In suit constructing S-scheme FeOOH/MgIn2S4 heterojunction with boosted interfacial charge separation and redox activity for efficiently eliminating antibiotic pollutant

MOF-Derived In2O3 Microrod-Decorated MgIn2S4 Nanosheets: Z-Scheme Heterojunction for Efficient Photocatalytic Degradation of Tetracycline

The construction of Z-scheme heterostructures using matching band semiconductors is an effective strategy for producing highly efficient photocatalysts. In this study, MgIn2S4(MIS) was grown in situ on In2O3 microrods created with an In-based MOF material (In-MIL-68) as a template to successfully establish a unique MIS-In2O3 heterojunction with a well-matched Z-scheme interface charge transfer channel. Tetracycline (TC) as a typical antibiotic was chosen as the target pollutant to evaluate the photocatalytic activity. After 120 min of visible light irradiation, the MIS-In2O3-(10:1) material had the greatest photocatalytic degradation activity of tetracycline with 96.55%, which was 2.39 and 4.26 times that of MIS and In2O3, respectively. The improved photocatalytic activity is attributed to the in situ growth of MIS on In2O3, forming a Z-scheme heterojunction at the interface, which not only increases the specific surface area, exposes the abundant active site, and improves light utilization but also facilitates the migration and separation of photogenic carriers. The photocatalytic degradation products of TC were detected by liquid chromatography-mass spectrometry (LC-MS), and a preliminary degradation pathway was proposed. Radical capture experiments and ESR analysis confirmed that the main active species were holes (h+), superoxide radicals (•O2-), and superoxide and hydroxyl radicals (•OH). Finally, combined with band position analysis, this study proposes a direct Z-scheme heterojunction mechanism to improve the photocatalytic degradation of tetracycline in MIS under visible light.

Dual Z-scheme BiOI/Bi2S3/MgIn2S4 composite photocatalyst for effective photocatalytic degradation of Congo red

The demand and use of dyes in modern life are increasing, and dye pollution has become a widespread concern worldwide; therefore, it is essential to develop novel environmentally friendly materials to deal with dye wastewater. Herein, a novel visible-light-driven ternary catalyst (BiOI/Bi2S3/MgIn2S4) was fabricated by employing the hydrothermal method. Compared to BiOI, the synthesized ternary catalyst exhibited better photocatalytic performance to decompose Congo red under visible light. Congo red was completely degraded after 0.5 h (0.5 g/L photocatalyst BiOI/Bi2S3/MIS-1) in the presence of visible light, which was 16.83 and 9.94 times of that of pure BiOI and MgIn2S4, respectively. A repetitive experiment showed that the BiOI/Bi2S3/MIS-1 could be reusable to degrade Congo red, demonstrating that it has excellent mechanical properties. The enhanced photocatalytic capability was due to addition of BiOI and Bi2S3, which increased the charge separation as well as suppressed the recombination of photo-induced holes and electrons. Electron paramagnetic resonance technique and free radical trapping tests were employed to determine the radicals produced in BiOI/Bi2S3/MgIn2S4 in the presence of visible light, indicating that ·O2- and h+ were major active species to decompose Congo red under photocatalytic process. Seventeen main intermediates or reaction products were identified by UPLC-MS. The tentative degradation pathway of Congo red was also proposed.

Dopant-driven recombination delay and ROS enhancement in nanoporous Cd1-xCuxS heterogeneous photocatalyst for the degradation of DR-23 dye under visible light irradiation

Developing an efficient heterogeneous photocatalyst for environmental remediation and treatment strategies using visible light harvesting processes is promising but challenging. Herein, Cd1-xCuxS materials have been synthesized and characterized by precise analytical tools. Cd1-xCuxS materials exhibited excellent photocatalytic activity for direct Red 23 (DR-23) dye degradation in visible light irradiation. The operational parameters, like dopant concentration, photocatalyst dose, pH, and initial concentration of dye were investigated during the process. The photocatalytic degradation process follows pseudo-first-order kinetics. As compared to other tested materials, 5% Cu doped CdS material revealed superior photocatalytic performance for the degradation of DR-23 (k = 13.96 × 10-3 min-1). Transient absorption spectroscopy, EIS, PL, and transient photocurrent indicated that adding copper to the CdS matrix improved the separation of photo-generated charge carriers by lowering the recombination rate. Spin-trapping experiments recognized the photodegradation primarily based on secondary redox products, i.e., hydroxyl and superoxide radicals. According to by Mott-Schottky curves, photocatalytic mechanism and photo-generated charge carrier density were elucidated regarding dopant-induced valence and conduction bands shifting. Thermodynamic probability of radical formation in line with the altered redox potentials by Cu doping has been discussed in the mechanism. The identification of intermediates by mass spectrometry study also showed a plausible breakdown mechanism for DR-23. Moreover, samples treated with nanophotocatalyst displayed excellent results when tested for water quality metrics such as DO, TDS, BOD, and COD. Developed nanophotocatalyst shows high recyclability with superior heterogeneous nature. 5% Cu-doped CdS also exhibit strong photocatalytic activity for the degradation of colourless pollutant bisphenol A (BPA) under visible light (k = 8.45 × 10-3 min-1). The results of this study offer exciting opportunities to alter semiconductors' electronic band structures for visible-light-induced photocatalytic activity for wastewater treatment.

