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In this study, the g-C3N4 with simultaneous isotype heterojunction and porous structure showed superior photocatalytic decomposition of tetracycline hydrochloride (TCH) under white LED light irradiation fabricated via a thermal polycondensation method using melamine and thiourea as precursors and NH4Cl as soft-template. X-ray diffraction and transmission electron microscopy demonstrated the successful fabrication of the heterojunction between two different phases of g-C3N4 metal-free semiconductor. Besides, the increase in surface area as well as the porosity of g-C3N4 isotype heterojunction compared with CN-M (the g-C3N4 was synthesized using melamine as precursor) or CN-T (the g-C3N4 was synthesized using thiourea as precursor) was confirmed through nitrogen adsorption–desorption isotherms. The improved photocatalytic degradation of TCH over CN-MT (the g-C3N4 was synthesized using melamine and thiourea as precursors and NH4Cl as soft-template) compared to CN-M and CN-T could be assigned to the visible light absorption expansion, the increase in surface area as well as the porosity and reduction of photo-generated electron–hole pair recombination. Specifically, the CN-MT-1:1 isotype heterojunction revealed the highest photocatalytic activity for TCH degradation (81.55%) within 180 min. Furthermore, this catalyst can be recycled four times, which demonstrates the potential of CN-MT as a visible light-sensitive catalyst for organic pollutant removal. [ABSTRACT FROM AUTHOR]

Graphitic carbon nitride (g-C3N4) has received much interest as a visible-light-driven photocatalyst for degrading pollutants such as organic dyes and antibiotics. However, g-C3N4 bulk activity could not meet expectations due to its rapid recombination of photogenerated electron–hole pairs and low specific surface area. In our study, melamine was thermally treated one-step in the presence of NH4Cl to produce g-C3N4 nanosheets. The characterizations of surface morphology and optical properties of all g-C3N4 samples were investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectrum (XPS), transmission electron microscopy (TEM), and UV–visible diffuse reflectance spectroscopy. Compared to bulk g-C3N4, g-C3N4 nanosheets demonstrated excellent photocatalytic activities, with approximately 98% RhB removal after 210 min of visible light irradiation. Furthermore, the effect of catalyst dosage, pH, and RhB concentration on the removal percentage dye of g-C3N4 nanosheets was also investigated. h+ and •O2− species were demonstrated as the key reactive species for the RhB. Besides, ECN exposed a tetracycline degradation efficiency of 80.5% under visible-light irradiation for 210 min, which is higher than BCN (60.8%). The improved photocatalytic activity of g-C3N4 nanosheets is due to the restriction of the recombination of photogenerated electrons/hole pairs, as provided by photoluminescence spectra and Nyquist plot. As a result, our research may offer an effective approach to fabricating g-C3N4 nanosheets with high photocatalytic activity and high stability for environmental decontamination. [ABSTRACT FROM AUTHOR]

The effects of the substitution of V5+ with Ni2+ at the corresponding sites in BiVO4 on the crystal structures, optical properties, and photocatalytic efficiency of BiVO4 was investigated. Ni2+ cations doped at the V5+ sites in BiVO4 was confirmed by X-ray diffraction, Raman, X-ray photoelectron spectroscopy, ultraviolet–visible diffuse reflectance spectra, and photoluminescence spectra. Ni-doped BiVO4 exhibited excellent degradation of crystal violet (CV) compared with the bare BiVO4. For optimal Ni2+ doping of 5%, the degradation rate of CV, which reached about 95% within 180 min of LED light irradiation, was obtained. Ni doping can introduce advantageous defect states that significantly increase the separation and diffusion efficiency of the photo-induced charge carriers, thereby boosting the photocatalytic activity of crystal structures. [ABSTRACT FROM AUTHOR]