• Applied Chemistry for Engineering
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• v.28 no.3
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• pp.279-285
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• 2017

In this study, the study of the selective catalytic oxidation (SCO) for controlling the $NH_3$ at $200{\sim}350^{\circ}C$ range was investigated. Physicochemical properties of the catalysts were determined using XRD and XPS analysis. In the case of catalytic activity according to thermal treatment condition, the reduction catalyst showed better activity than that of using the calcination catalyst. It was confirmed that the valence state of reduction catalyst was mainly $Pt^{2+}$ and $Pt^0$ as analyzed by XPS. Also, when comparing the reaction activities of $Pt/TiO_2$ catalysts according to the reduction temperature, the $NH_3$ conversion of the catalyst reduced at $700^{\circ}C$ showed the most excellent activity. However, the best activity of $NH_3$ conversion to $N_2$ was obtained for the catalyst reduced at $600^{\circ}C$.

• Korean Journal of Materials Research
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• v.26 no.11
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• pp.649-655
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• 2016

Ni nanoparticles (NPs)-graphitic carbon nanofiber (GCNF) composites were fabricated using an electrospinning method. The amounts of Ni precursor used as catalyst for the catalytic graphitization were controlled at 0, 2, 5, and 8 wt% to improve the photovoltaic performances of the nanoparticles and make them suitable for use as counter electrodes for dye-sensitized solar cells (DSSCs). As a result, Ni NPs-GCNF composites that were fabricated with 8 wt% Ni precursors showed a high circuit voltage (0.73 V), high photocurrent density ($14.26mA/cm^2$), and superb power-conversion efficiency (6.72%) when compared to those characteristics of other samples. These performance improvements can be attributed to the reduced charge transport resistance that results from the synergetic effect of the superior catalytic activity of Ni NPs and the efficient charge transfer due to the formation of GCNF with high electrical conductivity. Thus, Ni NPs-GCNF composites may be used as promising counter electrodes in DSSCs.

• Applied Chemistry for Engineering
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• v.3 no.4
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• pp.722-729
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• 1992

Mg-and Zn-ferrites having spinel structure, a kind of complex oxides showing the advantageous properties of constituently single metal oxides, were selected to find a relationship between their catalytic activities in the dehydrogenation of ethylbenzene to styrene and the catalytic properties. For the structural and physical analyses of ferrites, XRD, BET, DTA, XPS, TEM and TPD methods were employed. Potassium added to the catalyst played a role of bifunctional promoter which brought the electronic effect as well as the structural one for the increment of particle dispersion. K-addition decreased acid strength of the catalyst by neutralization and increased its acidity. In the dehydrogenation of ethylbenzene, K-addition let the selectivity to styrene be constant throughout the reaction by the proper acid strength of the ferrite for the reaction, which could be obtained from the neutralization of strong acid sites by potassium.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.490-490
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• 2011

Graphene, hexagonal network of carbon atoms forming a one-atom thick planar sheet, has been emerged as a fascinating material for future nanoelectronics. Huge attention has been captured by its extraordinary electronic properties, such as bipolar conductance, half integer quantum Hall effect at room temperature, ballistic transport over ${\sim}0.4{\mu}m$ length and extremely high carrier mobility at room temperature. Several approaches have been developed to produce graphene, such as micromechanical cleavage of highly ordered pyrolytic graphite using adhesive tape, chemical reduction of exfoliated graphite oxide, epitaxial growth of graphene on SiC and single crystalline metal substrate, and chemical vapor deposition (CVD) synthesis. In particular, direct synthesis of graphene using metal catalytic substrate in CVD process provides a new way to large-scale production of graphene film for realization of graphene-based electronics. In this method, metal catalytic substrates including Ni and Cu have been used for CVD synthesis of graphene. There are two proposed mechanism of graphene synthesis: carbon diffusion and precipitation for graphene synthesized on Ni, and surface adsorption for graphene synthesized on Cu, namely, self-limiting growth mechanism, which can be divided by difference of carbon solubility of the metals. Here we present that large area, uniform, and layer controllable graphene synthesized on Cu catalytic substrate is achieved by acetylene-assisted CVD. The number of graphene layer can be simply controlled by adjusting acetylene injection time, verified by Raman spectroscopy. Structural features and full details of mechanism for the growth of layer controllable graphene on Cu were systematically explored by transmission electron microscopy, atomic force microscopy, and secondary ion mass spectroscopy.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.199-199
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• 2011

