The rapid increase of the CO2 concentration in the Earth's atmosphere has resulted in numerous environmental issues, such as global warming, ocean acidification, melting of the polar ice, rising sea ...level, and extinction of species. To search for suitable and capable catalytic systems for CO2 conversion, electrochemical reduction of CO2 (CO2RR) holds great promise. Emerging heterogeneous carbon materials have been considered as promising metal‐free electrocatalysts for the CO2RR, owing to their abundant natural resources, tailorable porous structures, resistance to acids and bases, high‐temperature stability, and environmental friendliness. They exhibit remarkable CO2RR properties, including catalytic activity, long durability, and high selectivity. Here, various carbon materials (e.g., carbon fibers, carbon nanotubes, graphene, diamond, nanoporous carbon, and graphene dots) with heteroatom doping (e.g., N, S, and B) that can be used as metal‐free catalysts for the CO2RR are highlighted. Recent advances regarding the identification of active sites for the CO2RR and the pathway of reduction of CO2 to the final product are comprehensively reviewed. Additionally, the emerging challenges and some perspectives on the development of heteroatom‐doped carbon materials as metal‐free electrocatalysts for the CO2RR are included.
Emerging heterogeneous carbon materials are considered as promising metal‐free electrocatalysts for the electrochemical CO2 reduction reaction (CO2RR) with remarkable catalytic activity, long durability, and high selectivity. Various carbon materials with heteroatom doping as metal‐free catalysts for the CO2RR are highlighted, and recent advances on the identification of active sites for the CO2RR and the pathways for reduction of CO2 to the final product are comprehensively reviewed.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Wet chemistry using ionic liquids as the medium has proven to be highly efficient for the preparation of several types of metallic, metal oxides, and other kinds of semiconductor nanostructures, and ...so on. This article reviews state-of-the-art research activities in the field, focusing on the use of ionic liquids as a versatile regent for the synthesis of various nanoparticle systems. We begin with a survey of choices to explore the ability of ionic liquids to act as a reactant, solvent, and surfactant, as a function of other synthesis parameters, also denoted as ionic liquid precursors (or task-special ionic liquids), which offer many advantages over traditional solution-phase methods. We then examine the design and fabrication of functional inorganic materials by means of optimizing the effect models of ionic liquids. Many of the most recent advances in ionothermal or ionic liquid-assisted synthesis have been realized by appropriate choice of cations or anions of ionic liquids according to the need. This review also highlights crucial issues that should be addressed in future research activities.
In this article, we highlight the rational design of ionic liquids and understanding of the ionic liquid's effect on the molecular level based on solution-phase methods, mainly focusing on two major aspects: the ionic liquid precursor and the effect model of ionic liquids.
The effect of niobium (Nb) doping in one-dimensional (1D) nanostructured LiNi1/3Co1/3Mn1/3O2 (NCM) cathode has been investigated for this study. Nb-doped NCM nanofibres have been prepared through an ...electrospinning method followed by controllable sintering process. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results confirmed that Nb-doping can effectively reduce cation mixing, thus improve the structural stability. In addition, due to the valence compensation balance, Mn4+ ions are partially reduced to Mn3+ ions, which can further improve the conductivity and stable cycling performance. Therefore, increased discharge capacities, high first cycle efficiencies and superior cycling and rate behaviors are observed between normal voltage limits for the Nb-doped NCM compositions in electrochemical cells. Specifically, Nb-doped NCM nanofibres achieve a high discharge capacity of 200.4 mAh/g at 0.1 C with a high Coulombic efficiency of 92.3%. Moreover, a high discharge capacity of 118.7 mAh/g even at 5 C with 83.3% capacity retention after 200 cycles is also achieved. Also, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) results demonstrate that Nb-doping can mitigate the electrochemical polarization of NCM and improve the lithium ion diffusion coefficient, leading to the improvement of electrochemical performances. It is highly expected that our findings can provide a general approach to improve the electrochemical properties of cathode materials for lithium-ion batteries.
