Metal-Free, Hindered, Regioselective Access to Multifunctional Groups Diarylamines via SN Ar Substitution of P-Nitroso Aromatic Methyl Ether by Arylamines.

Multifunctional groups diarylamines, an innovative product, efficiently produced from arylamines and p-nitrosoanisole derivatives by intermolecular SN Ar under weak acid conditions. This SN Ar proceeds under mild reaction conditions, and more significantly, the substrates involved do not necessarily require strong electron-withdrawing groups. Moreover, this SN Ar is characterized by resistance to space crowding, tolerance to halogen and nitroso functional groups, and high regioselectivity. Mechanistic observations suggest that the SN Ar is the result of the transfer of the positive charge center of the protonated nitroso group to the p-methoxy group.

Adjusting grain boundary within NiCo2O4rod arrays by phosphating reaction for efficient hydrogen production.

In this work, the density and electronic structures of the metal active sites in NiCo2O4nanorod arrays were concurrently tuned by controlling the sample's exposure time in a phosphorization process. The results showed that both the density and electronic structure of the active adsorption sites played a key role towards the catalytic activity for water splitting to produce hydrogen. The optimal catalyst exhibited 81 mV overpotential for hydrogen evolution reaction (HER) at 10 mA cm-2and 313 mV overpotential towards oxygen evolution reaction at 50 mA cm-2. The assembled electrode delivered a current density of 50 mA cm-2at 1.694 V in a fully functional water electrolyzer. The further results of theoretical density functional theory calculations revealed the doping of P elements lowered down the H adsorption energies involved in the water splitting process on the various active sites of P-NiCo2O4-10 catalyst, and thus enhanced its HER catalytic activities.

Fabrication of a biomimetic hydrogel actuator with rhythmic deformation driven by a pH oscillator.

A diversified and biocompatible rhythmic deformation (RD) system is successfully fabricated by coupling a heterogeneous hydrogel with a pH oscillator. By tailoring the geometry of the building blocks, a heterogeneous hydrogel actuator with diversity could be easily constructed through interfacial adhesion. Moreover, the RD behaviour can be regulated by the system temperature and actuator shape.

Ammonia-assisted Ni particle preferential deposition in Ni-Fe pyrophosphates on iron foam to improve the catalytic performance for overall water splitting.

Designing efficient and cost-effective electrocatalysts for overall water splitting remains a major challenge in hydrogen production. Herein, ammonia was introduced to pyrophosphate chelating solution assisted Ni particles preferential plating on porous Fe substrate to form coral-like Ni/NiFe-Pyro electrode. The pyrophosphate with multiple complex sites can couple with nickel and iron ions to form an integrated network structure, which also consists of metallic nickel due to the introduction of ammonia. The large network structure in Ni/NiFe-Pyro significantly enhances the synergistic effect between nickel and iron and then improves the electrocatalytic performance. As a result, the coral-like Ni/NiFe-Pyro@IF exhibits good electrocatalytic activity and stability for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The electrolyzer assembled with Ni/NiFe-Pyro@IF as cathode and anode just needs a low water-splitting voltage of 1.54 V to obtain the current density of 10 mA cm-2. Meanwhile, the stability test of Ni/NiFe-Pyro@IF is performed at the current densities ranging from 10 to 400 mA cm-2 for 50 h without any significant decay, indicating robust catalytic stability for overall water splitting. This strategy for synthesizing metal/metal pyrophosphate composites may provide a new avenue for future studies of efficient bifunctional electrocatalysts.

Fishnet-like double active layer-loaded carbon fiber for electrical double-layer capacitors.

The rational design and controllable synthesis of high-performance energy storage materials are important measures to address the growing demand for energy storage devices. This work involves the growth of a fishnet-like Fe2O3 nanorod@oxygen-rich carbon layer structure directly onto carbon fiber cloth as a binder-free electrode for symmetric capacitors. The growth of Fe2O3 nanorods provided a large specific surface area, and the coating of an oxygen-rich carbon layer protected the Fe2O3 nanorods as an active substance. Furthermore, oxidation treatment created rich electrochemically active sites by loading oxygen-containing functional groups onto the composite surface. As a result, the optimal OC@Fe2O3-ACC sample exhibited a high areal specific capacitance of 1687 mF cm-2 at a current density of 1 mA cm-2. Meanwhile, an excellent capacity retention rate of 58.7% was achieved at 15 mA cm-2. Finally, the long-term cycling stability was verified with an 80% retention rate of the initial capacitance after 12 000 cycles.

Enhancement of Organic Oxygen Atoms on Metal Cobalt for Sulfur Adsorption and Catalytic Polysulfide Conversion.

