We discovered that chemically reduced graphene oxide, with an I(D)/I(G) >1.4 (defective to graphite) can effectively activate peroxymonosulfate (PMS) to produce active sulfate radicals. The produced sulfate radicals (SO(4)(•-)) are powerful oxidizing species with a high oxidative potential (2.5-3.1 vs 2.7 V of hydroxyl radicals), and can effectively decompose various aqueous contaminants. Graphene demonstrated a higher activity than several carbon allotropes, such as activated carbon (AC), graphite powder (GP), graphene oxide (GO), and multiwall carbon nanotube (MWCNT). Kinetic study of graphene catalyzed activation of PMS was carried out. It was shown that graphene catalysis is superior to that on transition metal oxide (Co(3)O(4)) in degradation of phenol, 2,4-dichlorophenol (DCP) and a dye (methylene blue, MB) in water, therefore providing a novel strategy for environmental remediation.

Carbon nitride (C3N4) is a layered, stable, and polymeric metal-free material that has been discovered as a visible-light-response photocatalyst. Owing to C3N4 having a higher conduction band position, most previous studies have been focused on its reduction capability for solar fuel production, such as hydrogen generation from water splitting or hydrocarbon production from CO2. However, photooxidation ability of g-C3N4 is weak and has been less explored, especially for decomposition of chemically stable phenolics. Carbon spheres prepared by a hydrothermal carbonization of glucose have been widely applied as a support material or template due to their interesting physicochemical properties and the functional groups on the reactive surface. This study demonstrated that growth of carbon nanospheres onto g-C3N4 (CN-CS) can significantly increase the photooxidation ability (to about 4.79 times higher than that of pristine g-C3N4) in phenol degradation under artificial sunlight irradiations. The crystal structure, optical property, morphology, surface groups, recombination rate of electron/hole pairs, and thermal stability of CN-CS were investigated by a variety of characterization techniques. This study contributes to the further promising applications of carbon nitride in metal-free catalysis.

Nanoscaled zerovalent iron (ZVI) encapsulated in carbon spheres (nano-Fe 0 @CS) were prepared via a hydrothermal carbonization method, using glucose and iron(III) nitrate as precursors. The properties of the nano-Fe 0 @CS were investigated by X-ray diffraction (XRD), thermogravimetric analysis-differential scanning calorimetry (TGA-DSC), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and nitrogen adsorption/desorption isotherms. Nano-Fe 0 @CS was demonstrated, for the first time, as an effective material in activating Oxone (peroxymonosulfate, PMS) for the oxidation of organic pollutants. It was found that the efficiency of nano-Fe 0 @CS was higher than ZVI particles, iron ions, iron oxides, and a cobalt oxide. The mechanism of the high performance was discussed. The structure of the nano-Fe 0 @CS not only leads to high efficiency in the activation of PMS, but also good stability. This study extended the application of ZVI from reductive destruction of organics to oxidative degradation of organics by providing a green material for environmental remediation.

Various cation and nitrogen doped and codoped TiO 2 photocatalysts, such as N-TiO 2 , Pt-TiO 2 , N-Fe-TiO 2 , N-Ni-TiO 2 , NAg -TiO 2 and N-Pt-TiO 2 , were prepared by an acid-catalysed sol-gel process. The photocatalysts were characterised by X-ray diffraction (XRD), nitrogen adsorption-desorption isotherms, UV-visible diffuse reflectance absorption spectroscopy (UV-vis DRS), and X-ray photoelectron spectroscopy (XPS). The activities of the photocatalysts were evaluated in photodegradation of phenol solutions under simulated sunlight irradiations. A negative effect of some transition metals (iron and nickel) on photocatalysis was observed on N-metal codoped TiO 2 , while enhancements in photocatalysis from noble metals (silver and platinum) were obtained. N-Pt codoped TiO 2 showed a higher activity under UV-vis irradiations than Degussa P25, with an enhancement of 5.9 times higher. The synergistic effect of N-Pt-codoping was ascribed to the multivalent states of platinum. In addition, photocatalytic activity of N-, Pt-doped and N-Pt-codoped materials were further investigated under visible light irradiations with λ > 430 nm and λ > 490 nm. This study therefore demonstrated a promising strategy for design of highly efficient photocatalysts for remediation of aqueous pollutants.

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