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The NiAlO and NiSiO complex oxides with high surface areas were prepared by the co-precipitation method through the control of acidity of solutions. Nickel species were found to be highly dispersed in these complex oxides and a remarkable feature was that the incorporation of large amount of nickel cations into SiO generated the great amount of surface acid sites. Upon the sulfidation by CS, the sulfided catalysts were found to be highly active for the conversion of 1-hexene to different products formed from the three main competitive reactions (skeletal isomerization, double bond isomerization and hydrogenation of all hexenes). The high yield of skeletal isomerization of 1-hexene on a sulfided NiSiO (55 %) could be attributed to the high density of acid sites for the adsorption of 1-hexene as well as the low hydrogenation activity of nickel species on this catalyst. In contrast, the high yields of direct hydrogenation and double bond isomerization of 1-hexene on the sulfided NiAlO might be due to the high hydrogenation activity of nickel species as well as the surface acidity and basicity on the catalyst. Graphical Abstract: The sulfided NiAlO and NiSiO complex oxides were highly active for the conversion of 1-hexene to different products. The high yield of skeletal isomerization of 1-hexene on the sulfided NS10 (55 %) could be attributed to the high density of acid sites for the adsorption of 1-hexene. [ABSTRACT FROM AUTHOR]

Hollow microspheres with a high surface area, sufficient void space, and short ion/electron transport distance have attracted much attention as a superior electrode structure for high-rate lithium-ion batteries. In this work, a facile and low-cost hydrothermal approach followed by annealing is developed to synthesize Co3V2O8 interconnected hollow microspheres, which are able to endure an extremely high current density of 20 A g−1 and achieve a reversible discharge capacity of 320 mA h g−1. Furthermore, a stable capacity of 424 mA h g−1 can be obtained after 300 cycles at 10 A g−1. Such remarkable rate capability and cycling performance make the Co3V2O8 interconnected hollow microspheres a promising anode material for lithium-ion batteries. [ABSTRACT FROM AUTHOR]

Developing rechargeable lithium ion batteries with fast charge/discharge rate, high capacity and power, long lifespan, and broad temperature adaptability is still a significant challenge. In order to realize the fast and efficient transport of ions and electrons during the charging/discharging process, a 3D hierarchical carbon-decorated Li3V2(PO4)3 is designed and synthesized with a nanoscale amorphous carbon coating and a microscale carbon network. The Brunauer-Emmett-Teller (BET) surface area is 65.4 m2 g−1 and the porosity allows for easy access of the electrolyte to the active material. A specific capacity of 121 mAh g−1 (91% of the theoretical capacity) can be obtained at a rate up to 30 C. When cycled at a rate of 20 C, the capacity retention is 77% after 4000 cycles, corresponding to a capacity fading of 0.0065% per cycle. More importantly, the composite cathode shows excellent temperature adaptability. The specific discharge capacities can reach 130 mAh g−1 at 20 C and 60 °C, and 106 mAh g−1 at 5 C and -20 °C. The rate performance and broad temperature adaptability demonstrate that this hierarchical carbon-decorated Li3V2(PO4)3 is one of the most attractive cathodes for practical applications. [ABSTRACT FROM AUTHOR]

Abstract: The novel ultrathin pre-lithiated V6O13 nanosheets are prepared through a low-temperature exfoliation in argon followed by a secondary hydrothermal lithiation. The smallest electrochemical devices based on nanosheet cathodes are fabricated to in situ probe the intrinsic advantages of pre-lithiated nanosheets. Pre-lithiated nanosheets show one order of magnitude higher in electrical conductivity compared with non-lithiated nanosheets. The conductance of ultrathin pre-lithiated V6O13 nanosheets still remains at the same level after discharge process while that of ultrathin non-lithiated nanosheets decreases over two orders of magnitude. The electrochemical performances of nanosheet cathodes before and after pre-lithiation are compared to further demonstrate the enhancement of the pre-lithiation. Ultrathin pre-lithiated V6O13 nanosheet cathodes exhibit a high discharge capacity of 301 mAh g−1 at the current density of 100 mA g−1. At a higher current density of 1000 mA g−1, the capacity retention after 150 cycles of ultrathin V6O13 nanosheet cathodes is greatly improved from 46% to 98% after pre-lithiation. The enhanced electrical conductance, excellent discharge capacities and cycling performance demonstrate the great potential of ultrathin pre-lithiated V6O13 nanosheets in next-generation high-performance energy storage applications. [Copyright &y& Elsevier]

