Fabrication of heterojunction ternary Fe3O4/TiO2/CoMoO4 as a magnetic photocatalyst for organic dyes degradation under sunlight irradiation

Metal-Organic-Framework Derived Co-Mo Multimetal Oxide Semiconductors: Selective Trace-Level Hydrogen Sulfide Detection

The development of a highly selective and trace-level gas sensing platform for detecting hydrogen sulfide (H2S) remains a formidable challenge. To solve this problem, Co-Mo multimetal oxide semiconductors are rationally tailored by employing metal organic frameworks (MOFs) as self-sacrificial templates. The MOF-derived Co3O4/β-CoMoO4 based gas sensors displays high sensitivity (Rg/Ra = 22) to 10 ppm of H2S and ultralow limit of detection (10 ppb H2S). The formation of p-p heterojunction and multivalence states of Mo play a crucial role in electron transfer and oxygen adsorption. A sensor array constructed from four Co3O4/β-CoMoO4 materials with different Co/Mo ratios demonstrates a superior selective discrimination of H2S from other VOCs and malodorous gases by principal component analysis (PCA). Besides, a H2S gas sensing and alarming platform was designed for monitoring the environment contaminated with H2S. This finding provides a feasible approach for the discovery of highly efficient gas sensors to monitor environmental H2S concentration.

Cationic and anionic cross-assisted synergistic photocatalytic removal of binary organic dye mixture using Ni-doped perovskite oxide

Organic dyes present in industrial wastewater are the major contributor to water pollution, which harm human health and the environment. Photocatalytic dye degradation is an effective strategy for water remediation by converting these organic dyes waste into non-harmful by-products. Therefore, in this study, Ni-doped LaFeO3 (NLFO) perovskite nanoparticles were extensively explored for photocatalytic degradation of cationic and anionic dyes and their mixture. The NLFO nanoparticles were successfully synthesized by surfactant assisted hydrothermal method under controlled Ni doping. The X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM) revealed the variation in size (40-70 nm) of orthorhombic crystalline LFO nanoparticles with Ni doping and hence the size of microspheres (0.78. to 1.78 μm). The kinetic studies revealed that the LaFe0·6Ni0·4O3 performed well by providing degradation efficiency of 99.2% in 210 min, 99.1% in 100 min, and 98.4% in 70 min for Crystal Violet (CV), Congo Red (CR), and their mixture with rate constant of 0.019, 0.039, and 0.055 min-1 respectively. The radical scavenger tests indicated the synergetic contributions of O2- and •OH- active radicals in faster degradation of CV and CR dye mixture. The stepwise fragmentation of dye molecule during the photocatalytic degradation identified from the LCMS indicates the degradation of CV dye through de-alkylation and benzene ring breaking, whereas azo bond cleavage and oxidation lead to low molecular weight intermediates for CR dye, which all together helped to degrade their dye mixture (50 mg L-1 and 100 mg L-1) in significantly lesser time (70 min). Overall, the Ni-doped LFO microsphere consisting of nanoparticles acts as a superior catalyst for the more efficient and faster degradation of binary dye mixture.

Magnetic Carbon Quantum Dots/Iron Oxide Composite Based on Waste Rice Noodle and Iron Oxide Scale: Preparation and Photocatalytic Capability

To provide an economical magnetic photocatalyst and introduce an innovative approach for efficiently utilizing discarded waste rice noodle (WRN) and iron oxide scale (IOS), we initially converted WRN into carbon quantum dots (CQDs) using a hydrothermal method, simultaneously calcining IOS to obtain iron oxide (FeOx). Subsequently, we successfully synthesized a cost-effective, magnetic CQDs/FeOx photocatalytic composite for the first time by combining the resulting CQDs and FeOx. Our findings demonstrated that calcining IOS in an air atmosphere enhanced the content of photocatalytically active α-Fe2O3, while incorporating WRN-based CQDs into FeOx improved the electron-hole pair separation, resulting in increased O2 reduction and H2O oxidation. Under optimized conditions (IOS calcination temperature: 300 °C; carbon loading: 11 wt%), the CQDs/FeOx composite, utilizing WRN and IOS as its foundation, exhibited exceptional and reusable capabilities in photodegrading methylene blue and tetracycline. Remarkably, for methylene blue, it achieved an impressive degradation rate of 99.30% within 480 min, accompanied by a high degradation rate constant of 5.26 × 10-3 min-1. This composite demonstrated reusability potential for up to ten photocatalytic cycles without a significant reduction in the degradation efficiency, surpassing the performance of IOS and FeOx without CQDs. Notably, the composite exhibited strong magnetism with a saturation magnetization strength of 34.7 emu/g, which enables efficient and convenient recovery in photocatalytic applications. This characteristic is highly advantageous for the large-scale industrial utilization of photocatalytic water purification.

