Innovative solvent-free compound-direct synthesis of defect-rich ultra-thin NiS nanosheets for high-performance supercapacitors.

Defect engineering in NiS nanosheets is an effective method to improve their surface properties and electronic structure for promoting electrochemical properties. However, a tunable, simple, and safe strategy for the introduction of abundant defect sites with a high activity into NiS with a special microstructure is worth developing. Herein, a novel hierarchical micro-flower-like NiS using graphene-like ultra-thin nanosheets with abundant defects as the building blocks was facilely synthesized by an innovative solvent-free compound-direct reaction strategy, which employed cost-efficient NaCl as the friction agent and dispersant to ensure adequate contact between sulfur ions and nickel ions and regulate the growth direction of NiS. Graphene-like ultra-thin NiS nanosheets effectively shorten the transport distance of ions and electrons. Defect engineering in NiS nanosheets provides more adsorption and storage sites for ions and high-activity sites for electrode materials, as well as adjusts the local electronic structure so as to effectively promote ion diffusion and charge transfer. The high performance of the as-obtained N-NiS electrode is illustrated by fabricating an asymmetric supercapacitor, which exhibits a specific capacitance of 351.5 F g-1 and energy density of 71.0 W h kg-1 at a power density of 229.3 W kg-1. The solvent-free compound-direct reaction strategy demonstrated in this study provides a new direction for the synthesis of high-performance nanomaterials for electrochemical energy storage applications.

Ball-in-ball NiS2@CoS2 heterojunction driven by Kirkendall effect for high-performance Mg2+/Li+ hybrid batteries.

Mg2+/Li+ hybrid batteries (MLHBs), which support the rapid insertion and removal of Mg2+/Li+ bimetallic ions, are promising energy storage systems. Inspired by the Kirkendall effect, ball-in-ball bimetallic sulfides with heterostructures were prepared as cathode materials for the MLHBs. First, a nickel-cobalt precursor (NiCo-X precursor) with three-dimensional (3D) nanosheets on its surface was prepared using a solvothermal method based on the association reaction between alkoxide molecules. Subsequently, the NiCo-X precursor was vulcanized at high temperature using the potential energy difference as the driving force to successfully prepare NiS2@CoS2 core-shell hollow spheres. When used as the positive electrode material for the MLHBs, the NiS2@CoS2 hollow spheres exhibited excellent Mg2+/Li+ ion storage capacity, high specific capacity, good rate performance, and stable cyclic stability owing to their tough hierarchical structure. At a current density of 500 mA g-1, a specific capacity of 536 mAh g-1 was maintained after 200 cycles. By explaining the transformation mechanism of Mg2+/Li+ in bimetallic sulfides, it was proven that Mg2+ and Li+ worked cooperatively. This study provides a new approach for developing MLHBs with good electrochemical properties.

Fabrication of Nitrogen-Doped Carbon-Coated NiS1.97 Quantum Dots for Advanced Magnesium-Ion Batteries.

Magnesium (Mg) batteries have garnered considerable interest because of their safety characteristics and low costs. However, the practical application of Mg batteries is hindered by the slow diffusion of Mg ions in the cathode materials. In this study, we prepared NiS1.97 quantum dot composites with nitrogen doping and carbon coating (NiS1.97 QDs@NC) using a one-step sulfurization process with NiO QDs/Ni@NC as the precursor. We applied the prepared NiS1.97 QDs/Ni@NC-based cathodes to Mg batteries because of the large surface area of the quantum dot composite, which provided abundant intercalation sites. This design ensured efficient deintercalation of magnesium ions during charge-discharge processes. The fabricated NiS1.97 QDs@NC displayed a high reversible Mg storage capacity of 259.1 mAh g-1 at 100 mA g-1 and a good rate performance of 96.0 mAh g-1 at 1000 mA g-1. Quantum dot composites with large surface areas provide numerous embedded sites, which ensure effective deintercalation of Mg ions during cycling. Thus, the proposed cathode synthesis strategy is promising for Mg-ion-based energy storage systems.

NiS2 nanoparticles by the NaCl-assisted less-liquid reaction system for the magnesium-ion battery cathode.