Green energy has been increasingly demanded with the rapid development of economy and population. The electrochemical performance of energy storage devices could be improved by using nanomaterials, but their fast capacity fading is still one of the key limitations. The intrinsic reasons of capacity fading need to be further understood. Here, we review some single nanowire electrode devices designed as a unique platform for in situ probing the direct relationship between electrical transport, structure, and other properties of the single nanowire electrode before and after cycling. It is found that the conductivity decrease of the nanowire electrode and the structural change during electrochemical reaction limited devices’ lifespan. Some strategies, such as prelithiation, conductive coating and structural construction, are designed and used to restrain the conductivity decrease and structural disorder/destruction, which improve the lifespan and rate capability of energy storage devices. Further, the stand-alone rechargeable nanobatteries built up by nanowires are able to meet the needs of energy storage in self-powered nanosystems. [ABSTRACT FROM PUBLISHER]

MoO3 has long suffered from poor conductivity and cyclability, which limit its high rate performance and ultralong cycling ability. Increasing the electronic conductivity with electron pathways of cathode materials can effectively enhance the lithium storage properties with stable cyclability and rate capability theoretically. Here the MoO3–reduced graphene oxide (rGO) hybrid nanobelts were designed and prepared and were tested as cathode materials for lithium batteries. It is demonstrated that the rGO is wrinkled and twisted around MoO3 nanobelts after reacting under high temperature and pressure conditions. The unique morphology of rGO, which has continuous electron pathways and stress buffering effects, endows the MoO3–rGO hybrid nanobelts with significantly increased rate capability and cycling ability. Meanwhile, it is demonstrated that MoO3–rGO hybrid nanobelts are promising cathode materials for use in rechargeable lithium batteries and our synthesis strategy is also versatile for exploiting advanced materials for Li-ion batteries. [ABSTRACT FROM AUTHOR]

Abstract: High-speed electron transfer channels and short Li ion transport distance are beneficial to improvement of Li ion battery properties. Here, a two-step solution phase synthesis method is developed to construct the V2O5 quantum dots/graphene hybrid nanocomposite by controlling nucleation and growth processes. It is demonstrated that the V2O5 quantum dots with an average size of 2-3 nm are uniformly anchored on the graphene sheets. The specific capacity can achieve 212mAhg−1 at 100mAg−1 after 100 cycles. Significantly, the novel V2O5 quantum dots/graphene shows a stable cycling performance with 89% capacity retention after 300 cycles. The improvement in electrochemical properties could be attributed to the short Li ion transfer distance, two-dimensional electron channels, homogeneous dispersion and immobilization of V2O5 quantum dots. Meanwhile, it indicates that V2O5 quantum dots/graphene is promising cathode material for use in long-life rechargeable lithium batteries. This design conception and synthesis strategy for V2O5 could also be extended to other electrode material systems. [Copyright &y& Elsevier]