1D Nb-doped LiNi1/3Co1/3Mn1/3O2 nanofibres (Nb-NCM) have been fabricated by an electrospinning method. When used as cathodes in lithium-ion batteries, Nb-NCM electrode manifests excellent cycling stability and rate capability. Display omitted
•1D Nb-doped LiNi1/3Co1/3Mn1/3O2 has been successfully fabricated by an electrospinning technique.•The effect of Nb-doping has been proposed.•1D Nb-NCM nanofibres manifest excellent cycling stability and rate capability.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In situ-growth of 1T/2H-MoS2 nanosheets on the CFC, ultra-small SnS2 nanoparticles are anchored on the surface of MoS2 nanosheets unifromly. When the SnS2/MoS2/CFC composites applied as a binder-free ...flexible anode, it exhibits excellent performances. A highly flexible full cell was fabricated, demonstrating remarkable flexibility and cycling stability.
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•In-situ growth SnS2/MoS2 on CFC by a hydrothermal method and water bath process.•SnS2/MoS2 shows a capacity of 1294 mA h g−1 at 0.1 A g−1 after 120 cycles.•The distribution of SnS2 on 1T/2H-MoS2 can enhance electrochemical properties.•A full cell is fabricated, showing high flexibility and electrochemical properties.
Flexible lithium ion batteries are important for wearable electronic devices. Herein, 1T/2H phase MoS2 nanosheets are grown on carbon fiber cloth, and the ultra-small SnS2 nanoparticles are anchored in the surface of MoS2 nanosheets uniformly. We fabricate the hierarchical nanostructures via a hydrothermal method then water bath process. During in-situ growth of 1T/2H phase MoS2, urea is used as the surfactant and NH4+ (produced by urea and ammonium molybdate tetrahydrate) is acted as insertion guest ions to stabilize 1T phase MoS2. The synergistic effects between MoS2 nanosheets and SnS2 nanoparticles can improve structural stability of the electrode and significant enhance the transport of Li ions and electrons, thereby ameliorate the electrochemical properties. When applied as a binder-free, flexible Li-ion battery anode, it exhibits admirable cycling stability and excellent rate performance. Due to the presence of 1T phase MoS2 and uniform distribution of ultra-small SnS2 nanoparticles on MoS2 nanosheets, the SnS2/MoS2/carbon fiber cloth composites maintain 1294 mA h g−1 when cycling at 100 mA g−1 after 120 cycles. A highly flexible battery based on SnS2/MoS2/carbon fiber cloth and LiCoO2 is fabricated, demonstrating excellent mechanical flexibility and cycling stability.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The composite with NiS nanorods anchored on reduced graphene oxide (rGO) has been prepared via a two-step hydrothermal method. With the corresponding precursors of hydroxide composites prepared ...during the first stage, ion exchange (from OH− to S2−) and reduction of GO are performed on subsequently, resulting in NiS/rGO composite. The NiS nanorods uniformly distribute on the surface of graphene, forming a 3D conductive network. The electrochemical performances of the composite are investigated in extenso as electrode materials for supercapacitors, and it exhibits preferable cycling performances and excellent capacitance. These satisfactory electrochemical behaviors can be attributed to the introduction of graphene, which enhances the specific surface area and electronic conductivity of the electrode, producing more active sites for the charging/discharging process and facilitating fast electron transport through the underlying graphene layers.
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•The NiS/rGO composite has been prepared via a two-step hydrothermal method.•Ion exchange and reduction of GO occur simultaneously during the second stage.•The introduction of rGO enhance the electronic conductivity of the composite.•The composite exhibits high specific capacity and excellent cycle stability.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
In this roadmap, two-dimensional materials including graphene, black phosporus, MXenes, covalent organic frameworks, oxides, chalcogenides, and others, are highlighted in energy storage and ...conversion.
