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We demonstrated the controlled growth of two-dimensional (2D) hexagonal tin disulfide (SnS2) nanoflakes with stacked monolayer atomic steps. The morphology was similar to flat-topped and step-sided mesa plateaus or step pyramids. The SnS2 nanoflakes were grown on mica substrates via an atmospheric-pressure chemical vapor deposition process using tin monosulfide and sulfur powder as precursors. Atomic force microscopy (AFM), electron microscopy, and Raman characterizations were performed to investigate the structural features, and a sequential layer-wise epitaxial growth mechanism was revealed. In addition, systematic Raman characterizations were performed on individual SnS2 nanoflakes with a wide range of thicknesses (1–100 nm), indicating that the A1g peak intensity and Raman shifts were closely related to the thickness of the SnS2 nanoflakes. Moreover, photoconductive AFM was performed on the monolayer-stepped SnS2 nanoflakes, revealing that the flat surface and the edges of the SnS2 atomic steps had different electrical conductive properties and photoconductive behaviors. This is ascribed to the dangling bonds and defects at the atomic step edges, which caused a height difference of the Schottky barriers formed at the interfaces between the PtIr-coated AFM tip and the step edges or the flat surface of the SnS2 nanoflakes. The 2D SnS2 crystals with regular monolayer atomic steps and fast photoresponsivity are promising for novel applications in photodetectors and integrated optoelectronic circuits.

Particulate matter (PM) pollution has become a serious environmental problem, especially in developing countries, owing to its severe threat to human health. Particularly, airborne PM 2.5 (mean aerodynamic diameter ≤2.5 µm) particles are extremely harmful, because the tiny particles can enter human respiratory system and even penetrate into circulatory system. Herein, we propose an effective strategy to recycle PM 2.5 carbon nanoparticles generated by diesel vehicle engine for the applications of clean energy. After thermal treatment and purification, the PM 2.5 derived carbon nanoparticles show a diameter distribution between 25 and 40 nm, mesoporous characteristics (with an average pore size of ~3.3 nm), and homogeneous nitrogen incorporation (with N content of ~1.1 at%). The PM 2.5 derived N-doped mesoporous carbon nanoparticles were used as an advanced electrode material in supercapacitors, exhibiting excellent specific capacity and superb stability over long-term cycling. Moreover, the recycled PM 2.5 carbon nanoparticles show attractive electrocatalytic properties for oxygen reduction reaction, presenting high onset potential and good immunity to methanol crossover. We expect this research can provide inspiration for air pollution control and sustainable energy utilization.

Here, we report a hierarchical Co3ZnC/carbon nanotube-inserted nitrogen-doped carbon concave-polyhedrons synthesized by direct pyrolysis of bimetallic zeolitic imidazolate framework precursors under a flow of Ar/H2 and subsequent calcination for both high-performance rechargeable Li-ion and Na-ion batteries. In this structure, Co3ZnC nanoparticles were homogeneously distributed in in situ growth carbon nanotube-inserted nitrogen-doped carbon concave-polyhedrons. Such a hierarchical structure offers a synergistic effect to withstand the volume variation and inhibit the aggregation of Co3ZnC nanoparticles during long-term cycles. Meanwhile, the nitrogen-doped carbon and carbon nanotubes in the hierarchical Co3ZnC/carbon composite offer fast electron transportation to achieve excellent rate capability. As anode of Li-ion batteries, the electrode delivered a high reversible capacity (∼800 mA h/g at 0.5 A/g), outstanding high-rate capacity (408 mA h/g at 5.0 A/g), and long-term cycling performance (585 mA h/g ...

Li-ion batteries have dominated the field of electrochemical energy storage for the last 20 years. It still remains to be one of the most active research fields. However, there are difficult problems still surrounding lithium ion batteries, such as high cost, unsustainable lithium resource and safety issues. Rechargeable batteries base on alternative metal elements (Na, K, Mg, Ca, Zn, Al, etc.) can provide relatively high power density and energy density using abundant, low-cost materials. Therefore, non-lithium ion batteries are regarded as promising candidates to partially replace lithium ion batteries in near future. In recent years, the research on non-lithium rechargeable batteries is progressing rapidly, but many fundamental and technological obstacles remain to be overcome. Here we provide an overview of the current state of non-lithium rechargeable batteries based on monovalent metal ions (Na+ and K+) and multivalent metal ions (Mg2+, Ca2+, Zn2+ and Al3+). The needs and possible choices of superior electrode materials and compatible electrolytes beneficial for ion transport were emphatically discussed in this review.

Considerable efforts have been devoted on the design and fabrication of non-platinum electrocatalysts with high performance and low cost for hydrogen evolution reaction (HER). However, the catalytic activity of existing electrocatalysts usually subjects to the limited amount of exposed active sites. Herein, we propose that self-assembled ultrathin NiCo2S4 nanoflakes grown on nickel foam (NiCo2S4/Ni foam) can serve as excellent electrocatalyst for HER in alkaline solution with high activity and stability. The NiCo2S4/Ni foam electrodes were prepared by the complete sulfidation of networked ultrathin NiCo-layered double hydroxide nanoflakes grown on Ni foam (NiCo-LDH/Ni foam). The advantages of this unique architecture are that the ultrathin and porous NiCo2S4 nanoflakes can provide a huge number of exposed active sites, the highly-conductive Ni foam can promote the transfer of electrons, and the three-dimensional-networked structure can facilitate the diffusion and penetration of electrolyte. Electrochemical measurements reveal that NiCo2S4/Ni foam electrodes exhibit greatly improved performance than NiCo-LDH/Ni foam for HER in alkaline solution with low onset overpotential (17 mV), small Tafel slope (84.5 mV/dec) and excellent long-duration cycling stability (maintaining an onset overpotential of ~20 mV and an overpotential of 155 mV at 50 mA/cm2 after testing for 100,000 s). In addition, the highly-flexible NiCo2S4/Ni foam electrodes show no obvious catalytic degradation after bending for 200 times, confirming the high flexibility and robustness under severe conditions.

