Latest ArticlesDeveloping applicable methods to forge linkages between sp3 and sp2-hydridized carbons is of great significance in drug discovery. We show here a new, Ni-catalyzed reductive cross-coupling reaction that forms Csp3−Csp2 bonds from aryl iodides and cyclic sulfonium salts. Notably, Csp3−Csp2 bonds can be forged selectively at the iodine-bearing carbon of bromo(iodo)arenes which is usually recognized as a huge challenge under the catalytic reductive cross-coupling (CRCC) conditions. Experimental and computational mechanistic studies support LNiⅠAr as an active species, while the untraditional anti-Markovnikov selective alkylation of asymmetric sulfonium salts is determined by the oxidative S-substitution of sulfonium salts with LNiⅠAr. This protocol further expands the range of alkyl electrophiles under the CRCC conditions and provides a new strategy for the construction of Csp3−Csp2 bonds.
In this study, the environmentally friendly precursor, tartaric acid (TA), was employed for the generation of CO2 anion radical (CO2•−) in an advanced UV/TA/Fe3+ system to reduce the hazardous -N in wastewater. To optimize this process, various factors, including the dosage of Fe3+, TA, and pH, were systematically investigated for their impact on the reduction process. Under the conditions of 3 mmol/L Fe3+ dosage, 10 mmol/L TA dosage, and a pH of 2.5, -N was effectively removed from the water within 60 min, selectively transformed into N2, with a remarkable N2 selectivity of 91.2%. In the optimal conditions, the -N reduction mechanism in the UV/TA/Fe3+ system and the critical role of were illustrated. Finally, this study explored the reduction of real nitrified seawater using the UV/TA/Fe3+ system. The results demonstrated that the UV/TA/Fe3+ system could completely eliminate -N and achieve a N2 selectivity of up to 90%, with minimal interference from coexisting ions. This work holds promising implications for the environmentally benign treatment of nitrite-polluted wastewater.
In electrochemical energy devices, the operating conditions always exert enormous influence on electrocatalysts' performances. Phosphoric acid (PA), acted as the proton carriers, can be adsorbed on Pt surface, block active sites and affect the electronic structure of Pt unfavorably, which severely restricts the performance of high-temperature proton exchange membrane fuel cells (HT-PEMFCs). Herein, simply basic organic compounds, such as dicyandiamide (DCD), melamine (Mel) and cyanuric acid (CA), are decorated on Pt surface (DCD-Pt/C, Mel-Pt/C and CA-Pt/C) to induce the adsorption transfer of proton carriers. The decoration can not only inject electrons to Pt and enhance oxygen reduction reaction (ORR) activity but also can induce PA to transfer from Pt surface to organic compounds, decontaminating active sites. In addition, the organic compounds with the larger conjugated system and the smaller electronegativity of ligating atoms would have a greater interaction with Pt, causing a larger decoration amount on Pt surface, which leads to more excellent ORR activity and resistance to PA blockage effect. Therefore, Mel-Pt/C shows a peak power density of 629 mW/cm2, exceeding commercial Pt/C (437 mW/cm2), DCD-Pt/C (539 mW/cm2) and CA-Pt/C (511 mW/cm2) with the same loading.
3d transition metal chalcogenides have attracted much attention due to their unique magnetic properties. Although various Cr, V, and Fe-based chalcogenides have been fabricated recently, the limited Curie temperature (TC) still hinders their practical application. Based on the structural and magnetic advantages of MFe2O4 and Fe3Se4, we developed a one-pot solution synthesis method for the fabrication of NiFe2Se4 nanostructures with structural continuity, to facilitate the investigation of their magnetic properties. Notably, the morphology of NiFe2Se4 can be controlled from nano-rods to nano-platelets by controlling the growth direction. The coercivity (HC) of NiFe2Se4 with nano-cactus structure exhibits a maximum of 12.77 kOe at 5 K. The coercivity of ferrimagnetic NiFe2Se4 nano-platelets can be further adjusted to 1.52 kOe at room temperature. These results show that the magnetic properties of NiFe2Se4 can be significantly modified by controlling their morphologies. We also extend the method to the synthesis of CoFe2Se4 nano-cactus with an ultrahigh coercivity of 17.85 kOe at 5 K. Obviously, the synthesis strategy and their excellent magnetic properties of MFe2Se4 have sparked interest in ternary transition metal selenides as potential hard magnetic materials.
1-(4-(1,1-Dimethylethyl)phenyl)-3-(4-methoxyphenyl)-1,3-propanedione (known as Avobenzone/AVB), widely used throughout the world as a highly effective UVA absorber, can prevent the progression of photoaging in skin, and is also known for the disadvantage of having a reduced capability to absorb UVA when exposed to sunlight for long periods. To address this challenge, ZnTi-CO3-LDH with a two-dimensional layered structure was used to improve stability and synergistically enhance UV absorption of AVB. A novel AVB loaded ZnTi-CO3-LDH (AVB@ZnTi-LDH) material was synthesized by reconstruction method and the loading content (LC) was about 46.8% investigated by high-performance liquid chromatography (HPLC). A possible mechanism for the binding of AVB with the ZnTi-LDH surface was proposed. X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations were used to confirm further the coordination between Zn on the layer and the oxygen atom of the carbonyl group of AVB. UV absorption and critical wavelength of AVB@ZnTi-LDH were superior to those of AVB and ZnTi-LDH precursors. Compared with pure AVB, the photodegradation rate was reduced from 15.06% to 4.06%. Especially in titanium dioxide, the decomposition rate was reduced from 29.75% to 7.92%. Furthermore, pure AVB often reacts with multivalent metal ions to induce an unpleasant color (light yellow to reddish brown), which is greatly mitigated with AVB@ZnTi-LDH. In this study, avobenzone was combined with hydrotalcite to prepare an organic-inorganic composite with excellent UV resistance and better stability, the composite has great promise for application in sunscreen cosmetics.
