Latest ArticlesPotassium-ion batteries (PIBs) are attracted tremendous interest for large-scale energy storage systems (ESSs) owing to their economic merits. However, the main challenges of the PIBs are sluggish K-ion diffusion and large volume variations in the potassium repeated intercalation/deintercalation. Herein, mesoporous carbon nanosheet-assembled flowers (abbreviated as F-C) are designed as an original anode for superior-performance PIBs. Specifically, the F-C anode exhibits a high K-storage capacity (e.g., 381 mAh/g at 50 mA/g during the 2nd cycle), excellent rate performance (e.g., 101 mAh/g at 2.0 A/g) and superior long cycle capability. Such excellent K-ion storage property is largely benefited from the large surface area (~141 m2/g) and reasonable pore volume (0.465 cm3/g), which not only stimulates rapid K-ions diffusion and relieves the huge volume strain, but also exposes extensive active sites for K-ion capacitive storage.
There is an increasing demand of using the low-cost and sustainable cobalt to replace its noble congeners (rhodium and iridium) as reflected by the recent upsurge of cobalt catalysis in the diverse organic transformations. Since all the redox reactivity of cobalt catalysis highly relies on the capability of the interconversion between their oxidation states (most frequently +1, +2 and +3), electrochemistry perfectly meets such a requirement owing to its outstanding performance in the redox manipulation. In this review, we highlight the recent advances in the merger of cobalt catalysis and electrochemistry in organic synthesis.
Conia-ene reactions, as a type of ene reactions, have not become a remarkable focus until the beginning of 21st century, when Lewis acids served as powerful catalysts and found an increasingly broad utilization in this field. Consequently, the catalytic Conia-ene reactions have gained great significance in synthetic chemistry due to their high efficiency and atom economy on the construction of valuable cyclic molecules. During the past two decades, the rapid development of transition-metal catalysis and organocatalysis has imposed a profound impact on the exploration of asymmetric Conia-ene reactions. As a result, several strategies have been developed and applied successfully. Organized on the basis of the catalytic system, this review comprehensively presents a summary of recent progress achieved in this emerging domain, aimed at highlighting the reactions' features, practicalities, and the mechanistic rationale is presented where possible.
Lithium-ion batteries (LIBs) have evolved into the mainstream power source of energy storage equipment by reason of their advantages such as high energy density, high power, long cycle life and less pollution. With the expansion of their applications in deep-sea exploration, aerospace and military equipment, special working conditions have placed higher demands on the low-temperature performance of LIBs. However, at low temperatures, the severe polarization and inferior electrochemical activity of electrode materials cause the acute capacity fading upon cycling, which greatly hindered the further development of LIBs. In this review, we summarize the recent important progress of LIBs in low-temperature operations and introduce the key methods and the related action mechanisms for enhancing the capacity of the various cathode and anode materials. It aims to promote the development of high-performance electrode materials and broaden the application range of LIBs.
Flexible rechargeable Zn-air batteries are considered as one of the most promising battery systems to drive flexible and wearable electronic devices owing to their high safety, high gravimetric energy density, low self-discharge and low cost. One of the key challenges is to develop air electrodes with high performance and high mechanical flexibility. This minireview discusses the recent progress in the design and fabrication of flexible air electrodes. It focuses on the latest innovations in bifunctional oxygen reduction reaction and oxygen evolution reaction electrocatalysts, mainly including carbon-based materials (e.g., heteroatom-doped carbon, metal-nitrogen moieties doped carbon), metal oxides (e.g., spinel oxides, perovskite oxides) and their composites. It aims to provide an insight into the structure-property relationship of bifunctional catalysts. We also discuss the challenges and future perspectives.
The recent boom in large-scale energy storage system promotes the development of lithium-oxygen batteries because of their high theoretical energy density. However, their applications are still limited by the sluggish kinetic, insoluble discharge product deposition and the undesired parasitic reaction. Herein, the free-standing nitrogen doped reduced graphene oxide/Co(OH)2 (NRGO/Co(OH)2) composite films were prepared by a facile hydrothermal method. The NRGO/Co(OH)2 composite films display interconnected three-dimensional conductive network, which can not only promote the diffusion of O2 and the transport of electrolyte ions, but also provide abundant storage space for discharge products. Moreover, the introduction of nitrogen-containing functional groups results in improved conductivity and electron adsorption ability, which can facilitate electron transport and enhance the surface catalytic activity. Combining with excellent catalytic performance, the lithium-oxygen batteries with NRGO/Co(OH)2 composite film cathodes deliver low charge overpotential and excellent cycling performance.
