Ultrathin Fe‐N‐C Nanosheets Coordinated Fe‐Doped CoNi Alloy Nanoparticles for Electrochemical Water Splitting

The development of highly active and cost‐effective catalyst materials toward electrochemical water splitting is of great importance for converting and storing the intermittent solar energy in the form of hydrogen. Herein, for the first time, an ultrathin Fe and N‐co‐doped carbon nanosheet encapsulated Fe‐doped CoNi alloy nanoparticle (FeCoNi@FeNC) composite is obtained and applied as a bifunctional catalyst for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). This catalyst exhibits prominent catalytic performances for both HER and OER, which only requires overpotentials of 102 and 330 mV, respectively, to reach a current density of 10 mA cm^?2 in alkaline media. The high catalytic activity is intrinsically associated with the presence of Fe in both nanosheets and nanoparticles, which has triggered the occurrence of coordinative effects between Fe‐N‐C and FeCoNi that are beneficial for HER and OER, as revealed by electrochemical techniques. In an overall water splitting electrolyzer, FeCoNi@FeNC is employed as both the cathode and anode catalysts, achieving 12 mA cm^?2 at 1.63 V for a duration of more than 12 h.     

Review of Sn‐Doped Hematite Nanostructures for Photoelectrochemical Water Splitting

Hematite (α‐Fe₂O₃) nanostructures have been extensively studied as photoanodes for photoelectrochemical (PEC) water splitting. However, the photoactivity of pristine hematite nanostructures is limited by a number of factors, including poor electrical conductiviy and slow oxygen evolution reaction kinetics. Previous studies have shown that using tin (Sn) as an n‐type dopant can substantially enhance the photoactivity of hematite photoanodes by modifying their optical and electrical properties. Here, the recent accomplishments in using Sn‐doped hematite photoanodes for solar water splitting are highlighted.     

Graphene‐Based Phosphorus‐Doped Carbon as Anode Material for High‐Performance Sodium‐Ion Batteries

Graphene‐based phosphorus‐doped carbon (GPC) is prepared through a facile and scalable thermal annealing method by triphenylphosphine and graphite oxide as precursor. The P atoms are successfully doped into few layer graphene with two forms of P–O and P–C bands. The GPC used as anode material for Na‐ion batteries delivers a high charge capacity 284.8 mAh g^?1 at a current density of 50 mA g^?1 after 60 cycles. Superior cycling performance is also shown at high charge?discharge rate: a stable charge capacity 145.6 mAh g^?1 can be achieved at the current density of 500 mA g^?1 after 600 cycles. The result demonstrates that the GPC electrode exhibits good electrochemical performance (higher reversible charge capacity, super rate capability, and long‐term cycling stability). The excellent electrochemical performance originated from the large interlayer distance, large amount of defects, vacancies, and active site caused by P atoms doping. The relationship of P atoms doping amount with the Na storage properties is also discussed. This superior sodium storage performance of GPC makes it as a promising alternative anode material for sodium‐ion batteries.     

A DFT‐based exploration augmented by X‐ray and NMR of the stereoselectivity in the 1,3‐dipolar cycloaddition of 1‐pyrroline‐1‐oxide to methyl cinnamate and benzylidene acetophenone

A B3LYP/6–31G* study was carried out for the reactions of 1‐pyrroline‐1‐oxide (N1) with methyl cinnamate (E1) and benzylidene acetophenone (E2) for getting a quantitative rationalization of the experimental findings. The product ratios were determined by NMR studies of the crude reaction mixtures. The conformation and stereochemistry of the isolated cycloadducts were finally confirmed by 2D NMR and X‐ray diffraction. The endo/exo‐selectivities were predicted through the computation of activation parameters on the basis of assumed concerted mechanism. The regioselectivity and reactivity were amply predicted by local and global electrophilicity indices and were found to be in good agreement with the experimental findings which were supportive of polar character and of the direction of charge transfer (CT) accompanying the cycloaddition. It was found that the cycloaddition involving methyl cinnamate was endo‐selective, while that with benzylidene acetophenone produced the exo‐isomer as the major adduct. Copyright © 2010 John Wiley & Sons, Ltd.     

