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Prevent hydrogen damage in α-Cr2O3/α-Fe2O3 (0?0?0?1) interface
摘要： By means of first-principles calculations based on the density-functional theory, we investigate the vacancy trappings prevent hydrogen damage in two dimension α-Cr2O3/α-Fe2O3 (0 0 0 1) interface structure. Our calculations show that H atoms prefer to occupy the unoccupied O atoms octahedral interstitial site (Osite) in the center of the interface structure without vacancy defect, weakening the cleavage strength of Fe and O atoms and decreasing the work function and stability of interface structure. To prevent hydrogen damage in this interface structure, we model three Fe, Cr and O vacancy defects in this interface structure, respectively. Fe and Cr vacancy defects with lower H binding energy and higher work function, are better hydrogen trappings compared to O vacancy. These results confirm the Fe and Cr vacancy defects are effective hydrogen trappings to prevent hydrogen damage for passive film of steel, which has significant practical implications.
关键词： Interface structure,Fe vacancy,Hydrogen trapping,Work function
更新于2025-09-23 15:22:29
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Interfacial Charge Transfer in 0D/2D Defect-Rich Heterostructures for Efficient Solar-Driven CO2 Reduction
摘要： Two-dimensional graphitic carbon nitride (g-C3N4) has been widely explored as a promising photocatalyst for solar CO2 conversion. However, rapid charge recombination and low visible-light utilization are severely detrimental to photocatalytic CO2 conversion. Zero-dimensional/two-dimensional (0D/2D) heterostructures are considered the promising materials with size tunability and enhanced charge separation efficiency for photocatalysis. Herein, a 0D/2D heterostructure of oxygen vacancy-rich TiO2 quantum dots confined in g-C3N4 nanosheets (TiO2-x/g-C3N4) was prepared by in-situ pyrolysis of NH2-MIL-125 (Ti) and melamine. Charge dynamics analysis by time-resolved photoluminescence (tr-PL) and femtosecond and nanosecond pump-probed transient absorption (TA) spectra revealed that charges transfer occured from 2D-g-C3N4 to 0D-TiO2 at an ultrafast subpicosecond time scale (<1 ps) through the intimate interface. The overall fast decay of the charge carriers was attributed to interfacial charge transfer, which was accompanied by recombination relaxation mediated by shallow trapped sites. Ultrafast interfacial charge transfer greatly promoted charge separation as well as electrons in shallow trapped sites were easily trapped by CO2. In addition, combing with the synergetic advantage of strong visible light absorption, high CO2 adsorption and large surface area, TiO2-x/g-C3N4 exhibited a superior CO evolution rate of 77.8 μmol g?1 h?1, roughly 5 times that of pristine g-C3N4 (15.1 μmol g?1 h?1). This work provides in-depth insights into optimizing the heterojunction for robust solar CO2 conversion.
关键词： TiO2 quantum dots,solar CO2 reduction,charge transfer,0D/2D heterostructures,oxygen vacancy
更新于2025-09-23 15:22:29
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3D Yolk@Shell TiO2-x/LDH Architecture: Tailored Structure for Visible Light CO2 Conversion
摘要： CO2 photo-conversion into hydrocarbon solar fuels by engineered semiconductors is considered as a feasible plan to address global energy requirements in times of global warming. In this regard, three dimensional yolk@shell hydrogenated TiO2/Co-Al layered double hydroxide (3D Y@S TiO2-x/LDH) architecture was successfully assembled by sequential solvothermal, hydrogen treatment and hydrothermal preparation steps. This architecture revealed a high efficiency for the photo-reduction of CO2 to solar fuels, without a noble metal co-catalyst. The time dependent experiment indicated that the production of CH3OH was almost selective until 2h (up to 251 μmol/gcat. h.), whereas the CH4 was produced gradually by increasing the time of reaction to 12h (up to 63 μmol/gcat. h.). This significant efficiency can be ascribed to the engineering of 3D Y@S TiO2-x/LDH architecture with considerable CO2 sorption ability in mesoporous yolk@shell structure, and LDH interlayer spaces. Also, oxygen vacancies in TiO2-x could provide excess sites for sorption, activation and conversion of CO2. Furthermore, the generated Ti3+ ions in the Y@S TiO2 structure as well as connecting of structure with LDH plates, can facilitate the charge separation and decrease the band gap of nanoarchitecture to the visible region.
