Photocatalytic Performance Of Catalysts Research Articles

CdIn2S4/self-assembled g-C3N4 composite material with boosted photocatalytic degradation performance: The significance of morphology and structure

The influence of morphology on the photocatalytic performance of catalysts is a critical aspect that merits further exploration. This study successfully synthesized a series of CdIn2S4/self-assembled g-C3N4 photocatalysts with varying morphologies and structures via an in-situ deposition approach. The unique combination of g-C3N4′s surface curvature and the radial-spreading layers significantly contributed to the superior photocatalytic activity observed in the optimal sample. This sample achieved an impressive 91.3 % degradation of methyl orange within 30 min and an 81.6 % degradation of tetracycline hydrochloride in 120 min. These degradation rates surpassed those of pristine g-C3N4 by factors of 13.12 and 1.14, respectively. The findings of this research offer a promising strategy for designing highly active heterojunction photocatalysts tailored for pollutant removal and guiding the uniform deposition of CdIn2S4.

Facile construction of novel Z-scheme MnWO4/Bi2S3 heterojunction with enhanced photocatalytic degradation of antibiotics

A novel Z-scheme MnWO4/Bi2S3 heterojunction was constructed by a hydrothermal method for the first time. The structure, morphology and optical absorption characterization of photocatalysts were comprehensively identified. The photocatalytic performance of catalysts was investigated by the cephalexin (CFX) and metronidazole (MTZ) degradation under LED irradiation. The degradation efficiency of binary composite was promoted compared to pure MnWO4 and Bi2S3. The enhanced performance was assigned to the Z-scheme construction, leading the broad visible-light adsorption spectrum, superior redox potential as well as impressive separation and reduced recombination of photo-induced charge carriers. The effect of catalyst dose, temperature and light intensity on photodegradation activity was studied. The effect of inorganic ions was investigated in order to simulate the actual situation. The optimal values of catalyst dose, temperature and illumination intensity were found to be 1.2 g/L, 25 °C and 400 W/m2, respectively. The maximum degradation efficiencies of 74.5% and 79.8% were achieved for CFX and MTZ, respectively. TOC removal analysis was applied to measure the mineralization of CFX (46%) and MTZ (65.2%). The degradation intermediates were distinguished by using the gas chromatography/mass spectrometry (GC/MS) analysis. The kinetic investigation of photodegradation followed the first order kinetic for both drugs. The novel binary composite depicted high stability after six cycles. The trapping experiments detected the hydroxyl (OH.) and superoxide (O2.) radicals as the main active species. This research revealed a novel Z-scheme photocatalyst as a promising strategy in order to remove antibiotics.

Advances in photocatalytic and electrocatalytic removal of chlorinated volatile organic compounds

