Photoelectrochemical Degradation Research Articles

Construction of 0D Ti3C2Tx MXene nanoparticles sensitized 1D TiO2 nanotube arrays for enhanced photocatalytic and photoelectrochemical properties

Developing efficient photocatalysts with highly active facets and appropriate cocatalyst hybridization to form heterostructure is a valid way to expedite the separation of photoexcited electron-hole pairs. Herein, a novel 0D/1D Ti3C2Tx MXene/TiO2 photocatalyst was fabricated for photoelectrochemical (PEC) water splitting and tetracycline antibiotic photocatalytic degradation. Meanwhile, highly-exposed TiO2 nanotube arrays were prepared by electrochemical anodizing method, and Ti3C2Tx nanoparticles with mixed terminal group were uniformly grown on the surface of TiO2 through the hydrothermal and solvothermal process, respectively. Compared with pure TiO2, the Ti3C2Tx/TiO2 heterostructure exhibited different degrees of enhancement in PEC and photocatalytic degradation activities under simulated sunlight. The TNT/M-h sample yielded a photocurrent density of 1.77 mA cm−2 at 0 V (vs. SCE) and achieved a 95.57 % photocatalytic removal rate of tetracycline within 140 min. The excellent performance originated from the strong interfacial contact and work function discrepancy between the ordered tubular structure of TiO2 and 0D Ti3C2Tx nanoparticles, which realized the high-efficiency photogeneration and transfer of electron-hole pairs.

H2O2-assisted photo-electrocatalytic and photocatalytic degradation of methyl violet by CuO-modified TiO2 nanotube arrays

Photoelectrocatalytic degradation is an environmental friendly and efficient technique providing solutions for the dire issue of water pollution. TiO2 nanotubes are widely used as the photocatalyst but its efficiency is restricted by the wide band gap. This study deals with the fabrication of CuO-modified TiO2 nanotubes by electrochemical anodization following the hydrothermal method to enhance the photocatalytic degradation. Optical studies revealed a reduction in the bandgap (2.12 eV) of CuO-modified TiO2 nanotubes, which plays an important role in increasing the photocatalytic activity. The effect of CuO loading on TiO2 nanotubes in photocatalytic degradation as well as the effect of bias and H2O2 on photo-electrocatalytic degradation were studied. In photocatalytic degradation, 0.05 M CuO–TiO2 photocatalyst produced a maximum degradation of 49.5 % in 8 h. Compared with the pristine TiO2 nanotubes, the photodegradation of CuO-loaded TiO2 nanotubes increased by 16 %. Furthermore, when an external bias was applied, the photodegradation efficiency increased by 36 %. In addition of H2O2 to the PEC system, 0.05 CuO–TiO2 photocatalyst produced 100 % degradation of methyl violet in 2.5 h. Reusability studies showed that the photocatalysts are stable and can therefore be used for practical applications such as photocatalytic degradation and photoelectrochemical degradation of methyl violet.

Tetragonal/orthorhombic phase Bi2WO6 homojunction for photoelectrochemical degradation of rhodamine B with high efficiency

Photoelectrochemical (PEC) degradation of organic pollutants to CO2 and H2O is a promising strategy to solve the growing environmental problems. Bismuth tungstate (Bi2WO6) has attracted much attention due to its good chemical stability and moderate conduction band valence band position. However, the PEC activity of Bi2WO6 catalysts is greatly limited due to its rapidly complex electron-hole. This article reports a rational low-cost design that successfully prepares tetragonal/orthorhombic Bi2WO6 homojunction on FTO conductive glass substrates through a simple two-step solvothermal method, significantly enhancing the PEC performance. The study investigated the effectiveness of photoelectrochemical degradation of the recalcitrant organic pollutant Rhodamine B (RhB) and conducted an in-depth exploration of the photoelectrocatalytic reaction process and mechanism. The experimental results indicate that the homojunction achieves a degradation rate of up to 100 % for the recalcitrant organic pollutant RhB within 30 minutes, significantly surpassing that of single-phase Bi2WO6, and at the same time the sample maintains good stability after five cycles of operation. Further analysis of the capture experiments indicates that holes (h+) and superoxide radicals (·O2⁻) are the primary active species responsible for RhB degradation. This study not only provides new insights into the design of high-efficiency photoelectrode, but also offers new solutions for environmental pollution control.