Spinel oxides, with the formula AB2O4 (A and B represent metal ions) perform superior electrocatalytic characteristic when A and B are transition metals like Co, Fe, Mn, etc. Abundant researches have been attached to the structure designments while methods are often energy-intensive and inefficient. Here, we devised a universal strategy to achieve rapid synthesis of nanocrystalline spinel materials with multiple components (Co3O4, Mn3O4, CoMn2O4 and CoFe2O4 are as examples), where phase formation is within 15 s. Under the Joule-heating shock, a crack-break process of microcosmic phase transformation is observed by in-situ transmission electron microscopy. The half-wave potential values of Co3O4—JH, Mn3O4—JH, CoMn2O4—JH and CoFe2O4—JH in the electrocatalytic oxygen reduction reaction were 0.77, 0.78, 0.79 and 0.76, respectively. This suggests that the Joule heating is a fast and efficient method for the preparation of spinel oxide electrocatalysts.
Zeolitic imidazolate frameworks (ZIFs) are a series of materials composited by metal ions and organic ligands with high specific surface area, which might be great precursors to produce metal oxides by calcination for gas sensor application. However, Zn-ZIF (ZIF-8) is hard to transform as ZnO in air and keeping the unique framework simultaneously. In this work, Fe2+ was introduced into the metal node to replace a part of Zn2+ ions, and it could be oxidized as Fe3+ in the calcination to facilitate the oxidation process of the 2-methylimdazole ligands to give Fe-ZnO complex shell with high specific surface area (108 m2/g) and abundant oxygen vacancies (48%). The micro electro mechanical systems (MEMS) sensor based on the 6%-Fe-ZnO complex shell performed outstanding gas sensing properties to the low-concentration acetone vapor, including high response (ΔR/Rg = 11.2 to 5 ppm acetone), superior selectivity (Sacetone/Sethanol = 5.6) and fast response speed (τres = 2.6 s). This work not only provided the research of an exceptional acetone MEMS sensor, but also induced a strategy to produce metal oxide derived from ZIFs with complex structures for the universal synthesis methodology.
SnO2 is a potential anode material with high theoretical capacity for lithium-ion batteries (LIBs), however, its applications have been limited by the severe volume expansion during charging-discharging process. In this work, an inverse opal TiO2/SnO2 composite with an interconnect network nanostructure was designed to confine SnO2 nanoparticles in the porous TiO2. Due to this nanoconfinement structure, the volume expansion in the process was effectively alleviated, therefore the safety performance and cycling stability of the battery were effectively improved. At the same time, with a large number of microporous structures in the framework, the appearance of pseudocapacitance improves the rate performance and reversible capacity. In terms of electrochemical kinetics, its framework provides the connected path for charge migration, effectively reducing the charge transfer impedance, meanwhile, quantities of micropores in its skeleton could provide a smoother channel for lithium ions, thus greatly improving the diffusion rate of LIBs. The design of this nanostructure provides a new idea for the research of SnO2-based anode with effectively enhanced electrochemical performance, which is promising anode for practical application.
Lithium–sulfur (Li–S) batteries are considered one of the most promising next-generation secondary batteries owing to their ultrahigh theoretical energy density. However, practical applications are hindered by the shuttle effect of soluble lithium polysulfides (LiPSs) and sluggish redox kinetics, which result in low active material utilization and poor cycling stability. Various copper-based materials have been used to inhibit the shuttle effect of LiPSs, owing to the strong anchoring effect caused by the lithiophilic/sulphilic sites and the accelerated conversion kinetics caused by excellent catalytic activity. This study briefly introduces the working principles of Li–S batteries, followed by a summary of the synthetic methods for copper-based materials. Moreover, the recent research progress in the utilization of various copper-based materials in cathodes and separators of Li–S batteries, including copper oxides, copper sulfides, copper phosphides, copper selenides, copper-based metal-organic frameworks (MOFs), and copper single-atom, are systematically summarized. Subsequently, three strategies to improve the electrochemical performance of copper-based materials through defect engineering, morphology regulation, and synergistic effect of different components are presented. Finally, our perspectives on the future development of copper-based materials are presented, highlighting the major challenges in the rational design and synthesis of high-performance Li–S batteries.
In order to solve the problem of poor conductivity of traditional LiFePO4 cathode binders, we developed sodium alginate-Congo red copolymers (SA-CR) as water-soluble electrically conductive and mechanically robust composite binder. Unlike most other electrically conductive polymer binders, the procedure is straightforward and low-cost to prepare SA-CR binder. Various SA -CR copolymers were prepared with different degree of compounding of CR to investigate the effect of CR on the electrochemical and physical properties of the prepared electrodes. The copolymer whose composition was filled with a mixture of SA and CR at a 3:1 mass ratio showed the best cell performance, due to the well-balanced electrical conductivity and mechanical properties. It exhibited a specific capacity of 118.8 mAh/g at the 100th cycle with 92.1% capacity retention, significantly better than the 108.5 mAh/g of conventional acetylene black electrodes. CR as a conduction-promoting agent in water-soluble composite binder favors the formation of continuous and homogenous conducting bridges throughout the electrode and increases the compaction density of electrode by reducing the conducting agent content of acetylene black and thus the improvement of electrode performance is realized.
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