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1.
To achieve excellent photoelectrochemical water‐splitting activity, photoanode materials with high light absorption and good charge‐separation efficiency are essential. One effective strategy for the production of materials satisfying these requirements is to adjust their band structure and corresponding bandgap energy by introducing oxygen vacancies. A simple chemical reduction method that can systematically generate oxygen vacancies in barium stannate (BaSnO 3 (BSO)) crystal is introduced, which thus allows for precise control of the bandgap energy. A BSO photoanode with optimum oxygen‐vacancy concentration (8.7%) exhibits high light‐absorption and good charge‐separation capabilities. After deposition of FeOOH/NiOOH oxygen evolution cocatalysts on its surface, this photoanode shows a remarkable photocurrent density of 7.32 mA cm ?2 at a potential of 1.23 V versus a reversible hydrogen electrode under AM1.5G simulated sunlight. Moreover, a tandem device constructed with a perovskite solar cell exhibits an operating photocurrent density of 6.84 mA cm ?2 and stable gas production with an average solar‐to‐hydrogen conversion efficiency of 7.92% for 100 h, thus functioning as an outstanding unbiased water‐splitting system. 相似文献
2.
Oxygen vacancies play crucial roles in defining physical and chemical properties of materials to enhance the performances in electronics, solar cells, catalysis, sensors, and energy conversion and storage. Conventional approaches to incorporate oxygen defects mainly rely on reducing the oxygen partial pressure for the removal of product to change the equilibrium position. However, directly affecting reactants to shift the reaction toward generating oxygen vacancies is lacking and to fill this blank in synthetic methodology is very challenging. Here, a strategy is demonstrated to create oxygen vacancies through making the reaction energetically more favorable via applying interfacial strain on reactants by coating, using TiO 2(B) as a model system. Geometrical phase analysis and density functional theory simulations verify that the formation energy of oxygen vacancies is largely decreased under external strain. Benefiting from these, the obtained oxygen‐deficient TiO 2(B) exhibits impressively high level of capacitive charge storage, e.g., ≈53% at 0.5 mV s ?1, far surpassing the ≈31% of the unmodified counterpart. Meanwhile, the modified electrode shows significantly enhanced rate capability delivering a capacity of 112 mAh g ?1 at 20 C (≈6.7 A g ?1), ≈30% higher than air‐annealed TiO 2 and comparable to vacuum‐calcined TiO 2. This work heralds a new paradigm of mechanical manipulation of materials through interfacial control for rational defect engineering. 相似文献
3.
Harnessing solar energy for the production of clean hydrogen by photoelectrochemical water splitting represents a very attractive, but challenging approach for sustainable energy generation. In this regard, the fabrication of Fe 2O 3–TiO 2 photoanodes is reported, showing attractive performances [≈2.0 mA cm −2 at 1.23 V vs. the reversible hydrogen electrode in 1 M NaOH] under simulated one‐sun illumination. This goal, corresponding to a tenfold photoactivity enhancement with respect to bare Fe 2O 3, is achieved by atomic layer deposition of TiO 2 over hematite (α‐Fe 2O 3) nanostructures fabricated by plasma enhanced‐chemical vapor deposition and final annealing at 650 °C. The adopted approach enables an intimate Fe 2O 3–TiO 2 coupling, resulting in an electronic interplay at the Fe 2O 3/TiO 2 interface. The reasons for the photocurrent enhancement determined by TiO 2 overlayers with increasing thickness are unraveled by a detailed chemico‐physical investigation, as well as by the study of photogenerated charge carrier dynamics. Transient absorption spectroscopy shows that the increased photoelectrochemical response of heterostructured photoanodes compared to bare hematite is due to an enhanced separation of photogenerated charge carriers and more favorable hole dynamics for water oxidation. The stable responses obtained even in simulated seawater provides a feasible route in view of the eventual large‐scale generation of renewable energy. 相似文献
4.
Here, a Sb‐doped SnO 2 (ATO) nanorod underneath an α‐Fe 2O 3 nanorod sheathed with TiO 2 for photoelectrochemical (PEC) water splitting is reported. The experimental results, corroborated with theoretical analysis, demonstrate that the ATO nanorod underlayer effect on the α‐Fe 2O 3 nanorod sheathed with TiO 2 enhances the PEC water splitting performance. The growth of the well‐defined ATO nanorods is reported as a conductive underlayer to improve α‐Fe 2O 3 PEC water oxidation performance. The α‐Fe 2O 3 nanorods grown on the ATO nanorods exhibit improved performance for PEC water oxidation compared to α‐Fe 2O 3 grown on flat fluorine‐doped tin oxide glass. Furthermore, a simple and facile TiCl 4 chemical treatment further introduces TiO 2 passivation layer formation on the α‐Fe 2O 3 to reduce surface recombination. As a result, these unique nanostructures show dramatically improved photocurrent density (139% higher than that of the pure hematite nanorods). 相似文献
5.