Rechargeable magnesium batteries are expected to be the next generation of energy storage devices. Therefore, it is of great significance to develop low-cost and long-life magnesium (Mg) electrode materials. However, the traditional method of synthesizing electrode materials is complicated, and it is difficult to remove potentially dangerous impurities. In this study, without adding any additional solvent, the crystal water in the reactant provides a liquid environment directly for the reaction, such that the whole reaction could be carried out safely and efficiently in the less liquid reaction system. Furthermore, NiS2 in the cotton-like form was synthesized under the spatial effect of NaCl solution in a confined space. The fabricated material was tightly connected and has abundant active sites, which promote the rapid transport of charge. This work provides a general strategy of preparation methods for metal sulfides and also points in a new direction for the improvement of electrochemical performance with less-liquid reaction systems without additional solvents.

In Situ Anchoring Anion-Rich and Multi-Cavity NiS2 Nanoparticles on NCNTs for Advanced Magnesium-Ion Batteries.

Magnesium (Mg)-ion batteries with low cost and good safety characteristics has attracted a great deal of attention recently. However, the high polarity and the slow diffusion of Mg2+ in the cathode material limit the development of practical Mg cathode materials. In this paper, an anion-rich electrode material, NiS2 , and its composite with Ni-based carbon nanotubes (NiS2 /NCNTs) are explored as the cathode materials for Mg-ion batteries. These NiS2 /NCNTs with excellent Mg2+ storage property is synthesized by a simple in situ growth of NiS2 nanoparticles on NCNTs. NiS2 with both a large regular cavity structure and abundant sulfur-sulfur (SS) bonds with high electronegativity can provide a large number of active sites and unobstructed transport paths for the insertion-disinsertion of Mg2+ . With the aid of 3D NCNTs skeleton as the transport channel of the electron, the NiS2 /NCNTs exhibit a high capacity of 244.5 mAh g-1 at 50 mA g-1 and an outstanding rate performance (94.7 mAh g-1 at 1000 mA g-1 ). It achieves capacitance retention of 58% after 2000 cycles at 200 mA g-1 . Through theoretical density functional theory (DFT) calculations and a series of systematic ex situ characterizations, the magnesiation/demagnesiation mechanisms of NiS2 and NiS2 /NCNTs and are elucidated for fundamental understanding.

Organosulfonate Counteranions-A Trapped Coordination Polymer as a High-Output Triboelectric Nanogenerator Material for Self-Powered Anticorrosion.

Selection of the friction electrode materials is crucial to the performance of a triboelectric nanogenerator (TENG). In the present study, a metal-organic coordination complex containing organosulfonate counteranions with electron-donating ability was synthesized through the coordination-driven self-assembly approach under mild reaction conditions and was chosen as a positive electrode material to construct a triboelectric nanogenerator, exhibiting high-output performance with a peak value of short circuit current density of 98.6 µA and an output voltage of 1180 V. As a practical application, it was shown to light up 1488 commercial green LEDs and power an anticorrosion system device to protect metals from corrosion.

Heterojunction α-Co(OH)2/α-Ni(OH)2 nanorods arrays on Ni foam with high utilization rate and excellent structure stability for high-performance supercapacitor.

The practical implementation of supercapacitors is hindered by low utilization and poor structural stability of electrode materials. Herein, to surmount these critical challenges, a three-dimensional hierarchical α-Co(OH)2/α-Ni(OH)2 heterojunction nanorods are built in situ on Ni foam through a mild two-step growth reaction. The unique lamellar crystal structure and abundant intercalated anions of α-M(OH)2 (M = Co or Ni) and the ideal electronic conductivity of α-Co(OH)2 construct numerous cross-linked ion and electron transport paths in heterojunction nanorods. The deformation stresses exerted by α-Co(OH)2 and α-Ni(OH)2 on each other guarantee the excellent structural stability of this heterojunction nanorods. Using nickel foam with a three-dimensional network conductive framework as the template ensures the rapidly transfer of electrons between this heterojunction nanorods and current collector. Three-dimensional hierarchical structure of α-Co(OH)2/α-Ni(OH)2 heterojunction nanorods provides a large liquid interface area. These result together in the high utilization rate and excellent structure stability of the α-Co(OH)2/α-Ni(OH)2 heterojunction nanorods. And the capacitance retention rate is up to 93.4% at 1 A g-1 from three-electrode system to two-electrode system. The α-Co(OH)2/α-Ni(OH)2//AC device also present a long cycle life (the capacitance retention rate is 123.6% at 5 A g-1 for 10000 cycles), a high specific capacitance (207.2 F g-1 at 1 A g-1), and high energy density and power density (72.6 Wh kg-1 at 196.4 W kg-1 and 40.9 Wh kg-1 at 3491.8 W kg-1), exhibiting a fascinating potential for supercapacitor in large-scale applications.