Degradation of formaldehyde by photo-Fenton process over n-ZVI/TiO2 catalyst

The degradation of formaldehyde in a photo-Fenton reaction was studied using n-ZVI/TiO2 as the catalyst. The effects of %n-ZVI loading, catalyst dosage, H2O2, and pH on formaldehyde degradation were studied. The n-ZVI/TiO2 catalysts were prepared by impregnation with chemical reduction, and their catalytic activity was evaluated in a batch reactor under UVC light. Transmission electron microscopy (TEM) was used to determine that the n-ZVI nanoparticle size was 39.41 nm. X-ray photoelectron spectroscopy (XPS) was used to study the oxidation states of 2%n‑ZVI/TiO2, and the Fe 2p spectrum of 2%n-ZVI/TiO2 indicated the presence of Fe0. The optimal conditions for the complete removal of formaldehyde within 30 min were an n-ZVI loading of 2 wt.%, a catalyst dosage of 0.5 g/L, 30 mM H2O2, and an initial pH of 3. After the reaction, the C-H functional group of formaldehyde was not observed due to the •OH radicals generated by Fe0 and H2O2 attacking the formaldehyde molecule. Moreover, no Fe leaching was observed, presenting an advantage compared with homogeneous Fe catalysts. Therefore, 2%n‑ZVI/TiO2 shows excellent potential as a photo-Fenton catalyst for the environmentally friendly degradation of formaldehyde.

Boosted Tetracycline and Cr(VI) Simultaneous Cleanup over Z-Scheme WO3/CoO p-n Heterojunction with 0D/3D Structure under Visible Light

In this study, a Z-Scheme WO₃/CoO p-n heterojunction with a 0D/3D structure was designed and prepared via a simple solvothermal approach to remove the combined pollution of tetracycline and heavy metal Cr(VI) in water. The 0D WO₃ nanoparticles adhered to the surface of the 3D octahedral CoO to facilitate the construction of Z-scheme p-n heterojunctions, which could avoid the deactivation of the monomeric material due to agglomeration, extend the optical response range, and separate the photogenerated electronhole pairs. The degradation efficiency of mixed pollutants after a 70 min reaction was significantly higher than that of monomeric TC and Cr(VI). Among them, a 70% WO₃/CoO heterojunction had the best photocatalytic degradation effect on the mixture of TC and Cr(VI) pollutants, and the removing rate was 95.35% and 70.2%, respectively. Meanwhile, after five cycles, the removal rate of the mixed pollutants by the 70% WO₃/CoO remained almost unchanged, indicating that the Z-scheme WO₃/CoO p-n heterojunction has good stability. In addition, for an active component capture experiment, ESR and LC-MS were employed to reveal the possible Z-scheme pathway under the built-in electric field of the p-n heterojunction and photocatalytic removing mechanism of TC and Cr(VI). These results offer a promising idea for the treatment of the combined pollution of antibiotics and heavy metals by a Z-scheme WO₃/CoO p-n heterojunction photocatalyst, and have broad application prospects: boosted tetracycline and Cr(VI) simultaneous cleanup over a Z-scheme WO₃/CoO p-n heterojunction with a 0D/3D structure under visible light.