Zinc gallate (ZnGa 2O 4) nanowires were directly grown on the amorphous carbon-coated silicon substrates using a facile chemical vapor deposition method without any metal catalysts. The growth mechanism can be attributed to a self-organization vapor-liquid-solid (VLS) process. The amorphous carbon layer plays an important role in the nucleation and growth process of the ZnGa 2O 4 nanowires. The photoluminescence (PL) of the nanowires shows a broad, strong green emission band centered at 532 nm and a weak UV emission band at 381 nm, which can be attributed to a large amount of ionized oxygen vacancies and the combination of Ga 3+ ions with free electrons in coordinated oxygen vacancies, respectively. 相似文献
6.
The homojunction of oxygen/metal vacancies and its interfacial n–p effect on the physiochemical properties are rarely reported. Interfacial n–p homojunctions of TiO 2 are fabricated by directly decorating interfacial p‐type titanium‐defected TiO 2 around n‐type oxygen‐defected TiO 2 nanocrystals in amorphous–anatase homogeneous nanostructures. Experimental measurements and theoretical calculations on the cell lattice parameters show that the homojunction of oxygen and titanium vacancies changes the charge density of TiO 2; a strong EPR signal caused by oxygen vacancies and an unreported strong titanium vacancies signal of 2D 1H TQ‐SQ MAS NMR are present. Amorphous–anatase TiO 2 shows significant performance regarding the photogeneration current, photocatalysis, and energy storage, owing to interfacial n‐type to p‐type conductivity with high charge mobility and less structural confinement of amorphous clusters. A new “homojunction of oxygen and titanium vacancies” concept, characteristics, and mechanism are proposed at an atomic‐/nanoscale to clarify the generation of oxygen vacancies and titanium vacancies as well as the interface electron transfer. 相似文献
7.
Hematite suffers from poor charge transport and separation properties for solar water splitting. This paper describes the design and fabrication of a 3D Fe 2O 3/Fe 2TiO 5 heterojunction photoanode with improved charge separation, via a facile hydrothermal method followed by atomic layer deposition and air annealing. A highly crystallized Fe 2TiO 5 phase forms with a distinct interface with the underlying Fe 2O 3 core, where a 4 nm Fe 2TiO 5 overlayer leads to the best photoelectrochemical performance. The favorable band offset between Fe 2O 3 and Fe 2TiO 5 establishes a type‐II heterojunction at the Fe 2O 3/Fe 2TiO 5 interface, which drives electron–hole separation effectively. The Fe 2O 3/Fe 2TiO 5 composite electrode exhibits a dramatically improved photocurrent of 1.63 mA cm ?2 at 1.23 V versus reversible hydrogen electrode (RHE) under simulated 1 sun illumination (100 mW cm ?2), which is 3.5 times that of the bare Fe 2O 3 electrode. Decorating the Fe 2O 3/Fe 2TiO 5 heterojunction photoanode with earth‐abundant FeNiO x cocatalyst further expedites surface reaction kinetics, leading to an onset potential of 0.8 V versus RHE with a photocurrent of 2.7 mA cm ?2 at 1.23 V and 4.6 mA cm ?2 at 1.6 V versus RHE. This sandwich photoanode shows an excellent stability for 5 h and achieves an overall Faradaic efficiency of 95% for O 2 generation. This is the best performance ever reported for Fe 2O 3/Fe 2TiO 5 photoanodes. 相似文献
8.
One of the key challenges in artificial photosynthesis is to design a photocatalyst that can bind and activate the CO 2 molecule with the smallest possible activation energy and produce selective hydrocarbon products. In this contribution, a combined experimental and computational study on Ni‐nanocluster loaded black TiO 2 (Ni/TiO 2[Vo]) with built‐in dual active sites for selective photocatalytic CO 2 conversion is reported. The findings reveal that the synergistic effects of deliberately induced Ni nanoclusters and oxygen vacancies provide (1) energetically stable CO 2 binding sites with the lowest activation energy (0.08 eV), (2) highly reactive sites, (3) a fast electron transfer pathway, and (4) enhanced light harvesting by lowering the bandgap. The Ni/TiO 2[Vo] photocatalyst has demonstrated highly selective and enhanced photocatalytic activity of more than 18 times higher solar fuel production than the commercial TiO 2 (P‐25). An insight into the mechanisms of interfacial charge transfer and product formation is explored. 相似文献
9.
