In situ single iron atom doping on Bi2WO6 monolayers triggers efficient photo-fenton reaction
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ABSTRACT:
SUBMITTER: Liu W
PROVIDER: S-EPMC11007430 | biostudies-literature | 2024 Mar
REPOSITORIES: biostudies-literature
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Project description:In this work, a series of Cu(ii)-doped Bi2WO6 nanomaterials with good photo-response properties were facile synthesized and used to obtain efficient peroxymonosulfate (PMS) activation activity for norfloxacin (NOF) removal under visible LED light irradiation. It was found that Cu-Bi2WO6 presents superior catalytic performance for NOF degradation in comparison with pristine Bi2WO6, attributed to the partial substitution of Bi3+ by Cu ions. Moreover, the effects of experimental conditions were carefully investigated, including PMS concentration, catalyst dosage and initial pH, and the experimental data fitted well with the pseudo-first-order model. Experimental results implied that there was a synergic effect of visible LED light energy and the sulfate radical (SR)-Fenton reaction. Additionally, the 5Cu-Bi2WO6 nanomaterial presented the best degradation efficiency of 89.27% and exhibited high NOF degradation in 5 cycles with limited Cu leaching. Furthermore, EPR and radical quenching experiments were performed to identify the reactive oxygen species presented in the SR-photo-Fenton reaction. Finally, the major degradation intermediates of NOF were detected, and a possible degradation pathway was given. Thus, a mechanism of the significant photocatalytic activity enhancement by copper doping of the Bi2WO6 catalyst was proposed.
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Project description:Here we present a magnetic recyclable photo-Fenton catalyst CoFe2O4@PPy with uniform morphology and excellent dispersibility prepared via simple in situ Fenton oxidization polymerization. The CoFe2O4 core provides good magnetic recyclability for the catalysts as well as the ion source for catalyzed decomposition of H2O2 in PPy coating. The optimal catalytic effect can be obtained by adjusting the ratio of CoFe2O4 and PPy. Methylene blue, Methyl orange and Rhodamine B (RhB) employed as model pollutants certificated that the catalyst exhibits a wide range of photodegradability. The decoloration rates reach nearly 100% in the photodegradation of 10 mg L-1 RhB after 2 h visible-light irradiation and only low toxicity small molecules are detected by LC-MS. Moreover, the catalytic activity remains after 5 cycles with decoloration rates up to 90%. The degradation measurement in the presence of scavengers of reactive species reveals that the positive holes (h+) and hydroxyl radical (·OH) are the main reactive oxygen species in the CoFe2O4@PPy system. The performance enhancement may be attributed to the combination of improved Fenton activity by coordinated Fe2+ and PPy redox pairs and photo-catalytic activity by broaden adsorption and photo-generated charge separation.
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Project description:Photo-Fenton is a promising photocatalytic technology that utilizes sunlight. Herein, an Fe-free 3%-CuO/Sr0.76Ce0.16WO4 photocatalyst was synthesized to apply simulated wastewater degradation via a photo-Fenton process under simulated sunlight. The photodegradation efficiency of RhB solution over the 3%-CuO/Sr0.76Ce0.16WO4 photocatalyst is 93.2% in the first 3 h; its photocatalytic efficiency remains at 91.6% even after three cycle experiments. The kinetic constant of the 3%-CuO/Sr0.76Ce0.16WO4 photocatalyst is 0.0127 min-1, which is 2.8-fold that of an intrinsic Sr0.76Ce0.16WO4 sample. The experiment of radical quenching revealed that the photogenerated electrons and holes are transferred to CuO to form hydroxyl radicals. Besides, the photocatalyst was characterized by scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), diffused reflectance spectroscopy (DRS), and X-ray photoelectron spectroscopy (XPS) measurements. It has some reference significance for the design of iron-free photocatalysts.
