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Hollow hierarchical structure Co0.85Se as efficient electrocatalyst for the triiodide reduction in dye-sensitized solar cells
摘要： The exploration of nonprecious metal-based electrocatalysts with high efficiency for the triiodide reduction is critical for the practical applications of the dye-sensitized solar cells. Herein, we develop a facile one-step hydrothermal method to synthesize hollow hierarchical structure Co0.85Se. Under the methanol-water reaction system, the product named as hollow hierarchical structure Co0.85Se-M has the largest specific surface area (215.36 m2 g?1) and the best crystallinity than other products obtained from other alcohol-water reaction systems. When this electrocatalyst is applied as a counter electrode for the dye-sensitized solar cells, it exhibits a small peak-to-peak separation (Epp, 97 mV) for the reduction of I3?/I? redox couple. It is found that the catalytic activity of Co0.85Se is closely dependent on the crystallinity. Moreover, the reactivity pathway is identified by density functional theory, which confirms that triiodide is reduced to iodide ion on Co0.85Se with a smaller energy barrier (～0.65 eV) than on Pt (～1.18 eV). Both experimental and theoretical results demonstrate Co0.85Se-M as an ideal counter electrode material for the dye-sensitized solar cells with a higher power conversion efficiency (8.76%) than Pt counter electrode (7.20%).
关键词： Dye-sensitized solar cells,Hollow hierarchical structure,Cobalt selenides,Electrocatalytic activity,Triiodide reduction
更新于2025-11-21 11:03:13
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In Situ Generation of AgI Quantum Dots by the Confinement of A?Supramolecular Polymer Network: A Novel Approach for Ultrasensitive Response
摘要： Currently, it is difficult to realize environmentally friendly synthesis of zeolites due to the use of the solvent. Therefore, it is of great importance to realize zeolite synthesis from iron ore tailings (IOTs) by a solvent-free method. In this work, in situ formed zeolite crystals are self-assembled and IOTs are converted into hierarchically porous ZSM-5. After that, the products prepared are characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and nitrogen adsorption. The results demonstrate that the samples show well-defined crystallinity and have micro-/mesoporous structures. The BET surface area is estimated to be 319.809 m2 g?1 and the external surface area is 92.693 m2 g?1, which indicate the as-synthesized ZSM-5 is a good hierarchically porous material. This work provides a reference for green synthesis of hierarchically porous ZSM-5 from IOT.
关键词： Hierarchical structure,Iron ore tailings,Solvent-free method,ZSM-5
更新于2025-11-14 15:15:56
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Engineering Charge Transfer Characteristics in Hierarchical Cu2S QDs @ ZnO Nanoneedles with p–n Heterojunctions: Towards Highly Efficient and Recyclable Photocatalysts
摘要： Equipped with staggered gap p-n heterojunctions, a new paradigm of photocatalysts based on hierarchically structured nano-match-shaped heterojunctions (NMSHs) Cu2S quantum dots (QDs)@ZnO nanoneedles (NNs) are successfully developed via engineering the successive ionic layer adsorption and reaction (SILAR). Under UV and visible light illumination, the photocatalytic characteristics of Cu2S@ZnO heterojunctions with different loading amounts of Cu2S QDs are evaluated by the corresponding photocatalytic degradation of rhodamine B (RhB) aqueous solution. The results elaborate that the optimized samples (S3 serial specimens with six cycles of SILAR reaction) by means of tailored the band diagram exhibit appreciable improvement of photocatalytic activities among all synthesized samples, attributing to the sensitization of a proper amount of Cu2S QDs. Such developed architecture not only could form p–n junctions with ZnO nanoneedles to facilitate the separation of photo-generated carries but also interact with the surface defects of ZnO NNs to reduce the electron and hole recombination probability. Moreover, the existence of Cu2S QDs could also extend the light absorption to improve the utilization rate of sunlight. Importantly, under UV light S3 samples demonstrate the remarkably enhanced RhB degradation efficiency, which is clearly testified upon the charge transfer mechanism discussions and evaluations in the present work. Further supplementary investigations illustrate that the developed nanoscale Cu2S@ZnO heterostructures also possess an excellent photo-stability during our extensive recycling photocatalytic experiments, promising for a wide range of highly efficient and sustainably recyclable photocatalysts applications.
