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Visible-light-triggered generation of persistent radical anions from perylenediimides: A substituent effect and potential application in photocatalytic reduction of Ag+
摘要： Three perylenediimide derivatives were reduced to their persistent radical anions in N-methyl-2-pyrrolidone (NMP) under ambient conditions by a visible light photoinduced electron transfer (PET). UV?vis and electron paramagnetic resonance (EPR) measurements were carried out to confirm the formation of radicals. The relationships between molecular structure, electrochemical property, phototransformation kinetics, and air stability of radical anions were investigated by the introduction of pyrimidine rings at the core position and fluoroalkylation substituents at the imide position. This study reveals that the electron-deficient pyrimidine rings and electron-withdrawing fluoroalkylation substituents can effectively enhance the phototransformation rate and the radical stability at ambient conditions. The effects of solvents and illuminance levels on the photoinduced reduction of perylenediimides were also studied. A photocatalytic reduction of Ag+ was successfully carried out using the perylenediimide with pyrimidine and fluoroalkylation substituents as catalyst upon irradiation with visible light.
关键词： Photocatalytic reduction,Perylene diimide derivative,Silver ion,Persistent radical anion,Visible light irradiation
更新于2025-11-14 17:03:37
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A novel Z-scheme Ag3VO4/BiVO4 heterojunction photocatalyst: Study on the excellent photocatalytic performance and photocatalytic mechanism
摘要： A novel three-dimensional microspheres mediator-free Z-scheme Ag3VO4/BiVO4 heterojunction photocatalyst was successfully obtained for the first time. The photocatalytic performance of the as-prepared photocatalyst was systematically examined via the photocatalytic reduction of Cr6+ and oxidation of Bisphenol S under visible-light irradiation. Among these samples, 0.24-Ag3VO4/BiVO4 exhibits the highest photocatalytic performances, the photocatalytic reduction and oxidation efficiency of 74.9 and 94.8 %, respectively, can be achieved. The enhanced photocatalytic performance is attributed to the build-in electric field assisted charge transfer between the Ag3VO4 and BiVO4, and the increasing lifetime of the charge carrier confirmed by the results of time-resolved fluorescence spectra and photoelectrochemical measures. Moreover, based on the results of free radical scavenging activity test, and EPR experiments, it has been verified that the Ag3VO4/BiVO4 heterostructures follow a typical Z-scheme charge transfer mechanism rather than conventional type-II heterojunction charge transfer mechanism. Furthermore, the theoretical understanding of the underlying mechanism was also supported, while the energy band structure, and Fermi level were systematically calculated using the density functional theory approach. The results show that a built-in electric field directed from Ag3VO4 to BiVO4 surface was established as an equalized Fermi level was reached, which benefits the separation of photogenerated charge carriers in the way of a Z-scheme charge transfer mechanism. The strategy to form the three-dimensional microspheres Z-scheme heterojunction photocatalyst may offer new insight into the Z-scheme charge transfer mechanism for applications in the field of solar energy conversion.
关键词： Bismuth Vanadate,Z-scheme heterojunction photocatalyst,photocatalytic reduction and oxidation.
