g-C3N4 Heterojunction Photocatalysts Research Articles

In-Situ Synthesis of Highly Efficient Direct Z-Scheme Cu3P/g-C3N4 Heterojunction Photocatalyst for N2 Photofixation

In this work, a highly efficient p-type Cu3P/[Formula: see text]-type g-C3N4 heterojunction photocatalyst was synthesized in situ. XRD, UV–Vis, N2 adsorption, TEM, XPS, PL, and EIS are used to characterize the as-prepared catalysts. The results show that Cu3P nanoparticles are highly dispersed onto the g-C3N4 surface, which obviously promotes the separation rate of electrons and holes. The charge transfer between Cu3P and g-C3N4 follows the “Z-scheme” mechanism. The as-prepared Cu3P/g-C3N4 heterojunction photocatalyst displays the ammonium ion production rate of 7.5[Formula: see text]mg[Formula: see text]L[Formula: see text][Formula: see text]h[Formula: see text][Formula: see text]g[Formula: see text], which is 28.8 times higher than that of neat g-C3N4, as well as good catalytic stability. The possible reaction mechanism is proposed.

Boosting photocatalytic activity under visible-light by creation of PCN-222/g-C3N4 heterojunctions

Metalloporphyrin metal-organic frameworks are excellent photocatalyst candidates due to their strong visible-light absorbing ability, high specific surface areas, and semiconductive properties. Herein, we constructed a visible-light driven PCN-222/g-C3N4 heterojunction via a facile one-pot solvothermal method. The optimum composite with 1.0 wt% PCN-222/g-C3N4 showed the superior photocatalytic activity for degradation of RhB and Ofloxacin under visible-light irradiation, which are 3.1 and 2.97 times higher than pure g-C3N4 under same conditions. The enhanced photocatalytic activity of the PCN-222/g-C3N4 composite is attributed to the extended light response range, fast generation and efficient separation of the photo-generated carrier, and enhanced adsorption capacity of organic contaminants. Besides O2− radical and hVB+ species, OH radical is also the active species in the PCN-222/g-C3N4 photocatalytic system, which may be additional evidence for the enhanced photocatalytic activity of PCN-222/g-C3N4 with respect to pristine g-C3N4. As-prepared PCN-222/g-C3N4 photocatalyst shows excellent recyclability, which can be reused four times without significant inactivation. Therefore, PCN-222/g-C3N4 heterojunction photocatalysts have great potentiality in organic wastewater treatment.

High-performance for hydrogen evolution and pollutant degradation of reduced graphene oxide/two-phase g-C3N4 heterojunction photocatalysts.

We have successfully synthesized the composites of two-phase g-C3N4 heterojunction photocatalysts by one-step method. And the reduced graphene oxide/two-phase g-C3N4 heterojunction photocatalyst was fabricated via a facile hydrothermal reduction method. The characterization results indicated that the two-phase g-C3N4 was integrated closely, and the common phenomenon of agglomeration for g-C3N4 was significantly reduced. Moreover, the oxidized graphene was reduced successfully in the composites and the graphene was overlaid on the surface or the interlayers of g-C3N4 heterojunction composite uniformly. In addition, we have carried out the photocatalytic activity experiments by H2 evolution and rhodamine B removal, tetracycline removal under the visible light irradiation. The results revealed that the composite has improved the separation efficiency a lot than the pure photocatalyst. The photocurrent test demonstrated that the recombination of electrons and holes were efficiently inhibited as well as enhanced the photocatalytic activity. The 0.4% rGO loaded samples, 0.4% rGOCN2, own the best performance. Its rate of H2 evolution was 15 times as high as that of the pure g-C3N4.

Fabrication of a TiO2 trapped meso/macroporous g-C3N4 heterojunction photocatalyst and understanding its enhanced photocatalytic activity based on optical simulation analysis

The enhanced photocatalytic performance of a TiO2 nanoparticle trapped meso/macroporous g-C3N4 heterojunction photocatalyst is strongly related to its enhanced light absorption as revealed by optical simulation.

