A novel heterojunction photocatalyst of Bi-rich bismuth oxyiodides (Bi4O5I2/Bi7O9I3) was synthesized via regulation of the alkalinity of solvent and followed by calcination, while its degradation performance was examined for ciprofloxacin (CIP) solution. The results showed that the structurally optimized composite heterogeneous catalyst Bi4O5I2/Bi7O9I3-3 exhibits excellent adsorption and photodegradation performance for CIP 20 mg/L solution. Its adsorption rate reaches 88.1% in dark conditions for 60 min, and then subsequently under a simulated sunlight irradiation for 30 min, the CIP is completely degraded. The Bi4O5I2/Bi7O9I3 presents a microsphere morphology composed of nanoparticles and nanosheets. Meanwhile, its large specific surface area provides abundant active sites for the catalytic reaction, and the formed type-II heterojunction with band cross-arrangement can accelerate the charge transfer. Furthermore, the holes (h+) are the main active substances for the degradation of CIP in the heterojunction Bi4O5I2/Bi7O9I3, while superoxide free radicals (⋅O2-) and hydroxyl free radicals (⋅OH) hardly participated in the reaction, thus making them high activity even in an oxygen-depleted environment or in an environment with free radical competition.
In this study, Cu2O/N,S-BiOBr photocatalysts were successfully synthesized by hydrothermal method, and their performance for catalytic degradation of tetracycline (TC) under visible light irradiation was systematically evaluated. The results showed that when the doping amount of Cu2O was 10% (mass fraction), the catalyst exhibited the optimal activity with a degradation rate of approximately 85.63% for TC within 100 min. This improved performance was mainly attributed to the efficient interfacial charge transfer and synergistic effect between Cu2O and N,S-BiOBr, which enhanced the separation efficiency of photogenerated electron-hole pairs, thereby improving the photocatalytic degradation ability. The results of electron paramagnetic resonance (EPR) tests indicated that superoxide radicals (⋅O2-) and hydroxyl radicals (⋅OH) were the main active substances in the photocatalytic degradation process of TC. This study provided a valuable reference for constructing efficient visible light-driven catalysts.
Bismuth nanoparticles (NPs) were successfully synthesized in-situ on Bi2O2CO3 nanosh-eets through a one-pot hydrothermal method employing paraformaldehyde as a dual carbon source and reducing agent. The Bi/Bi2O2CO3 hybrids were comprehensively analyzed using XRD, SEM, TEM, and XPS, with their optical characteristics investigated via UV-Vis DRS. Their photocatalytic efficacy was assessed by decomposing malachite green (MG) and ciprofloxacin (CIP) as target contaminants. The results indicate uniform dispersion of Bi NPs on Bi2O2CO3, with adjustable loading content by modulating the ratio of Bi precursor to paraformaldehyde. The most effective composite Bi/Bi2O2CO3 with mass ratio of 1:10 displayed significantly improved photocatalytic performance, exhibiting reaction rates 3.5 and 19.7 times higher than pure Bi2O2CO3 and pristine Bi powder, respectively. This enhancement is ascribed to the surface plasmon resonance (SPR) of metallic Bi and the developed Bi/Bi2O2CO3 heterojunction, which collectively enhance visible-light absorption, facilitate the charge separation and transfer, and inhibit the electron-hole recombination. Additionally, ESR and trapping experiments confirmed that the increased generation of ⋅O2- radicals and ⋅OH radicals play a pivotal role in the degradation mechanism.
A photocatalyst of Sb2S3/Sn3O4 S-scheme heterojunction was prepared via hydrothermal method by in-situ growing Sn3O4 nanosheets on the surface of Sb2S3 nanorods. The phase constituents, morphology, elemental distribution, light absorption properties, and charge separation efficiency of the acquired photocatalyst were characterized by using X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, UV-Visible absorption spectroscopy, photocurrent, electrochemical impedance spectroscopy and photoluminescence spectroscopy. The performance of Sb2S3/Sn3O4 heterojunction catalysts with different deposited amount of Sb2S3 for degradation of methyl orange (MO, initial concentration: 20 mg/L) was investigated under visible light irradiation. The results indicate that these photocatalysts with heterogeneous structure all exhibit significantly high photocatalytic activity, the optimized photocatalyst with 0.1 g of Sb2S3 achieves a degradation rate of 91% for MO within 40 min. The results of XPS analysis, band gap structure and free radical trapping analysis revealed that the photogenerated charge carriers in this heterostructure follow a S-scheme transfer mechanism.
