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Two-Stage Ultraviolet Degradation of Perovskite Solar Cells Induced by the Oxygen Vacancy-Ti4+ States
摘要： The failure of perovskite solar cells (PSCs) under ultraviolet (UV) irradiation is a serious barrier of commercial utilization. Here, a two-stage degradation process of TiO2-based PSCs is discovered under continuous UV irradiation in an inert atmosphere. In the first decay stage, oxygen vacancy-Ti3+ (Ti3+-VO) transform into active Ti4+-VO trap states under UV excitation and cause photocarrier loss. Furthermore, Ti4+-VO states can convert back into Ti3+-VO states through oxidizing I?, which result in the accumulation of I3?. Sequentially, the rapid decomposition of perovskite accelerated by increasing I3? replaces the photocarrier loss as the dominant mechanism leading to the second decay stage. Then, a universal method is proposed to improve the UV stability by blocking the transformation of Ti3+-VO states, which can be realized by polyethyleneimine ethoxylated (PEIE) modified layer. The optimized devices remain ~75% of its initial efficiency (20.51%) under UV irradiation at 72 days, whereas the normal devices fail completely.
关键词： Ti4+ states,Oxygen vacancy,UV degradation,Perovskite solar cells,TiO2,PEIE
更新于2025-09-23 15:19:57
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CdS quantum dots modified surface oxygen vacancy defect ZnO1-x-TiO2-x solid solution sphere as Z-Scheme heterojunctions for efficient visible light-driven photothermal-photocatalytic performance
摘要： CdS quantum dots (QDs) modified surface oxygen vacancy defect ZnO1-x-TiO2-x solid solution spheres were prepared by using a hydrothermal, chemical reduction and electroless plating strategy, which have sufficient negative conduction band potential while having a photoresponse in visible light region. According to the band energy alignment, Z-scheme structure is formed, which favors spatial charge separation. The obtained CdS QDs/ZnO1-x-TiO2-x heterojunctions with the gap of ~2.09 eV exhibit excellent photothermal performance and photocatalytic degradation of bisphenol A (~99.5%), 2,6-dichlorophenol (~99.1%), and 2,4,5-trichlorophenol (~98.9%). It can be attributed to the following reasons: (1) a solid solution strategy can be used to enhance the photocatalytic activity of a given semiconductor photocatalyst. (2) The presence of oxygen defects can extend the photoresponse to visible light region. (3) TiO2-x-ZnO1-x and CdS QDs can form Z-Scheme heterojunctions to increase the spatial separation of photogenerated electron-holes, which can promote photocatalytic performance. After recycle test, the resultant catalysts show high stability, which has superiority in practical application. So this novel CdS QDs modified surface oxygen vacancy defect ZnO1-x-TiO2-x solid solution sphere will have potential applications in environmental fields.
关键词： Photothermal-photocatalytic,Solid solution,Oxygen vacancy defect,Z-Scheme heterojunction,Quantum dot
更新于2025-09-23 15:19:57
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Controllable synthesis of transition metal ion-doped CeO2 micro/nanostructures for improving photocatalytic performance
摘要： Ceria (CeO2) micro/nanostructures with various sizes and shapes were successfully synthesized by doping with a series of transition metal ions without any surfactant or template. The crystal structure, morphology, and photocatalytic performance of CeO2 and Co-, Zr-, Cu-doped CeO2 were characterized. The lattice parameters, which indicate the crystal structure distortion and change of Ce4+, were changed by incorporating a transition metal into the CeO2. Doping with transition metal ion could broaden the absorption range from ultraviolet to visible region and enhance the concentration of oxygen vacancies, which exhibited a significantly lower optical band than pure CeO2. The photocatalytic studies revealed that CeO2 with a spate of oxygen vacancies displayed a higher photocatalytic activity than pure CeO2 in degrading the organic pollutant rhodamine B (RhB). Furthermore, the O2? and ?OH radicals formed during photocatalysis process were revealed by means of nitrotetrazolium blue chloride (NBT) reduction method and a terephthalic acid (TA) fluorescence probe method, respectively, which discovers that radicals were crucial for the degradation of RhB. The H2-TPR confirmed that a small amount of transition metal ions significantly affected the oxidation state of the surface cations and oxygen vacancies. This study clearly reveals the effects of different transition metal ion dopants on the morphologies and photocatalytic performance of transition metal ion-doped CeO2 micro/nanostructures.
