Photocatalytic Properties Of g-C3N4 Research Articles

Effect of processing temperature on structure and photocatalytic properties of g-C3N4

Graphitic carbon nitride (g-C3N4) photocatalysts were synthesized by thermal polycondensation of melamine at different temperatures (450°C, 550°C and 650°C). The crystalline structure, morphology, porosity, composition and light absorption of the materials were thoroughly investigated. Furthermore, their photocatalytic activity was evaluated by NO oxidation under UV and visible light irradiation. The results showed that the structural and optical properties highly depend on the process temperature and thus the degree of polycondensation. The best photocatalytic activity was exhibited by the sample prepared at 450°C and the possible reasons were discussed.

Microwave-assisted synthesis and enhanced visible-light-driven photocatalytic property of g-C3N4/Bi2S3 nanocomposite

g-C3N4/Bi2S3 composites have been prepared via microwave-assisted in situ crystal growth reaction and the products exhibit enhanced photocatalytic performances for degrading methyl orange (MO) under visible-light irradiation. X-ray diffraction (XRD) and transmission electron microscopy (TEM) results show that the Bi2S3 nanoparticles have good crystallinity and are uniformly deposited on the surface of g-C3N4 sheet. In addition, the size and morphology of the Bi2S3 nanoparticles were found to be mediated by g-C3N4. Optical measurement results evidence that the hybridization of Bi2S3 with g-C3N4 can increase visible-light absorption and facilitate the separation of photo-generated electron–hole pairs, thereby improving the photocatalytic activity of the g-C3N4/Bi2S3 composites. This study demonstrated a new strategy for the design of a heterostructure with favorable photocatalytic property.

Acid-treated g-C3N4 with improved photocatalytic performance in the reduction of aqueous Cr(VI) under visible-light

An alternative simple, economical and efficient acid-soaking method was proposed to improve the activity of g-C3N4 for photocatalytic reduction of aqueous Cr(VI) in this work. The improvement was achieved simply by soaking g-C3N4 (which was obtained by heating melamine in air at 550°C for 4h) in 5mol/L HNO3 or HCl aqueous solution for 2h (the HNO3 and HCl-treated samples were denoted as g-C3N4HNO3 and g-C3N4HCl, respectively). The compositions, structures, Brunner–Emmet–Teller (BET) specific surface areas, Zeta potentials and optical properties of g-C3N4, g-C3N4HNO3 and g-C3N4HCl were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, N2 adsorption/desorption isotherms, Zeta potential analyzer and UV–vis diffuse reflectance spectroscopy. The photocatalytic properties of g-C3N4, g-C3N4HNO3 and g-C3N4HCl were tested in the reduction of aqueous Cr(VI) under visible-light (λ>420nm) irradiation. It was observed that both g-C3N4HNO3 and g-C3N4HCl exhibited higher photocatalytic activity than g-C3N4. The higher photocatalytic activities of acid-treated samples may be attributed to their larger BET specific surface areas, positive surface charges and larger adsorption capacities for Cr(VI). Furthermore, the soaking treatment with 5mol/L HNO3 aqueous solution can not only remove the Cr(III) species deposited on the surface of g-C3N4HNO3 after use in photocatalytic reduction of aqueous Cr(VI), but also enhance the photocatalytic efficiency of g-C3N4HNO3 in reuse.