The ultrafast transfer of plasmon‐induced hot electrons is considered an effective kinetics process to enhance the photoconversion efficiencies of semiconductors through strong localized surface plasmon resonance (LSPR) of plasmonic nanostructures. Although this classical sensitization approach is widely used in noble‐metal–semiconductor systems, it remains unclear in nonmetallic plasmonic heterostructures. Here, by combining ultrafast transient absorption spectroscopy with theoretical simulations, IR‐driven transfer of plasmon‐induced hot electron in a nonmetallic branched heterostructure is demonstrated, which is fabricated through solvothermal growth of plasmonic W 18O 49 nanowires (as branches) onto TiO 2 electrospun nanofibers (as backbones). The ultrafast transfer of hot electron from the W 18O 49 branches to the TiO 2 backbones occurs within a timeframe on the order of 200 fs with very large rate constants ranging from 3.8 × 10 12 to 5.5 × 10 12 s ?1. Upon LSPR excitation by low‐energy IR photons, the W 18O 49/TiO 2 branched heterostructure exhibits obviously enhanced catalytic H 2 generation from ammonia borane compared with that of W 18O 49 nanowires. Further investigations by finely controlling experimental conditions unambiguously confirm that this plasmon‐enhanced catalytic activity arises from the transfer of hot electron rather than from the photothermal effect. 相似文献
10.
Increasing visible light absorption of classic wide‐bandgap photocatalysts like TiO 2 has long been pursued in order to promote solar energy conversion. Modulating the composition and/or stoichiometry of these photocatalysts is essential to narrow their bandgap for a strong visible‐light absorption band. However, the bands obtained so far normally suffer from a low absorbance and/or narrow range. Herein, in contrast to the common tail‐like absorption band in hydrogen‐free oxygen‐deficient TiO 2, an unusual strong absorption band spanning the full spectrum of visible light is achieved in anatase TiO 2 by intentionally introducing atomic hydrogen‐mediated oxygen vacancies. Combining experimental characterizations with theoretical calculations reveals the excitation of a new subvalence band associated with atomic hydrogen filled oxygen vacancies as the origin of such band, which subsequently leads to active photo‐electrochemical water oxidation under visible light. These findings could provide a powerful way of tailoring wide‐bandgap semiconductors to fully capture solar light. 相似文献
11.
In this paper, highly-ordered TiO 2 nanotube (TNT) electrodes fabricated by anodization at 20 V in 0.1 M F −-based solution were annealed in O 2, N 2 and CO respectively. The surface properties of the TiO 2 electrodes after annealing treatment by different gases were studied by means of photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical properties of the TNT electrodes were investigated by cyclic voltammetry, steady-state polarization and photocurrent response measurements. The results showed that Ti n+ (n = 0-3) cations and oxygen vacancies existed in the TNT electrode after annealing in CO, leading to a very efficient electron transfer rate of 1.34 × 10 − 3 cm/s. Steady-state polarization measurement and photocurrent response demonstrated that the electrode potential of oxygen evolution reaction (OER) reduced by 20% and the photocurrent response increased by 50% for CO-annealed TNT electrode compared with O 2-annealed TNT electrode. 相似文献
12.
The hydrogenation and introducing oxygen vacancies (VO) can lead to surface lattice disorder in TiO2, which is a new form of TiO2 named black TiO2, with excellent visible-light photocatalytic activity, but this TiO2 is easy to failure because oxidation makes the concentration of surface VO decrease rapidly in a short time. In this work, black TiO2 nanoparticles with VO almost concentrated inside nanoparticles were fabricated under ultrafast hydrogen flow. These bulk VO shortened the bandgaps of black TiO2, enhanced its visible light absorption, and meanwhile provided extremely strong stability. The location of VO in black TiO2 was evident from EPR, XPS with HRTEM investigation, and other characteristics of black TiO2 were obtained by XRD, UV-Vis, SEM, PL, and photocurrent techniques. The degradation experiments on Cr6+ or rhodamine B demonstrated the good visible-light photocatalytic performance of our material. After 18 months of natural aging treatment (in the air), our samples showed no discoloration and maintained 89.5% photocatalytic efficiency, and further study exhibited that this black TiO2 also contained excellent acid resistance and moderate alkaline resistance. This work could help design lattice disorder to obtain more stable and practical black TiO2. 相似文献
13.
