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Promoting Photocatalytic H <sub/>2</sub> Evolution on Organic–Inorganic Hybrid Perovskite Nanocrystals by Simultaneous Dual-Charge Transportation Modulation
摘要： Organic-inorganic hybrid perovskites have demonstrated great potential in solar cells fabrication due to the excellent optoelectronic properties. However, their success in solar cells has been hardly translated to producing solar fuels due to the instability issue and serious charge recombination at the nanoscale domain. Herein, we show for the first time that organic-inorganic hybrid perovskite methylammonium lead bromide (MAPbBr3) nanocrystals can be stabilized in aqueous HBr solution and achieve photocatalytic H2 production reaction under visible light. More impressively, by hybridizing MAPbBr3 with Pt/Ta2O5 and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) nanoparticles as electron and hole transporting motifs, respectively, drastically enhanced charge transportation on MAPbBr3 together with improved catalysis were achieved. As a consequence, the rate of photocatalytic hydrogen evolution on pristine MAPbBr3 was increased by ca. 52 times by introducing dual nanoscale charge transporting highways, achieving an apparent quantum efficiency of ca. 16.4% for H2 evolution at 420 nm.
关键词： Organic-inorganic hybrid perovskites,photocatalytic H2 evolution,visible light,charge transportation,MAPbBr3 nanocrystals
更新于2025-09-23 15:21:01
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The Stellar Contents of Intermediate-mass Disk Galaxies in the Virgo Cluster. I. GMOS Spectra
摘要： The stellar contents of six intermediate-mass early-type disk galaxies in the Virgo cluster are examined using deep long slit spectra. The isophotal and photometric properties of the galaxies at near- and mid-infrared wavelengths are also examined. Characteristic ages and metallicities are found by making comparisons with the strengths of lines measured from model spectra. The light from the central regions of these galaxies at visible/red wavelengths is not dominated by old populations. Rather, the central regions of four galaxies (NGC 4305, NGC 4306, NGC 4497, and NGC 4620) are dominated by populations with ages ～1.5–3 Gyr. Centrally concentrated line emission is found in two of the galaxies (NGC 4491 and NGC 4584), and the relative strengths of Hα and [S II]6746 are consistent with this emission originating in star-forming regions. The disks of these galaxies are dominated by populations that are at least 1 Gyr older than those near the centers, indicating that the quenching of star formation progressed from large radii inwards, and did not occur over a short timescale. NGC 4497 has the oldest disk, with a luminosity-weighted age of 10 Gyr. The metallicities of the galaxies in this sample are consistent with their integrated brightnesses, suggesting that they have not been subjected to large-scale stellar stripping. [Mg/Fe] is roughly solar, suggesting that these systems retained and enriched gas over timescales of at least 1 Gyr. The progenitors of these galaxies were likely late-type systems that were accreted by Virgo during intermediate or early epochs and have since been depleted of gas and dust.
关键词： galaxies: evolution,galaxies: stellar content
更新于2025-09-23 15:21:01
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[ACM Press the 2018 International Conference - Hong Kong, Hong Kong (2018.02.24-2018.02.26)] Proceedings of the 2018 International Conference on Image and Graphics Processing - ICIGP 2018 - The Optimized Level Set Image Segmentation Based on Saliency Maps
摘要： In order to improve the practicability of the level set method and reduce the computational cost, a optimized level set active contour model that embeds the image local information is proposed in this paper. Firstly, the optimal saliency method of the image is selected by comparing three saliency methods, which is helped to generate the initial contour of the image. Secondly, a new variational level set model integrating edge information and regional local information is presented, and a local energy term is added to the energy function. Finally, image segmentation is implemented by new level set methods based on optimal saliency method. Experiments demonstrate the results of the new level set method based on optimal saliency method are higher than the Distance Regularized Level Set Evolution (DRLSE) model in terms of both efficiency and accuracy. Moreover, the segmentation time of the optimization algorithm only needs 1.94% of the former, and it has high segmentation accuracy.
关键词： the level set method,Image segmentation,Saliency map,Distance Regularized Level Set Evolution (DRLSE)
更新于2025-09-23 15:21:01
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Spiky Nickel Electrodes for Electrochemical Oxygen Evolution Catalysis by Femtosecond Laser Structuring
摘要： Micro- and nanostructured Ni/NiO surfaces were generated by femtosecond laser structuring for oxygen evolution reaction in alkaline water electrolysis cells. For two different angles between the laser beam and the nickel surface, two different types of laser-structured electrodes were prepared, characterized, and compared with a plane tempered nickel electrode. Their electrochemical activities for the oxygen evolution reaction were tested by using cyclic and linear sweep voltammetry. The chemical surface composition was investigated by X-ray photoelectron spectroscopy. Laser structuring increased the overall electrochemical performance by more than one order of magnitude. The overpotential of the laser-structured electrodes for the oxygen evolution reaction was decreased by more than 100 mV due to high defect densities of the structures created by the laser ablation process.