Although transition metal oxides have attracted considerable attention for their high energy density as anode materials of lithium-ion batteries, they suffer from large volume expansion during lithiation process, which usually causes fast capacity degradation. Herein, we report a rational design and facile preparation strategy of copper oxide encapsulated mesoporous carbon multi-yolk-shell octahedra, in which multiple CuO nanoparticles are well-confined in the compartments of micro-scale octahedral carbon scaffolds. The advantages of the novel multi-yolk-shell design are that the three-dimensional carbon scaffolds can buffer the volume change and prevent aggregation of CuO nanoparticles during the charge/discharge cycles, provide pathways for electron transport and Li + diffusion, and restrict the thin solid-electrolyte interphase layer to the outer surface of carbon shells. The results demonstrate how the electrochemical properties of anodes can be significantly improved by the multi-yolk-shell nanostructures with greatly enhanced structural stability and electrochemical actuation. Moreover, the micrometer-size CuO@C octahedra reduce the relative quality of SEI, resulting in high Coulombic efficiency and long cycling stability. In Li-ion cells, the CuO@C multi-yolk-shell octahedra anodes deliver a highly-reversible capacity of 598 mA h g −1 at 250 mA g −1 , excellent rate capacity of 365 mA h g −1 at 3000 mA g −1 and exhibit long-term cyclability with a capacity of 512 mA h g −1 after 300 cycles at 500 mA g −1 .

Selenium (Se) has great promise to serve as cathode material for rechargeable batteries because of its good conductivity and high theoretical volumetric energy density comparable to sulfur. Herein, we report the preparation of mesoporous nitrogen-doped carbon scaffolds (NCSs) to restrain selenium for advanced lithium-selenium (Li-Se) batteries. The NCSs synthesized by a bottom-up solution-phase method have graphene-like laminar structure and well-distributed mesopores. The unique architecture of NCSs can severe as conductive framework for encapsulating selenium and polyselenides, and provide sufficient pathways to facilitate ion transport. Furthermore, the laminar and porous NCSs can effectively buffer the volume variation during charge/discharge processes. The integrated composite of Se-NCSs has a high Se content and can ensure the complete electrochemical reactions of Se and Li species. When used for Li-Se batteries, the cathodes based on Se-NCSs exhibit high capacity, remarkable cyclability, and excellent rate performance.

The design of electrochemically active materials with appropriate structures and compositions is very important for applications in energy conversion and storage devices. Herein, we demonstrate an effective strategy to prepare microporous heteroatom-doped carbon frameworks derived from naturally-abundant pine needles. The preparation procedure is based on the carbonization of pine needles, followed by KOH activation at a temperature range of 700–1000 °C. The resultant nitrogen-doped carbon consists of abundant micropores and an ultrahigh specific surface area (up to 2433 m2 g−1), leading to high performances in electrocatalytic hydrogen evolution reaction (HER) and supercapacitors. Specifically, when the pine needle-derived carbon (activated at 800 °C) serves as a HER electrocatalyst, it exhibits a low onset potential (∼4 mV), a small Tafel slope (∼45.9 mV dec−1) and a remarkable stability over long-term cycling. When evaluated as an electrode material for supercapacitors, the pine needle-derived carbon (activated at 900 °C) demonstrates high specific capacitance (236 F g−1 at 0.1 A g−1), remarkable rate capability (183 F g−1 at even 20 A g−1) and good long-term stability. Notably, the specific capacitance at 2.0 A g−1 increased from ∼205 to ∼227 F g−1 after cycling for 5000 times, owing to the further activation and wetting of the electrodes. This novel and low-cost biomass-derived carbon material is very promising for many applications, especially in electrocatalytic water splitting and supercapacitors.

Here, novel multifunctional electronic skins (E-skins) based on aligned few-walled carbon nanotube (AFWCNT) polymer composites with a piezoresistive functioning mechanism different from the mostly investigated theory of “tunneling current channels” in randomly dispersed CNT polymer composites are demonstrated. The high performances of as-prepared E-skins originate from the anisotropic conductivity of AFWCNT array embedded in flexible composite and the distinct variation of “tube-to-tube” interfacial resistance responsive to bending or stretching. The polymer/AFWCNT-based flexion-sensitive E-skins exhibit high precision and linearity, together with low power consumption (

Here an all-purpose fibrous electrode based on MoS2 is demonstrated, which can be employed for versatile energy harvesting and storage applications. In this coaxial electrode, ultrathin MoS2 nanofilms are grown on TiO2 nanoparticles coated carbon fiber. The high electrochemical activity of MoS2 and good conductivity of carbon fiber synergistically lead to the remarkable performances of this novel composite electrode in fibrous dye-sensitized solar cells (showing a record-breaking conversion efficiency of 9.5%) and high-capacity fibrous supercapacitors. Furthermore, a self-powering energy fiber is fabricated by combining a fibrous dye-sensitized solar cell and a fibrous supercapacitor into a single device, showing very fast charging capability (charging in 7 s under AM1.5G solar illumination) and an overall photochemical-electricity energy conversion efficiency as high as 1.8%. In addition, this wire-shaped electrode can also be used for fibrous Li-ion batteries and electrocatalytic hydrogen evolution reactions. These applications indicate that the MoS2-based all-purpose fibrous electrode has great potential for the construction of high-performance flexible and wearable energy devices.