Kyungpook National University

About: Kyungpook National University is a education organization based out in Daegu, South Korea. It is known for research contribution in the topics: Population & Catalysis. The organization has 20497 authors who have published 42107 publications receiving 834608 citations.

Facile synthesis of zinc oxide nanoparticles decorated graphene oxide composite via simple solvothermal route and their photocatalytic activity on methylene blue degradation.

Abstract: Zinc oxide nanoparticles decorated graphene oxide (ZnO@GO) composite was synthesized by simple solvothermal method where zinc oxide (ZnO) nanoparticles and graphene oxide (GO) were synthesized via simple thermal oxidation and Hummers method, respectively. The obtained materials were thoroughly characterized by various physico-chemical techniques such as X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Raman spectrum shows the intensity of D to G value was close to one which confirms the obtained GO and ZnO@GO composite possesses moderate graphitization. TEM images shows the ZnO nanoparticles mean size of 15±5nm were dispersed over the wrinkled graphene layers. The photocatalytic performance of ZnO@GO composite on degradation of methylene blue (MB) is investigated and the results show that the GO plays an important role in the enhancement of photocatalytic performance. The synthesized ZnO@GO composite achieves a maximum degradation efficiency of 98.5% in a neutral solution under UV-light irradiation for 15min as compared with pure ZnO (degradation efficiency is 49% after 60min of irradiation) due to the increased light absorption, the reduced charge recombination with the introduction of GO. Moreover, the resulting ZnO@GO composite possesses excellent degradation efficiency as compared to ZnO nanoparticles alone on MB.

Methanol steam reforming over Cu/ZnO/Al2O3 catalyst: kinetics and effectiveness factor

Abstract: Steam reforming of methanol over a commercial Cu/ZnO/Al2O3 catalyst was studied at atmospheric pressure and in a temperature range between 160 and 260 °C. The reaction rate depended upon methanol and hydrogen partial pressures, and was independent of the partial pressures of carbon oxides and water, which was in excess of the methanol partial pressure. Small amounts of carbon monoxide, less than 1% in the product gas, were formed at high temperatures; the amounts were well below the equilibrium amounts of reverse water–gas-shift reaction (RWGS). This was in support of the reaction sequence of methanol steam reforming followed by the RWGS. A power-law and a Langmuir–Hinselwood rate expression were developed for the reforming reaction by fitting the expressions to the experimental data. As the data were found to be affected by internal diffusion at high temperatures, the effectiveness factor of the catalyst particle was estimated in the fitting in order to obtain the intrinsic kinetics. Details of the estimation of the factor are elucidated. In order to predict a non-zero, finite rate in the absence of hydrogen, the hydrogen partial pressure term in the power-law expression was corrected by a fitted constant to avoid an infinite reaction rate, since the exponent of the hydrogen partial pressure was a negative number due to the hydrogen inhibition effect in the reforming; in the reaction mechanism for the Langmuir–Hinselwood expression, it was necessary to assume two different kinds of active sites on the catalyst: one for adsorbed methoxy and the other for adsorbed hydrogen. In addition, an excellent fitting of the data by the Langmuir–Hinselwood expression indicates that dehydrogenation of the adsorbed methoxy to the adsorbed oxymethylene is the rate-determining step (RDS), and that adsorption of all the species other than methoxy and hydrogen on the active sites is negligible.

Strategic Modification of BiVO4 for Improving Photoelectrochemical Water Oxidation Performance

Abstract: To improve the photoelectrochemical (PEC) performance of BiVO4, three different modifications (doping, heterojunction, and catalyst deposition) using earth-abundant elements are performed and their effects are compared in a 0.1 M phosphate electrolyte at pH 7 under AM1.5 light (100 mW/cm2). When a hexavalent element (Cr6+, W6+, or Mo6+) is doped at various levels, the Mo6+-doping effect is most significant at 10 atomic % with about two times higher photocurrent generation at the oxygen evolution potential (1.23 VRHE). Such enhancement is attributed to a decrease in charge transfer resistance (Rct) by donor doping, resulting in an approximate 2-fold increase in charge separation efficiency (ηsep) to about 25%. W6+ is less effective than Mo6+, whereas Cr6+ has a detrimental effect. To further improve the charge separation efficiency of Mo6+-doped BiVO4 (Mo-BiVO4), a approximate 600 nm thick WO3 layer is deposited under a similarly thick Mo-BiVO4 layer. This binary heterojunction (WO3/Mo-BiVO4) exhibits ηsep...

CMS Tracking Performance Results from early LHC Operation.

Abstract: The first LHC pp collisions at centre-of-mass energies of 0.9 and 2.36 TeV were recorded by the CMS detector in December 2009. The trajectories of charged particles produced in the collisions were reconstructed using the all-silicon Tracker and their momenta were measured in the 3.8 T axial magnetic field. Results from the Tracker commissioning are presented including studies of timing, efficiency, signal-to-noise, resolution, and ionization energy. Reconstructed tracks are used to benchmark the performance in terms of track and vertex resolutions, reconstruction of decays, estimation of ionization energy loss, as well as identification of photon conversions, nuclear interactions, and heavy-flavour decays.