As a newly developed material, carbon gels have been receiving considerable attention due to their multifunctional properties. Herein, we present a facile, green, and template-free route toward sponge-like carbonaceous hydrogels and aerogels by using crude biomass, watermelon as the carbon source. The obtained three-dimensional (3D) flexible carbonaceous gels are made of both carbonaceous nanofibers and nanospheres. The porous carbonaceous gels (CGs) are highly chemically active and show excellent mechanical flexibility which enable them to be a good scaffold for the synthesis of 3D composite materials. We synthesized the carbonaceous gel-based composite materials by incorporating Fe3O4 nanoparticles into the networks of the carbonaceous gels. The Fe3O4/CGs composites further transform into magnetite carbon aerogels (MCAs) by calcination. The MCAs keep the porous structure of the original CGs, which allows the sustained and stable transport of both electrolyte ions and electrons to the electrode surface, leading to excellent electrochemical performance. The MCAs exhibit an excellent capacitance of 333.1 F·g(-1) at a current density of 1 A·g(-1) within a potential window of -1.0 to 0 V in 6 M KOH solution. Meanwhile, the MCAs also show outstanding cycling stability with 96% of the capacitance retention after 1000 cycles of charge/discharge. These findings open up the use of low-cost elastic carbon gels for the synthesis of other 3D composite materials and show the possibility for the application in energy storage.

A magnetite/graphene oxide (M/GO) composite was synthesized via a chemical reaction with a magnetite particle size of 10–15 nm and was developed for the removal of heavy metal ions from aqueous solutions. The composite was characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The sorption of Co(II) on the M/GO composite was carried out under various conditions, that is, contact time, sorbent content, pH, ionic strength, foreign ions, and temperature. The sorption isotherms of Co(II) on the M/GO composite could be described well by the Langmuir model. The thermodynamic parameters (ΔH 0, ΔS 0, and ΔG 0) calculated from the temperature-dependent isotherms indicated that the sorption reaction of Co(II) on the M/GO composite was an endothermic and spontaneous process. M/GO can be separated and recovered by magnetic separation. Results show that the magnetic M/GO composite is a promising sorbent material for the preconcentration and separation of heavy metal ions from aqueous solutions.

N-doped TiO(2) nanoparticles modified with carbon (denoted N-TiO(2)/C) were successfully prepared by a facile one-pot hydrothermal treatment in the presence of L-lysine, which acts as a ligand to control the nanocrystal growth and as a source of nitrogen and carbon. As-prepared nanocomposites were characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, ultraviolet-visible (UV-vis) diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), electron paramagnetic resonance (EPR) spectra, and N(2) adsorption-desorption analysis. The photocatalytic activities of the as-prepared photocatalysts were measured by the degradation of methyl orange (MO) under visible light irradiation at λ≥ 400 nm. The results show that N-TiO(2)/C nanocomposites increase absorption in the visible light region and exhibit a higher photocatalytic activity than pure TiO(2), commercial P25 and previously reported N-doped TiO(2) photocatalysts. We have demonstrated that the nitrogen was doped into the lattice and the carbon species were modified on the surface of the photocatalysts. N-doping narrows the band gap and C-modification enhances the visible light harvesting and accelerates the separation of the photo-generated electrons and holes. As a consequence, the photocatalytic activity is significantly improved. The molar ratio of L-lysine/TiCl(4) and the pH of the hydrothermal reaction solution are important factors affecting the photocatalytic activity of the N-TiO(2)/C; the optimum molar ratio of L-lysine/TiCl(4) is 8 and the optimum pH is ca. 4, at which the catalyst exhibits the highest reactivity. Our findings demonstrate that the as-obtained N-TiO(2)/C photocatalyst is a better and more promising candidate than well studied N-doped TiO(2) alternatives as visible light photocatalysts for potential applications in environmental purification.

In this Article, we report a remarkably simple and efficient method for the preparation of layered double hydroxides and graphene oxide (LDHs/GO) nanocomposites with varying GO amounts via a hydrothermal process. The graphene nature in the resulting LDHs/GO nanocomposites was confirmed by X-ray diffraction (XRD), Fourier transformed infrared (FTIR) spectroscopy, field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), N2 adsorption-desorption, and X-ray photoelectron spectroscopy (XPS). The LDHs/GO nanocomposites exhibited swelling behavior in water and forming a gel. The adsorption performance of the LDHs/GO nanocomposites was evaluated for the removal of arsenate (As(V)) from aqueous solutions, and the results showed that the ratio of GO to LDHs in the nanocomposites significantly affected the adsorption capacity. Higher and lower amounts of GO in LDHs/GO nanocomposites showed lower adsorption capacity of As(V). A maximum adsorption capacity of 183.11 mg/g (2.44 mmol/g) was achieved on the LDHs/GO containing 6.0% GO due to the higher Brunauer-Emmett-Teller (BET) surface area than other samples. Owing to their high uptake capability of As(V), water-swellable LDHs/GO nanocomposites are expected to have potential applications as adsorbents for As(V) polluted water cleanup.

A composite material, containing magnetite particles, graphene and layered double hydroxides (LDHs) was fabricated through a simple two-step reaction. Graphene was used as the matrix for supporting magnetite particles and LDH nanoplates. The synthesized magnetite-graphene-LDH (MGL) composites were characterized by field emission scanning electron microscopic (FE-SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transformed infrared (FTIR) spectroscopy, N 2 adsorption-desorption, and Xray photoelectron spectroscopy (XPS). The MGL composites were applied to remove arsenate from aqueous solutions and could be easily separated by magnetic separation process. The results showed enhanced adsorption capacity of arsenate on the MGL as compared to that of pure Mg/Al LDHs. The surface area of MGL is greatly enhanced through the incorporation of magnetite particles and graphene, which provides more active sites for arsenate uptake. Moreover, LDHs were hybridized with mechanically and chemically stable graphene materials, providing an accessible diffusion pathway in the macropore domain, and therefore their adsorption capacity was enhanced. The fast and efficient adsorption of arsenate from solution to MGL suggests that the MGL composites are potential and suitable materials in the preconcentration of arsenate from large volumes of aqueous solutions in wastewater treatment.

This work reports a new graphene-based composite for supercapacitor material, and the maximum specific capacitance of 1760.72 F g(-1) at a scan rate of 5 mV s(-1), with excellent cycling stability.

Zinc oxide is one of the most important wide-band-gap (3.2 eV) materials with versatile properties, however, it can not be excited by visible light. In this work, we have developed an exquisite and simple way to prepare oxygen-deficient ZnO 1-x nanosheets with a gray-colored appearance and excellent visible light photocatalytic activity. Detailed analysis based on UV-Vis absorption spectra, X-band electron paramagnetic resonance (EPR) spectra, and photoluminescence (PL) spectra confirms the existence of oxygen vacancies in ZnO 1-x. The incorporation of oxygen defects could effectively extend the light absorption of ZnO 1-x into the visible-light region due to the fact that the energy of the localized state is located in the forbidden gap. Thus, our obtained ZnO 1-x shows a higher photodegradation of methyl orange (MO) compared to defect-free ZnO under visible light illumination. Additionally, the high content of ˙OH radicals with a strong photo-oxidation capability over the ZnO 1-x nanosheets significantly contributes to the improvement in the photocatalytic performance. Our oxygen deficient ZnO 1-x sample shows a very high photocatalytic activity for the degradation of MO even after 5 cycles without any obvious decline. The results demonstrate that defect engineering is a powerful tool to enhance the optoelectronic and photocatalytic performances of nanomaterials.

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