Haiyan Ji

Construction of a 2D Graphene‐Like MoS2/C3N4 Heterojunction with Enhanced Visible‐Light Photocatalytic Activity and Photoelectrochemical Activity

A novel graphene-like MoS2 /C3N4 (GL-MoS2/C3N4) composite photocatalyst has been synthesized by a facile ethylene glycol (EG)-assisted solvothermal method. The structure and morphology of this GL-MoS2/C3N4 photocatalyst have been investigated by a wide range of characterization methods. The results showed that GL-MoS2 was uniformly distributed on the surface of GL-C3N4 forming a heterostructure. The obtained composite exhibited strong absorbing ability in the ultraviolet (UV) and visible regions. When irradiated with visible light, the composite photocatalyst showed high activity superior to those of the respective individual components GL-MoS2 and GL-C3N4 in the degradation of methyl orange. The enhanced photocatalytic activity of the composite may be attributed to the efficient separation of electron-hole pairs as a result of the matching band potentials between GL-MoS2 and GL-C3N4. Furthermore, a photocatalytic mechanism for the composite material has been proposed, and the photocatalytic reaction kinetics has been measured. Moreover, GL-MoS2/C3N4 could serve as a novel sensor for trace amounts of Cu(2+) since it exhibited good selectivity for Cu(2+) detection in water.

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.

High yield synthesis of nano-size g-C3N4 derivatives by a dissolve-regrowth method with enhanced photocatalytic ability

Nano-size g-C3N4 derivatives were fabricated by a simple dissolve-regrowth method in HNO3 solution followed by a calcination process. X-ray diffraction (XRD), Z-potential, elemental analysis and IR are used to investigate the structure, composition and the properties of the samples. Scanning electron microscopy (SEM) shows the average size of the nano-size g-C3N4 derivatives increases with increasing calcination temperature. Methyl orange (MO) dye was used as the target pollutant to investigate the photoactivity of the samples. The pure g-C3N4 can only degrade about 1.1% MO, while the g-C3N4 derivatives calcined at 300 °C can decompose about 31.9% of MO in 4 h. Besides, when a small amount of methylene blue (MB) solution was introduced, the g-C3N4–HNO3-300 can decompose about 75.8% in 4 h. The photoactivity of g-C3N4 was greatly enhanced after the modification process (especially with the assistance of MB). Additionally, this work supplied a simple method to modify materials with enhanced photoactivity. Finally, the possible reactive species and the possible mechanism were proposed based on Electron spin resonance (ESR) and XPS results.

Magnetic g-C3N4/NiFe2O4 hybrids with enhanced photocatalytic activity

Composite photocatalysts have attracted considerable attention in the exploration of both highly efficient and low cost materials. In this study, novel magnetic g-C3N4/NiFe2O4 photocatalysts were fabricated by a facile chemisorption method. X-ray diffraction (XRD), transmission electron microscopy (TEM), infrared spectroscopy (IR), UV-vis diffuse reflectance spectroscopy (DRS) and X-ray photoelectron spectroscopy (XPS) were utilized to analyze the structure and properties of samples, which indicated that NiFe2O4 had been integrated onto the surface of g-C3N4 successfully. The as-prepared 7.5% g-C3N4/NiFe2O4, with the best photocatalytic activity, can maintain high photocatalytic activity and stability after five runs in the presence of hydrogen peroxide under visible light irradiation. During the catalytic reaction, the synergistic effect between g-C3N4 and NiFe2O4 can accelerate photogenerated charge separation and facilitate the photo-Fenton process to get an enhanced photocatalytic activity. Moreover, the collection and recycling of photocatalyst was readily achieved owing to the distinctive magnetism of g-C3N4/NiFe2O4.

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.

