Nanoparticles TiO2-photocatalyzed oxidation of selected cyclohexyl alcohols

Covalently anchoring silver nanoclusters Ag44 on modified UiO-66-NH2 with Bi2S3 nanorods and MoS2 nanoparticles for exceptional solar wastewater treatment activity

For the first time, covalently anchoring size selected silver nanoclusters [Ag44(MNBA)30] on the Bi2S3@UiO-66-NH2 and MoS2@UiO-66-NH2 heterojunctions were constructed as novel photocatalysts for photodegradation of methylene blue (MB) dye. The anchoring of Ag44 on MoS2@UiO-66-NH2 and Bi2S3@UiO-66-NH2 heterojunctions extended the light absorption of UiO-66-NH2 to the visible region and improved the transfer and separation of photogenerated charge carriers through the heterojunctions with a unique band gap structure. The UV-Vis-NIR diffuse reflectance spectroscopic analysis confirmed that the optical absorption properties of the UiO-66-NH2 were shifted from the UV region at 379 nm to the visible region at ~ 705 nm after its doping with Bi2S3 nanorods and Ag44 nanoclusters (Bi2S3@UiO-66-NH-S-Ag44). The prepared Bi2S3@UiO-66-NH-S-Ag44 and MoS2@UiO-66-NH-S-Ag44 photocatalysts exhibited exceptional photocatalytic activity for visible light degradation of MB dye. The photocatalysts exhibited complete decolorization of the MB solution (50 ppm) within 90 and 120 min stirring under visible light irradiation, respectively. The supper photocatalytic performance and recycling efficiency of the prepared photocatalysts attributed to the covalent anchoring of the ultra-small silver clusters (Ag44) on the heterojunctions surface. The X-ray photoelectron spectroscopic analysis confirmed the charge of the silver clusters is zero. The disappearance of the N-H bending vibration peak of primary amines in the FTIR analysis of Bi2S3@UiO-66-NH-S-Ag44 confirmed the covalent anchoring of the protected silver nanoclusters on the UiO-66-NH2 surface via the condensation reaction. The Bi2S3@UiO-66-NH-S-Ag44 catalyst exhibited excellent recyclability efficiency more than five cycles without significant loss in activity, indicating their good potential for industrial applications. The texture properties, crystallinity, phase composition, particle size, and structural morphology of the prepared photocatalysts were investigated using adsorption-desorption N2 isotherms, X-ray diffraction (XRD), HR-TEM, and FE-SEM, respectively.

Metal chalcogenides (CuS or MoS2)-modified TiO2 as highly efficient bifunctional photocatalyst nanocomposites for green H2 generation and dye degradation

Herein, we report the modification of TiO₂ nanostructures with two different metal chalcogenides (CuS or MoS₂). The effect of the preparation scheme (hydrothermal and coprecipitation methods) and the mass ratio of metal chalcogenides were investigated. The as-synthesized photocatalyst nanocomposites were fully characterized by various techniques. Moreover, the photo/electrochemical analysis were performed to investigate the photoelectric properties and photocatalytic mechanism. The photocatalytic performance was evaluated using two test reactions. In the case of H₂ generation via water splitting, it was found that 0.5 wt% CuS-TiO₂ synthesized via the coprecipitation method exhibited an initial hydrogen evolution rate (HER) of 2.95 mmol h^-1 g^-1. While, the optimized 3 wt% MoS₂-TiO₂ synthesized by the hydrothermal method, showed an HER of 1.7 mmol h^-1 g^-1. Moreover, the degradation efficiency of methylene blue dye was 98% under UV-Vis light irradiation within 2 h over 0.5 CT_PP and 3MT_HT. Under visible irradiation, the degradation efficiency was 100% and 96% for 3MT_PP and 0.5CT_HT in the presence of H₂O₂, respectively. This study has proven that metal chalcogenides can act as effective, stable, and low-cost bifunctional co-catalysts to enhance the overall photocatalytic performance.

Photocatalytic degradation of the fungicide Fenhexamid in aqueous TiO(2) suspensions: identification of intermediates products and reaction pathways

Liquid-chromatography interfaced with time-of-flight mass spectrometry (LC-TOF/MS) was used to separate and characterize the transformation products arising from TiO(2)-photocatalytic degradation of the fungicide Fenhexamid (FEX) in aqueous solution under simulated solar irradiation. Prior to identification, irradiated solutions of FEX (10mgL(-1)) were concentrated by solid-phase extraction. Assignments of the mass spectra ions were aided by elemental composition calculations, comparison of structural analogues and available literature, and acquired knowledge regarding mass spectrometry of related heterocyclic compounds. The primary transformation intermediates identified were hydroxyl and/or keto-derivatives. Several positional isomers are typically produced as a consequence of the non-selectivity of the ()OH radical attack. Moreover, products resulted from the cleavage of the amide and NH-dichlorophenol bonds were formed. Finally, cyclic - benzo[d]oxazole intermediates are also formed through an intramolecular photocyclization process and cleavage of halogen - carbon bond. In the case of the hydroxy and/or keto-derivatives, the generic fragmentation scheme obtained from the interpretation of the ESI-TOF-MS data cannot be diagnostic to precisely localize the position of the entering substituent on the FEX molecule, and thus to characterize all its possible oxygenated derivatives by assigning a plausible structure with confidence. On the basis of identified products different pathways of photocatalytic degradation of FEX were proposed and discussed.