Ce2(MoO4)3 synthesized with oleylamine and oleic acid as additives for photocatalysis: effect of preparation method

Ce₂(MoO₄)₃ was prepared using dielectric barrier discharge (DBD) plasma method, co-precipitation method and hydrothermal method, respectively, with water/ethanol (W/O) as solvent, oleylamine (OAm) and oleic acid (OAc) as additives. Preparation method showed significant influence on the morphological and structural properties, as well as photocatalytic performance. Ce₂(MoO₄)₃ synthesized with DBD plasma (MO-P) was mainly flowerlike nanosheets, which were beneficial to promoting electron transfer and providing more space for catalytic activity. Also, MO-P samples exhibited more oxygen vacancies, which were conducive to the photocatalytic performance. What's more, MO-P showed lower PL intensity and narrow energy gap, which implied a slow photoelectron-hole pair recombination rate and an increased electron transfer rate. The degradation rate of methyl orange (50 mg/L) could achieve 98% within 12 min with 0.5 g/L MO-P. Hydroxyl radicals (·OH) and superoxide radicals (·O₂^-) played a major effect. Plasma synthesis method exhibited potential application prospect in photocatalysts preparation.

Facile Synthesis and Characterizations of Mixed Metal Oxide Nanoparticles for the Efficient Photocatalytic Degradation of Rhodamine B and Congo Red Dyes

Photocatalytic degradation has been suggested to be a cheap and efficient way to dispose of organic pollutants, such as dyes. Therefore, our research team strives to produce nanophotocatalysts in a simple and inexpensive way. In this work, the Pechini sol-gel technique was employed for the facile synthesis of Mn_0.5Zn_0.5Fe₂O₄/Fe₂O₃ and Fe_0.5Mn_0.5Co₂O₄/Fe₂O₃ as mixed metal oxide nanoparticles for the efficient photocatalytic degradation of Rhodamine B and Congo Red dyes. XRD, FT-IR, a N₂ adsorption/desorption analyzer, EDS, FE-SEM, and an UV-Vis diffuse reflectance spectrophotometer were used to characterize the produced samples. The XRD patterns revealed that the average crystallite size of the Fe_0.5Mn_0.5Co₂O₄/Fe₂O₃ and Mn_0.5Zn_0.5Fe₂O₄/Fe₂O₃ samples is 90.25 and 80.62 nm, respectively. The FE-SEM images revealed that the Fe_0.5Mn_0.5Co₂O₄/Fe₂O₃ sample consists of cubic and irregular shapes with an average diameter of 1.71 µm. Additionally, the Mn_0.5Zn_0.5Fe₂O₄/Fe₂O₃ sample consists of spherical shapes with an average diameter of 0.26 µm. The energy gaps of the Fe_0.5Mn_0.5Co₂O₄/Fe₂O₃ and Mn_0.5Zn_0.5Fe₂O₄/Fe₂O₃ samples are 3.50 and 4.3 eV and 3.52 and 4.20 eV, respectively. In the presence of hydrogen peroxide, the complete degradation of 100 mL of 20 mg/L of Rhodamine B and Congo Red dyes occurred at pH = 8 and 3, respectively, within 50 min, using 0.1 g of the synthesized samples.

Study on Photocatalytic Degradation of Acid Red 73 by Fe3O4@TiO2 Exposed (001) Facets

Water pollution can be treated through the photocatalytic reaction of TiO2 or TiO2 compounds. A solvothermal method was used to prepare Fe3O4 and Fe3O4@TiO2 composite photocatalyst with (001) high-energy facets exposed in the anatase phase. TiO2 and Fe3O4@TiO2 were characterized by field emission scanning electron microscopy, ultraviolet–visible diffuse reflectance spectroscopy, X-ray diffraction spectroscopy and Raman spectroscopy. It was found that the composite Fe3O4@TiO2 can reduce the band gap and maintain a certain proportion of (001) high-energy facet exposure. The band gaps of Fe3O4@TiO2 and TiO2 are 2.5 eV and 2.9 eV, respectively. The exposure percentages of (001) facets of Fe3O4@TiO2 and TiO2 are about 25.2% and 12.1%, respectively. Fe3O4@TiO2 was used for photocatalytic degradation of Acid Red 73, and it was found that Fe3O4@TiO2 could improve the efficiency of photocatalytic degradation of Acid Red 73. The photocatalytic degradation rates of Fe3O4@TiO2 and TiO2 at 24 min were 93.56% and 74.47%, respectively. The cycle experiment of photocatalytic degradation of Acid Red 73 by Fe3O4@TiO2 showed that at the fifth cycle, the rate of dye degradation decreased to 77.05%, but the rate of dye degradation can reach more than 90% after self-cleaning treatment. The photocatalytic degradation mechanism is explained by the energy band theory and the first-order kinetic equation model.