Reduced electron/hole recombination in Z-scheme nanostructure of zeolitic imidazolate framework-11/graphitic carbon nitride as photocatalyst under visible light

Abstract

In this research, for the first time, the synthesis of nanostructure of zeolitic imidazolate framework-11/graphitic carbon nitride (ZIF-11/g-C3N4 X) with different weight of g-C3N4 (X: 0.01, 0.1, 0.3 g) is reported. Their performance was compared in photocatalytic degradation of MB under visible light. Synthetic samples were characterized by X-Ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectrometer (XPS), diffused reflectance spectroscopy (DRS), Field emission scanning electron microscopy (FE-SEM), Transmission electron microscope (TEM), Brunauer–Emmett–Teller (BET), Electrochemical Impedance Spectroscopy (EIS) and Photoluminescence (PL) analysis. Based on the results, Z-scheme ZIF-11/g-C3N4 0.3 was selected as the best sample. FESEM and TEM images indicated that g-C3N4 sheets were complicated on the surface of ZIF-11 with rhombic dodecahedron (RHO) morphology. The surface area and band gap of ZIF-11/g-C3N4 0.3 was determined as 174.5 m2/g and 2.58 eV, respectively. The recombination of charge carriers in the ZIF-11/g-C3N4 0.3 nanostructure was reduced. Photocatalytic degradation efficiency of MB (5 ppm), pH = 7, visible irradiation (120 W-60 min) using 0.1 g of ZIF-11/g-C3N4 0.3 was achieved 72.7% with first-order kinetic model and acceptable stability in three consecutive cycles. Further, the total organic carbon (TOC) removal rate by ZIF-11/g-C3N4 0.3 after 5 h were 66.5%.

One-step hydrothermal synthesis of CeVO4/bentonite nanocomposite as a dual-functional photocatalytic adsorbent for the removal of methylene blue from aqueous solutions

“…8 b). The photocatalyst surface has a positive and negative charge at pH values lower and higher than pH pzc , respectively 34 , 35 . Therefore, in high pH solutions, the photocatalyst surface has a more negative charge.…”

“…O 2 – ), and hydroxyl radical ( . OH) 35 . In this regards, the efficiency of photocatalytic degradation of MB after adding sodium chloride, ethanol, and methanol as h + , e – , and .…”

“…On the other hand, in the valence band of the photocatalyst, hydroxyl oxidizing radicals are formed from the reaction of h + with water molecules, which play an effective role in destroying dye adsorbed on the surface of the photocatalyst. The following chain reactions have been widely postulated 35 – 39 . …”