- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
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
-
Dual-Route Hydrogenation of the Graphene/Ni Interface
摘要： Nanostructured architectures based on graphene/metal interfaces might be efficiently exploited in hydrogen storage due to the attractive capability to provide adsorption sites both at the top side of graphene and at the metal substrate after intercalation. We combined in situ high resolution x-ray photoelectron spectroscopy and scanning tunneling microscopy with theoretical calculations to determine the arrangement of hydrogen atoms at the graphene/Ni(111) interface at room temperature. Our results show that at low coverage H atoms predominantly adsorb as monomers and that chemisorption saturates when ～25% of the surface is hydrogenated. In parallel, with a much lower rate, H atoms intercalate below graphene and bind to Ni surface sites. Intercalation progressively destabilizes the C-H bonds and triggers the release of the hydrogen chemisorbed on graphene. Valence band and near edge absorption spectroscopy demonstrate that the graphene layer is fully lifted when the Ni surface is saturated with H. Thermal programmed desorption was used to determine the stability of the hydrogenated interface. Whereas the H atoms chemisorbed on graphene remain unperturbed over a wide temperature range, the intercalated phase abruptly desorbs 50-100 K above room temperature.
关键词： storage,graphene,intercalation,desorption,nickel,hydrogenation
更新于2025-09-23 15:23:52
-
Doping modulation of quasi-free-standing monolayer graphene formed on SiC(0001) through Sn1-Ge intercalation
摘要： In order to modulate the transfer doping of quasi-free-standing monolayer graphene (QFMLG) formed on SiC(0001), Ge atoms were intercalated additionally into QFMLG already formed by Sn intercalation between ZL and 6H-SiC(0001). By postannealing the Ge-deposited surface at 600 °C, the Sn1-xGex film with the 4 × √3 structure, composed of a bilayer and adatoms with dangling bonds under QFMLG, has been formed. It turns out that, in this Sn1-xGex film, Ge atoms preferentially occupy the bottom layer bound to the top Si atoms of the substrate, while Sn atoms occupy the top adatom sites. Strong correlation among the electrons localized at these adatom sites induces a semiconducting alloy film. As the postannealing temperature is increased up to 800 °C, the concentration of Ge in the intercalated film of the same 4 × √3 structure is gradually increased and the Dirac point also shifts gradually from ?0.16 eV to +0.20 eV relative to the Fermi level. Such a result confirms that the transfer doping of QFMLG on SiC(0001) has been modulated by varying the alloy composition of the Sn1-xGex interfacial film.
关键词： Scanning tunneling microscopy,Quasi-free-standing graphene,SnGe alloy intercalation,Hubbard band,Doping modulation,Photoemission spectroscopy,SiC(0001)
更新于2025-09-23 15:23:52
-
Suppression of Electrochemically Driven Phase Transition in Nanostructured MoS2 Pseudocapacitors Probed Using Operando X-ray Diffraction
摘要： Pseudocapacitors with non-diffusion-limited charge storage mechanisms allow for fast kinetics that exceed conventional battery materials. It has been demonstrated that nanostructuring conventional battery materials can induce pseudocapacitive behavior. In our previous study, we found that assemblies of metallic 1T MoS2 nanocrystals show faster charge storage compared to the bulk material. Quantitative electrochemistry demonstrated that the current response is capacitive. In this work, we perform a series of operando X-ray diffraction studies upon electrochemical cycling to show that the high capacitive response of metallic 1T MoS2 nanocrystals is due to suppression of the standard first-order phase transition. In bulk MoS2, a phase transition between 1T and triclinic phases (LixMoS2) is observed during lithiation and delithiation in both the galvanostatic traces (as distinctive plateaus) and the X-ray diffraction patterns with the appearance of the additional peaks. MoS2 nanocrystal assemblies, on the other hand, show none of these features. We hypothesize that the reduced MoS2 crystallite size suppresses the first-order phase transition and gives rise to solid solution-like behavior, potentially due to the unfavorable formation of nucleation sites in confined space. Overall, we find that nanostructuring MoS2 suppresses the 1T-Triclinc phase transition and shortens Li-ion diffusion path lengths, allowing MoS2 nanocrystal assemblies to behave as nearly ideal pseudocapacitors.