The P2-type manganese-based Na0.7MnO2 cathode materials attract great interest due to their high theoretical capacity. However, these materials suffer from rapid capacity fading, poor rate performance and severe voltage decay resulting from phase transition and sluggish reaction kinetics. In this work we report a novel Nb-doped Na0.7[Ni0.3Co0.1Mn0.6]1-xNbxO2 with significantly suppressed voltage decay and enhanced cycling stability. The strong Nb-O bond can efficiently stabilize the TMO framework, and the as prepared material demonstrates much lower discharge midpoint voltage decay (0.132 V) than that of pristine one (0.319 V) after 200 cycles. Consequently, a remarkably improved cycling performance with a capacity retention of 87.9% after 200 cycle at 0.5 C is achieved, showing a 2.4 fold improvement as compared to the control sample Na0.7Ni0.3Co0.1Mn0.6O2 (~37% rotation). Even at 2 C, a capacity retention of 68.4% is retained after 500 cycles. Remarkably, the as prepared material can be applied at low temperature of −20 ℃, showing a capacity retention of 81% as compared to that at room temperature.
In many reactions involving selenosulfonate or thiosulfonate, the sulfone group often leaves in form of benzenesulfinic acid or sodium benzenesulfinate. A one-pot two-step reaction of selenosulfonate with isocyanides and allyl alcohol under aqueous conditions to afford selenocarbamates and allyl sulfone compounds is reported. The sulfinic acid as the first-step side product is converted to the allyl sulfone compound by water promoted reaction with allyl alcohol. Water acts as both an oxygen source of selenocarbamates and as a promoter to drive the second step reaction. The reactions have the advantages of mild conditions, green, environment-friendly, and high atomic economy.
Plant polyphenol-based coordination polymers (CPs) with ultra-small particle size and tailorable compositions are highly desired in biomedical applications, but their synthesis is still challenging due to the sophisticated coordination assembly process and unavoidable self-oxidation polymerization of polyphenol. Herein, a general ligand covalent-modification mediated coordination assembly strategy is proposed for the synthesis of water-dispersible CPs with tunable metal species (e.g., Gd, Cu, Ni, Zn, Fe) and ultra-small diameter (8.6–37.8 nm) using nontoxic plant polyphenol (e.g., tannic acid, gallic acid) as a polymerizable ligand. Polyphenol molecules react with formaldehyde firstly, which can effectively retard the oxidation induced self-polymerization of polyphenol and lead to the formation of metal ions containing CPs colloidal nanoparticles. These ultrafine nanoparticles with stably chelated metal ions are highly water dispersible and thus advantageous for bioimaging. As an example, ultra-small Gd contained CPs exhibit higher longitudinal relaxivity (r1 = 25.5 L mmol-1 s-1) value with low r2/r1 (1.19) than clinically used Magnevist (Gd-DTPA, r1 = 3.7 L mmol-1 s-1). Due to the enhanced permeability and retention effect, they can be further used as a positive contrast agent for T1-weighted MR imaging of tumour.
Research on pollution characteristics and toxicities of emerging polycyclic aromatic sulfur heterocycles (PASHs) in PM2.5 has not been reported due to the lack of analytical method with the needed performance. In the present study, a novel method for the determination of 14 PASHs in PM2.5 was developed using atmospheric pressure gas chromatography-tandem mass spectrometry (APGC-MS/MS). Atmospheric pressure chemical ionization was operated with multiple reaction monitoring in positive ionization mode. High sensitivity (method detection limit < 1.673 pg/m3), acceptable recoveries (67.6%–120.8%) and precisions (RSD of 2.2%–15.4%) were obtained. The method was successfully applied for analyzing PASHs in 10 PM2.5 samples collected from Taiyuan, a typical industrial city in China, in 2016. The total concentrations were from 929 pg/m3 to 14,593 pg/m3. The determined levels indicated that further investigations on environmental fate and toxicities of PM2.5-bound PASHs may be needed.
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