关键词： oxygen vacancy,CeO2,metal ion-doping,morphology,photocatalytic activity
更新于2025-09-23 15:19:57
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Oxygen-vacancy-related Giant permittivity and Ethanol sensing response in SrTiO3- ceramics
摘要： The ethanol sensing properties of SrTiO3-δ (δ=0.075 and 0.125) ceramics was analyzed by dielectric measurements. The ceramics were prepared by solid state reaction method followed by the creation of oxygen vacancies-δ, through a thermal activated process. The crystal symmetry, space group and unit cell dimensions were derived from the X-ray diffraction (XRD) data using FullProf software whereas grain’s size distribution was assessed by scanning electron microscopy (SEM). The prepared samples have been analyzed by impedance spectroscopy over the frequency range from 100 Hz to 1 MHz and temperature range from 240 to 340 K. The dielectric properties of SrTiO3-δ ceramics showed a quite remarkable stability of giant permittivity (> 104) as well as a low dielectric loss, which open ways for several applications such as over voltage protections of electronic devices. A low-frequency dielectric relaxation behavior was found, and the carriers for electrical conduction result from the first-ionization of oxygen vacancies. The conductivity and gas sensitivity of SrTiO3-δ-based sensors were investigated. Results demonstrated that the conductivity decreases after the introduction of the ethanol gas, and p-type semiconductor gas-sensing materials were obtained. Both characteristics present higher responses at lower optimal operating temperatures.
关键词： Oxygen vacancy,SrTiO3,Gas-sensor.,Giant permittivity
更新于2025-09-23 15:19:57
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Novel and efficient synthesis of Ag-ZnO nanoparticles for the sunlight-induced photocatalytic degradation
摘要： Plasmonic metal-semiconductor nanostructures endow them with an enormous potential application in photocatalysis, however, the uniform deposition of metal NPs as small as a few nanometers remains a challenge. Here, we demonstrate the effectiveness of two-step polymer-network gel process in the synthesis of Ag-ZnO nanocatalyst with superior photocatalytic properties. Because of uniform distributed Ag NPs, large specific surface area and abundant surface oxygen vacancies, the Ag-ZnO nanoparticles exhibit a super high photocatalytic efficiency in comparison to pure ZnO nanoparticles. The efficiency can be further improved by optimizing the external factors, such as catalyst dosage, ambient temperature and initial solution pH. Good stability and practicability indicate its potential application in environmental purification. Our work does not only provide a feasible strategy for the synthesis of high property Ag-ZnO nanophotocatalysts, but also enriches the understanding of metal-metal oxide nanostructures.
关键词： Surface oxygen vacancy,Photocatalytic efficiency,Nano-heterostructure,Two-step strategy,Ag-ZnO
更新于2025-09-19 17:15:36
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Electronic structure of CuWO<sub>4</sub>: dielectric-dependent, self-consistent hybrid functional study of a Mott-Hubbard type insulator
摘要： Copper tungstate, CuWO4, is a semiconducting oxide with interesting applications in photocatalysis. In this paper we present an accurate study of the electronic properties of stoichiometric and oxygen deficient CuWO4 based on a dielectric dependent hybrid density functional. In CuWO4 the Cu ions (Cu2+) are in a 3d9 configuration, so that the material must be classified as a magnetic insulator. Various magnetic configurations of CuWO4 have been considered, the most stable one being anti-ferromagnetic. The band structure, described in terms of density of states, exhibit the presence of a wide band dominated by W 5d states, separated by about 5 eV from the top of the valence band, consisting of O 2p states partly mixed with Cu 3d states. The empty component of the Cu 3d orbitals forms a narrow band 3.6 eV above the valence band maximum. The electronic structure emerging from the DOS curves and the Kohn-Sham energies is hard to reconcile with an experimental band gap of 2.1-2.3 eV. This gap can be rationalized within the Mott-Hubbard model of magnetic insulators, and has been computed from the total energies of the system with one electron removed from the O 2p band and one electron added to the Cu 3d states. Computing the charge transition levels for CuWO4, we come to a theoretical band gap of 2.1 eV, in excellent agreement with the experimental observations. We also studied the nature of the oxygen vacancy in CuWO4 with particular attention to the electron redistribution following the oxygen removal. The excess electrons, in fact, can occupy the localized 3d states of Cu or the localized 5d states of W. The resulting solution depends on various factors, including the concentration of oxygen vacancies.