关键词： Photocatalysis,QDs,ZnO@Cu2S hierarchical structure,Photostability,p-n heterojunctions
更新于2025-09-23 15:23:52
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Study on Band-Gap Behaviors of 2D Hierarchical Re-Entrant Lattice Structures
摘要： An investigation of Poisson’s ratios and band gap behaviors of 2D hierarchical re-entrant lattice structures is conducted using finite element method (FEM). The structure with a hierarchy order n (n≥1) is constructed by replacing each outmost vertex of the re-entrant octagons of a hierarchical structure of hierarchy order n?1 with a smaller self-similar re-entrant octagon. The dispersion relation and transmission spectrum of the proposed hierarchical structures are analyzed based on the Bloch’s theorem. The effects of geometrical parameters, order of rotational symmetry and orientation angle of some types of re-entrant polygon cores on the lattice Poisson’s ratio and band gap structures are also investigated. Results show that the re-entrant structures with first order hierarchy exhibit a wider band gap and a stronger attenuation effect compared with structures without structural hierarchy. The first order 2D hierarchical re-entrant structure with a negative Poisson’s ratio of ?0.032 exhibits the widest band gap, 17.8% wider than that of the zeroth order 2D re-entrant structure. The order of rotational symmetry and the orientation angle of the re-entrant polygon cores of the lattice have a strong impact on the lattice Poisson’s ratio and band structures.
关键词： re-entrant,negative Poisson’s ratio,band gap,hierarchical structure,transmission spectrum
更新于2025-09-23 15:23:52
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Hierarchical Sub-Pixel Anomaly Detection Framework for Hyperspectral Imagery
摘要： Anomaly detection is an important task in hyperspectral processing. Some previous works, based on statistical information, focus on Reed-Xiaoli (RX), as it is one of the most classical and commonly used methods. However, its performance tends to be affected when anomaly target size is smaller than spatial resolution. Those sub-pixel anomaly target spectra are usually much similar with background spectra, and may results in false alarm for traditional RX method. To address this issue, this paper proposes a hierarchical RX (H-RX) anomaly detection framework to enhance the performance. The proposed H-RX method consists of several different layers of original RX anomaly detector. In each layer, the RX’s output of each pixel is restrained by a nonlinear function and then imposed as a coef?cient on its spectrum for the next iteration. Furthermore, we design a spatial regularization layer to enhance the sub-pixel anomaly detection performance. To better illustrate the hierarchical framework, we provide a theoretical explanation of the hierarchical background spectra restraint and regularization process. Extensive experiments on three hyperspectral images illustrate that the proposed anomaly detection algorithm outperforms the original RX algorithm and some other classical methods.
关键词： hyperspectral image (HSI) analysis,RX,hierarchical structure,anomaly detection
更新于2025-09-23 15:21:01
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Hierarchical 3D VO2/ZnV2O4 microspheres as an excellent visible light photocatalyst for CO2 reduction to solar fuels
摘要： The photocatalytic reduction of CO2 has a great potential to produce fuels and chemicals, as well as, it reduces CO2 emission and addresses the environmental issues. To date single metal based catalysts still su?er from lower e?ciency, uncontrollable selectivity and instability. In this study, hierarchical microspheres (HMs) of ZnV2O4 with VO2 impurity were synthesized through the single step reduction process, to explore highly e?cient photocatalyst towards visible light responsive photocatalytic CO2 reduction. HMs of ZnV2O4 were successfully synthesized with mesoporous structure, higher surface area and functional under visible light irradiations. The ?1 were obtained over ZnV2O4 synthesized after highest yield of CO and CH3OH of 378 and 202 μmole g-cat 24 h of reaction time, respectively. The performance of optimized 3D HMs of ZnV2O4 for CO and CH3OH pro-duction was 2.30 folds and 10.7 folds higher than using ZnO/V2O5 composite sample, respectively. Other products detected with appreciable amounts were CH4 and C2H6. This reveals, HMs structure of ZnV2O4 not only allows the transfer of electrons towards CO2, but also provides short pathways for electron transfer and empty space in the microspheres will serve as the reservoirs to store the electrons, hence leading to enhanced photo-activity. In addition, VO2 presents in the sample further contribute to enhance performance of ZnV2O4 HMs due to enabling e?cient charge carrier separation. The prolong stability of ZnV2O4 in the CO2 reduction system con?rmed that 3D HMs structure provides controllable selectivity and stability. This brings to conclusions that fabrication of hierarchical structures will stimulate further development towards high performance photo-cat-alysts for the photocatalytic CO2 reduction to solar hydrocarbon fuels.