Photoelectrochemical degradation of selected organic pollutants on tungsten trioxide photoanodes

This study describes the photoelectrochemical degradation of model aromatic pollutants, viz. a herbicide (“monuron”, 3-(4-chlorophenyl)-1,1-dimethylurea) and an antimicrobial preservative (benzoic acid) on WO3 films prepared by aerosol pyrolysis. Crystalline WO3 films had a monoclinic structure, 4 μm thickness and a photocurrent density of 1 mA cm−2 at 1.2 V vs. RHE and illumination under 1 sun (simulated). The chemical and photoelectrochemical stability of WO3 films at various pH was evaluated. The dissolution rate at pH 1 and 4 was low (0.5 nm·h−1), whereas at pH 6 an increase in the dissolution rate to 15 nm·h−1 was observed. The course of the photoelectrochemical oxidation of selected pollutants was examined using HPLC. The achieved Faradaic efficiency of photoelectrooxidation of 1 mM benzoic acid divided by the number of charge equivalents per 1 mol of oxidised compound R, f/z, was 13 % and 12 % at pH 1 and 4, respectively, and for 1 mM monuron 7.2 % at pH 1 and 7.5 % at pH 4. Although the concentration of pollutants decreased significantly, UV–VIS and TOC (total organic carbon) analyses showed the prevalent presence of intermediates during the degradation. During the degradation of benzoic acid, hydroxybenzoic acid (salicylic acid) was found by HPLC as an early intermediary product.

The removal and transformation of fipronil using a photoelectrochemical device combined with a carbonized TiO2 nanocomposite electrode

Fipronil has been a critical environmental concern due to its potential risks to aquatic environments. However, research on the effective removal of fipronil using photoelectrochemical (PEC) devices is still limited. This study represents the pioneering application of a PEC device for the efficient removal of pesticides. A carbonized titanium dioxide nanocomposite electrode was employed as the electrode in the PEC device. The extent of fipronil degradation in the PEC device was also monitored. The PEC device demonstrated higher efficiencies than the reported oxidation treatments. The applied voltage and illumination from the light source initiated the formation of various reactive species, which exhibited the ability to degrade fipronil in the PEC device. Importantly, the presence of singlet oxygen and ozone in the PEC device was demonstrated for the first time, providing new insights into the degradation mechanism in the PEC system. Furthermore, this study unveiled four byproducts that were previously unreported. The presence of fipronil chlorinated byproducts in the device resulted in the generation of reactive chlorine species, which contributed to fipronil decomposition. When the detoxification of fipronil was compared between the PEC and electrochemical devices, the PEC device demonstrated higher degradation efficiencies and more effective detoxification, providing valuable insight into removing pesticides. Novelty statementThe degradation of fipronil and the identification of its degradation byproducts, along with toxicity testing, have been extensively investigated. Previous studies have indicated that many oxidation processes for fipronil degradation lead to the formation of byproducts with higher toxicity or require extended periods to reduce toxicity. In this study, a photoelectrochemical advanced oxidation process was applied for the first time to degrade pesticides. The developed PEC degradation process demonstrated the ability to rapidly remove fipronil and effectively reduce its toxicity, showing significant potential for various applications. Furthermore, our research revealed the formation of singlet oxygen and ozone in a PEC degradation system, providing novel insights into the degradation mechanism within the PEC system. Utilizing the carbonized titanium dioxide nanocomposite electrode developed in this study, successful fipronil decomposition was achieved for the first time through a PEC device.

Surface-tuning TiO2 NR photoanodes using CoOx interlayers and NiFe-LDH cocatalysts for photoelectrochemical wastewater treatment