更新于2025-09-23 15:23:52
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Enhanced Photoreduction of Chromium(VI) Intercalated Ion Exchange in BiOBr <sub/>0.75</sub> I <sub/>0.25</sub> Layers Structure by Bulk Charge Transfer
摘要： Owing to its low separating and utilizing efficiency of photo-generated charges in the bulk, the application of photocatalytic technique has been restricted for decades. In this paper, based on interlayer ion-exchange between BiOBr0.75I0.25 layers, we demonstrated a specific interfacial process of photocatalytic Cr(VI) reduction by a direct bulk-charge transfer. The results showed that Cr(VI) was effectively converted to nontoxic Cr(III), even under neutral conditions (pH = 7.0). According to ultraviolet-visible spectroscopy (UV-Vis), X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis, the CrO4 2? anion was readily intercalated into the anion lattice layer of BiOBr0.75I0.25 by ion-exchange with OH? in the interlayer, forming a =Bi-O-CrO3 ? complex. Electron paramagnetic resonance (EPR) and photoelectron-chemistry measurements further revealed that excitation of =Bi-O- CrO3 ? by irradiation was crucial for photocatalytic detoxification of Cr(VI) under pH 7.0. The excitation of =Bi-O-CrO3 ? in BiOBr0.75I0.25 strengthened the bulk-charge transfer as follows: (i) electron transfer from O-II to CrVI produced CrV and O-I, respectively, via ligand-to-metal charge transfer excitation; and (ii) electron injection from BiOBr0.75I0.25 to [=Bi-O?I-CrVO3 ?]* (or exportation hole to valence band) resulted in the reduction of Cr(V) to Cr(III). After that, the newly formed Cr(III) in the interlayer of BiOBr0.75I0.25 was de-intercalated into solution due to the space charge repulsion between Cr3+ and Bi2O2 2+ slab, resulting in stable Cr(VI) reduction performance in a wide pH range from 2.0 to 7.0.
关键词： Bulk-charge transfer,Intercalated ion-exchange,De-intercalation,Photocatalytic reduction
更新于2025-09-23 15:23:52
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Efficient and stable photocatalytic reduction of aqueous hexavalent chromium ions by polyaniline surface-hybridized ZnO nanosheets
摘要： ZnO/PNAI nanocomposites were obtained via a simple two-step method, in which a hierarchically ?ower-like ZnO, assembled from nanosheets, was ?rst synthesized by low temperature (80 °C) solution method without surfactant/template and then, an in-situ polymerization of aniline onto the ZnO nanosheets was carried out. The characterization was actualized on the synthesized nanocomposite using XRD, Raman, TG-DSC, UV–vis-DRS, PL, XPS, SEM, TEM and N2 adsorption-desorption analysis. An ef?cient and stable photocatalytic activity was exhibited by the synergistic ZnO/PNAI nanocomposites on the reduction of toxic Cr(VI) to benign Cr(III) in comparison with the pristine ZnO and other semiconductor/PANI materials reported. The in?uence of parameters such as solution pH, initial Cr(VI) concentration and the addition of organic sacri?ces on the Cr(VI) removal ef?ciency was investigated. It was found that the Cr(VI) removal was strongly pH-dependent and the optimum pH range was 4–7 for ZnO/PANI composite catalyst. The Langmuir–Hinshelwood kinetic examination showed that the surface photoreaction was the rate-determining step to compare the adsorption equilibrium. The organic additives such as EDTA and citric acid can promote the photocatalytic ef?ciency and the solution of EDTA/HCl can well restore the photoreduction ability of ZnO/PANI catalyst. Moreover, the reusability of photocatalyst was also tested to estimate the practicability.
关键词： ZnO/PANI nanocomposites,Photocatalytic reduction,Hexavalent chromium,Synergistic effect
更新于2025-09-19 17:15:36
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WS2 quantum dots seeding in Bi2S3 nanotubes: A novel Vis-NIR light sensitive photocatalyst with low-resistance junction interface for CO2 reduction
摘要： Efficient photocatalysts sensitive to visible and near infrared lights have attracted increased concerns owing to the high utilization efficiency of solar energy. Herein, WS2 quantum dots (WS2 QDs) doped Bi2S3 nanotubes with smooth surface were constructed by seed-mediated strategy with WS2 QDs as seeds, which show sensitive response to Vis-NIR lights. In WS2@Bi2S3 structure, exposed S atoms in WS2 QDs combined Bi3+ ions to form Bi-S bonds, and enabled the S-sharing between WS2 and Bi2S3 unit cells. The perfect junction interface between WS2 and Bi2S3 is straight and smooth without any disordered atoms, endowing low resistance for fast electron transfer on the interface and efficient separation of electron-hole pairs. Compared with pristine Bi2S3 nanotubes, the WS2@Bi2S3 nanotubes display enhanced photocatalytic activity in CO2 reduction, with 38.2 μmol g-1 of methanol and 27.8 μmol g-1 of ethanol achieved at optimal WS2 loading content (4 wt%) under Vis-NIR light irradiation for 4 h. It is proposed that the low-resistance interface between WS2@Bi2S3 heterojunction and the regulated electron pathway along Bi2S3 nanotubes account for the high photocatalytic activity, which enables WS2@Bi2S3 a promising and unique photocatalyst, and indicates a new direction for light harvest.
