Effect of transition metal ion (Cr 3+ , Mn 2+ and Cu 2+ ) doping on the photocatalytic properties of ZnWO 4 nanoparticles

Morphology-Controlled ZnO@ZnWO4 Hetero-Nanostructures for Efficient Photooxidation of Water in Near-Neutral pH

One-dimensional ZnO nanorods (NRs) have been extensively studied as photoanodes because of their unique optical properties, high electron mobility, and suitable band positions for water oxidation. However, their practical efficiency is often compromised by chemical instability during water oxidation and high carrier recombination rates. To overcome this issue, precise morphological control of ZnO@ZnWO4 core-shell structured photoanodes, featuring a ZnO core and a ZnWO4 shell was used. This was accomplished by depositing WO3 onto hydrothermally grown ZnO NRs using the thermal chemical vapor deposition process. The photoelectrochemical performance of ZnO@ZnWO4 with an optimized morphology outperforms that of pristine ZnO NRs. Systematic optical and electrochemical analyses of ZnO@ZnWO4 demonstrated that the enhancement is attributed to the enhanced charge transfer efficiency facilitated by the optimized ZnWO4 shells.

In Situ Hydrothermal Synthesis of Ni1-xMnxWO4 Nanoheterostructure for Enhanced Photodegradation of Methyl Orange

The monoclinic nanocrystalline Ni_1-xMn_xWO₄ heterostructure has been successfully synthesized by the hydrothermal technique for achieving better sensitive and photocatalytic performances. Different characterization techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible (UV-Vis), and photoluminescence (PL) spectroscopy have been employed to investigate their structural, microstructural, and optical properties. Mn-ion incorporation in the NiWO₄ lattice reduces the particle size of the sample compared with the pure undoped NiWO₄ sample, which has been confirmed from the transmission electron microscope image. The Tauc plot of the Ni_1-xMn_xWO₄ sample exhibits a significant decrease in bandgap energy compared with the pure undoped NiWO₄ sample due to the quantum confinement effect. Finally, the material was explored as a photocatalyst for the degradation of methyl orange (MO) dye from wastewater under visible light irradiation. Various reaction parameters such as pH, catalyst dose, reaction time, and kinetics of the photodegradation were studied using the batch method. The results showed that the Ni_1-xMn_xWO₄ is highly efficient (94.51%) compared with undoped NiWO₄ (65.45%). The rate of photodegradation by Ni_1-xMn_xWO₄ (0.067) was found to be 1.06 times higher than the undoped NiWO₄ (0.062).

Photocatalytic activity of P-doped TiO2 photocatalyst

In this study, P-doped TiO₂ photocatalysts with different molar percentages (in the range 0.071-1.25 mol %) of the non-metallic element were prepared and their photocatalytic activity under visible light irradiation was tested. All achieved samples were characterized by XRD, Raman, UV-Vis DRS and SEM-EDX techniques. XRD and Raman analysis showed that all doped photocatalysts were in anatase phase and evidenced that P ions were successfully incorporated into the TiO₂ crystal lattice, affecting also the crystallinity degree of the P-doped TiO₂ photocatalysts. Noticeably, the UV-Vis DRS spectra evidenced that the highest redshift in absorption edge was observed for the photocatalyst with the lowest P content (0.071PT), which showed also the lowest bandgap (2.9 eV). The photocatalytic performances of all P-doped TiO₂ samples were compared with that of commercial TiO₂ by evaluating the decolorization of methylene blue (MB) dye under visible light irradiation. Results showed that phosphorus doping strongly promoted photocatalytic activity in the presence of visible light. Furthermore, the most active photocatalyst in visible light tests (0.071PT) also showed better photocatalytic activity than commercial TiO₂ in the decolorization of MB under simulated sunlight irradiation. Finally, 0.071PT photocatalyst was preliminarily tested against Escherichia coli (E. coli) under simulated solar light, showing an inactivation efficiency of 90% after 2 h of treatment time.

A review on the applications of zinc tungstate (ZnWO4) photocatalyst for wastewater treatment

The monoclinic wolframite-phase structure of ZnWO₄ materials has been frequently synthesised, characterised, and applied in optical fibres, environmental decontamination, electrochemistry, photonics, catalysis, and not limited to magnetic applications. However, the problems of crystal growth conditions and mechanisms, growth, the crystal quality, stability, and the role of synthesis parameters of ZnWO₄ nanoparticles remain a challenge limiting its commercial applications. This review presents recent advances of ZnWO₄ as an advanced multi-functional material for Industrial wastewater treatment. The review also examines the influence of the synthesis parameters on the properties of ZnWO₄ and provides insight into new perspectives on ZnWO₄-based photocatalyst. Many researches have shown significant improvement in the efficiency of ZnWO₄ by mixing with polymers and doping with metals, nonmetals, and other nanoparticles. The review also provides information on the mechanism of doping ZnWO₄ with metals, non-metals, metalloids, metals oxides, and polymers based on different synthesis methods for bandgap reduction and extension of its photocatalytic activity to the visible region. The doped ZnWO₄ photocatalyst was a more effective and environmentally friendly material for removing organic and inorganic contaminants in industrial wastewater than ordinary ZnWO₄ nanocrystalline under suitable growth conditions.

