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Two types of SiC nanowires were synthesized via carbothermal reduction and subsequent wet chemical etching. Both SiC nanowires consisted of cubic β-SiC and exhibited numerous stacking fault nanolayers. The etching process was very selective to the stacking fault nanolayers and β-SiC; β-SiC was gradually corroded; however, the stacking faults were retained. Three strong and distinct photoluminescence (PL) emission peaks emerged in the PL spectra of both types of SiC nanowires as the excitation wavelength was increased from 290 to 490 nm. The strong ultraviolet emission and the blueshift of the PL peak were related to the quantum confinement effects of the stacking fault nanolayers having a thickness of <3 nm. This quantum confinement effect was responsible for the blue emission observed from the SiC nanowires. The thickness of the nanolayers was in good agreement with the theoretically predicted value (3–5.4 nm). The additional green emission and blueshift of the peak arose from surface structures induced by Si O and Si-OH. The green emission required a sufficiently large surface area and was only observed using longer-wavelength excitation to excite more SiC nanowires with larger sizes. • Photoluminescence (PL) of two types of SiC nanowires were evaluated at room temperature. • The strong ultraviolet emission and the blueshift of the PL peak due to the stacking fault nanolayers having a thickness of <3 nm. • The blue emission were related to the thickness of the nanolayers which in good agreement with the theoretically predicted value (3–5.4 nm). • The green emission and blueshift of the peak arose from surface structures induced by Si O and Si-OH. [ABSTRACT FROM AUTHOR]

Developing highly porous and conductive carbon electrodes are crucial for high-performance electrochemical double-layer capacitors. Herein, we provide a supercapacitor electrode material consisting of N-doped porous carbon tightly anchored on carbon nanotubes. This nanocomposite with high specific surface area of 659.5 m 2 g −1 is fabricated by pyrolyzing the ZIF-8/polypyrrole nanotubes. When the nanocompiste is used as supercapacitor electrodes, it deliveres high specific capacitance of 248 F g −1 and 97.3% of capacitance retention after 3000 cycles. The superior capacitive performance is attributed to the conductive network for electron transport constributed by CNTs and the abundant reservoir for the charge storage derived from ZIF-derived porous carbon. Benefiting from the unique structural features and high N doping, the PC-CNTs obtained by our route could be a promising candidate of electrode mateials for high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

A free-standing honerycomb-like N doped carbon (FHNC) was fabricated by one-step carbonization and activation of the commercial melamine foam loading coal tar pitch and KOH. The as-prepared FHNC exhibits three-dimensional interconnected architecture with hierarchical honeycomb-like structure, which has a large specific surface area of 3105 m2 g−1. The specific capacitance of FHNC is 280.3 F g−1 at 1 A g−1, and still maintains 185.4 F g-1 at 40 A g−1, indicating the good rate capability. • A free-standing honeycomb-like N doped carbon (FHNC) was fabricated by the commercial melamine foam and coal tar pitch. • FHNC electrodes have a large specific surface area of 3105 m2 g−1. • The specific capacitance of FHNC is 280.3 F g−1 at 1 A g−1. • The supercapacitors show 10.1 Wh kg−1 at a power density of 250 W kg−1. • The capacity retention of supercapacitor device is 96.3% after 10,000 cycles. A free-standing honeycomb-like N doped carbon foam (FHNC) is fabricated by one-step carbonization and activation of the commercial melamine foam loading coal tar pitch and KOH. The as-prepared FHNC exhibits the three-dimensional (3D) interconnected architecture with hierarchical honeycomb-like structure, which has a large specific surface area of 3105 m2 g−1. The specific capacitance of FHNC reaches up to 280.3 F g−1 at 1 A g−1, and still maintains 185.4 F g−1 at 40 A g−1, indicating the excellent rate capability. Additionally, the assembled symmetrical supercapacitor demonstrates the maximum energy density of 10.1 Wh kg−1 at a power density of 250 W kg−1, and excellent cycling stability (96.3% capacitance retention after 10,000 charge-discharge cycles at 5 A g−1). The outstanding electrochemical performance is assigned to the unique 3D interconnected architecture that endow the large accessible surface area, and rapid transfer pathway for ion and electron. [ABSTRACT FROM AUTHOR]