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Project description:This study presents a novel approach to fabricating anodic Co-F-WO3 layers via a single-step electrochemical synthesis, utilizing cobalt fluoride as a dopant source in the electrolyte. The proposed in situ doping technique capitalizes on the high electronegativity of fluorine, ensuring the stability of CoF2 throughout the synthesis process. The nanoporous layer formation, resulting from anodic oxide dissolution in the presence of fluoride ions, is expected to facilitate the effective incorporation of cobalt compounds into the film. The research explores the impact of dopant concentration in the electrolyte, conducting a comprehensive characterization of the resulting materials, including morphology, composition, optical, electrochemical, and photoelectrochemical properties. The successful doping of WO3 was confirmed by energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Raman spectroscopy, photoluminescence measurements, X-ray photoelectron spectroscopy (XPS), and Mott-Schottky analysis. Optical studies reveal lower absorption in Co-doped materials, with a slight shift in band gap energies. Photoelectrochemical (PEC) analysis demonstrates improved PEC activity for Co-doped layers, with the observed shift in photocurrent onset potential attributed to both cobalt and fluoride ions catalytic effects. The study includes an in-depth discussion of the observed phenomena and their implications for applications in solar water splitting, emphasizing the potential of the anodic Co-F-WO3 layers as efficient photoelectrodes. In addition, the research presents a comprehensive exploration of the electrochemical synthesis and characterization of anodic Co-F-WO3, emphasizing their photocatalytic properties for the oxygen evolution reaction (OER). It was found that Co-doped WO3 materials exhibited higher PEC activity, with a maximum 5-fold enhancement compared to pristine materials. Furthermore, the studies demonstrated that these photoanodes can be effectively reused for PEC water-splitting experiments.
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Project description:Photocatalytic reduction of CO2 has attracted enormous interest as a sustainable and renewable source of energy. In the past decade, numerous bulk-type semiconductors have been developed, but the existing designs suffer many limitations, namely rapid recombination of charge carriers and weak light absorption ability. Herein, a bottom-up approach was developed to design atomically thin sulfur-doped Bi2 WO6 perovskite nanosheets (S-BWO) with improved reduction ability, extended visible light absorption, prolonged lifetime of charge carriers, enhanced adsorption of CO2 , and reduced work function. Compared with pristine Bi2 WO6 (P-BWO), S-BWO nanosheets exhibited a 3-fold improvement in photocatalytic reduction of CO2 under simulated sunlight irradiation. Experimental studies and density functional theory calculations revealed the synergistic roles of atomically thin nanosheets and S atoms in promoting photocatalytic efficiency.
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Project description:Chemical doping constitutes an effective route to alter the electronic, chemical, and optical properties of two-dimensional transition metal dichalcogenides (2D-TMDs). We used a plasma-assisted method to introduce carbon-hydrogen (CH) units into WS2 monolayers. We found CH-groups to be the most stable dopant to introduce carbon into WS2, which led to a reduction of the optical bandgap from 1.98 to 1.83 eV, as revealed by photoluminescence spectroscopy. Aberration corrected high-resolution scanning transmission electron microscopy (AC-HRSTEM) observations in conjunction with first-principle calculations confirm that CH-groups incorporate into S vacancies within WS2. According to our electronic transport measurements, undoped WS2 exhibits a unipolar n-type conduction. Nevertheless, the CH-WS2 monolayers show the emergence of a p-branch and gradually become entirely p-type, as the carbon doping level increases. Therefore, CH-groups embedded into the WS2 lattice tailor its electronic and optical characteristics. This route could be used to dope other 2D-TMDs for more efficient electronic devices.
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Project description:Native defects and nonmetal doping have been shown to be an effective way to optimize the photocatalytic properties of Bi2WO6. However, a detailed understanding of defect physics in Bi2WO6 has been lacking. Here, using the Heyd-Scuseria-Ernzerhof hybrid functional defect calculations, we study the formation energies, electronic structures, and optical properties of native defects and nonmetal element (C, N, S, and P) doping into Bi2WO6. We find that the Bi vacancy (Bivac), O vacancy (Ovac), S doping on the O site (SO), and N doping on the O site (NO) defects in the Bi2WO6 can be stable depending on the Fermi level and chemical potentials. By contrast, the substitution of an O atom by a C or P atom (CO, PO) has high formation energy and is unlikely to form. The calculated electronic structures of the Bivac, Ovac, SO, and NO defects indicate that the band-gap reduction of Ovac 2+, Bivac 3-, and SO defects is mainly due to forming shallow impurity levels within the band gap. The calculated absorption coefficients of Ovac 2+, Bivac 3-, and SO show strong absorption in the visible light region, which is in good agreement with the experimental results. Hence, Ovac 2+, Bivac 3-, and SO defects can improve the adsorption capacity of Bi2WO6, which helps enhance its photocatalytic performance. Our results provide insights into how to enhance the photocatalytic activity of Bi2WO6 for energy and environmental applications through the rational design of defect-controlled synthesis conditions.