Functionalized 2D defect g-C3N4 for artificial photosynthesis of H2O2 and synchronizing tetracycline fluorescence detection and degradation

Artificial photosynthesis of H₂O₂ is a clean production technology, which brings the synergistic effect to photodegradation of pollutants. Inspired by defect engineering, 2D defective carbon nitride (g-C₃N₄) photocatalyst was obtained via potassium ion assisted synthesis. Defective g-C₃N₄ is protonated and applied to photosynthesis of H₂O₂, H₂O₂ concentration produced reached 477.7 μM, which was approximately 5.27 times that by pristine g-C₃N₄. Additionally, defective g-C₃N₄ materials are borrowed to synchronizing tetracycline (TC) fluorescence detection and degradation, suggesting the catalyst existed bifunctional characteristics of TC detection and degradation. Meanwhile, metal impregnation engineering (molybdenum) was borrowed enhancing the electron-trapping ability in local region of defective g-C₃N₄, which takes advantages to the efficient degradation of TC. Furthermore, optical and electrical properties of photocatalysts were investigated in details by advanced material characterization testing. This work provides potential applications in the field of artificial photosynthesis and pollution degradation.

Simultaneous S-scheme promoted Ag@AgVO3/g-C3N4/CeVO4 heterojunction with enhanced charge separation and photo redox ability towards solar photocatalysis

Photocatalytic removal of toxic contaminants is one of the emerging techniques for water remediation, but it suffers from low redox ability, charge recombination and poor light harvesting efficiency. The present work reports a simultaneous S-scheme promoted by CeVO₄/g-C₃N₄/Ag@AgVO₃. The formation of the S-scheme mechanism enhanced the generation of photogenerated carriers and also improved the redox ability of the electrons and holes in the reduction and oxidation photocatalysts. The ternary demonstrated remarkable photo switching properties along with efficient charge separation which was achieved through dual interfacial interaction within the ternary (Ag@AgVO₃/g-C₃N₄ and CeVO₄/g-C₃N₄). The heterojunction formation was verified through the shift in binding energy spectra in the X-ray Photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy analysis (HR-TEM). The ternary demonstrated reduced PL intensity, width of space charge region and an upsurge in photogenerated current density in the order of 93 μA/cm2 (∼6X higher than all the pristine). This resulted in efficient removal of methyl orange, methylene blue and endocrine disruptive bisphenol-A with a removal rate of 0.02 min^-1, 0.03 min^-1 and 0.0087 min^-1 and an apparent quantum yield of 4.6 × 10^-9 (Methylene Orange), 6.89 × 10^-9 (Methylene Blue) and 2 × 10^-9 (Bisphenol A/H₂O₂).

The Ovs surface defecting of an S-scheme g-C3N4/H2Ti3O7 nanoheterostructures with accelerated spatial charge transfer

Semiconductor photocatalysis was a rising star in the sustainable transformation of solar energy for environmental problems governance. Herein, an S-scheme g-C₃N₄/H₂Ti₃O₇ heterostructure was constructed and applied to tetracycline hydrochloride (TCH) destruction. The g-C₃N₄/H₂Ti₃O₇ composite has a superior photocatalytic property to degrade TCH in contrast with bare g-C₃N₄ and H₂Ti₃O₇. The 20% g-C₃N₄/H₂Ti₃O₇ (CNHTO20) composite exhibited the optimum photocatalytic performance, and the degradation efficiency of 20 mg/L TCH reached 87.37% within 3 h (K = 0.572 min^-1). The affluent active sites of the g-C₃N₄ nanosheet and effective interfacial charge separation of the S-scheme pathway facilitated the excellent performance. Moreover, the ample oxygen vacancies (Ovs) act as the electron mediator, not only reducing the band gap energy by producing the formation of defect levels, but also broadening the photo response range and promoting the interfacial charge transfer. The coordination complexes formed between TCH molecules and Ti (IV) ions in CNHTO20 composites induce strong visible light absorption through ligand-metal charge transfer (LMCT). The Ti⁴⁺/Ti³⁺ metal cycle in CNHTO20 was conducive to the separation of the photogenerated electron-hole pairs on the heterojunction interface as well. The ESR characterization and trapping experiments certified that the dominant substances were OH, O₂^- and h⁺. The AQY calculated by the COD removal rate was 0.16%. Conclusively, the S-scheme heterojunction between H₂Ti₃O₇ and g-C₃N₄ enabled the CNHTO photocatalyst with high redox ability and boosted photocatalytic performance accordingly. This study may shed some enlightenment on the construction of heterojunctions and the realistic treatment of wastewater.