Recent advances in photodegradation of antibiotic residues in water

Antibiotics are widely present in the environment due to their extensive and long-term use in modern medicine. The presence and dispersal of these compounds in the environment lead to the dissemination of antibiotic residues, thereby seriously threatening human and ecosystem health. Thus, the effective management of antibiotic residues in water and the practical applications of the management methods are long-term matters of contention among academics. Particularly, photocatalysis has attracted extensive interest as it enables the treatment of antibiotic residues in an eco-friendly manner. Considerable progress has been achieved in the implementation of photocatalytic treatment of antibiotic residues in the past few years. Therefore, this review provides a comprehensive overview of the recent developments on this important topic. This review primarily focuses on the application of photocatalysis as a promising solution for the efficient decomposition of antibiotic residues in water. Particular emphasis was laid on improvement and modification strategies, such as augmented light harvesting, improved charge separation, and strengthened interface interaction, all of which enable the design of powerful photocatalysts to enhance the photocatalytic removal of antibiotics.

Dysprosium-doped zinc tungstate nanospheres as highly efficient heterogeneous catalysts in green oxidation of terpenic alcohols with hydrogen peroxide

Dysprosium-doped zinc tungstate nanospheres efficiently catalyzed the epoxidation of terpenic alcohols using hydrogen peroxide, an inexpensive and environmentally benign oxidant.

Synthesis, Characterization, and Photocatalytic Evaluation of Manganese (III) Phthalocyanine Sensitized ZnWO4 (ZnWO4MnPc) for Bisphenol A Degradation under UV Irradiation

ZnWO₄MnPc was synthesized via a hydrothermal autoclave method with 1 wt.% manganese (iii) phthalocyanine content. The material was characterized for its structural and morphological features via X-ray diffraction (XRD) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, transmission emission microscopy (TEM), scanning electron microscopy-Energy dispersive X-ray spectroscopy (SEM-EDX), N₂ adsorption-desorption at 77K, X-ray photoelectron spectroscopy (XPS), and UV-visible/diffuse reflectance spectroscopy(UV-vis/DRS). ZnWO₄MnPc photocatalytic performance was tested on the degradation of bisphenol A (BPA). The ZnWO₄MnPc material removed 60% of BPA after 4 h of 365 nm UV irradiation. Degradation process improved significantly to about 80% removal in the presence of added 5 mM H₂O₂ after 4 h irradiation. Almost 100% removal was achieved after 30 min under 450 nm visible light irradiation in the presence of same concentration of H₂O₂. The effect of ions and humic acid (HA) towards BPA removal was also investigated.

Strong Photo-Oxidative Capability of ZnWO4 Nanoplates with Highly Exposed {0 1 1} Facets

ZnWO4 nanoplates with highly exposed {0 1 ¯ 1} facets were synthesized via a hydrothermal technique. The phase, morphology, and optical characteristics of ZnWO4 nanoplates were characterized with scanning electron microscopy, transmission electron microscopy, X–ray diffraction, diffuse ultraviolet–visible light (UV–Vis) reflectance spectroscopy, photoluminescence (PL) spectrophotometry, and PL lifetime spectroscopy. Optical characterizations, along with the density functional calculations, confirm that the strong blue PL band of ZnWO4 nanoplates originates from the intrinsic defects in ZnWO4 nanoplates. Furthermore, photocatalytic tests show that ZnWO4 nanoplates exhibit strong photo-oxidative capability of complete mineralization of the organic pollutant (methyl orange) in water, whereas ZnWO4 nanoparticles can only cleave the organic molecules into fragments. The superior photo-oxidative capability of ZnWO4 nanoplates can be attributed to the specific chemical bonding and stereochemistry on the exposed facets. This work demonstrates that crystal facet engineering is an efficient strategy to endow ZnWO4 with strong photo-oxidative capability.

Eu2+ and Eu3+ Doubly Doped ZnWO₄ Nanoplates with Superior Photocatalytic Performance for Dye Degradation

Eu²⁺ and Eu³⁺ doubly doped ZnWO₄ nanoplates with highly exposed {100} facets were synthesized via a facile hydrothermal route in the presence of surfactant cetyltrimethyl ammonium bromide. These ZnWO₄ nanoplates were characterized using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectrometry, diffuse UV-vis reflectance spectroscopy, photoluminescence spectrophotometry, and photoluminescence lifetime spectroscopy to determine their morphological, structural, chemical, and optical characteristics. It is found that Eu-doped ZnWO₄ nanoplates exhibit superior photo-oxidative capability to completely mineralize the methyl orange into CO₂ and H₂O, whereas undoped ZnWO₄ nanoparticles can only cleave the organic molecules into fragments. The superior photocatalytic performance of Eu-doped ZnWO₄ nanoplates can be attributed to the cooperative effects of crystal facet engineering and defect engineering. This is a valuable report on crystal facet engineering in combination with defect engineering for the development of highly efficient photocatalysts.