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Project description:Here we synthesized Bi2WO6 (BWO) using both solid-state reaction (SBWO) and hydrothermal (HBWO-U and HBWO-S) methods. The orthorhombic Pca21 phase purity in all samples is confirmed from Rietveld refinement of X-ray diffraction data, Raman spectroscopy, and Fourier transform infrared spectroscopy. The HBWO-U and HBWO-S morphology revealed rectangular, spherical, and rod-like features with an average particle size of 55 nm in field emission scanning electron micrographs. A high-resolution transmission electron micrograph showed spherical-shaped particles in the HBWO-U sample with an average diameter of ∼10 nm. The diffuse reflectance-derived indirect electronic band gaps lie within the 2.79-3.23 eV range. The BWO electronic structure is successfully modeled by Hubbard interaction Ud and Up corrected Perdew-Burke-Ernzerhof generalized gradient approximation GGA-PBE+Ud+Up with van der Waals (vdW) force in effect. The optimized (Ud, Up) values are further justified by tuning the Hartree-Fock (HF) exact-exchange mixing parameter αHF from 25% in Heyd-Scuseria-Ernzerhof (HSE06) to 20% in the PBE-HF20% functional. Moreover, no inconsistencies were seen in the GGA-PBE+Ud+Up+vdW simulated crystallographic parameters, and the elastic tensor, phonon, and linear optical properties. Overall, the computationally cheap GGA-PBE+Ud+Up with vdW force may have successfully probed the physical properties of BWO.
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Project description:The generation of radicals through photo-Fenton-like reactions demonstrates significant potential for remediating emerging organic contaminants (EOCs) in complex aqueous environments. However, the excitonic effect, induced by Coulomb interactions between photoexcited electrons and holes, reduces carrier utilization efficiency in these systems. In this study, we develop Cu single-atom-loaded covalent organic frameworks (CuSA/COFs) as models to modulate excitonic effects. Temperature-dependent photoluminescence and ultrafast transient absorption spectra reveal that incorporating acenaphthene units into the linker (CuSA/Ace-COF) significantly reduces exciton binding energy (Eb). This modification not only enhances peroxymonosulfate adsorption at Cu active sites but also facilitates rapid electron transfer and promotes selective hydroxyl radical generation. Compared to CuSA/Obq-COF (Eb = 25.6 meV), CuSA/Ace-COF (Eb = 12.2 meV) shows a 39.5-fold increase in the pseudo-first-order rate constant for sulfamethoxazole degradation (0.434 min-1). This work provides insights into modulating excitonic behavior in single-atom catalysts via linker engineering for EOCs degradation.
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Project description:To bridge the technical gap of heterojunction induction control in conventional semiconductor photocatalysts, a method of regulating the growth of heterojunctions utilizing biomimetic structures was designed to prepare a series of Bi2WO6/Bi2O3 vertical heterojunction nanocomposites for the disposal of environmentally hazardous tetracycline wastewater difficult to degrade by conventional microbial techniques. Porous Bi2O3 precursors with high-energy crystalline (110) dominant growth were produced using the sunflower straw bio-template technique (SSBT). Bi2WO6 with a (131) plane grew preferentially into 2.8 to 4 nm pieces on the (110) plane of Bi2O3, causing a significant density reduction between Bi2WO6 pieces and a dimensional decrease in the agglomerated Bi2WO6 spheres from 3 μm to 700 nm since Bi2WO6 grew on the structure of the biomimetic Bi2O3. The optimal 1:8 Bi2WO6/Bi2O3 coupling catalyst was obtained via adapting the ratio of the two semiconductors, and the coupling ratio of 1:8 minimized the adverse effects of the overgrowth of Bi2WO6 on degradation performance by securing the quantity of vertical heterojunctions. The material degradation reaction energy barrier and bandgap were significantly reduced by the presence of a large number of vertical heterojunction structures, resulting in a material with lower impedance and higher electron-hole separation efficiency; thus, the degradation efficiency of 1:8 Bi2WO6/Bi2O3 for tetracycline hydrochloride reached 99% within 60 min. In conclusion, this study not only successfully synthesized a novel photocatalyst with potential applications in water pollution remediation but also introduced a pioneering approach for semiconductor-driven synthesis.
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