关键词： Hierarchical structure,CO2 reduction,Ternary metal oxide,Zinc vanadium oxide,3D microspheres of ZnV2O4,Hydrocarbon fuels
更新于2025-09-23 15:21:01
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Metal Nanoclusters: Engineering Functional Metal Materials at the Atomic Level (Adv. Mater. 47/2018)
摘要： Customizing functional metal materials at an atom-by-atom basis is one of the most ambitious dreams of materials scientists. In article number 1802751, Jianping Xie and co-workers summarize recent progress in introducing such fine capability of structural modulation into functional metal nanoclusters, based on a protein-like hierarchical structure scheme.
关键词： structural modulation,metal nanoclusters,protein-like hierarchical structure
更新于2025-09-23 15:21:01
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Bayesian 3D X-Ray Computed Tomography with a Hierarchical Prior Model for Sparsity in Haar Transform Domain
摘要： In this paper, a hierarchical prior model based on the Haar transformation and an appropriate Bayesian computational method for X-ray CT reconstruction are presented. Given the piece-wise continuous property of the object, a multilevel Haar transformation is used to associate a sparse representation for the object. The sparse structure is enforced via a generalized Student-t distribution (S tg), expressed as the marginal of a normal-inverse Gamma distribution. The proposed model and corresponding algorithm are designed to adapt to specific 3D data sizes and to be used in both medical and industrial Non-Destructive Testing (NDT) applications. In the proposed Bayesian method, a hierarchical structured prior model is proposed, and the parameters are iteratively estimated. The initialization of the iterative algorithm uses the parameters of the prior distributions. A novel strategy for the initialization is presented and proven experimentally. We compare the proposed method with two state-of-the-art approaches, showing that our method has better reconstruction performance when fewer projections are considered and when projections are acquired from limited angles.
关键词： Haar transformation,X-ray computed tomography,generalized Student-t distribution,hierarchical structure,inverse problem,sparsity
更新于2025-09-19 17:15:36
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One dimensional hierarchical BiOCl microrods: their synthesis and their photocatalytic performance
摘要： In this work, one dimensional hierarchical BiOCl microrods were controllably synthesized via a hydrothermal method using sodium citrate as the structure-directing agent. Each hierarchical BiOCl structure is made up of many BiOCl nanosheets in which the size and thickness are controlled by the concentration of sodium citrate. The high-resolution transmission electron microscopy (HRTEM) measurements show that each nanosheet consists of the BiOCl hierarchical structure with exposed (001) (top surface) and (110) (side surface) facets. With the amount of sodium citrate increasing, the ratio (110)/(001) gradually increases. These hierarchical BiOCl architectures exhibit a more outstanding photocatalytic activity than BiOCl nanosheets with exposed (001) facets, and rhodamine B (RhB) and methyl orange (MO) can be degraded in 3 and 4 min, respectively. This enhanced photocatalytic performance is ascribed to the fast separation and transfer of photogenerated electron–hole pairs, the formation of hierarchical architectures and the large BET surface areas. Radical scavenger experiments indicate that holes (h+) and superoxide radicals (˙O2?) are the main active species for MO degradation during the photocatalytic process.
关键词： BiOCl,hydrothermal synthesis,photocatalytic activity,hierarchical structure,sodium citrate
更新于2025-09-19 17:15:36
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[IEEE 2019 22nd International Conference on Electrical Machines and Systems (ICEMS) - Harbin, China (2019.8.11-2019.8.14)] 2019 22nd International Conference on Electrical Machines and Systems (ICEMS) - A Self-Adaptive Control Strategy to Suppress Fluctuation of Distributed Photovoltaic Energy in Microgrids with Combined Heat and Power System
摘要： In order to improve the ability of consuming photovoltaic energy, a self-adaptive control strategy to stabilize the fluctuation of renewable energy based on heat pump and hybrid energy storage system (HESS) has been proposed in micro-grids. The power self-adaptive control strategy uses a hierarchical structure. It is the long time and short time control scales. The previous, also the upper layer, is the electro- thermal coupling control layer. The last is the low-level power control. The upper layer adopts the empirical mode decomposition (EMD) technique and makes the photovoltaic energy composed into low, medium and high frequency components. The fluctuations of low frequency are suppressed via a heat pump. Besides, this layer also considers the hot demand of terminal users to correct the output of heat pump. HESS suppresses the residual power fluctuations on the basis of power adaptive delivery strategy. Furthermore, simulation results show that the proposed strategy can achieve the optimal coordination of electric and heat energy flow and enhance the micro-grid control flexibility and complementary economy.
关键词： HESS,EMD,photovoltaic energy,hierarchical structure,self-adaptive
更新于2025-09-19 17:13:59