Dalian University of Technology

About: Dalian University of Technology is a education organization based out in Dalian, China. It is known for research contribution in the topics: Catalysis & Finite element method. The organization has 60890 authors who have published 71921 publications receiving 1188356 citations. The organization is also known as: Dàlián Lǐgōng Dàxué.

ZrO2 support imparts superior activity and stability of Co catalysts for CO2 methanation

Abstract: Screening of various supports reveals that Co catalysts supported on ZrO2 and Al2O3 show good initial activity for CO2 methanation. Co/ZrO2 and Co/Al2O3 catalysts prepared by impregnation with different metal loadings were further examined comparatively. The 10Co/ZrO2 catalyst showed high activity with CO2 conversion of 92.5% and CH4 selectivity of 99.9% without deactivation after 300 h time on stream (TOS). However, the 10Co/Al2O3 catalyst gave a lower CO2 conversion of 77.8% which decreased to 38.6% after 300 h TOS. The catalysts were characterized by STEM/EDS (scanning transmission electron microscopy/energy-dispersive X-ray spectroscopy), in situ XRD(X-ray diffractometer), H2-TPR(temperature programmed reduction), XPS (X-ray photoelectron spectroscopy), chemisorption of H2, CO, CH4, CO2 and NH3-TPD (temperature programmed desorption). Re-dispersion of Co species on the ZrO2 support during reduction by H2 was observed by STEM/EDS. New Co-Zr phase formed on the Co-ZrO2 interface was directly observed by TEM for the first time; the Co/ZrO2 catalyst exhibited high stability with high activity for CO2 conversion. In situ XRD, H2-TPR and XPS results indicate the promoting effect of ZrO2 on the reduction of Co3O4 to Co metal along with the negative effect of Al2O3. The oxygen vacancies on the ZrO2 detected by XPS may help to activate CO2 and H2O and resist deactivation. Co/Al2O3 catalyst deactivates rapidly due to coke deposition and spinel formation.

Tuning the intramolecular charge transfer of alkynylpyrenes: effect on photophysical properties and its application in design of OFF-ON fluorescent thiol probes.

Abstract: Green and yellow-emitting 1,6- and 1,8-bis(phenylethynyl) pyrenes (dyes 7, 8, 9, and 10) with different intramolecular charge transfer (ICT) feature were synthesized and the effect of ICT on the photophysical properties of these derivatives were studied by UV−vis absorption spectra, fluorescence emission spectra, and DFT/TDDFT calculations. For the dyes with electron-pushing group (e.g., -dimethylamino, dye 8 and dye 10), structureless and solvent polarity-sensitive fluorescence emission spectra were observed. Conversely, dye with electron-withdrawing group (e.g., −CN, dye 7) shows structured and solvent polarity-independent emission spectra. OFF−ON fluorescent thiol probes 11 and 12 with 2,4-dinitrobenzenesulfonyl protected ethynylpyrene fluorophore were designed based on DFT/TDDFT calculations, which predicts dark state (S1) for these thiol probes (e.g., oscillator strength f = 0.0086 for S1←S0 transition of the probe 11). This dark state is induced by the ICT effect with ethynylated pyrene fluorophore ...

Structures, mobilities, electronic and magnetic properties of point defects in silicene

Abstract: In the fabrication and processing of silicene monolayers, structural defects are almost inevitable. Using ab initio calculations, we systemically investigated the structures, formation energies, migration behaviors and electronic/magnetic properties of typical point defects in silicene, including the Stone-Wales (SW) defect, single and double vacancies (SVs and DVs), and adatoms. We found that SW can be effectively recovered by thermal annealing. SVs have much higher mobility than DVs and two SVs are very likely to coalesce into one DV to lower the energy. Existence of SW and DVs may induce small gaps in silicene, while the SV defect may transform semimetallic silicene into metallic. Adatoms are unexpectedly stable and can affect the electronic properties of silicene dramatically. Especially, Si adatoms as self-dopants in silicene sheets can induce long-range spin polarization as well as a remarkable band gap, thus achieving an all-silicon magnetic semiconductor. The present theoretical results provide valuable insights into identification of these defects in experiments and understanding their effects on the physical properties of silicene.

Multiple UAVs as Relays: Multi-Hop Single Link Versus Multiple Dual-Hop Links

Abstract: Unmanned aerial vehicles (UAVs) have found many important applications in communications. They can serve as either aerial base stations or mobile relays to improve the quality of services. In this paper, we study the use of multiple UAVs in relaying. Considering two typical uses of multiple UAVs as relays that form either a single multi-hop link or multiple dual-hop links, we first optimize the placement of the UAVs by maximizing the end-to-end signal-to-noise ratio for three useful channel models and two common relaying protocols. Based on the optimum placement, the two relaying setups are then compared in terms of outage and bit error rate. Numerical results show that the dual-hop multi-link option is better than the multi-hop single link option when the air-to-ground path loss parameters depend on the UAV positions. Otherwise, the dual-hop option is only better when the source-to-destination distance is small. Also, decode-and-forward UAVs provide better performances than the amplify-and-forward UAVs. The investigation also reveals the effects of important system parameters on the optimum UAV positions and relaying performances to provide useful guidelines.