Novel visible-light-driven Fe2O3/Ag3VO4 composite with enhanced photocatalytic activity toward organic pollutants degradation

In this study, a new type of high-performance visible light photocatalyst Fe2O3/Ag3VO4 was prepared by a two-step method. Fe2O3 was prepared by a solvothermal method first and then the Fe2O3/Ag3VO4 photocatalyst was synthesized with different mass ratios by a simple chemical precipitation method. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray energy dispersive spectrometry (EDS), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), UV-vis absorption spectroscopy (in DRS mode), and electrochemical impedance spectroscopy (EIS) were applied to characterize the as-prepared samples. The results showed that the as-prepared photocatalyst was uniform in the shape of particles. Photocatalytic properties of the as-prepared samples were evaluated by degrading RhB under visible light. The results showed that 1% Fe2O3/Ag3VO4 composite presented the highest photocatalytic activity. After 60 min, 96.1% of RhB was degraded by 1% Fe2O3/Ag3VO4 composite. Finally, trapping experiments confirmed that the hole (h+) and superoxide free radical (˙O2−) were the main active species in degrading RhB.

Facile synthesis of CNT/AgI with enhanced photocatalytic degradation and antibacterial ability

CNT/AgI composite with the diameter smaller than 1 µm was synthesized through a solvothermal method. The CNT/AgI hybrids were characterized by XRD, SEM, XPS, UV-Vis, photocurrent and so on. The results showed that the introduced CNT can greatly reduce the particle size of AgI without using surfactant. Besides, the introduced CNT transferred the electrons efficiently and enhanced the photoactivity of the CNT/AgI hybrids in degrading RhB dye. 0.3% CNT/AgI showed the highest photocatalytic activity, which was as high as about 2 times that of pure Ag/AgI. Trapping experiments and the electron spin resonance (ESR) results suggested the reactive species in the degradation process were h+, ˙OH and ˙O2−. Furthermore, the CNT/AgI still showed high photoactivity after 4 cycle experiments. Photocatalytic antibacterial experiments showed that the 0.3% CNT/AgI had better antibacterial ability than pure Ag/AgI. The results showed that the CNT/AgI can be used as a dual functional material in water treatment of removing the organic pollutant and killing the bacterium at the same time.

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.

Commercial Diatomite for Adsorption of Tetracycline Antibiotic from Aqueous Solution

Extensive use of antibiotics in human therapy and farming industry has resulted in their accumulation and potential hazards to the environment. In this study, diatomite, which is a siliceous rock with large surface area and high adsorptivity towards organic compounds, was used to adsorb the antibiotic tetracycline (TC) from aqueous media. The adsorption kinetics, isotherms, thermodynamics, and effects of the adsorbent amount and ionic strength were evaluated in batch adsorption experiments. The adsorption of TC onto diatomite followed the pseudo-second-order kinetics model, and the sorption equilibrium was reached in 120 min. The perfect adsorbent amount could be selected within the range of 1 ˜ 20 g·L−1. The equilibrium data at different temperatures was satisfactorily fitted to the Langmuir isotherm equation with high R2 above 0.999, and the maximum monolayer adsorption capacity of 303.03 mg·g−1 was obtained at 318 K using 1 g·L−1 diatomite. Thermodynamic parameters showed that the adsorption reaction was spontaneous and endothermic. Moreover, the adsorption of TC was insignificantly affected by the ionic strength of 0.05-1% NaCl and CaCl2, indicating that diatomite has a potential practical application as adsorbent media for removing TC from real water.

Biomimetic Superhydrophobic Surfaces

Lotus leaves are well known to be superhydrophobic and self-cleaning due to the hierarchical roughness of the leaf surfaces. The surfaces with controllable wettability may bring great advantages in a wide variety of applications and have received tremendous attention in recent years. In this review, the fundamental theories on the wettability of a hydrophobic rough solid surface and the biomimetic superhydrophobic surfaces created via various methods are summarized after a brief overview on superhydrophobic states definition. Particularly, new development of surfaces with reversible switching between superhydrophobicity and superhydrophilicity has been discussed in detail.