关键词： Solar fuel,Oxygen vacancy,Photocatalysis,CO2 conversion,Nanoarchitectures
更新于2025-09-23 15:22:29
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Measuring the Lower Critical Field of Superconductors Using Nitrogen-Vacancy Centers in Diamond Optical Magnetometry
摘要： The lower critical magnetic field, Hc1, of superconductors is measured by optical magnetometry using ensembles of nitrogen-vacancy centers in diamond. The technique is minimally invasive and allows accurate detection of the vector magnetic field with subgauss sensitivity and submicrometer spatial resolution. These capabilities are used for detailed characterization of the first vortex penetration into superconducting samples from the corners. Aided by the revised calculations of the effective demagnetization factors of actual cuboid-shaped samples, these measurements provide precise determination of Hc1 and the related absolute value of the London penetration depth, λ. We apply this method to three well-studied superconductors: optimally doped Ba(Fe1?xCox)2As2, stoichiometric CaKFe4As4, and the high-Tc cuprate YBa2Cu3O7?δ. Our results compared well with the values of λ obtained with other techniques, thus adding another noninvasive and sensitive method to measure these important parameters of superconductors.
关键词： optical magnetometry,nitrogen-vacancy centers,London penetration depth,superconductors,lower critical field
更新于2025-09-23 15:22:29
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The stability of graphene-based M?bius strip with vacancy and at high-temperature
摘要： The structural and electronic properties of mono-vacancy (MV) defect in graphene-based M?bius strip (GMS) are studied in the framework of density functional theory (DFT) combined with the molecular dynamics (MD) simulations. Two kinds of MV defects are observed: the 59-type MV (a configuration with one pentagon and one nonagon ring) located at the curved areas of M?bius strip, and the 5566-type MV (a configuration with two pentagon and two hexagon rings) with one sp3 hybridized carbon appeared in the twisted areas. The 5566-type MV defect is the most stable configuration at 0 K, while the DFT-MD calculations show that it is unstable at room-temperature and will transform into a 59-type MV. Additionally, the melting behavior of GMSs is investigated through empirical potential MD simulations, and we find that their melting temperatures are about 2750 K, which is lower than that of carbon nanotubes and graphene.
关键词： Graphene-based M?bius strip,mono-vacancy defect,melting temperature.
更新于2025-09-23 15:22:29
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Density Functional Theory Calculations of Oxygen-Vacancy Formation and Subsequent Molecular Adsorption on Oxide Surfaces
摘要： The surface oxygen vacancy formation energy (EOvac) is an important parameter in determining the catalytic activity of metal oxides. Estimating these energies can therefore lead to data-driven design of promising catalyst candidates. In the present study, we determine EOvac for various insulating and semiconducting oxides. Statistical investigations indicate that the band gap, bulk formation energy, and electron affinity are factors that strongly influence EOvac. Electrons enter defect states after O desorption, and these states can be in the valence band, mid-gap, or in the conduction band. Subsequent adsorption of O2, NO, CO, CO2, and H2 molecules on an O-deficient surface is also investigated. These molecules become preferentially adsorbed at the defect sites, and EOvac is identified as the dominant factor that determines the adsorption mode as well as a descriptor that shows good correlation with the adsorption energy.