关键词： intercalation pseudocapacitor,pseudocapacitance,MoS2,phase transition suppression,porous electrodes,nanocrystal assemblies,fast charging
更新于2025-09-23 15:23:52
-
Synthesis and X-ray absorption spectroscopic analysis of exfoliated perovskite oxynitride nanosheets obtained from LiLaTa2O6.15N0.57 precursor
摘要： Layered perovskite oxynitride LiLaTa2O6.15N0.57 with Dion-Jacobson phase was successfully exfoliated into colloidal suspension by using proton-exchange reaction and followed intercalation of ethylamine and tetrabutylammonium ion. According to the X-ray di?raction pattern, a basal spacing of the layered perovskite oxynitride concomitantly increased as the intercalation reaction with bulky cations proceeded. Transmission electron microscopy and atomic force microscopy analysis indicated that the exfoliated perovskite oxynitride was composed of single-layered and multi-stacked nanoplatelets. UV–vis di?use re?ectance showed that the self-reassembled perovskite oxynitride nanosheet also had characteristic absorption in a visible range, revealing that visible light harvesting property of the perovskite oxynitride maintained even after exfoliation and subsequent reassembling reaction. Extended X-ray absorption ?ne structure (EXAFS) analysis of samples clearly showed that structural disorder upon intercalation reaction resulted in damping of EXAFS oscillation, suggesting nanosized feature of the exfoliated nanosheet.
关键词： Exfoliation,XANES,Layered perovskite oxynitride,EXAFS,Intercalation
更新于2025-09-23 15:21:21
-
The role of ionic liquid breakdown in the electrochemical metallization of VO <sub/>2</sub> : An NMR study of gating mechanisms and VO <sub/>2</sub> reduction
摘要： Metallization of initially insulating VO2 via ionic liquid electrolytes, otherwise known as electrolyte gating, has recently been a topic of much interest for possible applications such as Mott transistors and memory devices. It is clear that the metallization takes place electrochemically and, in particular, there has previously been extensive evidence for the removal of small amounts of oxygen during ionic liquid gating. Hydrogen intercalation has also been proposed, but the source of the hydrogen has remained unclear. In this work, solid-state magic angle spinning NMR spectroscopy (1H, 2H, 17O and 51V) is used to investigate the thermal metal-insulator transition in VO2, before progressing to catalytically hydrogenated VO2 and electrochemically metallized VO2. In these experiments electrochemical metallization of bulk VO2 particles is shown to be associated with intercalation of hydrogen, the degree of which can be measured with quantitative 1H NMR spectroscopy. Possible sources of the hydrogen are explored, and by using a selectively deuterated ionic liquid, it is revealed that the hydrogenation is due to deprotonation of the ionic liquid; specifically, for the commonly used dialkyl-imidazolium based ionic liquids, it is the “carbene” proton which is responsible. Increasing the temperature of the electrochemistry is shown to increase the degree of hydrogenation, forming first a less hydrogenated metallic orthorhombic phase then a more hydrogenated insulating Curie-Weiss paramagnetic orthorhombic phase, both of which were also observed for catalytically hydrogenated VO2. The NMR results are supported by magnetic susceptibility measurements, which corroborate the degree of Pauli and Curie-Weiss paramagnetism. Finally, NMR spectroscopy is used to identify the presence of hydrogen in an electrolyte gated thin film of VO2, suggesting that electrolyte breakdown, proton intercalation and reactions with decomposition products within the electrolyte should not be ignored when interpreting the electronic and structural changes observed in electrochemical gating experiments.
关键词： metal-insulator transition,hydrogen intercalation,VO2,NMR spectroscopy,electrolyte gating,ionic liquid
更新于2025-09-23 15:21:21
-
The reactivity of solid rubrene with potassium: competition between intercalation and molecular decomposition
摘要： We present the synthesis and characterization of the K+ intercalated rubrene (C42H28) phase, K2Rubrene (K2R) and identify the co-existence of amorphous and crystalline materials in samples where the crystalline component is phase pure. We suggest this is characteristic of many intercalated alkali metal-polyaromatic hydrocarbon (PAH) systems, including those for which superconductivity has been claimed. The systematic investigation of K-rubrene solid state reactions using both K and KH sources reveals complex competition between K intercalation and the decomposition of rubrene, producing three K-intercalated compounds, namely, K2R, K(RR*), and KxR? (where R* and R? are rubrene decomposition derivatives C42H26 and C30H20, respectively). K2R is obtained as the major phase over a wide composition range and is accompanied by the formation of amorphous by-products from the decomposition of rubrene. K(RR*) is synthesized as a single phase and KxR? is obtained only as a secondary phase to the majority K2R phase. The crystal structure of K2R was determined using high resolution powder X-ray diffraction, revealing that the structural rearrangement from pristine rubrene creates two large voids per rubrene within the molecular layers in which K+ is incorporated. K+ cations accommodated within the large voids interact strongly with the neighbouring rubrene via η6, η3 and η2 binding modes to the tetracene cores and the phenyl groups. This contrasts with other intercalated PAHs where only a single void per PAH is created and the intercalated K+ weakly interact with the host. The decomposition products of rubrene are also examined using solution NMR, highlighting the role of the breaking of C-CPhenyl bonds. For the crystalline decomposition derivative products K(RR*) and KxR?, a lack of definitive structural information with regards to R* and R? prevents the crystal structures being determined. The study illustrates the complexity in accessing solvent-free alkali metal salts of reduced PAH of the type claimed to afford superconductivity.