Increasing multidrug-resistant pathogenic microbial around the world become a global problem, making it imperative to develop effective methods for bacterial inactivation in wastewater. In this study, we propose a multifunctional photoelectrochemical (PEC) system to successfully disinfect microbial cells and degrade orange (II) dyes. CoOx NP were synthesized by spin-coating onto hydrothermally synthesized TiO2 nanorod arrays followed by electrodeposited NiFe-LDH to develop the NiFe-LDH/CoOx NP-TiO2 NRs. Interestingly, spin-coated CoOx NP-TiO2 NRs exhibited a 1.5-fold enhancement in photocurrent (1.384 mA/cm2) than pristine TiO2 NRs (0.92 mA/cm2). A NiFe-layered double hydroxide (LDH) cocatalysts layer further exhibits the maximum photocurrent density of 1.64 mA/cm2 with IPCE of 84.5% at 1.0 VAg/AgCl at 380 nm. Furthermore, NiFe-LDH/CoOx-TiO2 NR photoanodes were effectually employed for photoelectrochemical bacteria disinfection and organic pollutant removals. With NiFe-LDH/CoOx-TiO2 NR, 99% (120 min) bacterial inactivation and 99% (60 min) orange II dye decomposition efficiency was achieved. Superoxide radicals (−O2•), hydroxyl radicals (HO•), and holes (h+) played a critical role in the PEC degradation systems. Due to the synergy between NiFe-LDH cocatalyst and CoOx interlayer, surface water oxidation reactions were accelerated over NiFe-LDH/CoOx NP-TiO2 NRs. The charge transport process in NiFe-LDH/CoOx NP-TiO2 NRs photoanode-based PEC system was proposed in detail.

Persulphate assisted photoelectrochemical degradation of organic pollutants in water on a silver nanoparticle modified Cu2O photoanode

This work presents the photoelectrochemical production of sulphate radicals using fluorine-doped tine oxide – silver nanoparticles – copper(I) oxide (FTO-AgNPs-Cu2O) photoanode in the presence of peroxydisulphate salt for the enhanced degradation of selected organic pollutants in water. Firstly, Cu2O was prepared via a facile and template-free one-pot method, then AgNPs were photo-reduced on the surface of the Cu2O, and the resultant product was immobilised on an FTO conductive substrate to form FTO-AgNPs-Cu2O photoanode. When the electrode was applied for the abatement of tetracycline in the presence of 3 mM peroxydisulphate salt and 1.5 V external potential, the degree of tetracycline degradation and mineralisation after 90 min was 82 % and 78 % respectively. Furthermore, the same system was able to achieve degradation of 81 % sulfamethoxazole degradation within 90 min and 100 % orange II dye degradation within 30 min. The photoanode was efficient in the treatment of real wastewater containing tetracycline. Scavenger studies reveal that holes, hydroxyl, and sulphate radicals significantly participated in the degradation process. The electrode is stable and therefore applicable for the abatement of other organic pollutants in a persulphate-assisted photoelectrochemical degradation system.

A Type-II CQDs regulating FeOOH decorated BiVO4 photoelectrode for highly efficient photoelectrochemical degradation of tetracycline

Bismuth vanadate (BiVO4) photoelectrode is of great potentials to be used for photoelectrochemical (PEC) removal of antibiotic pollutant. However, it still suffers from lower efficiency. Herein, a type-II FeOOH-CQDs/BiVO4 photoelectrode was fabricated via the in-situ growth of FeOOH nanoparticles over BiVO4 using Carbon quantum dots (CQDs) as mediator. Benefiting from the type-II heterojunction between BiVO4 and FeOOH, as well as the excellent charger transfer assisted by CQDs, FeOOH-CQDs/BiVO4 exhibited excellent PEC degradation performance towards a typical antibiotic- tetracycline (TC). In a typical PEC process, FeOOH-CQDs/BiVO4 photoelectrode (2 cm × 2 cm) yielded a high removal ratio of ∼ 99 % toward TC within 120 min at an applied potential of 0.6 V (vs. Hg/Hg2Cl2). Moreover, the PEC configuration was verified to be used for TC degradation in actual waters, such as tap water and lake water, with > 90 % of removal ratio. The radical trapping experiments revealed holes and superoxide radical dominated in the TC degradation process. This work provides an insight on the type-II heterojunction photoelectrode to enhance the PEC degradation of TC, which would help for the treatment of antibiotic wastewater.