<p indent=0mm>Chlorinated volatile organic compounds (Cl-VOCs), including chlorinated alkanes, chlorinated alkenes and chlorinated aromatic compounds and so on, is a typical kind of environmental pollutants. Due to their significant characteristics of high volatility and poor degradability, they can be transported over long distance and existed in the environmental medium for a long time. In addition, compared with ordinary VOCs, Cl-VOCs show a high toxicity and an obvious effect of mutagenesis, carcinogenesis and teratogenesis. Most of the Cl-VOCs have been listed as priority pollutants, and were monitored and controlled strictly. Therefore, the development of efficient purification and transformation technology for Cl-VOCs has attracted great attention all over the world. At present, a large number of Cl-VOCs purification and transformation technologies have been developed for different conditions and purposes, including recovery technologies (adsorption, absorption, membrane separation and condensation), destruction technologies (incineration, catalytic oxidation, photocatalytic degradation and biodegradation) and conversion technologies (dechlorination). For different types, concentrations and emission sources of Cl-VOCs, each technology shows different advantages and limitations. Among them, photocatalytic degradation and electrocatalytic dechlorination technologies have attracted extensive attention due to their advantages of highly catalytic efficiency, economic and environmental processes, and mild reaction conditions. Photocatalytic degradation mainly uses clean solar energy to stimulate the electronic transition of semiconductor materials, the excited electrons and generated holes reacted with adsorptive species on the material surface to form strong radicals. The Cl-VOCs molecules are attacked by the radicals and mineralized into inorganic molecules, like CO₂, H₂O and so on. Therefore, it is one of the most promising purification technologies for Cl-VOCs. The key of the development of photocatalytic degradation technology is the preparation of advanced photocatalysts. To accelerate the separation of photogenerated electrons and holes and improve the utilization of light energy, a series of photocatalysts have been developed, such as noble metal catalysts, transition metal catalysts and nonmetallic catalysts. Generally, the photocatalytic performance of catalyst is significantly influenced by the crystal structure, micro structure and electronic structure. Therefore, the methods of regulating physicochemical properties, semiconductor compounding (heterojunction), element doping have been used to design advanced catalyst. Furthermore, the analysis of the intermediate products and the prediction of possible degradation pathway can help us to understand the degradation reaction of Cl-VOCs. The highly environmental toxicity of Cl-VOCs mostly comes from the Cl group. The harm to environment will be greatly reduced if the Cl groups can be effectively removed. At the same time, the highly-valuable dechlorinated products can be recycled. Therefore, reductive dechlorination has become one of the most promising detoxification and remediation technologies for Cl-VOCs. Due to the high reduction potential of C−Cl bond, photocatalytic reduction of Cl-VOCs is difficult, and electrocatalytic reduction is regarded as the main method for dechlorination. According to the involved reductants, electrochemical dechlorination can be generally divided into direct electrochemical reduction method and electrocatalytic hydrodechlorination method. The developing of high performance electrocatalysts and exploring the reaction mechanism are the key points of electrochemical dechlorination technology. This paper aims to comprehensively introduce the research progress of photocatalytic degradation and electrocatalytic dechlorination technologies for Cl-VOCs purification and transformation, providing reference for the effective treatment and resource utilization of Cl-VOCs. Based on this, the mechanism of catalytic reaction and the factors affecting the activity of catalysts were summarized, which provided ideas for the rational design of advanced catalysts. Finally, the potential development trends and research directions in the field of Cl-VOCs purification and transformation were prospected.

Photocatalytic performance of crystalline titania polymorphs in the degradation of hazardous pharmaceuticals and dyes**Invited talk at 8th International Workshop on Advanced Materials Science and Nanotechnology (IWAMSN2016), 8–12 November 2016, Ha Long City, Vietnam.

In the present work, nano-sized TiO2 polymorphs (anatase, brookite, and rutile) were synthesized via hydrothermal treatment of an amorphous titania. Three polymorphs were characterized by XRD, Raman spectroscopy, SEM, UV–Vis DRS, and N2-sorption measurements. The photocatalytic degradation experiments were performed with low catalyst concentration, high organic loading under a 60 W UV–Vis solarium lamp irradiation. The photocatalytic degradation was monitored by UV–Vis spectroscopy and TOC measurements. Cinnamic acid, ibuprofen, phenol, diatrizoic acid and the dyes rhodamine B and rose bengal were used as model pollutants. The formation of intermediates was studied by ESI-TOF-MS measurements. The presence of active species was checked by quenching the activity by addition of scavengers. The photocatalytic activity decreased in the order: anatase ⩾ brookite > rutile, with growing recalcitrance of organic compounds. The differences in the activity are more pronounced in the degree of mineralization. The valence band holes and superoxide radicals were the major active species in the photocatalytic treatment with anatase and brookite, whereas hydroxyl radicals and superoxide radicals contributed mainly in the treatment with rutile explaining the lower activity of rutile. The complementary use of UV–Vis spectroscopy and TOC measurements was required to obtain a comprehensive realistic assessment on the photocatalytic performance of catalyst.

