Hierarchical porous nitrogen-doped carbon (HPNC) nanosheets (NS) have been prepared via simultaneous activation and graphitization of biomass-derived natural silk. The as-obtained HPNC-NS show favorable features for electrochemical energy storage such as high specific surface area (SBET: 2494 m(2)/g), high volume of hierarchical pores (2.28 cm(3)/g), nanosheet structures, rich N-doping (4.7%), and defects. With respect to the multiple synergistic effects of these features, a lithium-ion battery anode and a two-electrode-based supercapacitor have been prepared. A reversible lithium storage capacity of 1865 mA h/g has been reported, which is the highest for N-doped carbon anode materials to the best of our knowledge. The HPNC-NS supercapacitor's electrode in ionic liquid electrolytes exhibit a capacitance of 242 F/g and energy density of 102 W h/kg (48 W h/L), with high cycling life stability (9% loss after 10,000 cycles). Thus, a high-performance Li-ion battery and supercapacitors were successfully assembled for the same electrode material, which was obtained through a one-step and facile large-scale synthesis route. It is promising for next-generation hybrid energy storage and renewable delivery devices.

High-quality ultrathin two-dimensional nanosheets of α-Ni(OH)2 are synthesized at large scale via microwave-assisted liquid-phase growth under low-temperature atmospheric conditions. After heat treatment, non-layered NiO nanosheets are obtained while maintaining their original frame structure. The well-defined and freestanding nanosheets exhibit a micron-sized planar area and ultrathin thickness (<2 nm), suggesting an ultrahigh surface atom ratio with unique surface and electronic structure. The ultrathin 2D nanostructure can make most atoms exposed outside with high activity thus facilitate the surface-dependent electrochemical reaction processes. The ultrathin α-Ni(OH)2 and NiO nanosheets exhibit enhanced supercapacitor performances. Particularly, the α-Ni(OH)2 nanosheets exhibit a maximum specific capacitance of 4172.5 F g−1 at a current density of 1 A g−1. Even at higher rate of 16 A g−1, the specific capacitance is still maintained at 2680 F g−1 with 98.5% retention after 2000 cycles. Even more important, we develop a facile and scalable method to produce high-quality ultrathin transition metal hydroxide and oxide nanosheets and make a possibility in commercial applications.

We have developed a facile, scale up, and efficient method for the preparation of graphitic-C3N4 nanofibers (GCNNFs) as electrodes for supercapacitors and photocatalysts. The as-synthesized GCNNFs have 1D structure with higher concentration of nitrogen that is favorable for higher conductivity and electrochemical performance. Secondly, the high surface area of GCNNF provides a large electrode-electrolyte contact area, sufficient light harvesting and mass transfer, as well as increased redox potential. Thus, the GCNNF supercapacitor electrode shows high capacitance of 263.75 F g(-1) and excellent cyclic stability in 0.1 M Na2SO4 aqueous electrolyte with the capacitance retention of 93.6% after 2000 cycles at 1 A g(-1) current density. GCNNFs exhibit high capacitance of 208 F g(-1) even at 10 A g(-1), with the appreciable capacitance retention of 89.5%, which proves its better rate capability. Moreover, the GCNNF shows enhanced photocatalytic activity in the photodegradation of RhB in comparison to the bulk graphitic-C3N4 (GCN). The degradation rate constant of GCNNF photocatalyst is almost 4 times higher than GCN. The enhanced photocatalytic activity of GCNNF is mainly due to the higher surface area, appropriate bandgap, and fewer defects in GCNNF as compared to GCN. As an economical precursor (melamine) and harmless, facile, and template-free synthesis method with excellent performance both in supercapacitors and in photodegradation, GCNNF is a strong candidate for energy storage and environment protection applications.

CuS semiconductor nanometer‐sized hollow spheres are successfully synthesized by using a soft‐template method. A possible growth mechanism is proposed. The linear optical property of the CuS hollow spheres is examined by means of photoluminescence spectroscopy at room temperature. The optical‐limiting (OL) property of these nanostructures is characterized by using a nanosecond Q‐switched YAG laser and an optical parametric oscillator pumped with Surelite‐III. A strong OL response is detected for the CuS hollow spheres in both visible and near infrared (NIR) spectral ranges, which makes these promising materials for applications such as the protection of human eyes or as optical sensors for high‐power laser irradiation. The OL mechanism of the CuS hollow‐sphere nanostructure may be the combination of free‐carrier absorption (FCA) and nonlinear scattering.