Submerged photosynthesis of TiO2-CuO hetero-nanoparticles and their multiple applications for water issues under solar light

Environmental challenges, encompassing issues like agricultural ammonia discharge, industrial organic dye misuse, and high environmental polluted water evaporation, demanded urgent attention. In response, we proposed a method for synthesizing TiO2-CuO hetero-nanoparticles capable of different environmental protection commands. Submerged Photosynthesis of Crystallites (SPSC) was adopted due to its simplicity and eco-friendliness. Hetero-nanoparticles with varying Cu-Ti ratios were prepared, characterized, and assessed. CuO dispersion within TiO2 proved consistently even. Increasing Cu content increased Cu-Ti ratio until reaching an upper limit. All nanoparticle samples demonstrated excellent solar light absorption. Combining solar illumination and electrochemical techniques synergistically boosted pollutant degradation. The nanoparticle with a Cu-Ti ratio of 0.17 exhibited optimal photo-electrochemical degradation, enhancing efficiency by 150% under solar light compared to darkness. It also outperformed solar light alone by 32% and electrochemistry alone by 2% in RhB degradation. Furthermore, it enhanced water evaporation rate under solar light. The nanoparticle with a Cu-Ti ratio of 0.52 was the highest water evaporation rate, increasing up to 104% compared to the control group. We discussed the mechanisms underlying fabrication and degradation, elucidating the observed performance. In conclusion, our research underscored the potential of TiO2-CuO hetero-nanoparticles for solar-assisted solutions to different environmental issues, highlighting their environmental applicability.

Anodizing Tungsten Foil with Ionic Liquids for Enhanced Photoelectrochemical Applications.

This research examines the influence of adding a commercial ionic liquid to the electrolyte during the electrochemical anodization of tungsten for the fabrication of WO3 nanostructures for photoelectrochemical applications. An aqueous electrolyte composed of 1.5 M methanesulfonic acid and 5% v/v [BMIM][BF4] or [EMIM][BF4] was used. A nanostructure synthesized in an ionic-liquid-free electrolyte was taken as a reference. Morphological and structural studies of the nanostructures were performed via field emission scanning electron microscopy and X-ray diffraction analyses. Electrochemical characterization was carried out using electrochemical impedance spectroscopy and a Mott-Schottky analysis. From the results, it is highlighted that, by adding either of the two ionic liquids to the electrolyte, well-defined WO3 nanoplates with improved morphological, structural, and electrochemical properties are obtained compared to samples synthesized without ionic liquid. In order to evaluate their photoelectrocatalytic performance, the samples were used as photocatalysts to generate hydrogen by splitting water molecules and in the photoelectrochemical degradation of methyl red dye. In both applications, the nanostructures synthesized with the addition of either of the ionic liquids showed a better performance. These findings confirm the suitability of ionic liquids, such as [BMIM][BF4] and [EMIM][BF4], for the synthesis of highly efficient photoelectrocatalysts via electrochemical anodization.

Comprehensive two-dimensional liquid chromatography with high resolution mass spectrometry to investigate the photoelectrochemical degradation of environmentally relevant pharmaceuticals and their degradation products in water

The widespread presence of organic micropollutants in the environment reflects the inability of traditional wastewater treatment plants to remove them. In this context, advanced oxidation processes (AOPs) have emerged as promising quaternary wastewater treatment technologies since they efficiently degrade recalcitrant components by generating highly reactive free radicals. Nonetheless, the chemical characterization of potentially harmful byproducts is essential to avoid the contamination of natural water bodies with hazardous substances. Given the complexity of wastewater matrices, the implementation of comprehensive analytical methodologies is required. In this work, the simultaneous photoelectrochemical degradation of seven environmentally relevant pharmaceuticals and one metabolite from the EU Watch List 2020/1161 was examined in ultrapure water and simulated wastewater, achieving excellent removal efficiencies (overall >95%) after 180 min treatment. The reactor unit was linked to an online LC sample manager, allowing for automated sampling every 15 min and near real-time process monitoring. Online comprehensive two-dimensional liquid chromatography (LC × LC) coupled with high resolution mass spectrometry (HRMS) was subsequently used to tentatively identify degradation products after photoelectrochemical degradation. Two reversed-phase liquid chromatography (RPLC) columns were used: an SB-C18 column operated with 5 mM ammonium formate at pH 5.8 (1A) and methanol (1B) as the mobile phases in the first dimension and an SB-Aq column using acidified water at pH 3.1 (2A) and acetonitrile (2B) as the mobile phases in the second dimension. This resulted in a five-fold increase in peak capacity compared to one-dimensional LC while maintaining the same total analysis time of 50 min. The LC x LC method allowed the tentative identification of 12 venlafaxine, 7 trimethoprim and 10 ciprofloxacin intermediates. Subsequent toxicity predictions suggested that some of these byproducts were potentially harmful.This study presents an effective hybrid technology for the simultaneous removal of pharmaceuticals from contaminated wastewater matrices and demonstrates how multidimensional liquid chromatography techniques can be applied to better understand the degradation mechanisms after the treatment of micropollutants with AOPs.