Hydrangea-like α-Ni1/3Co2/3(OH)2 Reinforced by Ethyl Carbamate "Rivet" for All-Solid-State Supercapacitors with Outstanding Comprehensive Performance.

Improving the self-conductivity and structural stability of electrode materials is a key strategy to improve the energy density, rate performance, and cycle life of supercapacitors. Controlled intercalation of ethyl carbamate (CH3CH2OCONH2) as the rivet between Ni-Co hydroxide layers can be used to obtain sufficient ion transport channels and robust structural stability of hydrangea-like α-Ni1/3Co2/3(OH)2 (NC). Combining the improved electronic conductivity offered by the coexistence of Ni2+ and Co2+ optimizing itself electronic conductivity and the addition of carbon nanotubes (CNTs) as the electron transport bridge between the active material and the current collector and the large specific surface area (296 m2 g-1) reducing the concentration polarization, the capacitance retention ratio of NC-CNT from 0.2 to 20 A g-1 is up to 93.4% and its specific capacitance is as high as 1228.7 F g-1 at 20 A g-1. The large total hole volume (0.40 cm3 g-1) and wide crystal plane spacing (0.71 nm) provide an adequate space to withstand structure deformation during charge/discharge processes and enhance the structural stability of the NC material. The capacitance fading ratio of NC-CNT is only 4.5% at 10 A g-1 for 10 000 cycles. The aqueous supercapacitor (NC-CNT//AC) and all-solid-state supercapacitor (PVA-NC-CNT//PVA-AC) exhibit high energy density (35.2 W h kg-1 at 100.0 W kg-1 and 35.4 W h kg-1 at 100.7 W kg-1), ultrahigh rate performance (the specific capacitances at 20 A g-1 are 92.8 and 87.2% compared to that at 0.5 A g-1), and long cycling life span (the specific capacitances after 100 000 cycles at 10 A g-1 are 91.5 and 90.8% compared with that of their initial specific capacitances), respectively. Therefore, hydrangea-like NC could be a promising material for advanced next-generation supercapacitors.

α-Ni(OH)2/NiS1.97 heterojunction composites with excellent ion and electron transport properties for advanced supercapacitors.

It is recognized that an effective strategy to promote the industrialization of supercapacitors is to enhance the ion and electronic conductivities of electrode materials. In this work, it is demonstrated that the NO/NS-8 heterojunction material obtained via an epitaxial growth method based on ion exchange can be used as an outstanding electrode material for supercapacitors. The construction of heterojunctions between α-Ni(OH)2 and NiS1.97 allows the components to provide each other with ion or electron transport paths and endows NO/NS-8 with excellent ion and electron transport properties; this leads to a high utilization rate of active materials and an unprecedented high specific capacitance (up to 2375.8 F g-1 at 1 mV s-1 in a three-electrode system). Using the as-prepared NO/NS-8 heterojunction material as an electroactive material, an asymmetric supercapacitor with long cycle life (62.8% capacitance retention after 10 000 cycles at a current density of 5 A g-1) and high energy and power densities (128.4 W h kg-1 at a power density of 402.9 W kg-1 and 63.8 W h kg-1 at 7662.7 W kg-1) is finally demonstrated. This work provides a novel strategy for developing unique heterojunction materials for energy storage.

Bi-component synergic effect in lily-like CdS/Cu7S4 QDs for dye degradation.

CdS has attracted extensive attention in the photocatalytic degradation of wastewater due to its relatively narrow bandgap and various microstructures. Previous reports have focused on CdS coupled with other semiconductors to reduce the photocorrosion and improve the photocatalytic performance. Herein, a 3D hierarchical CdS/Cu7S4 nanostructure was synthesized by cation exchange using lily-like CdS as template. The heterojunction material completely inherits the special skeleton of the template material and optimizes the nano-scale morphology, and achieves the transformation from nanometer structure to quantum dots (QDs). The introduction of Cu ions not only tuned the band gap of the composites to promote the utilization of solar photons, more importantly, Fenton-like catalysis was combined into the degradation process. Compared with the experiments of organic dye degradation under different illumination conditions, the degradability of the CdS/Cu7S4 QDs is greatly superior to pure CdS. Therefore, the constructed CdS/Cu7S4 QDs further realized the optimization of degradation performance by the synergic effect of photo-catalysis and Fenton-like catalysis.

