Solar-Light-Responsive Titanium-Sheet-Based Carbon Nanoparticles/B-BiVO4/WO3 Photoanode for the Photoelectrocatalytic Degradation of Orange II Dye Water Pollutant

Optimizations of Liquid Phase Deposition Processes for Enhanced Photoelectrocatalytic Activities of Tungsten Oxide Thin Films

This study focuses on the preparation of tungsten oxide (WO3) as the photoanode for water oxidations by the liquid phase deposition (LPD) technique and its optimizations to improve the photoelectrochemical performance. The alternative precursor large stock solution process was achieved to simplify the LPD process for WO3 thin film preparation. The effect of boric acid in the precursor solutions on the physicochemical properties of the deposited WO3 thin films was investigated. As a result, we found that the optimized concentration of boric acid realized the highest photoelectrochemical performance. Through the optimizations of reaction conditions and surface analyses, we concluded that the preparations of a semiconductor film via the LPD technique had the potential to obtain high-performance photoelectrocatalytic applications.

Sn(IV)-Porphyrin-Based Nanostructures Featuring Pd(II)-Mediated Supramolecular Arrays and Their Photocatalytic Degradation of Acid Orange 7 Dye

Two robust Sn(IV)-porphyrin-based supramolecular arrays (1 and 2) were synthesized via the reaction of trans-Pd(PhCN)2Cl2 with two precursor building blocks (SnP1 and SnP2). The structural patterns in these architectures vary from 2D to 3D depending on the axial ligation of Sn(IV)-porphyrin units. A discrete 2D tetrameric supramolecule (1) was constructed by coordination of {(trans-dihydroxo)[5,10-bis(4-pyridyl)-15,20-bis(phenyl) porphyrinato]}tin(IV) (SnP1) with trans-PdCl2 units. In contrast, the coordination between the {(trans-diisonicotinato)[5,10-bis(4-pyridyl)-15,20-bis(phenyl)porphyrinato]}tin(IV) (SnP2) and trans-PdCl2 units formed a divergent 3D array (2). Axial ligation of the Sn(IV)-porphyrin building blocks not only alters the supramolecular arrays but also significantly modifies the nanostructures, including porosity, surface area, stability, and morphology. These structural changes consequently affected the photocatalytic degradation efficiency under visible-light irradiation towards acid orange 7 (AO) dye in an aqueous solution. The degradation efficiency of the AO dye in the aqueous solution was observed to be between 86% to 91% within 90 min by these photocatalysts.

Enhanced Photocatalytic Degradation of Tetracycline and Oxytetracycline Antibiotics by BiVO4 Photocatalyst under Visible Light and Solar Light Irradiation

The efficient degradation of a toxic antibiotic from an aqueous solution is essential for environmental protection. Our research aimed to fabricate a bismuth vanadate (BiVO4) catalyst via a facile hydrothermal method. The prepared catalyst exhibited a monoclinic phase with a band gap energy of 2.33 eV, indicating the excellent visible-light-active properties of a semiconductor. The photocatalytic performance of the synthesized BiVO4 catalyst was studied by determining the removal of tetracycline (TC) and oxytetracycline (OTC) antibiotics. After 240 min, under sunlight conditions, a high performance of 72% and 83% degradation of TC and OTC, respectively, was achieved. The photocatalytic degradation of the antibiotics correlates well with a first-order reaction, with a high rate constant of 0.0102 min−1. Photogenerated electrons and holes played an important role in the removal of the pollutant. After photocatalytic study, the structural stability of the prepared bismuth vanadate photocatalyst was confirmed. The photocatalyst provided a promising performance even after five successive runs. The result indicates the excellent cycling ability of the sample. The present work demonstrates a promising route for the preparation of a BiVO4 catalyst for the complete removal of toxic antibiotics in aqueous solutions.

Step-scheme BiVO4/WO3 heterojunction photocatalyst under visible LED light irradiation removing 4-chlorophenol in aqueous solutions

In the present study, photodegradation of 4-chlorophenol (4-CP) using a step-scheme BiVO₄/WO₃ heterostructure under visible LED light irradiation (Vis LED) from aqueous solutions was investigated. The photocatalyst was synthesized through the hydrothermal process and characterized physically and chemically via X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), energy-dispersive X-ray (EDX), and Brunnauer-Emmett-Teller (BET) techniques. The effects of the operational parameters i.e., solution pH, contact time, nanocomposite dosage, and initial 4-CP concentration were evaluated. Results indicated that BiVO₄/WO₃/Vis LED process has higher efficiency in 4-CP degradation than BiVO₄/Vis LED, WO₃/Vis LED, and BiVO₄/WO₃ systems. At BiVO₄/WO₃ concentration of 0.125 g/L, initial pH of 7, and initial 4-CP concentration of 25 mg/L, complete degradation of 4-CP (>97%) was achieved in reaction time of 60 min. The phenol, chlorobenzene, catechol, 4-chlorocatechol, 5-chloro-1,2,4-benzenetriol, hydroquinone, hydroxyhydroquinone, p-benzoquinone, o-benzoquinone, formic acid, acetic acid, and oxalic acid were identified as the major intermediates of 4-CP degradation. In optimal condition, 67.5% and 88.5% of TOC and COD removal rates were obtained in 120 min contact time, respectively. The degradation of 4-CP was pseudo-first-order kinetics. Through the use of tert-Butyl alcohol (TBA) and ethylenediamine tetraacetic acid (EDTA) as radical scavengers, hydroxyl radicals and holes were identified as the main active species in photocatalytic degradation. Also, a tentative pathway for 4-CP degradation using the Vis LED/BiVO₄/WO₃ process was proposed.

The application of FTO-Cu2O/Ag3PO4 heterojunction in the photoelectrochemical degradation of emerging pharmaceutical pollutant under visible light irradiation

We report the photoelectrochemical application of a visible light active FTO-Cu₂O/Ag₃PO₄ photoanode for the abatement of sulfamethoxazole in water. The as-synthesised photoanodes were characterised using XRD, field emission SEM, EDX, diffuse reflectance UV-vis, impedance spectroscopy and chronoamperometry. The results obtained confirmed a successful formation of p-n heterojunction at the Cu₂O/Ag₃PO₄ interface. The highest photocurrent response of 0.62 mAcm^-2 was obtained for the composite photoanode which was four times higher than pure Cu₂O and about three times higher than pristine Ag₃PO₄. The photoanode gave 67% removal efficiency within 2 h upon its photoelectrochemical application in the degradation of sulfamethoxazole with 1.5 V bias potential at pH 6.2. The FTO-Cu₂O/Ag₃PO₄ electrode was also applied in the treatment of a cocktail of synthetic organics containing sulfamethoxazole and orange II dye. The photogenerated holes was found to be the major oxidant and the photoanodes was stable and reusable.