Photoelectrochemical degradation of organic compounds via formed reactive chlorine and sulfate species by WO3-based photoanodes

Contamination of aquatic environment and drinking water with various organic compounds and microorganisms has negative effect on human and animal health. Conventional cleaning systems consume a lot of energy and are not fully effective, so new cleaning systems are being sought. Photoelectrochemical (PEC) oxidation systems are based on the light-assisted degradation of organic materials on semiconductor electrodes. In this work tungsten oxide (WO3) photoanodes were formed using hydrothermal synthesis. Synthesis was optimized via adjustment of temperature and addition of polyethylene glycol as a structure-directing agent. X-ray diffraction and scanning electron microscopy analysis were performed to evaluate the phase composition, crystallite size and morphology of the layers. PEC activity of the coatings was evaluated using cyclic voltammetry and chronoamperometry. Faradaic efficiencies of light-induced production of reactive sulfate and reactive chlorine species in 0.1 M Na2SO4 and 0.1 M NaCl electrolytes were in the range of 62–93% and 91–96%, respectively. All coatings demonstrated excellent stability during 4 h lasting photoelectrolysis performed in both electrolytes, however photocurrents in chloride medium were found to be almost twice higher compared to sulfate electrolyte. The efficiency of rhodamine B photoelectrochemical degradation in 0.1 M Na2SO4 was significantly lower than in 0.1 M NaCl, however diclofenac was more efficiently decomposed in sodium sulfate electrolyte. Based on a comparative study of PEC and chemical oxidizing treatments, it has been proposed that highly reactive chlorine, sulfate and hydroxyl radicals are the key promoters of photoelectrochemical degradation of organic molecules, however efficiency of degradation is strongly dependent on the nature of organic molecule.

Water remediation for pharmaceutical and personal care products (PPCPs) with metal organic frameworks: A review

Over the last two decades various contaminants of emerging concerns such as endocrine disrupting compounds including PPCPs have been of interests to water industry because of their incomplete removal during the typical water and waste water treatment processes. Till date number of methods including photo catalytic, electrochemical and biological degradation have been utilized. Recently the potential environmental applications of metal organic frameworks (MOFs) have gained attention as promising sorptive material for removal of emerging contaminants due to their advantage of adjustable composition diverse structure, high surface area controllable pore size and recyclability. The present review critically addresses the performances of the MOF for the adsorptive removal of different categories of PPCPs from waste water.

The design and characterisation of a Z-scheme Bi2O2S/ZnO heterojunction photoanode for the photoelectrochemical removal of ciprofloxacin in synthetic and real wastewater

Towards the engineering of semiconductors for improved visible light photoelectrochemical degradation of organic pollutants in wastewater, we present the preparation of a Z-scheme heterojunction of Bi2O2S and ZnO nanoparticles for the removal of ciprofloxacin from wastewater. The Bi2O2S/ZnO nanocomposite heterojunction was synthesised via an in-situ hydrothermal method and deposited on FTO substrate to form the photoanode. The semiconductors and the photoanodes were characterised with electron microscopy, XRD, photo-electrochemistry, photoluminescence, XPS and UV/Vis diffusive reflectance techniques. The degradation of ciprofloxacin was enhanced by the heterojunction in comparison with the Bi2O2S and ZnO photoanodes. We attribute the enhanced performance to the presence of an internal electric field (IEF), the low rate of recombination of photogenerated electrons and holes, lower charge transfer resistance, and high photocurrent density of the heterojunction based on data from photoluminescence, electrochemical impedance spectroscopy, XPS, and photocurrent response. The extent of mineralisation of ciprofloxacin was calculated as 86 % from total organic carbon (TOC) measurement. LC-MS analysis provided the degradation pathway and premise for the reaction scheme, while quantitative structure–activity relationship (QSAR) model was used to predict the toxicity of the intermediate and by-product. The Bi2O2S/ZnO photoanode was stable after seven treatment cycles. The photoelectrochemical reactor was used in the treatment of ciprofloxacin in real wastewater with 87 % TOC removal. Thus, the paper reveals the performance of a unique Z scheme band gap engineering of semiconductors for application in the removal of pharmaceuticals in wastewater.