Lithium–oxygen batteries have an ultrahigh theoretical energy density, almost ten times higher than lithium‐ion batteries. The poor conductivity of the discharge product Li 2O 2, however, severely raises the charge overpotential and pulls down the cyclability. Here, a simple and effective strategy is presented for regular formation of lithium vacancies in the discharge product via tuning charge/discharge mode, and their effects on the charge transfer behavior. The effects of the discharge current density on the lithium vacancies, ionic conductivity, and electronic conductivity of the discharge product Li 2O 2 are systematically investigated via electron spin resonance, spin‐alignment echo nuclear magnetic resonance, and tungsten nanomanipulators, respectively. The study by density functional theory indicates that the lithium vacancies in Li 2O 2 generated during the discharge process are highly dependent on the current density. High current can induce a high vacancy density, which enhances the electronic conductivity and reduces the overpotential. Meanwhile, with increasing discharge current, the morphology of the Li 2O 2 changes from microtoroids to thin nanoplatelets, effectively shortening the charge transfer distance and improving the cycling performance. The Li 2O 2 grown in fast discharge mode is more easily decomposed in the following charging process. The lithium–oxygen battery cycling in fast‐discharge/slow‐charge mode exhibits low overpotential and long cycle life. 相似文献
14.
Ultrathin TiO 2 anatase nanowires (NWs) were successfully prepared via a rapid and facile hydrothermal route. Consequently, the TiO 2 NWs and TiO 2 nanoparticles (NPs) composites electrodes were prepared with different weight ratios (25, 50 and 100 %) for a dye sensitized solar cell, and the photoelectrical performance has been systematically studied. It is observed that although the amount of absorption dye decreases, the composite solar cells exhibit a higher power conversion efficiency compared to either pure TiO 2 NP or NW solar cells by rationally tuning the weight ratios. The behavior was attributed to a combination of the rapid carrier transport in NW framework and the high dye loading on P25 surface. 相似文献
15.
A strategy is presented for the in situ synthesis of single crystalline CuO nanorods and 3D CuO nanostructures, ultra‐long Cu nanowires and Cu nanoparticles at relatively low temperature onto various substrates (Si, SiO 2, ITO, FTO, porous nickel, carbon cotton, etc.) by one‐step thermal heating of copper foam in static air and inert gas, respectively. The density, particle sizes and morphologies of the synthesized nanostructures can be effectively controlled by simply tailoring the experimental parameters. A compressive stress based and subsequent structural rearrangements mechanism is proposed to explain the formation of the nanostructures. The as‐prepared CuO nanostructures demonstrate promising electrochemical properties as the anode materials in lithium‐ion batteries and also reversible wettability. Moreover, this strategy can be used to conveniently integrate these nanostructures with other nanostructures (ZnO nanorods, Co 3O 4 nanowires and nanowalls, TiO 2 nanotubes, and Si nanowires) to achieve various hybrid hierarchical (CuO‐ZnO, CuO‐Co 3O 4, CuO‐TiO 2, CuO‐Si) nanocomposites with promising properties. This strategy has the potential to provide the nano society with a general way to achieve a variety of nanostructures. 相似文献
16.
A brown mesoporous TiO 2‐x/MCF composite with a high fluorine dopant concentration (8.01 at%) is synthesized by a vacuum activation method. It exhibits an excellent solar absorption and a record‐breaking quantum yield (Φ = 46%) and a high photon–hydrogen energy conversion efficiency (η = 34%,) for solar photocatalytic H 2 production, which are all higher than that of the black hydrogen‐doped TiO 2 (Φ = 35%, η = 24%). The MCFs serve to improve the adsorption of F atoms onto the TiO 2/MCF composite surface, which after the formation of oxygen vacancies by vacuum activation, facilitate the abundant substitution of these vacancies with F atoms. The decrease of recombination sites induced by high‐concentration F doping and the synergistic effect between lattice Ti 3+–F and surface Ti 3+–F are responsible for the enhanced lifetime of electrons, the observed excellent absorption of solar light, and the photocatalytic production of H 2 for these catalysts. The as‐prepared F‐doped composite is an ideal solar light‐driven photocatalyst with great potential for applications ranging from the remediation of environmental pollution to the harnessing of solar energy for H 2 production. 相似文献
17.
A novel type of hierarchical nanocomposites consisted of MoS 2 nanosheet coating on the self‐ordered TiO 2 nanotube arrays is successfully prepared by a facile combination of anodization and hydrothermal methods. The MoS 2 nanosheets are uniformly decorated on the tube top surface and the intertubular voids with film appearance changing from brown to black color. Anatase TiO 2 nanotube arrays (NTAs) with clean top surfaces and the appropriate amount of MoS 2 precursors are key to the growth of perfect compositing TiO 2@MoS 2 hybrids with significantly enhanced photocatalytic activity and photocurrent response. These results reveal that the strategy provides a flexible and straightforward route for design and preparation nanocomposites based on functional semiconducting nanostructures with 1D self‐ordered TiO 2 NTAs, promising for new opportunities in energy/environment applications, including photocatalysts and other photovoltaic devices. 相似文献
18.