Large scale and facile synthesis of novel Z-scheme Bi2MoO6/Ag3PO4 composite for enhanced visible light photocatalyst

In this paper, a facile template-free in situ chemical method has been developed for the synthesis of novel Z-scheme Bi2MoO6/Ag3PO4 composite. The morphology, structure, crystallinity and light absorption wavelength range are investigated by using scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectrometer (EDS) and UV–vis diffuse reflectance spectroscopy (DRS). The results show that Bi2MoO6 nanoparticles uniformly disperse on the surface of Ag3PO4 photocatalyst. Furthermore, photocatalytic performance of catalysts is evaluated by degrading methylene blue (MB) under 410nm LED light, and Bi2MoO6/Ag3PO4 composite shows higher photocatalytic activity than Bi2MoO6 and Ag3PO4. Finally, Z-scheme photocatalytic mechanism is discussed.

Alcohol solvents evaporation-induced self-assembly synthesis of mesoporous TiO2−x−y C x N y nanoparticles toward visible-light driven photocatalytic activity

A one-step solvent evaporation-induced self-assembly (SEISA) process was demonstrated to prepare carbon and nitrogen co-doping mesoporous TiO2 nanoparticles (MesoTiO2−x−yCxNy-S) using an ionic liquid as carbon and nitrogen sources as well as mesoporous template. After the evaporation of different solvents (methanol, ethanol, and isopropanol) and subsequent calcinations at 773 K, the obtained MesoTiO2−x−yCxNy-S samples were systematically characterized by a variety of spectroscopic and analytical techniques, including small- and large-angle X-ray diffraction (XRD), Raman, transmission electron microscopy (TEM), N2 adsorption–desorption isotherms, Fourier transform infrared (FTIR), and X-ray photoelectron (XPS) spectroscopies. The results indicate that the solvents play an essential role on the chemical microstructure, doping elemental states, and photocatalytic performance of catalysts. The MesoTiO2−x−yCxNy-I samples have the lowest band gap of ca. 2.75 eV and strongest absorbance of visible light in the range of 400–600 nm. Among the MesoTiO2−x−yCxNy-S photocatalysts, the MesoTiO2−x−yCxNy-M catalysts show superior photocatalytic activity of hydrogen generation in methanol aqueous solution under visible light irradiation as compared to MesoTiO2−x−yCxNy-E, MesoTiO2−x−yCxNy-I, and commercial Degussa TiO2. This result could be attributed to the moderate C,N co-doping amounts on their developed mesoporous texture (pore size = 8.0 nm) and high surface area (107 m2 g−1) of TiO2 (crystallite size = 9.9 nm) in the MesoTiO2−x−yCxNy-M catalysts.

High photocatalytic activity of silver-loaded ZnO-SnO2 coupled catalysts

Abstract In order to improve the photocatalytic activity of ZnO, ZnO-SnO2 coupled catalysts and Ag/ZnO-SnO2 catalysts with different Ag contents (1–5%) were prepared through the coprecipitation method. The samples were characterized by X-ray diffraction, UV–vis diffuse reflectance spectroscopy, specific surface area, and transmission electron microscopy combined with energy dispersive spectroscopy. The degradation rate of methyl orange shows that the photocatalytic activity of ZnO-SnO2 coupled catalyst prepared at pH 7 was higher than that of the coupled catalyst prepared at pH 10. After Ag was loaded on the surface of coupled catalysts prepared at pH 7, the photocatalytic performance of catalysts was greatly improved. The optimum Ag loading amount was found to be around 3%. The activity of 3%Ag/ZnO-SnO2 catalyst was higher than that of the pure ZnO catalyst and the ZnO-SnO2 coupled catalyst prepared at pH 7 by 84 and 88%, respectively. Our study demonstrates that the combination of noble metal loading and the semiconductor coupling on the surface of a semiconductor catalyst would be an effective way to improve the photocatalytic activity of catalysts.