关键词： crystal structure,decomposition,rubrene,intercalation
更新于2025-09-23 15:21:21
-
Commitment Between Roughness and Crystallite Size in the Vanadium Oxide Thin Film opto-electrochemical Properties
摘要： The V2O5 thin films has been widely studied because it has application as ionic host in electrochromic and lithium-ion batteries, two technologies that have an intimate connection with sustainability as substitutes for fossil energies and as agents for improving energy efficiency. In electrochromic technology, V2O5 is applied as a passive electrode due to its high transmittance and small contrast, and its reversibility on electrochemical reactions. To contribute to increase the optical and charge efficiency of V2O5 thin film passive electrodes, were investigated in this work the influence of the morphological properties, crystallite size and roughness, on the reversible specific charge capacity and the respective optical responses. The films morphological properties were modified by varying their thickness to the nanoscale. The films were deposited by thermal evaporation from powdered V2O5. The crystallite size and surface roughness were measured respectively by XRD and AFM. The results showed that the charge capacity is directly proportional to the surface roughness and inversely proportional to the crystallite size. The film optical contrast and the nominal transmittance shows to be improved according to their morphological properties. In conclusion, the V2O5 opto-electrochemical properties can be improved, increasing the efficiency on the light control processes.
关键词： Thermal evaporation,electrochromism,vanadium oxide,lithium intercalation
更新于2025-09-23 15:21:01
-
Ni-B coupled with borate-intercalated Ni(OH)2 for efficient and stable electrocatalytic and photocatalytic hydrogen evolution under low alkalinity
摘要： To convert solar energy into storable chemical fuel hydrogen via water splitting, it is highly required to develop efficient, low-cost and stable HER (hydrogen evolution reaction) catalysts and systems. For practical application, the HER catalysts can work in low alkaline or neutral reaction systems. However, in these reaction systems, water dissociation into proton is a rate-determining step, which can be overcome by loading metal oxide or hydroxides onto the HER catalysts. Ni(OH)2 is a well-reported cocatalyst to assist water dissociation. Herein, Ni-B@Ni(OH)2 [Ni-B with loaded Ni(OH)2] as a HER catalyst at weak alkalinity has been investigated. Very interestingly, we find that when borate is added into the above reaction systems, the resultant catalyst Ni-B@Ni(OH)2-BI shows much better HER activity and stability than Ni-B@Ni(OH)2. The reason is that borate ions can intercalate into Ni(OH)2 interlayers, which increases proton transport ability and stability of Ni(OH)2 loaded on Ni-B. These findings provide new insights for design new composite catalysts of HER in low alkaline reaction systems.
关键词： Hydrogen evolution,Borate intercalation,Low alkalinity,Ni(OH)2,Ni-B
更新于2025-09-23 15:21:01
-
Modifying the geometric and electronic structure of hexagonal boron nitride on Ir(111) by Cs adsorption and intercalation
摘要： Epitaxial hexagonal boron nitride on Ir(111) is significantly modified by adsorption and intercalation of alkali-metal atoms. Regarding geometry, intercalation lifts the two-dimensional layer from its substrate and reduces the characteristic corrugation imprinted by direct contact with the metal substrate. Moreover, the presence of charged species in close proximity to the hexagonal boron nitride (hBN) layer strongly shifts the electronic structure (valence bands and core levels). We used scanning tunneling microscopy, low-energy electron diffraction, x-ray photoelectron spectroscopy (XPS), and the x-ray standing wave technique to study changes in the atomic structure induced by Cs adsorption and intercalation. Depending on the preparation, the alkali-metal atoms can be found on top and underneath the hexagonal boron nitride in ordered and disordered arrangements. Adsorbed Cs does not change the morphology of hBN/Ir(111) significantly, whereas an intercalated layer of Cs decouples the two-dimensional sheet and irons out its corrugation. XPS and angle-resolved photoelectron spectroscopy reveal a shift of the electronic states to higher binding energies, which increases with increasing density of the adsorbed and intercalated Cs. In the densest phase, Cs both intercalates and adsorbs on hBN and shifts the electronic states of hexagonal boron nitride by 3.56 eV. As this shift is not sufficient to move the conduction band below the Fermi energy, the electronic band gap must be larger than 5.85 eV.
关键词： hexagonal boron nitride,Cs adsorption,electronic structure,geometric structure,intercalation
更新于2025-09-23 15:21:01