A Z-scheme heterojunction composite CuFe2O4/BaTiO3 with piezoelectric-photocatalytic synergistic effect was synthesized via sol-gel method. The crystal structure, morphology, optical absorption properties, valence band structure, and charge separation efficiency of the composite were systematically characterized using XRD, SEM, UV-Vis DRS, XPS, and PL spectroscopy. Under combined ultrasound vibration and 300 W xenon lamp irradiation, the influence of the composite CuFe2O4/BaTiO3 with different ratio of CuFe2O4 to BaTiO3 on the degradation of tetracycline (TC) was investigated. The results revealed that the incorporation of CuFe2O4 augmented the photocatalytic oxidation efficiency of BaTiO3. For a solution with TC concentration of 30 mg/L by pH 10.5, a removal efficiency of 82.3% was achieved within 30 min of xenon lamp irradiation. Radical trapping experiments confirmed that h+ and ⋅O2- served as the dominant active species in the TC degradation process. Based on the band structures of CuFe2O4 and BaTiO3, it is inferred that under light and ultrasound synergy, the photogenerated carriers in the CuFe2O4/BaTiO3 heterojunction follow a Z-scheme transfer mechanism. The piezoelectric effect induced by ultrasound generates an intrinsic electric field within BaTiO3, which can effectively suppress the recombination of photogenerated carriers. This work may offer new insights and directions for the synergistic application of piezoelectric and photocatalytic processes in antibiotic degradation.
The Ni-TiN@CN nanocomposites with multi-heterostructures were successfully synthesized via an integrated procedure involving DC arc-discharge plasma processing, dopamine (DA) self-polymerization, and controlled heat treatment. The influence of varying amounts of magnetic Ni addition on the electromagnetic wave absorption performance was systematically investigated. The phase composition, microstructure and electromagnetic wave absorption properties of the nanocomposites were comprehensively characterized by means of X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy and vector network analyzer, respectively. The results showed that the prepared Ni-TiN@CN with a Ni: Ti mass ratio of 3:7 exhibited exceptional microwave absorbing capability, achieving optimal reflection loss of -48.97 dB at 6.78 GHz, along with a broad effective absorption bandwidth (≤ -20 dB) spanning 5 GHz. The incorporation of magnetic Ni particles introduced magnetic loss mechanisms, while the multiple intrinsic defects within the heterogeneous structure synergistically generated defect dipole polarization and conductive loss. Notably, the strategic addition of Ni facilitates the construction of heterogeneous interfaces, achieving enhanced interface polarization effect. This work demonstrated successful dual regulation of dielectric and magnetic loss mechanisms in the nanocomposites through structural engineering strategies, achieving exceptional synergy between electromagnetic attenuation enhancement and impedance matching optimization, significantly improved the overall microwave absorption performance of the nanocomposites.
Plates of a directional solidification DZ411 alloy with different Ta-content (namely 3%, 3.5% and 4% Ta) were prepared by means of liquid metal cooling directional solidification technique, and subjected to standard heat treatment in atmosphere. Then, the effect of Ta content and heat treatment temperatures (800 oC, 900 oC, 1000 oC) on the fatigue crack growth behavior of DZ411 alloy plates along the direction parallel to the grain growth direction (L-direction), i.e., the direction of directional solidification of the alloy were investigated via electro-hydraulic servo fatigue testing machine by constant load with increment K method in air at room temperature, 450 oC and 900 oC respectively, while calculating the crack length through flexibility method, as well as field emission scanning electron microscopy with energy spectrometer. The results show that at room temperature, an increase in Ta content leads to a higher fatigue crack growth rate, with the crack propagation path perpendicular to the loading direction and primarily influenced by carbides. The process can be differentiated into three stages: I) the crack passes through the primary dendrite axis; II) the crack bypasses the primary dendrite axis and cuts through the secondary dendrite arm; III) the crack completely bypasses the dendrite axis and propagates along the interdendritic region. At 450 oC, the Ta-content has no significant effect on the stable crack growth stage. The crack propagation path is influenced by grain orientation, tending to enter high-Schmidt factor grains and adjacent grain boundaries. At 900 oC, an increase in Ta-content results in an overall decrease in the fatigue crack growth rate, with the crack propagation path similar to that at room temperature. However, the influence of carbides weakens, and the crack does not fully enter stage III even at fracture.
Mo1-x Mn x S2 thin films with different Mn doping amount were prepared by chemical vapor deposition, and the effect of Mn doping on the crystal structure and magnetic properties of Mo1-x Mn x S2 thin films were systematically investigated. XPS results showed that Mn atoms were efficiently doped into the MoS2 films. Their hysteresis loops measured at 2 K showed that Mn doping effectively enhanced the magnetic properties of the films, correspondingly, the saturation magnetization was 0.0096 emu/mm3 at x~9.7%, which is about three times of that of the MoS2 doped with a small amount of Mn, and the coercivity was about 160 Oe. The results also revealed that the enhancement of the magnetism of the Mn-doped MoS2 films may be mainly attributed to the introduction of the local magnetic moments and the enhanced magnetic exchange interactions of the Mn atoms. The study of the magnetic properties of Mo1-x Mn x S2 2D thin films tuned by Mn doping may provide a reference for expanding the applications of these 2D materials in spintronics and magnetic memory devices.