Sn-Doped Hematite Films as Photoanodes for Photoelectrochemical Alcohol Oxidation

Here, the modification of semiconductor thin film hematite photoanode by doping with Sn ions is reported. Undoped and Sn-doped hematite films are fabricated by the electrochemical deposition of FeOOH from aqueous alkaline electrolyte, followed by calcination in air. The photoanodes were tested in photoelectrocatalytic oxidation of water, methanol, ethylene glycol, and glycerol. It is shown that modification by tin dramatically increased the activity of hematite in the photoelectrochemical oxidation of alcohols upon visible light irradiation. The photoelectrocatalytic activity of Sn-modified hematite increased in the sequence of: H2O < MeOH < C2H2(OH)2 < C3H5(OH)3. The quantum yield of photocurrent in the oxidation of alcohols reached 10%. The relatively low photocurrent yield was ascribed to the recombination of photoexcited holes within the hematite layer and on surface states located at the hematite/electrolyte interface. Intensity-modulated photocurrent spectroscopy (IMPS) was used to quantify the recombination losses of holes via surface states. The IMPS results suggested that the hole acceptor in the electrolyte (alcohol) influences photocurrent both by changing the charge transfer rate in the photoelectrooxidation process and by the efficient suppression of the surface recombination of generated holes. Thin-film Sn-modified hematite photoanodes are promising instruments for the photoelectrochemical degradation of organic pollutants.

Heterostructured YFeO3/CeO2 as efficient photoelectrode for photoelectrochemical degradation of organic pollutants under visible light irradiation

A YFeO3/CeO2 catalyst is developed using a sol-gel procedure to overcome the recombination of photogenerated electron–hole pairs, which limits its degradation efficiency. The YFeO3/CeO2 catalyst is characterized by two distinct orthorhombic YFeO3 and CeO2 phases, with the size of YFeO3 crystal smaller than that of its parent phase. YFeO3/CeO2 with a higher CeO2 content (YC-30) reveals not only a porous morphology and hydrophilicity, but also a reduced energy bandgap (1.74 eV) that is lower than that of either single YFeO3 (1.90 eV) or CeO2 (2.86 eV). In the photocatalysis assessment of the YC-30 electrode, a high photocurrent density of up to 156.3 μA cm−2 at 1.4 V (vs. Ag/AgCl) under simulated sun irradiation is achieved. Furthermore, the YC-30 electrode achieves a favorable photoelectrocatalytic efficiency of 75.2 % under visible light irradiation for Reactive Black 5 dye degradation, which is better than those of the YFeO3 (31.9 %) and CeO2 (46.9 %) electrodes. The improved degradation performance of the YC-30 catalyst can be attributed to its smaller crystallite size, porous structure, and a certain amount of YFeO3/CeO2 heterojunction, which is conducive to the separation of electron–hole pairs owing to electron diffusion driven by the difference in electron density between YFeO3 and CeO2.

Electrochemical and photoelectrochemical degradation of Rhodamine B using a novel BHP@ZnO photoelectrode: Synthesis, characterization, and statistical study

This study focuses on the preparation of a novel photoanode by combining BAHPO4 (BHP) and ZnO, aiming to harness their synergistic impact on degrading Rhodamine B dye (RhB). Characterization involved X-ray diffraction (XRD), SEM-EDX morphological analysis, FT-IR vibrational analysis, and UV-Vis DRS optical analysis. Both semiconductors exhibited band gaps in the UV region, with ZnO at 3.1 eV and BHP at 3.9 eV. Electrochemical analyses, including Mott-Schottky (MS), open circuit potential (OCP), photocurrent (PT), and linear sweep voltammetry (LSV), were conducted. The electrocatalytic investigation of BHP@ZnO was optimized using statistical CCD-RSM analysis, identifying key parameters for improved degradation efficiency: applied current density, pollutant concentration, supporting electrolyte concentration, and pH. Remarkably, degradation efficiency achieved 100% within 30 min. Furthermore, photoelectrocatalytic experiments under UV light reduced degradation time to 8 min. Examination of trap states at the n-n junction of BHP@ZnO unveiled insights into the degradation mechanism, pinpointing •O2- as the primary radicals accountable. The photoanode demonstrated sustained stability and repeatability, showcasing its potential as a dependable and effective tool for RhB degradation. this study presents a promising approach utilizing BHP and ZnO within a novel photoanode, highlighting their synergistic effect in degrading RhB and contributing to the field of advanced photocatalytic materials.