关键词： CuWO4,Mott-Hubbard model,Dielectric-dependent hybrid functionals,semiconducting oxide,oxygen vacancy,density functional theory (DFT)
更新于2025-09-19 17:15:36
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Synergistic effect of surface oxygen vacancies and interfacial charge transfer on Fe(III)/Bi2MoO6 for efficient photocatalysis
摘要： Novel Fe(III) clusters grafted Bi2MoO6 nanosheets with surface oxygen vacancies (denoted as F/BMO-SOVs) heterostructured composite have been firstly fabricated via a reliable calcination process combined with impregnation approach. The surface oxygen vacancies (SOVs) in Bi2MoO6 were formed due to controlled calcination process. The presence of Fe (III) clusters was confirmed by HRTEM, XPS, and UV-Vis DRS. Under visible light irradiation, the optimum molar ratio of 15% F/BMO-SOVs achieved 93.4% degradation efficiency of phenol within 180 min, representing nearly 80 times higher activity than the pure Bi2MoO6, confirmed by both absorption spectrum and TOC measurement. The dramatically enhanced photocatalytic activity is attributed to the synergistic effect between the SOVs, Fe(III) clusters and Bi2MoO6, which not only narrows the band gap, improving the visible light response ability, but also facilitates the direct interfacial charge transfer (IFCT) from the SOVs to the surface Fe(III) clusters, greatly promoting the efficient separation of photogenerated electron-hole pairs. According to the trapping experiments and ESR measurements results, ·O2-, ·OH-, and h+ all participated in the phenol photodegradation process over F/BMO-SOVs. Thus, this work not only provides a synergistic effect between SOVs, Fe(III) clusters and Bi2MoO6 involving an IFCT process, but also proposes an efficient approach to fabricating highly active photocatalysts in environmental remediation and solar fuel synthesis.
关键词： Surface oxygen vacancy,Phenol degradation,Synergistic effect,Interfacial charge transfer,Heterostructured Fe(III)/Bi2MoO6
更新于2025-09-19 17:15:36
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Oxygen vacancy-assistant enhancement of photoluminescence performance of Eu3+ and La3+-codoped BiOCl ultrathin nanosheets
摘要： The Eu3+ and La3+ co-doped BiOCl ultrathin nanosheets were prepared through a facile solvothermal method. The samples were characterized using different techniques to study the structure, morphology, and luminescence. The solvothermal derived samples exhibit the morphology of ultrathin nanosheet. The photoluminescence spectrum of the Eu3+ ions doped BiOCl sample shows a broad emission band in the wavelength range of 380–480 nm due to the oxygen vacancies present in the sample. The spectrum also shows sharp characteristic emission peaks of Eu3+ ions. The intensity of this broad emission band increases with the incorporation of La3+ ions, due to the increase in oxygen vacancies. These results were demonstrated by the XPS spectra for all the samples. It was found that the overall luminescence intensity for the BiOCl: Eu3+, La3+ ultrathin nanosheet was about 300% stronger than the BiOCl: Eu3+ ultrathin nanosheet. As the La3+ ions concentration increases the CIE values shift from bluish-white region to white.
