Porous carbon/Co nanocomposites were fabricated by a sol-gel method. The electromagnetic parameters were measured in the 2–18GHz range. Compared with porous carbon composite, porous carbon/Co nanocomposite has larger dielectric loss due to the enhanced interfacial polarization relaxation loss and Ohmic loss. The maximum reflection loss of the porous C(Co) nanocomposite can reach 40dB at 4.2GHz with 5mm in thickness and the primary microwave absorptive mechanism is ascribed to the dielectric loss. The effect of porous structure on microwave absorption property of the carbon/Co nanocomposite was also discussed.

Solar steam generation is regarded as a perspective technology, due to its potentials in solar light absorption and photothermal conversion for seawater desalination and water purification. Although lots of steam generation systems have been reported to possess high conversion efficiencies recently, researches of simple, cost-effective, and sustainable materials still need to be done. Here, inspired by natural young sunflower heads’ property increasing the temperature of dish-shaped flowers by tracking the sun, we used 3D-structured carbonized sunflower heads as an effective solar steam generator. The evaporation rate and efficiency of these materials under 1 sun (1 kW m–2) are 1.51 kg m–2 h–1 and 100.4%, respectively, beyond the theoretical limit of 2D materials. This high solar efficiency surpasses all other biomass-based materials ever reported. It is demonstrated that such a high capability is mainly attributed to the 3D-structured top surface, which could reabsorb the lost energy of diffuse reflection and thermal radiation, as well as provide enlarged water/air interface for steam escape. 3D-structured carbonized sunflower heads provide a new method for the future design and fabrication of high-performance photothermal devices.

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Here we report a method to fabricate porous carbon with small mesopores around 2-4 nm by simple activation of charcoals derived from carbonization of seaweed consisting of microcrystalline domains formed by the "egg-box" model. The existence of mesopores in charcoals leads to a high specific surface area up to 3270 m(2) g(-1), with 95% surface area provided by small mesopores. This special pore structure shows high adaptability when used as electrode materials for an electric double layer capacitor, especially at high charge-discharge rate. The gravimetric capacitance values of the porous carbon are 425 and 210 F g(-1) and volumetric capacitance values are 242 and 120 F cm(-3) in 1 M H2SO4 and 1 M TEA BF4/AN, respectively. The capacitances even remain at 280 F g(-1) (160 F cm(-3)) at 100 A g(-1) and 156 F g(-1) (90 F cm(-3)) at 50 A g(-1) in the aqueous and organic electrolytes, demonstrating excellent high-rate capacitive performance.

Abstract"Nano tungsten oxide (WO3) particles were synthesized on the surface of graphene (GR) sheets by using a simple sonochemical method. The obtained composite, WO3@GR, was characterized by X-ray diffraction, N-2 adsorption/desorption analysis, thermo-gravimetric analysis, Raman spectroscopy and UV-vis diffuse reflectance spectra measurements. It was found that chemical bonds between the nano WO3 particles and the GR sheets were formed. The average particle size of the WO3 was evidenced to be around 12 nm on the GR sheets. When used as photocatalyst for water splitting, the amount of evolved O-2 from water for the WO3@GR composite with 40 wt% GR inside was twice and 1.8 times as much as that for pure WO3 and mixed-WO3/GR, respectively. The excellent photocatalytic property of the WO3@GR composite is due to the synergistic effects of the combined nano WO3 particles and GR sheets. The sensitization of WO3 by GR enhances the visible light absorption property of WO3@GR. The chemical bonding between WO3 and GR minimizes the interface defects, reducing the recombination of the photo-generated electron-hole pairs. Furthermore, the GR sheets in the WO3@GR composite enhance electrons transport by providing low resistance conduction pathways, leading to improved photo-conversion efficiency. The methodology opens up a new way of obtaining photoactive GR-semiconductor composites for photodissociating water under visible light." Nano tungsten oxide (WO 3 ) particles were synthesized on the surface of graphene (GR) sheets by using a simple sonochemical method. The obtained composite, WO 3 @GR, was characterized by X-ray diffraction, N 2 adsorption/desorption analysis, thermo-gravimetric analysis, Raman spectroscopy and UV-vis diffuse reflectance spectra measurements. It was found that chemical bonds between the nano WO 3 particles and the GR sheets were formed. The average particle size of the WO 3 was evidenced to be around 12 nm on the GR sheets. When used as photocatalyst for water splitting, the amount of evolved O 2 from water for the WO 3 @GR composite with 40 wt% GR inside was twice and 1.8 times as much as that for pure WO 3 and mixed-WO 3 /GR, respectively. The excellent photocatalytic property of the WO 3 @GR composite is due to the synergistic effects of the combined nano WO 3 particles and GR sheets. The sensitization of WO 3 by GR enhances the visible light absorption property of WO 3 @GR. The chemical bonding between WO 3 and GR minimizes the interface defects, reducing the recombination of the photo-generated electron-hole pairs. Furthermore, the GR sheets in the WO 3 @GR composite enhance electrons transport by providing low resistance conduction pathways, leading to improved photo-conversion efficiency. The methodology opens up a new way of obtaining photoactive GR-semiconductor composites for photodissociating water under visible light.

We prepare group VI transitional metal dichalcogenides (TMDs, or MX) from the 1T phase with quantum-sized and monolayer features via a quasi-full electrochemical process. The resulting two-dimensional (2D) MX (M = W, Mo; X = S, Se) quantum dots (QDs) are ca. 3.0-5.4 nm in size with a high 1T phase fraction of ca. 92%-97%. We attribute this to the high Li content intercalated in the 1T-MX lattice (mole ratio of Li:M is over 2:1), which is achieved by an increased lithiation driving force and a reduced electrochemical lithiation rate (0.001 A/g). The high Li content not only promotes the 2H → 1T phase transition but also generates significant inner stress that facilitates lattice breaking for MX crystals. Because of their high proportion of metallic 1T phase and sufficient active sites induced by the small lateral size, the 2D 1T-MoS QDs show excellent hydrogen evolution reactivity (with a typical η of 92 mV, Tafel slope of 44 mV/dec, and J of 4.16 × 10 A/cm). This electrochemical route toward 2D QDs might help boost the development of 2D materials in energy-related areas.

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High-efficiency solar steam generators are facilely constructed based on a bifunctional bio-structure of sugarcane stem.