Photoelectrocatalytic degradation of emerging organic pollutants in water on an FTO/BiVO4/NiS photoanode

This study demonstrates the facile synthesis of bismuth vanadate-nickel sulfide (BiVO4/NiS) heterojunction via a solvothermal process coated on a fluorine-doped tin oxide (FTO) substrate for photoelectrochemical (PEC) degradation of sulfamethoxazole (SMX) and Rhodamine B (RhB). The two semiconductors were rationally designed for the p-n heterojunction as it enhances the charge-separation and light-absorbing properties for efficient degradation of organic pollutants. The successful preparation of the BiVO4/NiS composite was confirmed using structural, morphological, and optical analysis such as X-ray diffraction (XRD), transmitted electron microscopy (TEM), energy dispersive X-ray analysis (EDX), scanning electron microscopy (SEM), ultraviolet–visible diffuse reflectance spectroscopy (UV-DRS). The electrochemical and photoelectrochemical properties were investigated using electrochemical impedance spectroscopy (EIS), Mott-Schottky (M−S), and photocurrent response. Compared with the individual components, the FTO/BiVO4/NiS photoanode showed an enhanced photocurrent response of 0.4 mA/cm2 at 1.5 V potential, 16 and folds higher than the pristine BiVO4. The composite showed a band gap of 1.9 eV, 2.28 eV, and 2.18 eV for the FTO/NiS, FTO/BiVO4, and FTO/BiVO4/NiS, respectively. Moreover, the PEC degradation of the two analytes indicated that the FTO/BiVO4/NiS photoanode successfully degraded SMX (58%) and RhB (73%) in 120 min time intervals with a rate constant of 0.00755 min−1 and 0.108 min−1. Scavenger studies revealed that holes and superoxides were significant contributors to the mineralization of the analytes.

Photoelectrocatalytic Activity of ZnO-Modified Hematite Films in the Reaction of Alcohol Degradation.

Thin-film nanocrystalline hematite electrodes were fabricated by electrochemical deposition and loaded with electrodeposited zinc oxide in various amounts. Under visible light illumination, these electrodes demonstrate high activity in the photoelectrochemical degradation of methanol, ethylene glycol and, in particular, glycerol. Results of intensity-modulated photocurrent spectroscopy show that the photoelectrocatalysis efficiency is explained by the suppression of the electron-hole pair recombination and an increase in the rate of photo-induced charge transfer. Thus, zinc oxide can be considered an effective modifying additive for hematite photoanodes.

Photoelectrochemical activation of peroxymonosulfate using Sn-doped α-Fe2O3 thin film for degradation of anti-inflammatory pharmaceutical drug

Introduction of oxygen vacancies (OVs) has been investigated as a promising way to improve the electrical and catalytic characteristics of a hematite (α-Fe2O3) based photoelectrode. In this work, we develop a novel method for preparing porous Sn-doped α-Fe2O3 (Sn:Fe2O3) thin films with intrinsic OVs. The procedure included spin-coating an iron precursor onto a fluorine-doped tin oxide (FTO) substrate, followed by thermal treatment at elevated temperatures. The influence of Sn dopant on the optoelectronic properties of α-Fe2O3 was demonstrated by X-ray photoelectron spectroscopy and photoelectrochemical (PEC) measurements. The combined effect of OVs and Sn doping was found to play a synergistic role in reducing the charge recombination’s. The Sn:Fe2O3 photoanodes were used as a dual catalyst to oxidise water and break down an anti-inflammatory drug called 2-(4-isobutylphenyl)propanoic acid (IBPA). The Sn:Fe2O3 thin film with a 30-minute heat treatment time displayed the highest incident photon-to-current efficiency. For the first time, Sn:Fe2O3 thin films were utilised in the effective PEC degradation of IBPA employing peroxymonosulfate (PMS) under visible light illumination. The hydroxyl radicals (OH), singlet oxygen (1O2), photogenerated holes (h+), and sulfate radicals (SO4−) were discovered to be the main reactive species during PEC degradation. IBPA degradation and the formation of new compounds were verified using liquid chromatography-mass spectrometry. The Lepidium sativum L phytotoxicity test reveals that PEC-treated wastewater with IBPA exhibits decreased toxicity.