关键词： Oxygen vacancy,Solvothermal,Photoluminescence,BiOCl,Ultrathin nanosheet
更新于2025-09-19 17:15:36
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Evaluation of the relationship between the magnetism and the optical properties in SrTiO3-δ defective systems: Experimental and theoretical studies
摘要： To explore the relationship between optical properties, oxygen vacancies and magnetism in SrTiO3, we prepared a series of SrTiO3-δ (δ=0.00, 0.125 and 0.250) samples by solid state reaction method followed by the creation of oxygen vacancies-δ. Surface composition and chemical valence state in the synthesized compounds were examined by X-ray photoelectron spectroscopy (XPS). The Fourier Transform Infrared spectroscopy (FT-IR) spectra showed that the transmission properties change with oxygen vacancies introduction. Ultraviolet-visible absorption revealed that optical properties were highly dependent on oxygen vacancies concentrations. When the magnetic field was applied, magnetization showed weak-ferromagnetism at room temperature on SrTiO3-δ non-sto?chiometric systems. Yet, it was reversed showing diamagnetism on SrTiO3 perfect crystal. The large concentration of oxygen vacancies (δ=0.250) reduced ferromagnetism and optical absorption, implying the possible presence of a relationship between the magnetism and the optical properties. Theoretical results showed two types of electronic contributions to magnetism, one of which emanates from localized states below the conduction band minimum, and the other comes from itinerant electrons of Ti atoms lying further away from the oxygen-vacancy. The electronic structures and magnetic properties were calculated by Full-Potential Linear Augmented Plane Wave (FP-LAPW) method within the Generalized Gradient Approximation (GGA) and the atomic relaxations introduced by the oxygen vacancies host in a fully self-consistent way. The results shed some light on the promising magneto-optical properties of the SrTiO3-δ materials.
关键词： Density Functional Theory (DFT),Optical properties,Oxygen vacancy,SrTiO3,Magnetism
更新于2025-09-19 17:15:36
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P-functionalized and O-de???cient TiOn/VOm nanoparticles grown on Ni foam as electrode for supercapacitor: epitaxial grown heterojunction and visible-light-driven photoresponse
摘要： P-TiOn-VOm nanowires were grown on nickel foam (NF) by one-pot hydrothermal and further vapor deposition/phosphorization method. It is found low valence states of titanium oxide and deficient-oxygen coexist in P-TiOn-VOm/NF. Furthermore, (TiO1.25)3.07 (denoted as TiOn) and VO (denoted as VOm) possess similar structures and matched facets, their epitaxial growth leads to the formation of TiOn/VOm heterostructure with a formation energy of -1.59 eV. P-TiOn-VOm/NF possesses good electron conductivity, and electrons can be transferred from Ti to V centers, as evidenced by DFT calculations and XPS spectra. As a result, the specific capacity of P-TiOn-VOm/NF can reach 785 C g-1 at 1 A g-1 in the potential range of 0~ 0.55 V vs Hg/HgO, which is much larger than those of VOm/NF, P-VOm/NF and P-TiO2-VOm/NF. On the other hand, the TiOn/VOm heterostructure also favors for the separation and transfer of photoinduced electrons and holes, and P-TiOn-VOm/NF exhibits visible-light-driven photoresponse. Under the visible light illumination, the specific capacity of P-TiOn-VOm/NF is increased 6.2 % relative to that in dark. Furthermore, the P-TiOn-VOm/NF//activated carbon (/ AC) asymmetric supercapacitor (ASC) shows an energy density of 37.2 Wh kg-1 at power density of 1 kW kg-1, and excellent cycling performance with 93.6 % capacity retention after 10000 cycles at 5 A g?1, which is comparable to and even superior to those of titanium oxides and vanadium oxides. It is proposed a promising achievement to improve the energy storage performance of P-TiOn-VOm through the P-functionalization and O-deficiency in this work.
关键词： Phosphorus functionalized,Oxygen vacancy,TiOn-VOm,Supercapacitors
更新于2025-09-19 17:13:59