Metals and their compounds effectively suppress the polysulfide shuttle effect on the cathodes of a lithium-sulfur (Li-S) battery by chemisorbing polysulfides and catalyzing their conversion. However, S fixation on currently available cathode materials is below the requirements of large-scale practical application of this battery type. In this study, perylenequinone was utilized to improve polysulfide chemisorption and conversion on cobalt (Co)-containing Li-S battery cathodes. According to IGMH analysis, the binding energies of DPD and carbon materials as well as polysulfide adsorption were significantly enhanced in the presence of Co. According to in situ Fourier transform infrared spectroscopy, the hydroxyl and carbonyl groups in perylenequinone are able to form O-Li bonds with Li2Sn, facilitating chemisorption and catalytic conversion of polysulfides on metallic Co. The newly prepared cathode material demonstrated superior rate and cycling performances in the Li-S battery. It exhibited an initial discharge capacity of 780 mAh g-1 at 1 C and a minimum capacity decay rate of only 0.041% over 800 cycles. Even with a high S loading, the cathode material maintained an impressive capacity retention rate of 73% after 120 cycles at 0.2 C.

Using sp2 N atom anchoring effect to prepare ultrafine vanadium nitride particles on porous nitrogen-doped carbon as cathode for lithium-sulfur battery.

Porous carbon-supported transition metals and their compounds have attracted much attention as sulfur host materials for cathodes of lithium-sulfur batteries, due to their high chemisorption capacity and ability to catalyze the conversion of polysulfides. However, actual activity of these materials is not very high because of low specific surface areas of transition metal compounds synthesized at high temperatures. In this study, ultra-fine vanadium nitride particles with an average particle size of ca. 4 nm (VN/M/NC) are successfully grown on the surface of nitrogen-doped three-dimensional carbon using sp2 nitrogen atoms, resulting from melamine pyrolysis in the presence of ammonium metavanadate, as anchor points to lock vanadium atoms in the VN/M/NC material. When used as a cathode for lithium-sulfur battery, VN/M/NC demonstrates initial discharge specific capacity of 1080 mAh g-1 at 0.2 C, and retains a discharge capacity of 475 mAh g-1 at a high rate of 2 C. With capacity attenuation of only 0.037% per cycle after 500 cycles at 1 C, the newly obtained VN/M/NC can be a promising cathode material for lithium-sulfur batteries.

Synergistic Effect between Monodisperse Fe3O4 Nanoparticles and Nitrogen-Doped Carbon Nanosheets to Promote Polysulfide Conversion in Lithium-Sulfur Batteries.

Effective fabrication of electrocatalysts active in anchoring and converting lithium polysulfides is critical for the manufacturing of high-performance lithium-sulfur batteries (LSBs). In this study, original Fe3O4 nanospheres with diameters close to 12 nm were finely dispersed over a porous nitrogen-doped carbon matrix by the freeze-drying method to produce a three-dimensional composite material (nano-Fe3O4/PNC) suitable for application as a sulfur host in LSBs. Nano-Fe3O4/PNC loaded with sulfur (S@nano-Fe3O4/PNC) was used as a cathode in a Li-S cell, whose initial discharge specific capacity reached 1256 mA h g-1 at a 0.1 C rate. After 100 charge-discharge cycles at a 0.2 C rate, the reversible capacity of S@nano-Fe3O4/PNC remained at 745 mA h g-1, demonstrating a capacity retention rate of 70%. Importantly, a high Coulombic efficiency of more than 99% was achieved, indicating effective inhibition of the polysulfides' "shuttle effect" by nano-Fe3O4/PNC. The use of electrolytes containing lithium nitrate further reduces the "shuttle effect" of polysulfides. This study demonstrates the synergistic effect between metal oxide nanoparticles and N-doped carbon, which plays an important role in promoting the adsorption and conversion of polysulfides in LSBs.

FeCo/Fe3C-cross-linked N-doped carbon via synergistic confinement and efficient catalyst to enable high-performance Li-S batteries.

Lithium-sulfur batteries (LSB) with high specific energy capacity and low material costs promise to be the next generation of energy storage devices. However, their commercialization is holding back by the poor cycling stability and fast capacity fading resulting from the shuttle effect and slow redox reaction. In this work, the FeCo/Fe3C-CNC composite was prepared by anchoring FeCo/Fe3C nanoparticles onto the crosslinked N-doped Carbon (CNC). The results showed that the addition of Co element improved the electrochemical activity of Co-Fe alloy through tuning the electronic structure of Fe atoms. The carbon nanotubes (CNTs) grown around Co-Fe alloy and Fe3C nanoparticles exhibited a strong affinity to polysulfide species and superior catalytic capability as nano-reactors. The N-doping CNTs/carbon sheets (CS) facilitated the formation of Li2S compound by promoting the Li+ ions transport while hindering the polysulfide shuttle effect. Hence, the issues of slow redox reactions and loss of polysulfide species were effectively rectified. As a result, the composite cathode FeCo/Fe3C-CNC-based LSB delivered a good specific capacity of 1401 mAh g-1 at 0.1C, and a low apacity fading rate of 0.029% per cycle at 1C. Besides, the structural stability of the FeCo/Fe3C-CNC composite confirms its potential for the deployment in LSB applications.