关键词： nickel electrodes,femtosecond laser structuring,alkaline water electrolysis,electrochemical catalysis,oxygen evolution reaction
更新于2025-09-23 15:21:01
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Carbon coated-Cu nanoparticles as a cocatalyst of g-C3N4 for enhanced photocatalytic H2 evolution activity under visible-light irradiation
摘要： The photocatalytic H2 evolution is an important technology to solve the energy crisis. The hydrogen evolution rate of the g-C3N4 system in triethanolamine solution as sacrificial agent is obvious higher than in methanol solution. But up to now, most of the Cu nanoparticles as cocatalyst of g-C3N4 photocatalytic systems for hydrogen evolution are performed in methanol solution because Cu nanoparticles are unstable in triethanolamine solution. Here, carbon coated-Cu nanoparticles as cocatalyst of g-C3N4 composites (Cu@C/g-C3N4) were prepared by simple two-steps technology of annealing then grinding. The compositions, morphology and optical and photoelectrochemical (PEC) properties of the composites were characterized by means of physicochemical techniques. The prepared composition was used to generate hydrogen under visible light irradiation in triethanolamine solution. The results displayed that the hydrogen evolution rate of the optimal Cu@C/g-C3N4 was up to 265.1 μmol g-1 h-1 that is close to the activity of 0.5% Pt/g-C3N4, and after four repeated reactions, the photocatalytic activity decreased only by about 15%. The good photocatalytic activity and stability result from Cu nanoparticles increase the transfer efficiency of charge carriers by trapping the photogenerated electrons produced by g-C3N4 and the protective effect of carbon layer on Cu nanoparticles.
关键词： Cu nanoparticles,Visible-light,Graphite carbon nitride,Photocatalytic H2 evolution,Carbon coating layer
更新于2025-09-23 15:21:01
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Electrochemical Exfoliation of MoS <sub/>2</sub> Crystal for Hydrogen Electrogeneration
摘要： Transition metal dichalcogenides (TMDs) have recently emerged within the group of 2D materials due to their electrical, catalytic and optical properties significantly enhanced and useful when down-sized to single layer. In particular, MoS2 has attracted much attention due to its semiconducting nature with a useful band gap when present as single layer, the enhanced photoluminescence, but also importantly the excellent catalytic properties towards the electrochemical hydrogen evolution. We present here the preparation of thin layers MoS2 nanosheets with enhanced catalytic properties towards the hydrogen evolution reaction by means of an easy and fast electrochemical top-down exfoliation procedure in aqueous solution from a naturally occurring MoS2 crystal. After structural and chemical characterization with STEM, AFM, XPS and Raman spectroscopy electrochemical investigations were performed to test catalytic properties in acidic solution for the electrogeneration of hydrogen and compare it to MoS2 nanosheets obtained through the widely employed chemical Li intercalation/exfoliation. Electrochemically exfoliated MoS2 shows lower Tafel slope than its counterpart obtained with chemical exfoliation.
关键词： hydrogen evolution reaction,molybdenum sulfide,electrochemistry,layered compound,exfoliation
更新于2025-09-23 15:21:01
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Insight into efficient pollutant degradation from paramorphic SnO2 hierarchical superstructures
摘要： Three-dimensional (3D) hierarchical architectures are currently attracting extensive interests owing to their fascinating morphology-dependent properties and potential applications. In this work, we have developed a facile template-free hydrothermal method to synthesize various 3D SnO2 hierarchical superstructures. It is found that the amount of urea, pH value and the pre-oxidation process play a crucial role in the micro/nanostructural evolutions of building blocks and final products. Oriented attachment and self-assembling dual-controlled mechanisms are then proposed to illustrate the formation of 3D hierarchical superstructures. The application in photocatalysis for the degradation of methylene blue (MB) demonstrates that the as-synthesized SnO2 hierarchical superstructures have highly efficient photocatalytic activity for the degradation of organic pollutants. Particularly, the SnO2 hierarchical superstructure constructed by ultrathin nanosheets can degrade 93% of MB within 150 min, which is much higher than that of commercial SnO2 powders. The enhanced photocatalytic performances can be attributed to the high surface-to-volume ratio, the abundant active sites and the efficient separation of photogenerated electrons and holes induced by the unique 3D loose and microporous superstructures. These new insights obtained in this study will be beneficial for the practical applications of oxide semiconductor materials for photocatalytic degradation of organic pollutants.