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Energy storage and conversion have attained significant interest owing to its important applications that reduce CO2 emission through employing green energy. Some promising technologies are included metal-air batteries, metal-sulfur batteries, metal-ion batteries, electrochemical capacitors, etc. Here, metal elements are involved with lithium, sodium, and magnesium. For these devices, electrode materials are of importance to obtain high performance. Two-dimensional (2D) materials are a large kind of layered structured materials with promising future as energy storage materials, which include graphene, black phosporus, MXenes, covalent organic frameworks (COFs), 2D oxides, 2D chalcogenides, and others. Great progress has been achieved to go ahead for 2D materials in energy storage and conversion. More researchers will join in this research field. Under the background, it has motivated us to contribute with a roadmap on ‘two-dimensional materials for energy storage and conversion.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this work, four well-defined morphologies, including nanorod, nanowire, nanoflower and nanowall, of MnO sub(2) nanostructures with different crystal phases ( alpha -, beta -, and delta -MnO ...sub(2)) have been synthesized employing a simple hydrothermal process. The samples are characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy (EDS), and Brunauer-Emmett-Teller (BET) spectrometry. Our experimental results demonstrate that the concentration of KMnO sub(4) plays a key role in forming different shapes and phases of MnO sub(2) nanostructures. Specifically, the K super(+) concentration can affect the crystal phase of MnO sub(2) seeds in the nucleation processes and the decomposition rate of MnO sub(4) super(-) can influence the number of MnO sub(2) nuclei at the initial nucleating stage and also can affect the subsequent crystal growth process. Moreover, the effects of reaction temperature on the morphology of the delta -MnO sub(2) nanowall are systematically studied. The electrochemical performances of the as-prepared MnO sub(2) as the positive material of rechargeable Li-ion batteries have also been researched. It is found that the delta -MnO sub(2) nanowall possesses largely enhanced electrochemical activity compared to alpha -MnO sub(2) nanowires and beta -MnO sub(2) nanorods. The vast difference in electrochemical activity is discussed in terms of the morphology, crystal phase and specific surface area of MnO sub(2) nanostructures. It is highly expected that these findings are useful in understanding the formation of MnO sub(2) nanocrystals with different morphologies, which are also applicable to other metal oxides nanocrystals.
CuO mesocrystals have been synthesized by nonclassical crystallization in the presence of an ionic liquid and n -butylamine under hydrothermal conditions. The resultant mesocrystals are composed of ...anisotropic nanosheets and nanorods as building blocks and possess distinct 3D hierarchical superstructure exposed {001} crystal planes. The mechanisms underlying the sequential formation of the mesocrystals are as follows: amorphous particles first appeared under a high degree of supersaturation according to the Ostwald rule of stages; then, nanosheet subunits were favored to form due to the protection of the {001} planes by n -butylamine molecules and etching of the {010} planes by a hydrolysis reaction, leading to the formation of a large number of dangling bonds in the {010} planes. Therefore, the ionic liquid can interact with these primary particles to facilitate a self-assembled superstructure by π–π interactions along the 010 direction due to the highly ionic nature, resulting in a 3D framework structure of primary particles composed of nanosheet and nanorod subunits by oriented attachment. Moreover, owing to the inherent porosity associated with well-defined nanoparticle orientation, the 3D hierarchical CuO mesocrystals achieved a higher electrochemical property as anodes for Li-ion batteries, surpassing the performance of CuO nanosheets and CuO nanorods. The unique characteristics of the hierarchical mesostalline electrodes show an ideal geometry to form a stable SEI film, which offers a facile route for designing high-performance electrodes for long-life Li-ion batteries.
Ultrathin BiOCl nanoflakes, nanoplate arrays, and curved nanoplates have been successfully synthesized via an ionothermal synthetic route by using an ionic liquid 1-hexadecyl-3-methylimidazolium ...chloride (C16MimCl) as “all-in-one” solvent, simply adjusting reaction temperature. The samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM) and Fourier transform infrared spectroscopy (FT-IR), separately. Possible formation mechanisms of various nanostructures were proposed in terms of crystal growth habit and dynamics. In addition, the excellent adsorption performance of the as-prepared BiOCl nanoplates makes them useful with potential applications in the aspect of wastewater treatment.
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IJS, KILJ, NUK, PNG, UL, UM
Hexagonal (h-WO3) mesocrystals with biconical morphology were prepared by a straightforward ionic liquid-assisted hydrothermal route and investigated as anodic materials for lithium-ion batteries. ...Compared to the alternatives, the biconical tungsten trioxide mesocrystal exhibited excellent lithium insertion with good cyclability and rate capability, making it a promising candidate as the anode material for high-performance lithium-ion batteries.
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