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Porous g-C3N4 composed of nanosheets (p-gCN-NS) was synthesized through firstly grinding the hydrochloric acid-treated melamine with ammonium chloride (NH4Cl) and then calcining the mixture at 550° C for 2 h. The photocatalytic properties were determined by degrading Rhodamine B (RhB) and tetracycline (TC) aqueous solution (10 mg/L, 100 mL). Results show that the crystallinity, size and thickness of g-C3N4 in p-gCN-NS reduced dramatically compared with those in g-C3N4 sample synthesized without the addition of NH4Cl (gCN). Specific surface area of p-gCN-NS was 63.65 m2·g−1, which was 6.7 times that of gCN. After photocatalysis for 50 min, the degradation rate of RhB achieved 99.32% by p-gCN-NS (100 mg), whose reaction rate constant (k = 0.09317 min−1) was 10.6 times higher than that of gCN. p-gCN-NS also exhibited excellent photocatalytic activity for degrading colorless tetracycline aqueous solution. The significant improvement of photocatalytic performance can be credited to the reduced sized and thickness of g-C3N4, higher specific surface area and pore structure, as well as the weakened recombination rate of photogenerated electron–hole pairs in p-gCN-NS. This work provides a feasible and facile method for synthesis porous g-C3N4 composed of nanosheets with excellent photocatalytic performance. [ABSTRACT FROM AUTHOR]

Flower-like Mg–Al–CO 3 layered double hydroxide (MgAl-LDH) nanospheres with specific surface area of 221.95 m2/g were synthesized by modified aqueous miscible organic solvent treatment method. Via the electrostatic self-assembly method, MgAl-LDH and g-C 3 N 4 nanosheets (CNNS), with the mass ratio of 1:10, 3:10, 5:10, 7:10, and 10:10, respectively, were assembled to prepare MgAl-LDH/g-C 3 N 4 composites (MCN-X, X = 1, 3, 5, 7, and 10). The mass ratio of MgAl-LDH to g-C 3 N 4 nanosheets affected the microstructure, optical and photo-electrochemical properties, and the removal efficiency toward methyl orange (MO), of MCN-X composites. The adsorption and photocatalytic degradation performance for MO by all MCN-X composites were better than those by pure g-C 3 N 4 nanosheets. With the increasing of MgAl-LDH content, the adsorption rate and removal rate of MO by MCN-X composites increased firstly and then decreased gradually. The optimum performance was achieved by MCN-5, which removed 93.58 % of MO molecules after 30 min of dark adsorption and 120 min of photocatalytic degradation, and its pseudo-first-order reaction rate constants (k) value (0.0177 min−1) was 3.4 times that of CNNS. Reasons for these results were the enhanced specific surface area, the narrowed band gap, the inhibited recombination and the improved separation and migration of photo-generated carriers, as well as the excellent adsorption ability of MCN-5. This work provides a feasible strategy for synthesizing high performance MgAl-LDH/g-C 3 N 4 composite photocatalyst. [ABSTRACT FROM AUTHOR]

Three phase nanocomposites g-C 3 N 4 /rGO/TiO 2 were synthesized successfully under hydrothermal reaction conditions using g-C 3 N 4 nanosheets as matrix, as well as TiO 2 sol and graphene oxide as the precursors of nano-size anatase and reduced graphene oxide (rGO), respectively. The photocatalytic performance of samples was investigated by degrading Rhodamine B (RhB) solution under sunlight irradiation with a xenon lamp. The results show that g-C 3 N 4 /rGO/TiO 2 three-phase composite nanomaterial was successfully prepared. g-C 3 N 4 /rGO/TiO 2 exhibited a satisfactory photocatalytic activity and cycle stability when the mass ratio of g-C 3 N 4 nanosheets (0.6 g) to nano-TiO 2 (0.2 g) was 3:1, the mass of GO was 0.002 g, the hydrothermal temperature and time were 160 °C and 6 h, respectively. When photocatalysis for 60 min, the degradation rate of RhB solution (100 mL, 10 mg/L) by g-C 3 N 4 /rGO/TiO 2 (100 mg) reached 99.63%. Main reasons for these results lie in the significantly improved separation efficiency of photogenerated electron-hole pairs due to the construction of g-C 3 N 4 /TiO 2 heterojunction, the enhanced optical absorption and the increased specific surface area. [Display omitted] • g-C 3 N 4 /rGO/TiO 2 nanocomposite was prepared by a facile process. • The g-C 3 N 4 nanosheets were below 10 nm and the diameter of nano-TiO 2 was about 10 nm. • g-C 3 N 4 /rGO/TiO 2 nanocomposite exhibited excellent photocatalytic activity and degraded RhB within 50 min under visible light. • Rate constant value of g-C 3 N 4 /rGO/TiO 2 is 8.99 times higher than that of common g-C 3 N 4. [ABSTRACT FROM AUTHOR]