Yanhua Song

Exfoliated graphene-like carbon nitride in organic solvents: enhanced photocatalytic activity and highly selective and sensitive sensor for the detection of trace amounts of Cu2+

Due to their unprecedented electronic, surface and optical properties, the atomic-thick graphene-like materials have aroused great interest. Compared with the bulk counterparts, the graphene-like material can not only enhance the internal properties, but also gives rise to new promising properties. Herein, the graphene-like carbon nitride (graphene-like C3N4) was synthesized via liquid exfoliation from the bulk graphitic carbon nitride (g-C3N4) in 1,3-butanediol (1,3-BUT) for the first time. And the graphene-like C3N4 was characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), transmission electron microscopy (TEM), thermogravimetric analysis (TG), and X-ray photoelectron spectroscopy (XPS). The obtained graphene-like C3N4 exhibited a two-dimensional thin-layer structure with about 3–6 atoms thickness, a high specific surface area of 32.54 m2 g−1, increased photocurrent responses, improved electron transport ability and enhanced photocatalytic activity. The photocatalytic reaction for the organic dye methylene blue (MB) by the graphene-like C3N4 followed first-order kinetics. Moreover, the graphene-like C3N4 exhibited a higher apparent rate of 0.1262 min−1, which was 3.1 times higher than that of the bulk g-C3N4 (0.0409 min−1). The enhanced photocatalytic reaction was due to a high specific surface area and a larger bandgap (by 0.14 eV). The yield of the graphene-like C3N4 was up to ∼0.35 mg mL−1. Moreover, the graphene-like C3N4 had a new property that it could be used as the sensor for trace amounts of Cu2+ determination, so the graphene-like C3N4 is a new but promising candidate for heavy metal ions (Cu2+) determination in water environment. Photoelectrochemical selective sensing of trace amounts of Cu2+ was also discussed.

Synthesis and characterization of g-C3N4/Ag2CO3 with enhanced visible-light photocatalytic activity for the degradation of organic pollutants

A facile, simple method was developed for the synthesis of g-C3N4/Ag2CO3 at room temperature. The samples were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), transmission electron microscopy (TEM), diffuse reflectance spectroscopy (DRS) and Fourier transformed infrared (FT-IR) spectroscopy. The photocatalytic activity of g-C3N4/Ag2CO3 composites for the photo-degradation of methyl orange (MO) was much higher than that of the pure Ag2CO3. The kinetics of the g-C3N4/Ag2CO3 composites were proposed. The electrochemical impedance spectroscopy of g-C3N4/Ag2CO3 composites and a series of radical trapping experiment were also carried out to explore the possible photocatalytic mechanism. The results indicated that the enhanced photocatalytic activity of g-C3N4/Ag2CO3 composites under visible light irradiation was attributed to the formed heterostructure between g-C3N4 and Ag2CO3, which was beneficial to the separation of the photoinduced electron–hole pairs.

Ion-exchange preparation for visible-light-driven photocatalyst AgBr/Ag2CO3 and its photocatalytic activity

The AgBr/Ag2CO3 composite was synthesized by an ion-exchange reaction. The physical and chemical properties of the catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), transmission electron microscopy (TEM), diffuse-reflection spectra (DRS) and photocurrent techniques. The photocatalytic performance of the samples was evaluated by photocatalytic oxidation of methylene blue (MB) dye under visible-light irradiation. The XRD, SEM-EDS, TEM, and XPS analyses indicated that the heterojunction structure had been obtained. The results indicated that the AgBr/Ag2CO3 heterojunction had exhibited a much higher photocatalytic activity than the pure Ag2CO3. The enhancement of photocatalytic activity was related to the efficient separation of electron–hole pairs because of the stagger band potentials between AgBr and Ag2CO3.

Graphene-analogue boron nitride/Ag3PO4 composite for efficient visible-light-driven photocatalysis

Graphene-analogues BN modified Ag3PO4 photocatalysts were successfully prepared. The composites were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), UV-visible diffuse reflectance spectroscopy (DRS), Fourier transformed infrared (FT-IR) spectroscopy and photoelectrochemical experiments. The results showed that after adding a small amount of graphene-analogue BN, the composite photocatalysts exhibited significantly enhanced photocatalytic activity and good stability for the photocatalytic degradation of RhB. The 0.5 wt% BN content sample showed the best photocatalytic activity. The increasing photocatalytic efficiency of the graphene-analogue BN/Ag3PO4 photocatalyst could be attributed to the synergetic role between graphene-analogue BN and Ag3PO4, which suppressed the recombination of photogenerated electron–hole pairs. It was found that the photocatalytic degradation of RhB by the photocatalyst followed pseudo-first-order kinetics. The photocatalytic mechanism of the graphene-analogue BN/Ag3PO4 composite was also investigated.

Modification of Ag3VO4 with graphene-like MoS2 for enhanced visible-light photocatalytic property and stability

Graphene-like MoS2 photocatalysts were synthesized by the hydrothermal method. The obtained graphene-like MoS2/Ag3VO4 composites were characterized using a series of techniques to determine their structures and properties. Due to elevated photogenerated electron separation and strong hole oxidizability as well as light harvesting, the obtained graphene-like MoS2/Ag3VO4 composites display enhanced properties for the degradation of methylene blue (MB) and rhodamine B (RhB) in comparison with pure Ag3VO4 under visible light illumination. The degradation kinetics of the graphene-like MoS2/Ag3VO4 composites for MB and RhB were calculated to demonstrate their excellent photocatalytic activities. Electrochemical impedance spectroscopy (EIS) Nyquist plots were obtained to determine the electron transfer and recombination processes of the graphene-like MoS2/Ag3VO4 composite. The possible photocatalytic mechanism of the graphene-like MoS2/Ag3VO4 composites is proposed based on active species trapping experiments. Results show that the formative interface between graphene-like MoS2 and Ag3VO4 accelerates the electron transfer performance.