[Display omitted] • A scalable, facile, and low-cost technology constructed the porous structure. • The influence of copper content on initial coulombic efficiency was explored. • The effect of porosity on the stability of the composite electrode was studied. • Si/Cu/void@C-14 anode exhibited a high rate and long cycle durability. Silicon is an advanced anode material for lithium-ion batteries due to its ultra-high theoretical capacity. However, its commercial application is limited by the enormous volume change and low electrical conductivity. Herein, we synthesize a copper-doped silicon/carbon porous composite that can effectively solve the current dilemma. Uniform anchoring of copper particles on silicon significantly improves the electronic conductivity of composites. By adjusting the content of copper, the initial coulombic efficiency is increased substantially from 60.7 % to 87.6 %. The effect of porosity on the electrochemical properties is systematically studied. The optimized Si/Cu/void@C-14 anode exhibits excellent rate capability (529.3 mAh g−1 at 2 C) and cycle stability (1076.2 mAh g−1 after 300 cycles). The reasons are that the Li+ diffusion coefficient is increased effectively to 3.32 × 10-10-2.54 × 10-9 cm2 s−1, and the volume expansion rate is reduced vastly to 8.8 %. In addition, the full cells coupling LiNi 0.8 Co 0.1 Mn 0.1 O 2 cathode with perlithiated Si/Cu/void@C-14 anode provide a high energy density of 491.5 Wh kg−1 after 100 cycles. It is worth noting that the Si/Cu/void@C-14 composite is synthesized with low-cost raw materials through facile and scalable processes, revealing that the composites have promising potential as high capacity anode materials in a commercial application. [ABSTRACT FROM AUTHOR]

The schematic diagram of MoSe 2 /NiSe‖Na 3 V 2 (PO 4) 3 /C full-cell, and the schematic diagram of charge–discharge process is shown in the Figure. [Display omitted] • The 3D flower spheres MoSe 2 /NiSe heterojunction can effectively alleviate the volume expansion during sodiation/desodiation process. • The DFT calculation results reveal the charge transfer mechanism between MoSe 2 and NiSe. • The MoSe 2 /NiSe possesses a good cyclability over 3000 cycles with a capacity of 172 mAh/g at 5.0 A/g. • The full cell with Na3V2(PO4)3/C cathode shows high-rate performance of 276 mAh/g at 2.0 A/g. Due to the large size of Na+ and the slow redox kinetics, the energy storage performance of sodium ion batteries (SIBs) is far from satisfactory. Heterojunction with layered structure has great potential in advanced material of SIBs. Herein, the 3D flower spheres MoSe 2 /NiSe heterostructure with fast dynamic properties was proposed, which shows enhancement in the adsorption and storage capacity of Na+ with a low migration energy barrier. Unique structure design can further effectively alleviate the volume expansion during sodiation/desodiation process. Furthermore, the DFT calculation results reveal the charge transfer mechanism between NiSe and MoSe 2 , as well as improved intrinsic electric structure of MoSe 2 /NiSe. In consequence, the designed MoSe 2 /NiSe possesses a good cyclability over 3000 cycles with a capacity of 172 mAh/g at 5.0 A/g, and the full cell with Na3V2(PO4)3/C cathode shows high-rate performance of 276 mAh/g at 2.0 A/g, which solidly proves the feasibility of the designed MoSe 2 /NiSe anode in the practical application. This work shows that the heterojunction can achieve long-lasting sodium electrochemistry and expand to other energy storage fields. [ABSTRACT FROM AUTHOR]