关键词： WS2 quantum dots,Bi2S3 nanotube,photocatalytic reduction of CO2,seed-mediated,heterojunction interface
更新于2025-09-12 10:27:22
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Two-step Synthesis of Laminar Vanadate via a Facile Hydrothermal Route and Enhancing the Photocatalytic Reduction of CO2 into Solar Fuel through Tuning the Oxygen Vacancies by in situ Vacuum Illumination Treatment
摘要： Monoclinic LaVO4, tetragonal CeVO4 and monoclinic Pb2V2O7 with laminar structures composed of nanosheets have been successfully fabricated using a two-step facile hydrothermal route. The narrow-bandgap LaVO4, CeVO4 and Pb2V2O7 vanadate exhibited photocatalytic activity towards the photoreduction of CO2 into C2H5OH in the liquid phase. The existence of oxygen vacancies on LaVO4 surface further enhanced the photocatalytic activity for photoreduction of CO2 into CO in gas phase, which can be easily obtained using a vacuum illumination treatment. The EPR, PL and FTIR results indicated that oxygen vacancies are beneficial to the separation of electrons by prolonging the lifetime of the photogenerated electrons and enhancing the chemisorption of CO2 on the photocatalyst surface.
关键词： Laminar structure,Photocatalytic reduction of CO2,Vanadate,Oxygen vacancy,Photocatalytic activity
更新于2025-09-10 09:29:36
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Insight into Reinforced Photocatalytic Activity of CNT-TiO <sub/>2</sub> nanocomposite for CO <sub/>2</sub> Reduction and Water Splitting
摘要： Using titanium dioxide (TiO2) and its modified forms for photocatalytic reduction of CO2 reduction and production of hydrogen are promising routes for providing solutions to the world energy demand in the foreseeable future. Here, we report the synthesis of a series of efficient, stable TiO2 nanoparticles modified with multi-walled carbon nanotubes (CNT) via a simple, combined sonothermal method followed by a hydrothermal treatment. In comparison to bare TiO2, the synthesized CNT-TiO2 photocatalysts showed improved photocatalytic activities for CO2 reduction under UVA as well as under visible light; and water (H2O) splitting under visible light at ambient temperature and pressure. The 2.0CNT-TiO2 has performed the best for methanol, hydrogen and formic acid production from the reduction of CO2 with yield rates of 2360.0, 3246.1 and 68.5 μmol g-1 h-1 under UVA, respectively. Its potential was further tested under visible light for methanol production, 1520.0 μmol g-1 h-1. Also, the highest rate of hydrogen yield from water splitting was 69.41 μmol g-1 h-1 with 2.0CNT-TiO2 under visible light at pH 2. The primary photocatalytic reactions of CNT-TiO2 composites and their intimate structure were studied computationally. It was demonstrated that the binding of CNT to TiO2 nanoparticles are preferable at (101) surfaces compared to (001) facets. Interaction of CNT with TiO2 results in common orbitals within TiO2 band gap that enables visible light excitation of the CNT-TiO2 composites can lead to charge transfer between TiO2 and CNT; while UV light excitation can result in charge transfer in any direction, from CNT to TiO2 and from TiO2 to CNT. The latter process is operative in the presence of sacrificial electron donor TEOA.
