Chunquan Li

Facile synthesis of two clay minerals supported graphitic carbon nitride composites as highly efficient visible-light-driven photocatalysts

To overcome rapid electron-hole recombination and low adsorption capacity of single g-C3N4 photocatalyst, the present work reports on the fabrication of two kinds of visible-light-driven composite photocatalysts (g-C3N4/kaolinite and g-C3N4/illite composites). 2D/2D assembly was successfully achieved in this work. Furthermore, the as-synthesized composites exhibited significantly enhanced photocatalytic activity under visible-light irradiation, whose reaction rate constants were almost 4.13 times (g-C3N4/kaolinite) and 3.18 times (g-C3N4/illite) that of pure g-C3N4. A plausible reaction mechanism over the as-prepared composite photocatalysts was also proposed based on the experimental results obtained. The photocatalytic enhancement of synthesized composites should be attributed to the intimate interface contact between g-C3N4 and layered minerals, resulting in better dispersion performance, higher charge separation efficiency as well as stronger adsorption ability.

Facile synthesis and enhanced visible-light photoactivity of a g-C3N4/mullite composite

A novel g-C3N4/mullite composite with enhanced visible light-driven photoactivity was prepared through a facile wetting chemical method. The microstructure, interfacial and optical properties of the obtained g-C3N4/mullite composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), surface area measurement (BET), and UV-visible diffused reflectance spectroscopy (UV-vis DRS), respectively. It is indicated that a tight interfacial combination was formed between g-C3N4 and mullite, which is beneficial for the transfer of electrons and the enhancement of quantum efficiency. Compared with pure g-C3N4 or a g-C3N4 + mullite physical mixture, the synthesized g-C3N4/mullite composites exhibit significantly enhanced photoactivity under visible light irradiation, almost 6.5 times that of the pure g-C3N4 and around 10.0 times that of a g-C3N4 + mullite physical mixture for the degradation of tetracycline. The enhanced photoactivity of the g-C3N4/mullite composite could be attributed not only to its stronger visible light adsorption and enhanced adsorption capacity for pollutants but also to the strong interfacial combination between g-C3N4 and mullite, effectively reducing the recombination probability of photogenerated electron–hole pairs.

Synthesis of novel ternary heterogeneous BiOCl/TiO2/sepiolite composite with enhanced visible-light-induced photocatalytic activity towards tetracycline

In this study, the novel ternary heterogeneous BiOCl/TiO2/sepiolite composite with enhanced visible-light-induced photocatalytic activity was synthesized via the hydrolysis precipitation method followed by a calcination crystallization process. The as-prepared samples were characterized by X-ray diffraction (XRD), UV-VIS diffused reflectance spectroscopy (DRS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption-desorption, X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL), respectively. Compared with bare BiOCl and TiO2, the ternary heterogeneous structure in BiOCl/TiO2/sepiolite significantly improved the visible-light-induced photocatalytic performance towards tetracycline (TC), and also contributed to the separation efficiency and recyclability of the photocatalyst. In addition, the influence of the mass ratio of BiOCl in the composites was also discussed, and the optimal mass ratio is identified as 50% (mBiOCl/(mTiO2 + mBiOCl). Furthermore, TC degradation by-products were further detected by HPLC-MS/MS, and a possible degradation pathway was proposed. Besides, ESR (Electron spin resonance) results indicated that the main active radical species were photo-induced holes (h+) and superoxide radical (O2-) in the TC degradation process. Hence, the enhanced photocatalytic activity of the prepared ternary composite was mainly attributed to the remarkable synergistic effect within the BiOCl/TiO2/sepiolite ternary heterogeneous system, resulting in the superior adsorption activity, the outstanding visible-light response performance and the efficient separation of the photogenerated electron-hole pairs. It is speculated that the novel ternary heterogeneous BiOCl/TiO2/sepiolite composite would have a broad application prospect in the field of wastewater treatment.