Non-metal photocatalyst nitrogen-doped carbon nanotubes modified mpg-C3N4: facile synthesis and the enhanced visible-light photocatalytic activity

Nitrogen-doped carbon nanotubes (N-CNT) is a promising metal-free candidate and electronic acceptor. It has been employed to modify mesoporous carbon nitride (mpg-C3N4) for photocatalytic degradation of organic dye and antibiotics under visible-light irradiation. Herein, we report a facile synthesis strategy involving polymerization of cyanamide as the precursor in the presence of N-CNT via thermal polycondensation. The morphology and structure of as-prepared N-CNT/mpg-C3N4 were analyzed by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The N-CNT/mpg-C3N4-15 exhibited increased photocatalytic activity for rhodamine B (RhB), methyl orange (MO) and tetracycline hydrochloride (TC) degradation compared with the pure one under visible-light irradiation, which is mainly due to the efficiently separation of photogenerated electron-hole pairs for the introduction of N-CNT as electronic acceptor. The photocatalytic reaction can fit the first order kinetics. Additionally, superoxide radical (O2-) was regarded as main reactive species participating in the photodegradation reaction process. Furthermore, the reason for enhancing photocatalytic activity of N-CNT/mpg-C3N4 is mainly attributed to synergistic effects between mpg-C3N4 as main ingredient and N-CNT as electron acceptor.

Hydrothermal synthesis of mpg-C3N4 and Bi2WO6 nest-like structure nanohybrids with enhanced visible light photocatalytic activities

To overcome the shortcomings of low photocatalytic efficiency, mpg-C3N4/Bi2WO6 photocatalysts have been successfully designed via a facile hydrothermal method. A succession of techniques was used to explore the morphology, structure, surface composition and photocatalytic property of the mpg-C3N4/Bi2WO6 material. The mpg-C3N4/Bi2WO6 nanohybrid has high photocatalytic performance for the degradation of tetracycline hydrochloride (TC) and rhodamine B (RhB). Holes, ·O2− and ·OH radicals are determined to be the active species in the process of photocatalytic degradation by ESR and capture experiments. The ultrathin thickness of nest-like Bi2WO6 and the introduction of mpg-C3N4 into the Bi2WO6 matrix can improve the photocatalytic efficiency. The photocatalytic Z-scheme mechanism of the system was also discussed in detail. This work paves the way for preparing visible-light-driven nanocomposites for pollutant degradation.

A silver on 2D white-C3N4 support photocatalyst for mechanistic insights: synergetic utilization of plasmonic effect for solar hydrogen evolution

A photocatalyst integrating silver surface plasmon effect into two-dimensional g-C3N4 nanosheets (2D white-C3N4) was prepared successfully. The crystal structure, chemical states, morphology and photocatalytic performance of the prepared samples were researched by the comprehensive characterization methods. The photocatalytic activities of Ag/2D white g-C3N4 composites were dramatically enhanced under visible light irradiation. When Ag content was optimized, 2% Ag/white g-C3N4 exhibited the best photocatalytic activity. The electrochemical investigation verified the role of the hot electrons from the plasmonic Ag in the photocatalytic reaction. The plasmonic hot electron injection and advantages of 2D ultrathin structure improved the density of the electrons with reducibility and led to more efficient separation of photogenerated electron and hole pairs. The photocatalytic mechanism was also researched in detail via ESR analysis.

Synthesis and characterization of BN/Bi2WO6 composite photocatalysts with enhanced visible-light photocatalytic activity

Bi2WO6 modified with few-layer BN was synthesized by an impregnation method. The as-prepared products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible diffuse reflection spectroscopy (DRS) and Fourier transform infrared spectroscopy (FT-IR). The as-prepared BN/Bi2WO6 photocatalysts exhibited a higher photocatalytic activity for the degradation of Rhodamine B (RhB) than the pure Bi2WO6. The 3 wt% BN/Bi2WO6 photocatalyst showed the best photocatalytic activity and high stability after five runs under visible light irradiation. The enhanced visible-light photocatalytic activity could be attributed to the synergetic effect of few-layer BN and Bi2WO6.

WO3 nanorod photocatalysts decorated with few-layer g-C3N4 nanosheets: controllable synthesis and photocatalytic mechanism research

Novel WO3 nanorod (WO3 NRs) photocatalysts decorated with few-layer g-C3N4 nanosheets (flg-C3N4) have been synthesized by a typical hydrothermal process. The structure, morphology, optical and electronic properties were researched by comprehensive characterization methods. The photocatalytic performance of flg-C3N4/WO3 NRs nanocomposites was assessed by degrading Rhodamine B (RhB) dye under visible light irradiation. When the loading amount of the flg-C3N4 is 20 wt%, the flg-C3N4/WO3 NRs nanocomposites exhibit the highest activity and the Chemical Oxygen Demand (COD) values decreased by about 64%. The improved light harvesting ability and higher separation efficiency of photoinduced electron–hole pairs by the decoration of flg-C3N4 lead to the boosting photocatalytic performance. In addition, through ESR analysis and a trapping experiment, the photocatalytic mechanism was also researched.