关键词： catalytic activity,molecular adsorption,oxygen vacancy formation energy,metal oxides,density functional theory
更新于2025-09-23 15:21:21
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Comprehensive Understanding and Controlling the Defect Structures: An Effective Approach for Organic-Inorganic Hybrid Perovskite-Based Solar-Cell Application
摘要： Understanding the defect structure in organic-inorganic hybrid perovskite material (OHP) is a crucial role to explain several physical properties such as material stability, energy band, carrier mobility, and so on. In the solar-cell applications using OHP, finding, understanding, and controlling defects is essential to making a more advanced device with high efficiency and stability. Naturally, we need to find, understand, and control the possible defects in OHP. However, the defect research field in OHP material is just beginning now. In this short review, we will explore the kinds of defects and their effects on OHP.
关键词： molecular defect,organic-inorganic hybrid perovskite,Schottky/Frankel defect,vacancy,delocalized defect,thin film,defect,solar-cell
更新于2025-09-23 15:21:21
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Magnetic and optical behaviors of SnO2-x thin films with oxygen vacancies prepared by atomic layer deposition
摘要： SnO2-x thin films with different concentration oxygen vacancies were prepared by Atomic Layer Deposition (ALD). Specifically, the oxygen vacancy concentration was controlled by the oxidation pulse time during the ALD process. The crystal structure of the as-prepared thin films was determined by XRD, and the magnetic properties were measured by VSM, while the optical properties were measured by optical transmittance spectrum. The results showed that the oxygen vacancy concentration of the SnO2-x could be controlled by the oxidation pulse time, and the crystal structures, magnetic properties, and optical properties were largely impacted by the concentration of oxygen vacancy.
关键词： microstructure,thin film,magnetic,diffraction,nanocrystal,oxygen vacancy
更新于2025-09-23 15:21:21
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Effects of carbon doping and vacancy defect on the magnetism of anatase TiO2
摘要： The magnetism origin and mechanism of anatase TiO2 with C doping and vacancy remain controversial. In this study, the effects of C doping and vacancy defect on the magnetism of TiO2 were investigated by generalized gradient approximation and Hubbard U method based on density functional theory. Systems with coexisting interstitial C and O vacancies achieved half-metallic ferromagnetism, and the Curie temperature was above the room temperature. The system used as electron injection source reached 100% electron spin polarization. The Ti32CO2O62 system exhibited ferromagnetism, and the Curie temperature was above the room temperature. The magnetism source of Ti16CiO31 and Ti32CO2O62 demonstrated strong hybrid coupling electron exchange effects among Ti-3d, O-2p, and C-2p orbits which is consistent with the RKKY model of d-p orbital electron exchange.
关键词： Carbon doping and vacancy defect,Magnetism,Anatase TiO2,First-principles
更新于2025-09-23 15:21:21
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Nanophotonic energy storage in upconversion nanoparticles
摘要： In nanophotonic energy storage, an energy conversion model is established for intrinsic nanophotonic energy storage (NPES) effects. Here we realize that the charge inhomogeneous distribution on the surface of upconversion nanoparticles (UCNPs) would persistently exist as well as the formation and migration of surface defects states despite of the compound component ratio, even following the stringent stoichiometric ratio. Our preliminary efforts on NPES effect has recognized from the recent published work [Nature 561, 88 (2018)], which the surface quantum confinement arose because of a recently found surface vacancy induced Coulomb states (SVIC) states. Further in-depth excavation on surface charge density distributions and defect orbitals of surface localized electronics and holes have affirmatively repeated the Guerra’s theory [Nature 554, 346 (2018)] and reflected the existence of surface defect states in both stoichiometric and non-stoichiometric compounds. Therefore, beyond the experimental trail-based multi-doping chemical modifications, we proposed the surface electronic process for efficient NPES effect can be modulated by an intrinsic level-matching induced surface resonant quantum tunneling (LM-SRQT) in this work. The UCNP size-effect can be confirmed that simply might be not an influencing factor of dominating NPES effect while the surface degree of non-crystallizations indeed matters.
关键词： level-matching induced surface resonant quantum tunneling (LM-SRQT),surface vacancy induced Coulomb states (SVIC) states,nano energy,nanophotonic energy storage (NPES),electron-transfer surface mechanism
更新于2025-09-23 15:21:21