloids phakellstatin and phakellin. The relative stereochemistry of the functionalized DKPs was confirmed by single-crystal X-ray analysis and/or NOE experiments. Bis-functionalization of the DKPs was also found to proceed with high levels of diastereoselectivity.     

Biosynthesis of a retrochalcone,echinatin: a feeding study with advanced precursors

Feeding experiments with ¹⁴C-labeled compounds established that a dibenzoylmethane, licodione($\text{3}$), is an obligate intermediate in the biosynthesis of a retrochalcone, echinatin(1$\text{1}$).     

Scalable construction of SiO/wrinkled MXene composite by a simple electrostatic self-assembly strategy as anode for high-energy lithium-ion batteries

Available onlineSilicon monoxide(SiO) is a promising anode material fo r lithium-ion batteries(LIBs) due to its high theoretical specific capacity(～2400 mAh/g),low working potential(<0.5 V vs.Li⁺/Li),low cost,easy synthesis,nontoxicity,abundant natural source and smaller volume expansion than Si.However,low intrinsic electrical conductivity,low initial Coulombic efficiency(ICE) and inevitable volume expansion(～200%) impede its practical application.Here we fabricate SiO/wrinkled MX...     

AFM study of advanced composite materials for organic photovoltaic cells with active layer based on P3HT:PCBM and chiral photosensitive liquid crystalline dopants

Advanced composite materials aimed for construction of organic photovoltaic cells have been studied by atomic force microscopy (AFM). The composites are based on poly(3-hexylthiophene) (P3HT), [6,6]-phenyl C₆₁-butyric acid methyl ester (PCBM) and two different chiral photosensitive liquid crystalline (LC) materials. The objective of the study was to examine the nanoscale morphology of the active layer without and after annealing at specific temperature. The preliminary results of AFM observation of the morphological changes done on the investigated composites revealed an increase in the surface ordering. The surface area ratio decreases for both studied composites, while the basic roughness parameters (S_a and S_q) have been found toughly dependent on the structure of the photosensitive LC dopant.     

Development of a general separation strategy by countercurrent chromatography using sanshools from Zanthoxylum bungeanum oleoresin as a case study

Three kinds of sanshools were separated from Zanthoxylum bungeanum oleoresin by high-speed countercurrent chromatography. Sanshools are a series of amide compounds extracted from the Zanthoxylum bungeanum. Due to similar structures, polarities, and dissociation constants, it was challenging to select an appropriate solvent system for their complete separation by countercurrent chromatography. To address this challenge, a solvent-system-selection strategy was proposed to identify a relatively suitable solvent system. Additionally, a separation procedure incorporating multi-elution modes selection was established to separate similar compounds in a logical order. Ultimately, a solvent system comprising n-hexane:ethyl acetate:methanol:water in a ratio of 19:1:1:5.67 was selected. Three amide compounds with high purity were obtained through the use of recycling elution mode to improve separation resolution: hydroxy-ε-sanshool (8.4 mg; purity: 90.64%), hydroxy-α-sanshool (326.4 mg; purity: 98.96%), and hydroxy-β-sanshool (71.8 mg; purity: 98.26%) were obtained from 600 mg sanshool crude extract. The summarized solvent-system-selection strategy and separation procedure incorporating multi-elution modes may instruct countercurrent chromatography users, particularly novices, seeking to separate compounds with highly similar chemical properties.     

Oriented organic islands and one-dimensional chains on a Au(111) surface fabricated by electrodeposition: an STM study

Organic islands and oriented one-dimensional (1D) chains are fabricated on a Au(111) surface by electrodeposition. The cyclic voltammograms (CVs) of Au(111) in solutions containing nitrobenzene and picric acid show an electrochemical reaction in a negative potential region, which results in irreversible reductive deposition. The deposition process is monitored by in situ electrochemical scanning tunneling microscopy (ECSTM). At the double layer potential region, for example, nitrobenzene molecules form a well-defined adlayer in a (square root(3) x square root(3)) structure. With potential shifting negative to the reductive region, nitrobenzene is reduced to hydroxyaminobenzene. Organic islands were formed first and then aggregated into ordered 1D chains. The formation of these organic islands and 1D chains is completely potential-dependent. Intriguingly, the so-prepared islands and 1D chains are well-oriented along the reconstructed lines of the underlying Au(111) substrate and stable under ambient conditions even if the sample was removed from electrolyte solution. The results reported here provide a simple and effective method to fabricate oriented organic nanodots and nanowires on a solid surface by an electrochemical technique.     

