http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Lim, Dongwook,Park, Seongmin,Ro, Hyeyoon,Shin, Kyuchul,Lee, Huen American Chemical Society 2015 The Journal of Physical Chemistry Part C Vol.119 No.19
<P>Guest-host hydrogen bonding strongly affects the physical properties of clathrate hydrate, such as the thermodynamic stability, water dynamics, and dielectric properties, but attempts to quantify the effects of hydrogen bonding on these properties are rare thus far. As a preliminary work, this study investigates methane clathrate hydrates with three diazine isomers, pyrazine, pyrimidine, and pyridazine, which expect nearly the same van der Waals volumes due to their similar molecular shapes and sizes, and their guest-host hydrogen-bonding behaviors. The crystal structures of all three binary diazine + CH4 hydrate phases were identified as a cubic Fd (3) over barm structure, including diazine molecules in the 5(12)6(4) cavity, commonly termed as structure II hydrate, by a high-resolution powder diffraction pattern analysis. The phase equilibrium curves of their clathrate hydrates were obtained by the P-T trajectory of the hydrate formation and dissociation process, and the thermodynamic stability trend was well-explained by the guest-host hydrogen bonding behavior as evaluated by the molecular polarities, proton affinities, and ring-breathing vibration frequencies of the three diazine isomers obtained from Raman spectroscopy. This study provides useful information that contributes to the realization of the expansion of the thermodynamics of clathrate hydrates to include guest-host hydrogen-bonding interactions.</P>
Lim, Dongwook,Kim, Yoonkyung,Nam, Daehyeon,Hwang, Sungwon,Shim, Sang Eun,Baeck, Sung-Hyeon Elsevier 2018 JOURNAL OF CLEANER PRODUCTION Vol.197 No.1
<P><B>Abstract</B></P> <P>In this paper, Ti/SnO<SUB>2</SUB>-Sb electrodes with different Sb dopant amounts were successfully fabricated on acid-treated Ti substrates by a thermal decomposition method; this was done in an attempt to examine the effect of the doping amount on the electrochemical activity and stability of the electrode. The physicochemical properties of the prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM)-energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). The electrochemical properties were investigated by linear sweep voltammetry (LSV), and the stability was studied via accelerated lifetime testing. The electro-catalytic activity of the prepared Ti/SnO<SUB>2</SUB>-Sb electrodes was strongly dependent on the amount of the Sb dopant, leading to a change in the OER overpotential. Among the prepared samples, the Ti/SnO<SUB>2</SUB> electrode with 10% of a Sb dopant showed the highest catalytic activity for oxygen evolution reaction (OER), and 87% of COD removal with 20 mA cm<SUP>−2</SUP> of current density for 60 min was achieved in the presence of 10.0 g L<SUP>−1</SUP> of chloride. The findings reported herein suggest that the Ti/SnO<SUB>2</SUB> electrode with an optimized Sb dopant amount shows enhanced electro-catalytic performance by easily generating active hydroxyl radicals, which act as strong oxidizing agents.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ti/SnO<SUB>2</SUB>-Sb electrodes with different amounts of Sb doping were prepared by thermal decomposition. </LI> <LI> The prepared electrodes exhibited a cracked surface morphology and were not crystalline. </LI> <LI> The efficiency of COD elimination depended largely on the amount of Sb. </LI> </UL> </P>
Bimetallic NiFe alloys as highly efficient electrocatalysts for the oxygen evolution reaction
Lim, Dongwook,Oh, Euntaek,Lim, Chaewon,Shim, Sang Eun,Baeck, Sung-Hyeon Elsevier 2020 CATALYSIS TODAY - Vol.352 No.-
<P><B>Abstract</B></P> <P>In this study, binary NiFe alloy nanoparticles are successfully prepared using a simple hydrothermal method followed by H<SUB>2</SUB> reduction. The nanoparticles are then applied as electrocatalysts for oxygen evolution reaction (OER). Compared to unary Ni or Fe, the binary NiFe alloy electrocatalyst exhibits a much lower overpotential of 298 mV at a current density of 10 mA cm<SUP>−2</SUP>, and it exhibits electrocatalytic activity for OER superior to that of state-of-the-art RuO<SUB>2</SUB> and IrO<SUB>2</SUB> noble metal oxide catalysts. Moreover, the alloy catalyst exhibits substantial long-term durability after 1000 cyclic voltammetry tests. This remarkable electrochemical performance mainly originates from the synergistic effects of Fe incorporation into Ni species, leading to the improved charge transfer kinetics and intrinsic activity of the catalyst. These results provide a promising avenue for developing cost-effective and high-performance electrocatalysts as advanced electrodes for energy storage and conversion systems.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Bimetallic Fe<SUB>0.64</SUB>Ni<SUB>0.36</SUB> Alloys were prepared by a hydrothermal method followed by mild H<SUB>2</SUB> reduction. </LI> <LI> The binary metal alloys exhibited a low overpotential and substantial long-term stability for oxygen evolution reaction. </LI> <LI> This outstanding OER performance and durability can be attributed to the synergistic effect of binary metal. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Lim, Dongwook,Han, Sang-Il,Lee, Young-Wook,Roh, Dong-Goo,Sohn, Young-Jong,Chun, Sang-Hyun,Lee, Jae-Woo,Johnson, Christian I. IOP Publishing 2015 The Astrophysical journal, Supplement series Vol.216 No.1
<P>There is increasing evidence for the presence of multiple red giant branches (RGBs) in the color-magnitude diagrams of massive globular clusters (GCs). In order to investigate the origin of this split on the RGB, we have performed new narrow-band Ca photometry and low-resolution spectroscopy for M22, NGC 1851, and NGC 288. We find significant differences (more than 4 sigma) in calcium abundance from the spectroscopic HK' index for M22 and NGC 1851. We also find more than 8 sigma differences in CN-band strength between the Ca-strong and Ca-weak subpopulations for these GCs. For NGC 288, however, a large difference is detected only in the CN strength. The calcium abundances of RGB stars in this GC are identical to within the errors. This is consistent with the conclusion from our new Ca photometry where the RGB splits are confirmed in M22 and NGC 1851, but not in NGC 288. We also find interesting differences in the CN-CH correlations among these GCs. While CN and CH are anti-correlated in NGC 288, they show a positive correlation in M22. NGC 1851, however, shows no difference in CH between the two groups of stars with different CN strengths. We suggest that all of these systematic differences would be best explained by how strongly Type II supernovae enrichment has contributed to the chemical evolution of these GCs.</P>
Lim, Dongwook,Lee, Young-Wook,Pasquato, Mario,Han, Sang-Il,Roh, Dong-Goo American Astronomical Society 2016 The Astrophysical journal Vol.832 No.2
<P>Most globular clusters (GCs) are now known to host multiple stellar populations with different abundances of light elements. Here we use narrow-band photometry and low-resolution spectroscopy for NGC. 362 and NGC. 6723 to investigate their chemical properties and radial distributions of subpopulations. We confirm that NGC. 362 and NGC. 6723 are among the GCs with multiple populations showing bimodal CN distribution and CN-CH anticorrelation without a significant spread in calcium abundance. These two GCs show more centrally concentrated CN-weak, earlier generation stars compared to the CN-strong, later generation stars. These trends are reversed with respect to those found in previous studies for many other GCs. Our findings, therefore, seem contradictory to the current scenario for the formation of multiple stellar populations, but mass segregation acting on the two subpopulations might be a possible solution to explain this reversed radial trend.</P>