The addition of a carbanion to ${\yen}{\acute{a}}{\yen}{\hat{a}}$-unsaturated carbonyl compounds is of importance in the C-C bond formation reactions for modern pharmaceuticals and organic synthesis. Recently, heterogeneous asymmetric catalysis became more attractive area of research because of the easy recovery and separation of the catalyst from the reaction system. Most of synthetic methods for heterogeneous catalysts were grafting or immobilization of homogeneous catalyst onto the solid supports. Trans-1,2-Diaminocyclohexane(DACH) and L-proline ligands have been enormously used as chiral ligands in several catalytic transformation under homogenous conditions. Our group prepared l-proline functionalized mesoporous silica was synthesized under acidic condition using a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer template (EO20PO70EO20, Pluronic P-123, BASF). Furthermore, we successfully directly synthesized trans-1,2 diaminocyclohexane functionalized mesoporous silica by using microwave method. The direct functionalization of chiral ligand into the framework of mesoporous materials is expected to be useful for the heterogeneous asymmetric catalysis. So, we adopt the direct synthesis of chiral ligand functionalized mesoporous silica by using thermal and microwave irradiation. Then, chiral ligand functionalized mesoporous silicas were applied to enantioselective asymmetric catalytic reactions.

• Applied Chemistry for Engineering
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• v.10 no.8
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• pp.1200-1209
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• 1999

Prediction model was composed by optimal parameter estimation from best fitting on reactant temperature profile, inlet and outlet temperature of coolant and yield of dual fixed-bed catalytic reactor(FBCR) which was measured in the industrial field. In order to design the FBCR which could obtain maximum conversion and yield, we investigated the effect of catalyst bed length and reactor radius changes. An uniform activity FBCR showed the best performance at z = 2.8 m of total catalysst bed length in case of reactor radius r = 0.01241 m and z =2.80 m(upper layer: 1.88 m, lower layer: 0.92 m) under reactor radius r = 0.01254 m for a dual activities FCBR. In case of reactor radius changes, the axial temperature profile and maximum radial temperature was rapidly risen for radius increase. The reactor radius decrease showed the opposite result.

• Applied Chemistry for Engineering
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• v.31 no.5
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• pp.581-584
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• 2020

The effect of a chemical pretreatment on the surface carbon was investigated using a scanning electron microscope (SEM) and electrochemical methods. Primitive carbon has a reducing power likely due to incompletely oxidized functional groups on the surface. We aim to control this reducing power by chemical treatment and apply for the spontaneous deposition of nanoparticles (NPs). Highly ordered pyrolytic graphite (HOPG) was initially treated with a reducing agent, NaBH4 or an oxidizing agent, KMnO₄, for 5 min. Subsequently, the pretreated carbon was immersed in a platinum (Pt) precursor. Unexpectedly, SEM images showed that the reducing agent increased spontaneous PtNPs deposition while the oxidizing agent decreased Pt loading more as compared to that of using bare carbon. However, the amount of Pt on the carbon obviously decreased by NaBH₄ treatment for 50 min. Secondly, spontaneous reduction on pretreated glassy carbon (GC) was investigated using the catalytic hydrogen evolution reaction (HER). GC electrode treated with NaBH4 for a short and long time showed small (onset potential: -640 mV vs. MSE) and large overpotential for the HER, respectively. Although the mechanism is unclear, the electrochemistry results correspond to the optical data. As a proof-of-concept, these results demonstrate that chemical treatments can be used to design the shapes and amounts of deposited catalytic metal on carbon by controlling the surface state.