In the hydrogen evolution reaction (HER), energy-level matching is a prerequisite for excellent electrocatalytic activity. Conventional strategies such as chemical doping and the incorporation of defects underscore the complicated process of controlling the doping species and the defect concentration, which obstructs the understanding of the function of band structure in HER catalysis. Accordingly, 2H-MoS 2 and 1T-MoS 2 are used to create electrocatalytic nanodevices to address the function of band structure in HER catalysis. Interestingly, it is found that the 2H-MoS 2 with modulated Fermi level under the application of a vertical electric field exhibits excellent electrocatalytic activity (as evidenced by an overpotential of 74 mV at 10 mA cm -2 and a Tafel slope of 99 mV per decade), which is superior to 1T-MoS 2 . This unexpected excellent HER performance is ascribed to the fact that electrons are injected into the conduction band under the condition of back-gate voltage, which leads to the increased Fermi level of 2H-MoS 2 and a shorter Debye screen length. Hence, the required energy to drive electrons from the electrocatalyst surface to reactant will decrease, which activates the 2H-MoS 2 thermodynamically., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The rational design of flexible electrodes is essential for achieving high performance in flexible and wearable energy-storage devices, which are highly desired with fast-growing demands for flexible electronics. Owing to the one-dimensional structure, nanowires with continuous electron conduction, ion diffusion channels, and good mechanical properties are particularly favorable for obtaining flexible freestanding electrodes that can realize high energy/power density, while retaining long-term cycling stability under various mechanical deformations. This Minireview focuses on recent advances in the design, fabrication, and application of nanowire-based flexible freestanding electrodes with diverse compositions, while highlighting the rational design of nanowire-based materials for high-performance flexible electrodes. Existing challenges and future opportunities towards a deeper fundamental understanding and practical applications are also presented., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

On-chip electrochemical energy storage devices have attracted growing attention due to the decreasing size of electronic devices. Various approaches have been applied for constructing the microsupercapacitors. However, the microfabrication of high-performance microsupercapacitors by conventional and fully compatible semiconductor microfabrication technologies is still a critical challenge. Herein, unique three-dimensional (3D) Co 3 O 4 nanonetwork microelectrodes formed by the interconnection of Co 3 O 4 nanosheets are constructed by controllable physical vapor deposition combined with rapid thermal annealing. This construction process is an all dry and rapid (≤5 minutes) procedure. Afterward, by sputtering highly electrically conductive Pt nanoparticles on the microelectrodes, the 3D Co 3 O 4 /Pt nanonetworks based microsupercapacitor is fabricated, showing a high volume capacitance (35.7 F cm -3 ) at a scan rate of 20 mV s -1 due to the unique interconnected structures, high electrical conductivity and high surface area of the microelectrodes. This microfabrication process is also used to construct high-performance flexible microsupercapacitors, and it can be applied in the construction of wearable devices. The proposed strategy is completely compatible with the current semiconductor microfabrication and shows great potential in the applications of the large-scale integration of micro/nano and wearable devices.

A novel process to fabricate a carbon-microelectromechanical-system-based alternating stacked MoS 2 @rGO-carbon-nanotube (CNT) micro-supercapacitor (MSC) is reported. The MSC is fabricated by successively repeated spin-coating of MoS 2 @rGO/photoresist and CNT/photoresist composites twice, followed by photoetching, developing, and pyrolysis. MoS 2 @rGO and CNTs are embedded in the carbon microelectrodes, which cooperatively enhance the performance of the MSC. The fabricated MSC exhibits a high areal capacitance of 13.7 mF cm -2 and an energy density of 1.9 µWh cm -2 (5.6 mWh cm -3 ), which exceed many reported carbon- and MoS 2 -based MSCs. The MSC also retains 68% of capacitance at a current density of 2 mA cm -2 (5.9 A cm -3 ) and an outstanding cycling performance (96.6% after 10 000 cycles, at a scan rate of 1 V s -1 ). Compared with other MSCs, the MSC in this study is fabricated by a low-cost and facile process, and it achieves an excellent and stable electrochemical performance. This approach could be highly promising for applications in integration of micro/nanostructures into microdevices/systems., (© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Hybrid nanostructural VO2 (B) composed of nanoscrolls, nanobelts and nanowires is synthesized through a hydrothermal-driven splitting and self-rolled method. The hybrid nanostructure with nanoscroll buffered effect provides facile strain relaxation for swelling during lithiation/delithiation, resulting in the excellent structural stability and cyclability. The interior of nanoscrolls and the interconnected voids shorten the ion diffusion pathway, which greatly enhances the rate performance., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)