High efficiency visible-light-driven Fe2O3-xSx/S-doped g-C3N4 heterojunction photocatalysts: Direct Z-scheme mechanism

Several nanoporous Fe2O3-xSx/S-doped g-C3N4 (CNS) Z-scheme hybrid heterojuctions have been successfully synthesized by one-pot in situ growth of the Fe2O3-xSx particles on the surface of CNS. The characterization results show that S-doping in the g-C3N4 backbone can greatly enhance the charge mobility and visible light harvesting capability. In addition, porous morphology of hybrid composite provides available open pores for guest molecules and also improves light absorbing property due to existence of multiple scattering effects. More importantly, the Fe2O3-xSx nanoparticles formed intimate heterojunction with CNS and developed the efficient charge transfer by extending interfacial interactions occurred at the interfaces of both components. It has been found that the Fe2O3-xSx/CNS composites have an enhanced photocatalytic activity under visible light irradiation compared with isolated Fe2O3 and CNS components toward the photocatalytic degradation of methylene blue (MB). The optimal loaded Fe2O3-xSx value obtained is equal to 6.6wt% that provided 82% MB photodegradation after 150min with a reaction rate constant of 0.0092min−1 which was faster than those of the pure Fe2O3 (0.0016min−1) and CNS (0.0044min−1) under the optimized operating variables acquired by the response surface methodology. The specific surface area and the pore volume of Fe2O3(6.6)/CNS hybrid are 33.5m2/g and 0.195cm3/g, which are nearly 3.8 and 7.5 times greater compared with those of the CNS, respectively. The TEM image of Fe2O3(6.6)/CNS nanocomposite exhibits a nanoporous morphology with abundant uniform pore sizes of around 25nm. Using the Mott-Schottky plot, the conduction and valence bands of the CNS are measured (at pH=7) equal to −1.07 and 1.48V versus normal hydrogen electrode (NHE), respectively. Trapping tests prove that OH and O2− radicals are major active species in the photocatalytic reaction. It has been established that formation of the Z-scheme Fe2O3(6.6)/CNS heterojunction between CNS and Fe2O3 directly produces OH as well as O2− radicals which is consistent with the results obtained from trapping experiments.

Visible-light-driven in situ inactivation of Microcystis aeruginosa with the use of floating g-C3N4 heterojunction photocatalyst: Performance, mechanisms and implications

The frequent cyanobacterial harmful algal blooms (cyano-HABs) occurring in aquatic ecosystems pose a threat to human and animal health. In this study, a novel floating, visible-light-driven catalyst was prepared by depositing g-C3N4 on a composite expanded perlite (i.e., EP/Al2O3) via a facile impregnation-calcination method for the photocatalytic inactivation of Microcystis aeruginosa. Consideration has been given to the influence of different dosages of g-C3N4 precursors with the synthesized photocatalysts characterized using XRD, N2 adsorption/desorption, electron microscopy, FT-IR spectra, XPS and UV–vis absorption spectra. Results of this study show that sheet-like g-C3N4 were well dispersed on the surface of EP/Al2O3 with the heterojunction photocatalyst (CAE-2) with a dicyandiamide to EP/Al2O3 ratio of 2:1 demonstrating the highest specific surface areas (i.e., 56.7 m2/g). Under 6 h of irradiation, 74.4% of M. aeruginosa at an initial concentration of 2.7 × 106 cells/mL could be removed with the use of CAE-2 of 2 g/L. In the photocatalytic inactivation process, algae cell lysis is mainly ascribed to the attack by the reactive oxygen species (ROSs) generated on the semiconductor surface, with the predominant species (i.e., HO) causing the damage of membrane permeability with cations and cellular organic matters released into the solution though the cellular organic matters including microcystin-LR could readily be removed by the photocatalysts. Continuous monitoring by using flow cytometry and measuring the maximum photochemical efficiency of PSII indicated that cell apoptosis and reduction of photosynthetic activity occurred as a result of the inactivation. This study presents a promising technology for the remediation of cyano-HABs in open waters.

2D graphitic-C3N4 hybridized with 1D flux-grown Na-modified K2Ti6O13 nanobelts for enhanced simulated sunlight and visible-light photocatalytic performance

Novel 1D/2D hybrid Na-K2Ti6O13/g-C3N4 heterojunction photocatalysts with enhanced simulated sunlight and visible-light photocatalytic performance have been successfully fabricated using a facile mixing–calcination method.