Development of high-utilization honeycomb-like α-Ni(OH)2 for asymmetric supercapacitors with excellent capacitance.

The low utilization rate of active materials has been a critical obstacle for the industrialization of ultracapacitors. In this study, a thin layer of cross-structured ultrathin α-Ni(OH)2 nanosheets was successfully grown in situ on the surface of a nickel foam as a high-conductivity framework by a vibratory water bath route under a low temperature (80 °C) and mild conditions. Combining the ultrathin α-Ni(OH)2 nanosheets and ultrashort electron transport, the strategy of a perfect intercalation structure of α-Ni(OH)2 and a thin layer of active material on a continuous conductive framework resulted in a high utilization rate of active material, which further achieved high specific capacitance of 213.55 F g-1 at 1 A g-1 in a two-electrode system and high capacitance retention from three to two electrode system (753.79 F g-1 at 1 A g-1 in the three-electrode system). Meanwhile, the device also achieved high energy density of 74.94 W h kg-1 at power density of 197.4 W kg-1 and still retained 24.87 W h kg-1 at power density of 3642 W kg-1.

Urchin-Like Ni1/3Co2/3(CO3)1/2(OH)·0.11H2O for Ultrahigh-Rate Electrochemical Supercapacitors: Structural Evolution from Solid to Hollow.

Portable electronics and electric or hybrid electric vehicles are developing in the trend of fast charge and long electric mileage, which ask us to design a novel electrode with sufficient electronic and ionic transport channels at the same time. Herein, we fabricate a uniform hollow-urchin-like Ni1/3Co2/3(CO3)1/2(OH)·0.11H2O electrode material through an easy self-generated and resacrificial template method. The one-dimensional chain-like crystal structure unit containing the metallic bonding and the intercalated OH- and H2O endow this electrode material with abundant electronic and ionic transport channels. The hollow-urchin-like structure built by nanorods contributes to the large electrode-electrolyte contact area ensuring the supply of ions at high current. CNTs are employed to transport electrons between electrode material and current collector. The as-assembled NC-CNT-2//AC supercapacitor device exhibits a high specific capacitance of 108.3 F g-1 at 20 A g-1, a capacitance retention ratio of 96.2% from 0.2 to 20 A g-1, and long cycle life. Comprehensive investigations unambiguously highlight that the unique hollow-urchin-like Ni1/3Co2/3(CO3)1/2(OH)·0.11H2O electrode material would be the right candidate for advanced next-generation supercapacitors.

Consecutive Reaction to Construct Hierarchical Nanocrystalline CuS "Branch" with Tunable Catalysis Properties.

New CuS nanocrystals with a 3D hierarchical branched structure are successfully synthesized through in situ consecutive reaction method with copper foam as template. The formation mechanism of the 3D hierarchical branched structure obtained from the secondary reaction is investigated by adjusting the reaction time. The morphology of CuS nanosheet arrays with the 3D hierarchical branched structure is changed through Cu(2+) exchange. In this method, the copper foam reacted completely, and the as-synthesized CuS@Cu9S5 nanocrystals are firmly grown on the surface of the 3D framework. This tunable morphology significantly influence the physical and chemical properties, particularly catalytic performance, of the materials. The as-obtained material of Cu@CuS-2 with the 3D hierarchical branched structure as catalyst for methylene blue degradation exhibits good catalytic performance than that of the material of Cu@CuS with 2D nanosheets in dark environment. Furthermore, the cation exchange between Cu and Cu(2+) indicates that Cu(2+) in wastewater could be absorbed by Cu@CuS-2 with the 3D hierarchical branched structure. The exchanged resultant of CuS@Cu9S5 retains its capability to degrade organic dyes. This in situ consecutive reaction method may have a significant impact on controlling the crystal growth direction of inorganic material.

Double metal ions synergistic effect in hierarchical multiple sulfide microflowers for enhanced supercapacitor performance.