• Journal of Hydrogen and New Energy
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• v.18 no.1
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• pp.32-39
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• 2007

CO oxidation and selective CO oxidation of $La_xCe_{1-x}Co_yCu_{1-y}O_{3-{\alpha}}$ perovskite(x=1, 0.9, 0.7. 0.5; y=1, 0.9, 0.7, 0.5) were investigated. For CO oxidation, catalytic activities were studied according to different preparation conditions such as pH and calcination temperature. The influence of the change of the $O_2$ concentration for selective CO oxidation was studied, too. The substitution of Ce for La improved the catalytic activity for CO oxidation and selective CO oxidation and best activity was observed for $La_{0.7}Ce_{0.3}CoO_3$ prepared at pH 11 and calcined at $600^{\circ}C$. The temperature of 90% CO conversion for CO oxidation using $La_{0.7}Ce_{0.3}CoO_3$ was $230^{\circ}C$. In contrast to the enhancement effect by Ce substitution, the partial substitution of Cu for Co in $LaCo_yCu_{1-y}O_{3-{\alpha}}$ decreased catalytic activities for CO oxidation reaction compared to that using $LaCoO_3$. For selective CO oxidation, the best CO conversion was 66% at $230^{\circ}C$ for $La_{0.7}Ce_{0.3}CoO_3$. The CO conversion of $La_{0.7}Ce_{0.3}CoO_3$ was greatly increased from 66% to 91% as increasing $O_2$ concentration from 1% to 2%.

• Korean Chemical Engineering Research
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• v.53 no.2
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• pp.262-268
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• 2015

In this study, two types of catalysts were prepared via conventional metal supporting method and encapsulation of metal nanoparticles in the polyelectrolyte multilayers constructed on support. The resulting catalysts were applied to the direct synthesis of hydrogen peroxide, and the effect of catalyst preparation method on the catalyst life as well as hydrogen peroxide productivity was investigated. The catalytic activity was strongly dependent upon the acid strength of support regardless of the catalyst preparation methods and HBEA (SAR=25) with strong acidity was superior to other supports to promote the reaction. In the case of metal supported catalyst, while hydrogen peroxide productivity was higher than that of polyelectrolyte multilayered counterpart, the reaction performance was sharply decreased during catalyst recycling due to the metal leaching. On the other hand, construction of polyelectrolyte multilayers on support weakened the influence of acid support on the reaction medium and therefore resulted in the decrease of catalytic activity and the increase of hydrogen peroxide decomposition as well. It is noted, however, that the catalytic activity was maintained after 5 recycles, which suggests that the introduction of polyelectrolyte multilayers on the support is very effective to suppress the unfavorable metal leaching phenomenon during a reaction.

• Macromolecular Research
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• v.16 no.5
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• pp.441-445
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• 2008

A series of aluminum complexes supported by $\beta$-ketoamino, ligand-bearing, 3-position substituents $LAlEt_2$ ($L=CH_3C(O)C(Cl)=C(CH_3)NAr\;(L_1)$, $L=CH_3C(O)C(H)=C(CH_3)NAr\;(L_2)$, $L=CH_3C(O)C(Ph)=C(CH_3)NAr\;(L_3)$, and $L=CH_3C(O)C(Me)=C(CH_3)NAr\;(L_4)$, $Ar=2,6-^iPr_2C6H_3$) were synthesized in situ and employed in the ring-opening polymerization (ROP) of $\varepsilon$-caprolactone ($\varepsilon$-CL) and cyclohexene oxide (CHO). The 3-position substituents on the $\beta$-ketoamino ligand backbone of the aluminum complexes influenced the catalyst activity remarkably for both ROP of $\varepsilon$-CL and CHO. Aluminum $\beta$-ketoamino complexes displayed different catalytic behavior in ROP of $\varepsilon$-CL and CHO. The order of the catalytic activity of $LAlEt_2$ was $L_1AlEt_2$>$L_2AlEt_2$>$L_3AlEt_2$>$L_4AlEt_2$ for ROP of $\varepsilon$-CL, being opposite to the electron-donating ability of the 3-position substituents on the $\beta$-ketoamino ligand, while the order of the catalytic activity for ROP of CHO was $L_1AlEt_2$>$L_3AlEt_2$>$L_4AlEt_2$>$L_2AlEt_2$. The effects of reaction temperature and time on the ROP were also investigated for both $\varepsilon$-CL and CHO.