关键词： Hierarchical superstructure,Tin dioxide,Photocatalysis,Micro/nanostructural evolution
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Understanding Measurement Artifacts Causing Inherent Cation Gradients in Depth Profiles of Perovskite Photovoltaics with TOF-SIMS
摘要： Utilizing cumulative correlation information already existing in an evolutionary process, this paper proposes a predictive approach to the reproduction mechanism of new individuals for differential evolution (DE) algorithms. DE uses a distributed model (DM) to generate new individuals, which is relatively explorative, whilst evolution strategy (ES) uses a centralized model (CM) to generate offspring, which through adaptation retains a convergence momentum. This paper adopts a key feature in the CM of a covariance matrix adaptation ES, the cumulatively learned evolution path (EP), to formulate a new evolutionary algorithm (EA) framework, termed DEEP, standing for DE with an EP. Without mechanistically combining two CM and DM based algorithms together, the DEEP framework offers advantages of both a DM and a CM and hence substantially enhances performance. Under this architecture, a self-adaptation mechanism can be built inherently in a DEEP algorithm, easing the task of predetermining algorithm control parameters. Two DEEP variants are developed and illustrated in the paper. Experiments on the CEC’13 test suites and two practical problems demonstrate that the DEEP algorithms offer promising results, compared with the original DEs and other relevant state-of-the-art EAs.
关键词： evolution path (EP),Cumulative learning,evolutionary computation,differential evolution (DE)
更新于2025-09-23 15:19:57
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Massive and dusty Hα emitters in protocluster revealed by ALMA and JVLA
摘要： We investigate the physical properties of Hα emitters (HAEs) associated to the protocluster 4C23.56 at z ～ 2.5 using continuum observations at submm (270 GHz) and radio (3 GHz) frequencies with Atacama Large Mm/submm Array (ALMA) and K. Jansky Very Large Array (JVLA). For more details see Lee et al. (in prep).
关键词： radio continuum: galaxies,galaxies: high-redshift,galaxies: structure,submillimeter,galaxies: evolution
更新于2025-09-23 15:19:57
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Structural Evolutions of Vertically-Aligned Two-Dimensional MoS <sub/>2</sub> Layers Revealed by <i>In Situ</i> Heating Transmission Electron Microscopy
摘要： Benefited from a large density of layer edges exposed on the surface, vertically-aligned two-dimensional (2D) molybdenum disulfide (MoS2) layers have recently harvested excellent performances in the field of electrochemical catalysis and chemical sensing. With their increasing versatility for high-temperature demanding applications, it is vital to identify their thermally-driven structural and chemical stability as well as clarify its underlying principle. Despite various ex situ and in situ characterizations on horizontally-aligned 2D MoS2 layers, the direct in situ heating of vertically-aligned 2D MoS2 layers and the real-time observation of their near-atomic scale dynamics have never been approached, leaving their thermal stability poorly understood. Moreover, the geometrical advantage of the surface-exposed vertically-aligned 2D MoS2 layers is anticipated to unveil the structural dynamics of interlayer van der Waals (vdW) gaps and its correlation with thermal energy, unattainable with 2D MoS2 layers in any other geometry. Herein, we report a comprehensive in situ heating TEM study on cleanly transferred vertically-aligned 2D MoS2 layers up to 1000 °C. Several striking phenomena were newly observed in the course of heating: (1) formation and propagation of voids between the domains of vertical 2D MoS2 layers with distinct grain orientations starting at ~875 °C, (2) subsequent decompositions of the 2D MoS2 layers accompanying a formation of Mo nanoparticles at ~950 °C, much lower than the melting temperature of their bulk counterpart, and (3) initiation of decomposition from the surface-exposed 2D layer vertical edge sites, congruently supported by molecular dynamics (MD) simulation. These new findings will offer critical insights into better understanding the thermodynamic principle that governs the structural stability of general vdW 2D crystals as well as providing useful technological guidance for materials design and optimization in their potential high-temperature applications.
关键词： van der Waals gaps,in situ heating,structural evolution,MoS2,two-dimensional,vertically-aligned,transmission electron microscopy,thermal stability,molecular dynamics simulation
更新于2025-09-23 15:19:57