In this paper, the design, synthesis, and measurement of a new and hierarchically structured series of NixCo1-xS1.097 electroactive materials are reported. The materials were synthesized through an ion-exchange process using hierarchically structured CoS1.097 as precursors, and a strategy utilizing the synergistic effect of double metal ions was developed. Two complementary metal ions were used to enhance the performance of electrode materials. The specific capacitance of the electroactive materials was continuously improved by increasing the nickel ion content, and the electric conductivity was also enhanced when the cobalt ion was varied. Experimental results showed that the nickel ion content in NixCo1-xS1.097 could be adjusted from x = 0 to 0.48. Specifically, when x = 0.48, the composite exhibited a remarkable maximum specific capacitance approximately 5 times higher than that of the CoS1.097 precursors at a current density of 0.5 A g(-1). Furthermore, the specific capacitance of Ni0.48Co0.52S1.097 electrodes that were modified with reduced graphene oxide could reach to 1152 and 971 F g(-1) at current densities of 0.5 and 20 A g(-1) and showed remarkably higher electrochemical performance than the unmodified electrodes because of their enhanced electrical conductivity. Thus, the strategy utilizing the synergistic effect of double metal ions is an alternative technique to fabricate high-performance electrode materials for supercapacitors and lithium ion batteries.

Ag+ insertion into 3D hierarchical rose-like Cu(1.8)Se nanocrystals with tunable band gap and morphology genetic.

In this study, novel hierarchical rose-like Cu1.8Se microspheres with a porous three-dimensional (3D) framework were successfully synthesized by using a one-pot in situ growth method at low temperature (60 °C). The Cu1.8Se microspheres covered the surface of the 3D porous framework. The formation mechanism was investigated in detail by adjusting the volume ratio of DMF and EDA, as the blend solvents, and the reaction time. Then, the chemical composition of the Cu1.8Se microspheres was altered by Ag(+) exchange without changing their morphology and structure. In this way, the binary Cu1.8Se was efficiently converted into the ternary CuAgSe. Notably, the band gap of materials was tuned continuously from 3.83 eV to 3.03 eV, and CuAgSe was produced continuously by adjusting the replacement time. This work provides a novel concept and a simple method that can serve as a good reference for improving the performance of tunable materials and the preparation of multielement alloy materials.

Tunable properties induced by ion exchange in multilayer intertwined CuS microflowers with hierarchal structures.

Novel hierarchical wool-ball-like copper sulfide (CuS) microflowers with a three-dimensional (3D) porous framework were successfully synthesized by the direct reaction of copper with sulfur powder using a one-pot in situ growth method at low temperature (60 °C). The CuS microflowers covered firmly the surface of the 3D porous framework. The formation mechanism was examined in detail by adjusting the amount of hydrochloric acid and reaction time. Most importantly, the chemical composition of the CuS microflowers was altered by the Se exchange without changing their morphology and structure. In this way, pure CuSe and Cu1.8Se crystalline materials were obtained on the surface of the porous microtube at different reaction times and the appropriate amount of Se powder. And interestingly, the core material remained as CuS. This behavior greatly affects the physical and chemical properties of the materials. The catalytic ability of the as-obtained CuSe@CuS and CuSe1.8@CuS composite materials to degrade methylene blue and rhodamine B is several times greater than that of the as-synthesized CuS microflowers.

La4Cu(3-x)Zn(x)MoO12: zinc-doped cuprates with Kagomé lattices.

Two solid solutions, La4Cu(3-x)Zn(x)MoO12 (0.05 < or = x < or = 0.20, SS1) and La4Cu(3-x)Zn(x)MoO12 (0.30 < or = x < or = 2.40, SS2), were synthesized at ambient pressure and at temperatures from 1025 to 1200 degrees C by traditional solid-state reactions. Their structures were determined from X-ray powder diffraction with the help of electron and neutron diffraction. The atomic arrangements of SS1 and SS2 are similar, but their space groups are different, Pmnm for SS1 and P-1 for SS2, respectively. The copper, zinc, and molybdenum are coordinated by oxygen in corner-sharing trigonal bipyramids that are sandwiched between layers of lanthanum cations. In the transition metal cations layer of SS2, the copper and zinc cations order into a Kagomé-like lattice of triangular clusters. The magnetism has been measured from 2 to 300 K and is highly influenced by the geometric arrangement of the Cu(II) and Zn(II) cations. The number of free electrons per three Cu atoms is close to one for all samples in SS1 and SS2 indicating that the system can be well expressed by independent Cu(II)3 clusters. Spontaneous magnetization was observed in the system.