Revealing the configuration and crystal packing of organic compounds by solid-state NMR spectroscopy: methoxycarbonylurea, a case study

The molecular configuration and intermolecular arrangement of polycrystalline methoxycarbonylurea (MCU) has been studied by a combination of chemical editing, rotational echo double resonance (REDOR) spectroscopy and ab initio calculations. From the multispin IS(n) REDOR experiments several dipolar couplings were determined and converted into distance constraints. Intra- and intermolecular dipolar couplings were distinguished by isotope dilution. The configuration of the MCU molecule can be determined from three torsion angles Psi1, Psi2, and Psi3. Ab initio calculations showed that these angles are either 0 degrees or 180 degrees (Z or E). From the REDOR experiments, the E configuration was found for Psi1 and Psi2 and the Z configuration for Psi3. Thus the configuration of MCU in the solid state was determined to be EEZ. Distance constraints for the intermolecular arrangement of MCU were obtained by performing REDOR experiments on 13C15N2 MCU with different degrees of isotope dilution and on a cocrystallized 1:1 mixture of 13C(urea) MCU and 15N(amide) MCU. By combining these distance constraints with molecular modeling, three different possible packing motifs for MCU molecules were found. The molecules in these motifs are arranged as linear chains with methoxy groups at the borders of the chains. All the intermolecular hydrogen bond donors and acceptors in the interior of the chain are saturated.     

Highly effective removal of 22Na, 134Cs and 60Co from aqueous solutions by titanosilicate: a radiotracer study

Sorption of Na(I), Cs(I) and Co(II) radionuclides from aqueous solutions by titanosilicate have been investigated. The time dependent studies for metal ions showed relatively rapid sorption kinetics between 5 and 30 min to reach equilibrium. A batch adsorption model based on assumption of the pseudo-second-order mechanism was applied to predict the sorption rate, while the equilibrium capacity was calculated at different temperatures. The adsorption of different radionuclides onto titanosilicate was found to be favored at high ions concentrations and low temperature for Na⁺ and Co²⁺ while at high temperature for Cs⁺. Activation energy of adsorption was computed to be 2.35, 24.11 and 5.74 kJ/mol for adsorption of Na(I), Cs(I) and Co(II), respectively. The results revealed that the adsorption of Cs⁺ is the highest relative to Na⁺ and Co²⁺ at different conditions which may be attributed to its low hydration energy. Further, the equilibrium isotherm for the interested ions was analyzed and it was found to obey Frundlich equation.     

Separation and preconcentration by a cloud point extraction procedure for determination of metals: an overview

Recently, cloud point extraction (CPE) has been an attractive subject as an alternative to liquid–liquid extraction. The technique is based on the property of most non-ionic surfactants in aqueous solutions to form micelles and become turbid when heated to the cloud point temperature. This review covers a selection of the literature published on applications of CPE in determination of metal ions over the period between 2004 and 2008.     

Electrochemical noise of a lithium electrode in organic electrolytes: A study by a correlation function method

Fluctuations of the potential of a lithium electrode in conditions of galvanostatic polarization in aprotic organic electrolytes are studied by a method of correlation functions. Computer-aided removal of heavy interference in the form of slow variation of the electrode potential proved to be possible to perform with use made of fifth-power polynomials. The time coordinate of the first zero in the correlation function weakly depends on the electrolyte type and lies within the limits 1.5–3 s. At the same time, the electrolyte type affects the dispersion of the electrode potential fluctuations in a substantial manner. In so doing, lithium systems that feature a high cycling efficiency possess a lower level of noise.     

Structure,stability, and disproportionation mechanisms of organic interhalides of the cholinium series: an experimental and theoretical study

The stability constants of acetylcholinium, carbamoylcholinium, and cholinium diiodochlorides and diiodobromides in chloroform solutions were determined and the kinetics of disproportionation of these systems in 1 : 9 CHCl₃—MeOH (MeCN) mixtures were studied by UV spectroscopy. A possible mechanism of mutual transformations of the polyhalides is proposed and an interrelation between the nature of the iodine-coordinating solvent and the extent of reversibility of the process is established. The electronic structures and relative stabilities of acetylcholinium iodohalides and charge-transfer complexes S·XI₂ ^– and S·I₂ (S = MeOH, MeCN, CHCl₃; X = Cl, Br, I) were studied by ab initio RHF and MP2(full) methods in the HW+(3d) and 6-31G++(d,p) basis sets. It was found that all the solvents studied favor the decomposition of the iodohalide anions to liberate molecular iodine; however, disproportionation of I₂ is possible only for the S·I₂ complexes with a high extent of charge transfer.