environmentally friendly energy storage devices. As an emerging energy powering sources, supercapacitors (SCs) hold a vital and individual position owing to their high power density, excellent cycling stability, fast charge/discharge process as well as noticeable reliability, tremendously bridging the gap between rechargeable batteries and traditional capacitors in terms of energy density and power density. [1][2][3][4] Nevertheless, their commercial applications are still seriously impeded since energy densities of SCs are far lagging behind rechargeable batteries. [5,6] In the light of the critical parameters that decide the energy density (E = 1/2CV 2 ) of supercapacitor devices, [7][8][9] substantial efforts have been dedicated to maximizing the energy density via elevating the overall cell voltage (V) and total specific capacitance (C) governed by negative and positive electrodes. Configuration of asymmetric supercapacitors (ASCs) has emerged as a desirable strategy because of the expanded V arised from the absolutely opposite potential window of the two dissimilar electrode materials. [10][11][12] Accordingly, considerable research interest has been invested in constructing highly capacitive negative and positive electrode materials.Until now, transition metal oxides, hydroxides, or phosphides, especially Ni-Co compounds with low cost, natural abundance, and environmentally benign, are mostly employed as positive electrode materials in ASCs because they can present variable oxidation states, favorable electrochemical activity, and large theoretical-specific capacitance based on redox reactions, so they have received extensive attentions as perfect candidates in ASCs. [13][14][15][16][17][18] However, in comparison of the extraordinary advancement obtained by positive electrode materials, the lack of desired negative electrodes restricts the progress of high-performance ASCs. Previously, carbonaceous materials are still the most widely used as negative electrode, giving rise to low-specific capacitance of 100-250 F g −1 . [19][20][21][22][23] In this regard, pseudocapacitive negative electrode materials are proposed to be hopeful alternatives, whereas the restricted studies and poor , even when charging the device within 6.5 s, the energy density can still maintain as high as 45 W h kg −1 at 26.1 kW kg −1 , and the ASC manifests long cycling lifespan with 86.6% capacitance retention even after 5000 cycles. This pioneering work not only offers an attractive strategy for rational construction of high-performance SiC NW-based nanostructured electrodes materials, but also provides a fresh route for manufacturing next-generation high-energy storage and conversion systems.

In this paper, a mild solvothermal method has been employed to successfully synthesize a series of Cr-doped ZnO nanoparticles (NPs) with different Cr(3+) contents, which is a kind of novel and high-efficiency absorbent for the removal of acid dye methyl orange (MO) from aqueous solution. The as-prepared products were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), Brunauer, Emmet, and Teller (BET), and Zeta potential measurements. In accordance with the adsorption capacity of the products, the obtained optimal Cr/Zn molar ratio is 6%. The adsorption process of MO on Cr-doped ZnO was investigated by kinetics, thermodynamics, and isotherm technologies, which, respectively, indicated that the adsorption was fast (adsorption reached equilibrium in 2 h) and followed a pseudo-second-order model, that the adsorption process was spontaneous and endothermic, and that it agreed well with the Langmuir isotherm with a maximum adsorption capacity of 310.56 mg g(-1). Moreover, a reasonable mechanism was proposed to elucidate the reasons for their adsorption behavior. In addition, a simple and low-cost chemical method was developed to separate and recycle ZnO and MO from the used adsorbent, effectively avoiding the secondary pollution. This work can not only describe efficient experimental approaches for obtaining novel adsorbents and recycling them but also offer valuable clues for the preparation and property study of other semiconductor adsorbents.

An asymmetric supercapacitor with high energy was assembled by using the N-GNTs@OV-Bi2O3 NSAs and N-GNTs@CoNi2S4 NPs as negative and positive electrodes, respectively.

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In this paper, we successfully employed SiC nanowires (SiC NWs) with splendid anticorrosion, antioxidation, heat-resistant properties, excellent conductivity, and large specific surface area directly deposited on carbon cloth (CC) as scaffolds to grow first the loose, porous and ultrathin NiCo 2 O 4 /NiO nanosheets (NiCo 2 O 4 /NiO NSs) via a facile hydrothermal technology coupled with annealing treatment to form a free-standing and stable hybrid electrode for asymmetric supercapacitor (ASC). Benefiting from the smart combination of SiC NWs and NiCo 2 O 4 /NiO NSs, illustrating a promising synergistic strategy, the electrode delivered an ultrahigh specific capacitance of 1801 F g −1 at 1 mA cm −2 as well as a remarkable rate capability of 1499 F g −1 at 10 mA cm −2 . Furthermore, the additive-free functionalized SiC NWs@NiCo 2 O 4 /NiO NSs on CC acted as the positive electrode, assembled with the activated carbon (AC) on nickel foam (NF) negative electrode to fabricate an advanced ASC with intriguing electrochemical performances in terms of huge energy density (60 Wh kg −1 at 1.66 kW kg −1 ) in addition to exceptional cycling stability (90.9% capacitance retention after 2000 cycles). This novel strategy can not only further widen the application of SiC NWs-based materials but also provide new insight into the development of next-generation supercapacitors with high energy/power densities. ■ INTRODUCTIONOwing to the restricted usability of fossil fuel and the increasingly urgent concern over ecological environment influence of traditional energy technologies, hunting for ecofriendly and reproducible advanced energy storage devices is one of the most stringent challenges facing us today. Recently, as an alternative to batteries and traditional electrostatic capacitors, supercapacitors (also called electrochemical capacitors) with irreplaceable performances of enhanced power density, fast charge−discharge rate (in seconds) and superior cycling stability, have raised widespread concerns about potential high-power applications such as heavy transport, hybrid electric vehicles and a number of microdevices. 1−4 However, supercapacitors possess relatively lower energy density compared with batteries, which seriously precludes their large-scale industrial utilizations in energy storage. 5 Thus, to meet the industrial demand, novel nanostructured electrode materials should be rationally designed and synthesized to boost the operating voltage and specific capacitances and improve the energy density for the development of supercapacitors.Among various supercapacitor electrode materials, nickel oxide (NiO) and spinel nickel cobaltite (NiCo 2 O 4 ) have recently been paid much attention due to their versatile merits, such as high theoretical capacitance, excellent redox property, favorable electrochemical activity, lower cost, high abundance and environmentally benign. 6−12 These intriguing advantages are beneficial to its application in high-performance supercapacitors. Nevertheless, previous attempts to fabricate NiO or NiCo...