A Facile Method for Synthesis of Porous NiCo2O4 Nanorods as a High‐Performance Anode Material for Li‐Ion Batteries

Porous electrode materials with large specific surface area, relatively short diffusion path, and higher electrical conductivity, which display both better rate capabilities and good cycle lives, have huge benefits for practical applications in lithium‐ion batteries. Here, uniform porous NiCo₂O₄ nanorods (PNNs) with pore‐size distribution in the range of 10–30 nm and lengths of up to several micrometers are synthesized through a convenient oxalate co‐precipitation method followed by a calcining process. The PNN electrode exhibits high reversible capacity and outstanding cycling stability (after 150 cycles still maintain about 650 mA h g^?1 at a current density of 100 mA g^?1), as well as high Coulombic efficiency (>98%). Moreover, the PNNs also exhibit an excellent rate performance, and deliver a stable reversible specific capacity of 450 mA h g^?1 even at 2000 mA g^?1. These results demonstrate that the PNNs are promising anode materials for high‐performance Li‐ion batteries.     

NiWO3 Nanoparticles Grown on Graphitic Carbon Nitride (g‐C3N4) Supported Toray Carbon as an Efficient Bifunctional Electrocatalyst for Oxygen and Hydrogen Evolution Reactions

Catalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are at the heart of water oxidation reactions. Despite continuous efforts, the development of OER/HER electrocatalysts with high activity at low cost remains a big challenge. Herein, a composite material consisting of TC@WO₃@g‐C₃N₄@Ni‐NiO complex matrix as a bifunctional electrocatalyst for the OER and HER is described. Though the catalyst has modest activity for HER, it exhibits high OER activity thereby making it a better nonprecious electrocatalyst for both OER and HER and is further improved by g‐C₃N₄. The catalytic activity arises from the synergetic effects between WO₃, Ni‐NiO, and g‐C₃N₄. A Ni‐NiO alloy and WO₃ nanoparticles decorated on the g‐C₃N₄ surface supported toray carbon (TC) matrix (TC@WO₃@g‐C₃N₄@Ni‐NiO) by a facile route that show an excellent and durable bifunctional catalytic activity for OER and HER in the alkaline medium are developed. This carbon nitride with binary metal/metal‐oxide matrix supported with TC exhibit an overpotential of 0.385 and 0.535 V versus RHE at a current density of 10 mA cm^?2 (Tafel slopes of 0.057 and 0.246 V dec^?1 for OER and HER, respectively), in 0.1 m NaOH . The catalyst is tested in water electrolysis for 17 h.     

A non‐enzymatic model based on an acyl transfer reaction for the formation of energy‐rich acetyl phosphate in organic solvents and in a biphasic system

The formation of acetyl phosphate (AcP), an energy‐rich phosphate compound, was studied through the reaction of 2,4‐dinitrophenyl acetate with H₂PO solubilized with Kryptofix® 222 or as a tetra‐n‐butylammonium ((n‐C₄H₉)₄N⁺) salt in organic media. The results indicated that the rate of the reaction in acetonitrile is strongly inhibited by the addition of water, suggesting that the water added to the medium preferentially solvates the H₂PO anion, inhibiting its action as a nucleophile and allowing it to act as a general base catalyst, which leads to the hydrolysis of the ester. The utilization of various organic solvents in the acetyl transfer process demonstrated that the specific interaction of the solvent with water accelerates the process, by desolvation of H₂PO, which can act as a nucleophile. Finally, a formation/transformation cycle of AcP was studied in a biphasic system (water/CH₂Cl₂) using Kryptofix® 222 and (n‐C₄H₉)₄N⁺BF as both the carrier and solubilizing agent for KH₂PO₄. Copyright © 2010 John Wiley & Sons, Ltd.     

A High‐Performance Anode Material for Li‐Ion Batteries Based on a Vertically Aligned CNTs/NiCo2O4 Core/Shell Structure

3D vertically aligned carbon nanotubes (CNTs)/NiCo₂O₄ core/shell structures are successfully synthesized as binder‐free anode materials for Li‐ion batteries (LIBs) via a facile electrochemical deposition method followed by subsequent annealing in air. The vertically aligned CNTs/NiCo₂O₄ core/shell structures are used as binder‐free anode materials for LIBs and exhibit high and stable reversible capacity (1147.6 mAhg^?1 at 100 mAg^?1), excellent rate capability (712.9 mAh g^?1 at 1000 mAg^?1), and good cycle stability (no capacity fading over 200 cycles). The improved performance of these LIBs is attributed to the unique 3D vertically aligned CNTs/NiCo₂O₄ core/shell structures, which support high electron conductivity, fast ion/electron transport in the electrode and at the electrolyte/electrode interface, and accommodate the volume change during cycling. Furthermore, the synthetic strategy presented can be easily extended to fabricate other metal oxides with a controlled core/shell structure, which may be a promising electrode material for high‐performance LIBs.