Catalytic oxidation of ibuprofen over bulk heterojunction photocatalysts based on conjugated donor-acceptor configured benzoselenadiazole molecule

The use of photocatalysts for acquiring direct photon energy from sunlight is a promising way to clean the environment, particularly the remediation of contaminants from water. In this work, firstly π-conjugated organic semiconductor configuring benzoselenadiazole, 4-(3,5-bis(trifluoromethyl) phenyl)-7-(5'-hexyl-[2,2'-bithiophen]-5-yl)-benzo [c] (Kümmerer, 2009; Chen et al., 2018; Randeep et al., 201) selenadiazole, abbreviated as (RTh-Se-F), was synthesized. The designed RTh-Se-F with an extended π-conjugation showed good optical properties in the visible region and estimated a low optical band gap of ∼2.02 eV . The molecular orbitals i.e. HOMO (-5.33 eV) and LUMO (-3.31 eV) for RTh-Se-F organic semiconductor were suitably aligned to energy levels of (Madhavan et al., 2010Madhavan et al., 2010)-Phenyl-C₇₁-butyric acid methyl esters (PC₇₁BM) which resulted in the broadening of absorption and covering of entire visible region. RTh-Se-F was integrated with varied weight percentages (wt %) of PC₇₁BM to obtain bulk heterojunction (BHJ) and applied as efficient visible light driven BHJ photocatalyst for an effective oxidation of ibuprofen. RTh-Se-F@PC₇₁BM (1:2, wt %) BHJ photocatalyst showed the superior ibuprofen degradation of ∼93% within 90 min under visible light illumination. The maximum degradation rate by BHJ photocatalyst might be accredited to the broadening of absorption capacity and improved lifetime of photogenerated electron-hole pairs which might be resulted from high absorption properties of RTh-Se-F organic semiconductor.

Z-scheme promoted heterojunction photocatalyst (Ag@AgVO3 /rGO/CeVO4) with improved interfacial charge transfer for efficient removal of aqueous organics irradiated under LED light

A facile hydrothermal route was followed to obtain a ternary composite Ag@AgVO₃/rGO/CeVO₄ with in-situ deposition of Ag nanoparticles over the AgVO₃ nano-belts. The in-situ deposition was promoted and enhanced with the introduction of GO. The as-synthesized composite demonstrated remarkable visible light harvesting efficiency greater than 75% in the visible region. The charge separation and light harvesting properties were achieved through the Z-scheme mechanism mediated through rGO and the electron trapping/Schottky barrier effect from Ag nanoparticles. The reduction in the width of space charge region (∼2.5 times) and simultaneous increase in the density of charge carriers (2.3∗10¹⁸) promoted the LED irradiated photocatalytic performance. The decay time of the charge carriers were prolonged in the order of 4.46 s implying the enhancement in the charge separation. The studies were extended to charge trapping and the band structure modelling. The later emphasized on the prominence of Z-scheme mechanism with hole mediated degradation pathway. The LED photocatalysis demonstrated a removal efficiency of 87.20% for MB and 55.51% for phenol with a average AQE of 29.28% (MB) and 13.90% (phenol) for the ternary. The mineralization efficiency determined through TOC analysis was found to be 71.72%, and 66.43% for MB and phenol system respectively.

Photocatalytic oxidation degradation of tetracycline over La/Co@TiO2 nanospheres under visible light

The oxygen-vacancy-rich La/Co@TiO₂ nanospheres for the photo catalytic degradation of tetracycline were prepared by a simple two-step method. 3 wt%La/Co@TiO₂ nanospheres had better photocatalytic performance of the degradation of tetracycline than that of the other catalysts under visible light may be due to the synergistic effect between La/Co and TiO₂ and nano-confined effect. The catalytic experimental results showed the degradation ratio of tetracycline (40 mg/L) were 100% for 90 min. XPS, Raman, and photoelectrochemical results showed appropriate number of oxygen vacancies existed on the surface of TiO₂, which could improve the activation efficiency of dissolved oxygen in tetracycline solution because they accelerated the electron transfer rate in the system and inhibited the photoelectron-hole pair recombination under visible light. The EPR and radical scavenger tests showed h⁺, O₂^-, and ·OH were the main active species for the degradation of tetracycline. Also, the possible mechanism and intermediates of the tetracycline degradation process were speculated under the visible light. La/Co@TiO₂ nanospheres would be a promising photocatalyst for wastewater treatment.