TiO 2 as an anode for sodium‐ion batteries (NIBs) has attracted much recent attention, but poor cyclability and rate performance remain problematic owing to the intrinsic electronic conductivity and the sluggish diffusivity of Na ions in the TiO 2 matrix. Herein, a simple process is demonstrated to improve the sodium storage performance of TiO 2 by fabricating a 1D, multichannel, porous binary‐phase anatase‐TiO 2–rutile‐TiO 2 composite with oxygen‐deficient and high grain‐boundary density (denoted as a‐TiO 2?x /r‐TiO 2?x ) via electrospinning and subsequent vacuum treatment. The introduction of oxygen vacancies in the TiO 2 matrix enables enhanced intrinsic electronic conductivity and fast sodium‐ion diffusion kinetics. The porous structure offers easy access of the liquid electrolyte and a short transport path of Na + through the pores toward the TiO 2 nanoparticle. Furthermore, the high density of grain boundaries between the anatase TiO 2 and rutile TiO 2 offer more interfaces for a novel interfacial storage. The a‐TiO 2?x /r‐TiO 2?x shows excellent long cycling stability (134 mAh g ?1 at 10 C after 4500 cycles) and superior rate performance (93 mAh g ?1 after 4500 cycles at 20 C) for sodium‐ion batteries. This simple and effective process could serve as a model for the modification of other materials applied in energy storage systems and other fields. 相似文献
19.
Titanium dioxide (TiO 2) has been widely investigated and used in many areas due to its high refractive index and ultraviolet light absorption, but the lack of absorption in the visible–near infrared (Vis–NIR) region limits its application. Herein, multifunctional Fe@γ‐Fe 2O 3@H‐TiO 2 nanocomposites (NCs) with multilayer‐structure are synthesized by one‐step hydrogen reduction, which show remarkably improved magnetic and photoconversion effects as a promising generalists for photocatalysis, bioimaging, and photothermal therapy (PTT). Hydrogenation is used to turn white TiO 2 in to hydrogenated TiO 2 (H‐TiO 2), thus improving the absorption in the Vis–NIR region. Based on the excellent solar‐driven photocatalytic activities of the H‐TiO 2 shell, the Fe@γ‐Fe 2O 3 magnetic core is introduced to make it convenient for separating and recovering the catalytic agents. More importantly, Fe@γ‐Fe 2O 3@H‐TiO 2 NCs show enhanced photothermal conversion efficiency due to more circuit loops for electron transitions between H‐TiO 2 and γ‐Fe 2O 3, and the electronic structures of Fe@γ‐Fe 2O 3@H‐TiO 2 NCs are calculated using the Vienna ab initio simulation package based on the density functional theory to account for the results. The reported core–shell NCs can serve as an NIR‐responsive photothermal agent for magnetic‐targeted photothermal therapy and as a multimodal imaging probe for cancer including infrared photothermal imaging, magnetic resonance imaging, and photoacoustic imaging. 相似文献
20.
An efficient and low‐cost electrocatalyst for reversible oxygen electrocatalysis is crucial for improving the performance of rechargeable metal?air batteries. Herein, a novel oxygen vacancy–rich 2D porous In‐doped CoO/CoP heterostructure (In‐CoO/CoP FNS) is designed and developed by a facile free radicals–induced strategy as an effective bifunctional electrocatalyst for rechargeable Zn–air batteries. The electron spin resonance and X‐ray absorption near edge spectroscopy provide clear evidence that abundant oxygen vacancies are formed in the interface of In‐CoO/CoP FNS. Owing to abundant oxygen vacancies, porous heterostructure, and multiple components, In‐CoO/CoP FNS exhibits excellent oxygen reduction reaction activity with a positive half‐wave potential of 0.81 V and superior oxygen evolution reaction activity with a low overpotential of 365 mV at 10 mA cm ?2. Moreover, a home‐made Zn–air battery with In‐CoO/CoP FNS as an air cathode delivers a large power density of 139.4 mW cm ?2, a high energy density of 938 Wh kg Zn?1, and can be steadily cycled over 130 h at 10 mA cm ?2, demonstrating great application potential in rechargeable metal–air batteries. 相似文献
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