关键词： photocatalytic reduction,CO2 reduction,UVA light,water splitting,visible light,CNT-TiO2 nanocomposite,hydrogen production
更新于2025-09-09 09:28:46
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Construction of two dimensional composite derived from TiO2 and SnS2 for enhanced photocatalytic reduction of CO2 into CH4
摘要： Photocatalytic reduction of CO2 does effectively mitigate the concern of environment issue and energy shortage. As one of the effective techniques for improving photocatalytic performance, highly efficient compounding between semiconductor and cocatalyst is capable of inhibiting electrons and holes recombination. Herein, we build a 2D-2D heterojunction photocatalyst (SnS2/TiO2) to proffer a highly ameliorated effect on the photocatalysis. The catalyst was prepared by hydrothermally depositing ultrathin SnS2 nanosheets onto TiO2 nanosheets. The prepared composite is systematically analyzed and confirmed by the corresponding characterizations. Further practical application of the as-synthesized catalysts demonstrates that when the loaded amount of SnS2 is 5wt%, the activity of 2D-2D SnS2/TiO2 catalyst exhibits the optimum catalytic activity with the CH4 yield of 23μmol/g, which is 20, 10 and 9 times greater than that conducted by P25, TiO2 nanosheet and SnS2 nanosheet, respectively. According to the PL, PEC and TEM characterization, along with the increment of the contact interface between the two components, the combination of electrons and holes is greatly reduced.
关键词： Z-Scheme,Co-exposed,Photocatalytic reduction,2D-2D heterojunction
更新于2025-09-09 09:28:46
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Photocatalytic reduction of uranyl: Effects of organic ligands and UV light wavelengths
摘要： Although previous studies demonstrate the photochemical reduction of uranyl (UO2) in the presence of various organic compounds, the actual roles of organic molecules as ligands and electron donors during the photoreaction are poorly understood. In this study, photochemical reduction of uranyl is examined with respect to organic ligands as electron donors and complexing agents, the role of titanium oxide (TiO2) nanoparticles as a photocatalyst, and the influence of UV light irradiation with emission peaks in the UV-A, UV-B, and UV-C ranges. Organic compounds with different binding affinities to uranyl such as acetate, ethylenediaminetetracetate (EDTA), oxalate, and hydroquinone were selected. Uranyl solutions prepared with one organic compound in a 1:8 molar ratio were irradiated under anoxic and acidic conditions (O2 < 1 ppm, pH 2.5). Uranyl removal by UV irradiation was better than 70 percent in the presence of oxalate and acetate, followed by hydroquinone (≈ 45 %) and EDTA (≈ 10 %). Uranyl removal was nearly constant at the UV-A, UV-B, and UV-C regions in the presence of acetate and oxalate whereas greater removal was observed in the EDTA and hydroquinone solutions exposed to UV-C and UV-A, respectively. These results reveal that uranyl reduction is mediated primarily by TiO2 nanoparticles and is highly dependent on the electron-donor compound. Addition of acetate enhances the uranyl photoreaction in hydroquinone solution. Dissolved EDTA species act as good electron donors at limited EDTA concentrations (1:2 to 1:4 uranyl to EDTA ratios) but at higher concentrations (for example, 1:8), uranyl-EDTA complexes such as [(UO2)HEDTA] compete for the surface sites on the TiO2 nanoparticles, hindering the photoreduction of uranyl. X-ray photoelectron spectroscopy (XPS) of the dried TiO2 powder shows that more than 70 percent of uranium partitioned into the solid phase is present as reduced forms with oxidation states (V) and (IV). The U4f spectra of U partitioned to the solid phase from the photoreaction with acetate reveal the predominance of U(IV) over U(V), whereas U(V) is the dominant oxidation state as a result of the photoreduction with EDTA. Our results suggest that formation of uranium-ligand complexes plays a critical role in controlling the reactivity of uranyl species and the stability of reduced uranium species in the course of the photoreaction.
关键词： organic ligand,rutile,P25,UV wavelength,electron donor,photocatalytic reduction of uranyl,anatase
更新于2025-09-09 09:28:46