In this work, g-C3N4/TiO2 composites were fabricated through a hydrothermal method for the efficient photocatalytic degradation of imidacloprid (IMI) pesticide. The composites were fabricated at varying loading of sonochemically exfoliated g-C3N4 (denoted as CNS). Complementary characterization results indicate that the heterojunction between the CNS and TiO2 formed. Among the composites, the 0.5CNS/TiO2 material gave the highest photocatalytic activity (93% IMI removal efficiency) under UV-Vis light irradiation, which was 2.2 times over the pristine g-C3N4. The high photocatalytic activity of the g-C3N4/TiO2 composites could be ascribed to the band gap energy reduction and suppression of photo-induced charge carrier recombination on both TiO2 and CNS surfaces. In addition, it was found that the active species involved in the photodegradation process are OH and holes, and a possible mechanism was proposed. The g-C3N4/TiO2 photocatalysts exhibited stable photocatalytic performance after regeneration, which shows that g-C3N4/TiO2 is a promising material for the photodegradation of imidacloprid pesticide in wastewater.
This research employed g-C3N4 nanosheets in the hydrothermal synthesis of TiO2/g-C3N4 hybrid photocatalysts. The TiO2/g-C3N4 heterojunctions, well-dispersed TiO2 nanoparticles on the g-C3N4 nanosheets, are effective photocatalysts for the degradation of monochlorophenols (MCPs: 2-CP, 3-CP, and 4-CP) which are prominent water contaminants. The removal efficiency of 2-CP and 4-CP reached 87% and 64%, respectively, after treatment of 25 ppm CP solutions with the photocatalyst (40TiO2/g-C3N4, 1 g/L) and irradiation with UV–Vis light. Treatment of CP solutions with g-C3N4 nanosheets or TiO2 alone in conjunction with irradiation gave removal efficiencies lower than 50%, which suggests the two act synergically to enhance the photocatalytic activity of the 40TiO2/g-C3N4 nanocomposite. Superoxide and hydroxyl radicals are key active species produced during CP photodegradation. In addition, the observed nitrogen and Ti3+ defects and oxygen vacancies in the TiO2/g-C3N4 nanocomposites may improve the light-harvesting ability of the composite and assist preventing rapid electron-hole recombination on the surface, enhancing the photocatalytic performance. In addition, interfacial interactions between the MCPs (low polarity) and thermally exfoliated carbon nitride in the TiO2/g-C3N4 nanocomposites may also enhance MCP degradation.
An n-type organic carbon nitride semiconductor, C 2 N, was synthesized by the pyrolysis of uric acid, and its properties were investigated by scanning electron and transmission electron microscopies, X-ray powder diffraction, and vibrational, UV-visible and X-ray photoelectron spectroscopies. This novel material, composed of crystalline flakes, featured a broad absorption centered at 700 nm, possibly due to charge transfer, and a 2.49 eV band gap. Its catalytic performance was assessed for the treatment of effluents with the diazo dye Congo red, comparing it with that of boron carbon nitrogen oxide, BCNO. Both wide band gap semiconductors exhibited decolorizing activity in the dark, although the mechanisms were different and were not photocatalytic: BCNO was more effective towards the adsorptioncoordination due to the presence of B-O, while C 2 N was effective towards the adsorption and the advancement of the oxidation reaction. Their kinetic constants (0.19 and 0.02 min-1 for BCNO and C 2 N, respectively) were comparable to those of intermetallic compounds studied for azo dyes degradation in dark conditions. In view of the high color removal efficiency (97% after 20 min) and good reusability of BCNO, this study suggests a potential application of this catalyst for wastewater treatment, alone or in combination with C 2 N.
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