The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are the cornerstone of many renewable energy storage and conversion technologies such as metal-air batteries, fuel cells, and water electrolysis. [1][2][3] Both reactions, however, need highly active catalysts to achieve high efficiency since the oxygen electrode is a strongly irreversible system associated with high activation overpotential and sluggish kinetics. Noble metals (e.g., Pt) and their oxides (e.g., RuO 2 , IrO 2 ) have been found to be the most active catalysts for electrocatalytic reduction and evolution of molecular oxygen. However, their large-scale application is greatly prohibited by high cost, supply scarcity, and inferior durability. [4,5] On the other hand, as the universal choice of ORR catalyst, the OER activity of Pt is limited by the in situ formation of insulating platinum oxides in the process. IrO 2 and RuO 2 are unstable at high potentials due to the in situ transformation to higher-valent oxides, in spite of the highest activity towards OER. [6] To fulfill the demands in practical use, the development of lowcost yet durable bifunctional electrocatalysts with high activity toward both ORR and OER process is highly desired to reduce the cost and complexity of the renewable energy storage and conversion systems.Recent studies highlighted that transitional metal-N-doped carbon (NC) nanohybrids (MNC, MFe, Co, Ni, etc.) hold promise as substitutes of noble metal electrocatalysts in both acidic and alkaline medium. [7][8][9] In such catalysts, the presence of transitional metals helps to greatly improve the crystallinity and electrical conductivity of carbon matrix by catalytic graphitization upon preparation at high temperature, which in turn function to protect the metals from corrosion and aggregation during the electrochemical reactions. [10,11] More importantly, the interaction and synergy of metal species, the doped N species, and carbon lattice create sufficient localized reactive sites by modifying the charge distribution on carbon surface via the promoted electron transfer effect, which changes the local work function for O 2 adsorption and consequently facilitate the ORR or OER. [12,13] Very recently, the synergistic effect of metal@C nanoparticles and neighboring metal-N x coordination sites has been demonstrated to promote the O 2 adsorption The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are cornerstone reactions for many renewable energy technologies. Developing cheap yet durable substitutes of precious-metal catalysts, especially the bifunctional electrocatalysts with high activity for both ORR and OER reactions and their streamlined coupling process, are highly desirable to reduce the processing cost and complexity of renewable energy systems. Here, a facile strategy is reported for synthesizing double-shelled hybrid nanocages with outer shells of Co-N-doped graphitic carbon (Co-NGC) and inner shells of N-doped microporous carbon (NC) by templating against core-shell metal-orga...

Nitride phosphors are suitable for white light-emitting diode applications. In this study, the structure of phosphor has been modified through cation substitution to induce charge variation and a rearrangement of neighboring nitride clusters, and consequently enhance its luminescent behavior. Substitution of Ca(2+) by Sr(2+) cations expanded the lattice volume and the bc plane, but shortened the distance between the layers along the a axis. Lattice distortion of the framework introduced high-coordination sites in the Sr/Eu centers and adequate space, thereby facilitating charge variation of activators under reduced atmosphere, as detected through X-ray absorption near-edge structure spectroscopy. As such, the photoluminescent intensity of the phosphors increased by more than 10% and a blue shift occurred. The microstructures of the samples were also analyzed using high-resolution transmission electron microscopy. Cation substitution induced a special change in the anion environment, as indicated in the solid-state Raman spectra. Moreover, typical ordering variations in the SiN4 and AlN4 clusters are generated in the lattice. Meanwhile, neighbor sequence of (Si/Al)N4 around the divalent centers were observed through solid-state nuclear magnetic resonance spectroscopy. The modified ordering distribution resulted in a rigid structure and improved the thermal quenching behavior. Thermal stability has been enhanced by 10% at 473 K when x = 0.9 in SrxCa0.993-xAlSiN3:Eu(2+)0.007 compared with that at x = 0. This study promotes the research of neighbor sequence for selective tetrahedral sites such as Li, Mg, Al, and Si coordinated by N atoms in contact with cation sites.

We report a simple solvothermal synthesis approach to the growth of CuInS(2) nanocrystals with zincblende- and wurtzite-phase structures. Zincblende nanocrystals with particle sizes of 10-20 nm were produced using oleylamine as the solvent. When ethylenediamine was used as the solvent, similarly sized wurtzite nanocrystals with some degree of particle aggregation were formed. Use of a mixture of these solvents gave products with mixed phases including some polyhedral nanostructures. The crystal phases of these nanocrystals were carefully determined by X-ray diffraction and transmission electron microscopy analysis. All the samples exhibit strong absorption from the entire visible light region to the near-infrared region beyond 1300 nm. Pure-phase zincblende and wurtzite CuInS(2) nanocrystals were employed as ink in the fabrication of solar cells. The spray-coated nanocrystal layer was subjected to a selenization process. A power conversion efficiency of ~0.74% and a good external quantum efficiency profile over broad wavelengths have been measured. The results demonstrate that wurtzite and zincblende CuInS(2) nanocrystals may be attractive precursors to light-absorbing materials for making efficient photovoltaic devices.

While there is a large number of recent studies of Au nanocatalysts supported on metal oxides, low-temperature CO oxidation under an acidic environment has not yet been accomplished. Over a novel acidic Al-SBA-15 support, uniformly distributed gold nanoparticles with sizes approximately 2.7 nm were obtained by a successive procedure of aminosilane grafting, gold adsorption-reduction, and then high-temperature hydrogen treatment. The catalyst system, Au@Al-SBA-15, exhibits extraordinarily high activity for CO oxidation at 80 degrees C. By varying the Si/Al ratio of the support, the dependence of the catalytic activity on the support Si/Al ratio was found in the CO oxidation reaction.

Abstract-This paper presents a novel synthetic aperture radar (SAR) image simulation approach to target recognition, which consists of two frameworks, referred to as the satellite SAR images simulation and the target recognition and identification. The images simulation makes use of the sensor and target geo-location relative to the Earth, movement of SAR sensor, SAR system parameters, radiometric and geometric characteristics of the target, and target radar cross section (RCS), orbital parameters estimation, SAR echo signal generation and image focusing to build SAR image database. A hybrid algorithm that combines the physical optics, physical diffraction theory, and shooting and bouncing rays was used to compute the RCS of complex radar targets. Such database is vital for aided target recognition and identification system Followed by reformulating the projection kernel in an optimization equation form, the target's reflectivity field can be accurately estimated. Accordingly, the target's features can be effectively enhanced and extracted, and the dominant scattering centers are well separated. Experimental results demonstrate that the simulated database developed in this paper is well suited for target recognition. Performance is extensively tested and evaluated from real images by Radarsat-2 and TerraSAR-X. Effectiveness and efficiency of the proposed method are further confirmed.

Mn -doped fluoride phosphors have been widely used in wide-gamut backlighting devices because of their extremely narrow emission band. Solid solutions of Na (Si Ge )F :Mn and Na (Ge Ti )F :Mn were successfully synthesized to elucidate the behavior of the zero-phonon line (ZPL) in different structures. The ratio between ZPL and the highest emission intensity υ phonon sideband exhibits a strong relationship with luminescent decay rate. First-principles calculations are conducted to model the variation in the structural and electronic properties of the prepared solid solutions as a function of the composition. To compensate for the limitations of the Rietveld refinement, electron paramagnetic resonance and high-resolution steady-state emission spectra are used to confirm the diverse local environment for Mn in the structure. Finally, the spectral luminous efficacy of radiation (LER) is used to reveal the important role of ZPL in practical applications.

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