Popcorn-derived porous carbon flakes have been successfully fabricated from the biomass of maize. Utilizing the "puffing effect", the nubby maize grain turned into materials with an interconnected honeycomb-like porous structure composed of carbon flakes. The following chemical activation method enabled the as-prepared products to possess optimized porous structures for electrochemical energy-storage devices, such as multilayer flake-like structures, ultrahigh specific surface area (S: 3301 m g), and a high content of micropores (microporous surface area of 95%, especially the optimized sub-nanopores with the size of 0.69 nm) that can increase the specific capacitance. The as-obtained sample displayed excellent specific capacitance of 286 F g at 90 A g for supercapacitors. Moreover, the unique porous structure demonstrated an ideal way to improve the volumetric energy density performance. A high energy density of 103 Wh kg or 53 Wh L has been obtained in the case of ionic liquid electrolyte, which is the highest among reported biomass-derived carbon materials and will satisfy the urgent requirements of a primary power source for electric vehicles. This work may prove to be a fast, green, and large-scale synthesis route by using the large nubby granular materials to synthesize applicable porous carbons in energy-storage devices.

We have established a facile and scaleable approach to fabricate tubular graphitic-C3N4 using melamine. The construction of the unique tubular morphology is a result of the pre-treatment of melamine with HNO3. Herein, for the first time, we have explored the electrochemical properties of g-C3N4 as an electrode material for supercapacitors. Tubular g-C3N4 has significant advantages due to its distinctive morphology, high surface area (182.61 m 2 g -1 ) and combination of carbon with nitrogen. Therefore, tubular g-C3N4 demonstrated a good specific capacitance of 233 F g -1 at a current density of 0.2 A g -1 in 6 M KOH electrolyte. Furthermore, tubular g-C3N4 maintained a high capacitance retention capability (90%) after 1000 cycles. The photocatalytic activity of tubular g-C3N4 was evaluated using the organic dyes such as Methylene Blue (MB) and Methylene Orange (MO) under visible light. Tubular g-C3N4 demonstrated good photocatalytic activity and enhanced stability compared to bulk g-C 3N4. The enhanced performance is because of the high surface area, which contains more active sites for reaction. The encouraging performance of tubular g-C3N4 in supercapacitors and as a photocatalyst points toward it being a prospective material for energy storage that is environmentally clean. The Royal Society of Chemistry. We have established a facile and scaleable approach to fabricate tubular graphitic-C 3 N 4 using melamine.The construction of the unique tubular morphology is a result of the pre-treatment of melamine with points toward it being a prospective material for energy storage that is environmentally clean.

No abstract

hollow nano-micro hierarchical microspheres (NCM-HS) are synthesized using MnCO 3 both as a self-template and Mn source. The hollow microspheres with diameters of about 1 mm have walls about 250 nm thick, which are composed of approximately 100 nm primary nanoparticles. NCM-HS cathodes have an initial discharge capacity of 212 mA h g À1 at 0.1 C between 2.5 and 4.5 V. After 40 charge-discharge cycles, the capacity retention at 0.1 C is 85.1%. At higher rates, the reversible capacities of the NCM-HS cathodes are 208.9 (0.5 C), 204.8 (1 C), 180.7 (2 C), 155.7 (5 C) and 135.9 mA h g À1 (10 C). The high performances can be attributed to the distinctive hollow microspherical structures with the 100 nm building blocks, which could effectively reduce the path of Li ion diffusion, increase the contact area between electrodes and electrolyte and buffer the volume changes during the Li ion intercalation/deintercalation processes. † Electronic supplementary information (ESI) available: SEM images and XRD proles of MnCO 3 and MnO 2 microspheres, XPS prole of NCM-HS, SEM image of NCM-bulk, one more TEM image of NCM-HS, the rst ve cyclic voltammetry (CV) curves of NCM-HS cathode. See