Enhanced photocatalytic and antimicrobial performance of a multifunctional Cu-loaded nanocomposite under UV light: theoretical and experimental study

Due to modern industrialization and population growth, access to clean water has become a global challenge. In this study, a metal-semiconductor heterojunction was constructed between Cu NPs and the Co_0.5Ni_0.5Fe₂O₄/SiO₂/TiO₂ composite matrix for the photodegradation of potassium permanganate, hexavalent chromium Cr(VI) and p-nitroaniline (pNA) under UV light. In addition, the electronic and adsorption properties after Cu loading were evaluated using density functional theory (DFT) calculations. Moreover, the antimicrobial properties of the prepared samples toward pathogenic bacteria and unicellular fungi were investigated. Photocatalytic measurements show the outstanding efficiency of the Cu-loaded nanocomposite compared to that of bare Cu NPs and the composite matrix. Degradation efficiencies of 44% after 80 min, 100% after 60 min, and 65% after 90 min were obtained against potassium permanganate, Cr(VI), and pNA, respectively. Similarly, the antimicrobial evaluation showed high ZOI, lower MIC, higher protein leakage amount, and cell lysis of nearly all microbes treated with the Cu-loaded nanocomposite.

Low temperature curable titanium-based sols for visible light photocatalytic coatings for glass and polymeric substrates

Titanium oxide (TiO2) is a widely used material in photocatalytic coatings in which efficiency generally lies in the ultraviolet (UV) spectrum of light. Sol-gel method provides a simple and versatile...

Preparing a dual-function BiVO4/NiFe-LDH composite photoanode for enhanced photoelectrocatalytic wastewater treatment and simultaneous hydrogen evolution

The proposed PEC degradation over the BiVO4/NiFe-LDH photoelectrode under visible light irradiation and simultaneous hydrogen evolution at the cathode.

Z-Scheme MoS2/TiO2/graphene nanohybrid photocatalysts for visible light-induced degradation for highly efficient water disinfection and antibacterial activity

A new Z-scheme MoS2/TiO2/graphene nanohybrid effectively degraded antibiotics, heavy metals and microorganisms under visible irradiation.

Anchoring ZnIn2S4 nanosheets on ZSM-5 for boosting photocatalytic Cr(vi) reduction

ZSM-5@ZnIn2S4 is constructed for highly efficient photocatalytic Cr(vi) reduction.

Oxygen vacancy and p–n heterojunction in a g-C3N4 nanosheet/CuFeO2 nanocomposite for enhanced photocatalytic N2 fixation to NH3 under ambient conditions

In this article, the nitrogen fixation process over g-C3N4 nanosheets/CuFeO2 p–n heterojunction photocatalyst is presented.

Facile synthesis of MOF-808/AgI Z-scheme heterojunction with improved photocatalytic performance for the degradation of tetracycline hydrochloride under simulated sunlight

The MOF-808/AgI Z-scheme heterojunction expanded the light absorption range and promoted the separation of electron–hole pairs, thus enhancing the photocatalytic activity.

FeOOH activating resorcinol-formaldehyde resin nanospheres for the photo-Fenton degradation of organic pollutants

Relative to the traditional homogeneous Fenton process, heterogeneous photo-Fenton system be of superiorities in cost, pH range of application, and environmental compatibility for the degradation of organic pollutants. For the...

Pharmaceuticals removal by synergistic adsorption and S-scheme photocatalysis using nano-CeO2-coupled Fe3O4 on a CTAB matrix and investigation of the nanocomposite's antibacterial and antibiofilm activities: intrinsic degradation mechanism

S-Scheme photocatalytic mechanism of a fabricated nano-heterojunction.

Photo-induced charge separation Z-scheme mechanism in ternary Bismuth Sulfide coupled SnS/Al2O3 nanostructure

The establishment of solid-state Z-scheme heterojunction photocatalytic system to efficiently tailor the photo induced charge separation is of great significance to water purification. Metal sulfides nanoparticles, tin monosulphide (SnS) and...

A carbon nanowire-promoted Cu2O/TiO2 nanocomposite for enhanced photoelectrochemical performance

We started with earth abundant materials to design a heterojunction nanocomposite with excellent visible light photoelectrochemical performance and enhanced durability.

Preparation of Bi3Fe0.5Nb1.5O9/g-C3N4 heterojunction photocatalysts and applications in the photocatalytic degradation of 2,4-dichlorophenol in environment

The energy band relationship and the active substances were studied to determine photocatalyst accords with the Z-type transfer mechanism.

A novel S-scheme heterojunction based on 0D/3D CeO2/Bi2O2CO3 for photocatalytic degradation of organic pollutants

A distinct S-scheme heterojunction of 0D/3D CeO2/Bi2O2CO3 photocatalyst was successfully synthesized via hydrothermal method employing for photocatalytic degradation of methylene blue (MB), tetracycline (TC) and aureomycin (AM). Compared with bare...