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Synthesis of Durable Small-sized Bilayer Au@Pt Nanoparticles for High Performance PEMFC Catalysts
Dorjgotov, Altansukh,Jeon, Yukwon,Hwang, Jeemin,Ulziidelger, Byambasuren,Kim, Hyeong Su,Han, Byungchan,Shul, Yong-Gun Elsevier 2017 ELECTROCHIMICA ACTA Vol.228 No.-
<P><B>Abstract</B></P> <P>Design of small-sized Au@Pt core-shell nanocatalysts with high activity and stability is crucial area for a wide range of electronic and chemical devices. Here, we report a novel reduction method using UV treatment at room temperature by a weak reducing agent of H<SUB>2</SUB>O<SUB>2</SUB> enabling to produce carbon-supported small Au nanoparticles as the core of Pt shells. Different thicknesses of Pt layers are deposited on the Au to configure small-sized core@shell nanocatalysts. We acquire superior catalytic activity of Au@Pt catalysts toward cyclic voltammetry analysis and oxygen reduction reaction (ORR) via atomic level control of the particle size and the electronic structure. Underlying mechanism of the ORR activity is described from the aspect of compressive strain caused by shorter Au-Au distance than the bulk counterpart. The thickness of the Pt shell is shown to play an important role in stabilizing the nanocatalyst. Using density functional theory (DFT) calculations we validate the experimental outcomes. Top-quality power density above 2Wcm<SUP>−2</SUP> at low Pt loading (0.1mgcm<SUP>−2</SUP>) is achieved by a bilayer small-size Au@Pt core-shell catalyst with an excellent durability over 10,000 cycles by ADT, which is, indeed, beyond the recent DOE targets for a proton exchange membrane fuel cell system.</P>
Ulziidelger Byambasuren,Yukwon Jeon,Dorjgotov Altansukh,Yunseong Ji,Yong-Gun Shul 한국탄소학회 2016 Carbon Letters Vol.17 No.-
Nitrogen (N)-doped ordered mesoporous carbons (OMCs) with a dual transition metal system were synthesized as non-Pt catalysts for the ORR. The highly nitrogen doped OMCs were prepared by the precursor of ionic liquid (3-methyl-1-butylpyridine dicyanamide) for N/C species and a mesoporous silica template for the physical structure. Mostly, N-doped carbons are promoted by a single transition metal to improve catalytic activity for ORR in PEMFCs. In this study, our N-doped mesoporous carbons were promoted by the dual transition metals of iron and cobalt (Fe, Co), which were incorporated into the N-doped carbons lattice by subsequently heat treatments. All the prepared carbons were characterized by via transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). To evaluate the activities of synthesized doped carbons, linear sweep was recorded in an acidic solution to compare the ORR catalytic activities values for the use in the PEMFC system. The dual transition metal promotion improved the ORR activity compared with the single transition metal promotion, due to the increase in the quaternary nitrogen species from the structural change by the dual metals. The effect of different ratio of the dual metals into the N doped carbon were examined to evaluate the activities of the oxygen reduction reaction.
Catalytic activity and characterization of V2O5/γ-Al2O3 for ammoxidation of m-xylene system
설용건,Yukwon Jeon,Sung wook Row,Altansukh Dorjgotov,Sang Duek Lee,Kyeongseok Oh 한국화학공학회 2013 Korean Journal of Chemical Engineering Vol.30 No.8
An ammoxidation of m-xylene was evaluated in a fixed-bed reactor using V2O5 on various oxides. Catalysts were prepared by wet impregnation method. At first, the loading of V2O5 was varied from 5 wt% to 20 wt% on γ-Al2O3support to estimate the most effective amount of V2O5. Second, the effect of catalyst supports was examined at 10 wt%loading of V2O5. V2O5/TiO2 and V2O5/SiO2 catalysts were employed to compare the ammoxidation reaction with V2O5/γ-Al2O3. Most catalytic activity was observed when γ-Al2O3 was used as a support. Careful characterization was followed by physicochemical techniques, such as BET measurement, X-ray diffraction (XRD), Raman spectroscopy and temperature-programmed reduction (TPR). The results provided the clue that monolayer V2O5 was favorably dispersed on the surface of γ-Al2O3 up to 10 wt%, which led to the highest yield of isophthalonitrile (IPN).
Yong-Gun Shul,Ulziidelger Byambasuren,Yu Kwon Jeon,Dorjgotov Altansukh,Yunseong Ji 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.6
The particle size effect of N-doped mesoporous carbon was investigated for ORR activity in acid condition and for issue of a mass transfer and gas diffusion in PEMFCs. As for a non-Pt ORR catalyst, nitrogen (N)-doped ordered mesoporous carbons (OMCs) with a various particle sizes with the range of the average 20, 45 and 75 μm were synthesized by the precursor of polyaniline for the N/C species, and a mesoporous silica template was used for the physical structure for preparation of nitrogen doped OMCs. The N-doped mesoporous carbons are promoted by a transition metal (Fe) to improve catalytic activity for ORR in PEMFCs. All the prepared carbons were characterized by via scanning electron microscopy (SEM), and to evaluate the activities of synthesized doped carbons, linear sweep was recorded in an acidic solution to compare the ORR catalytic activities values for the use in the PEMFC system. The surface area and pore volume were increased as the particles decreased, which was effective for the mass transfer of the reactant for higher activity at the limiting current regions.
Kim, Hyeong Su,Lee, Yeayeon,Lee, Jin Goo,Hwang, Ho Jung,Jang, Jeongseok,Juon, So Mi,Dorjgotov, Altansukh,Shul, Yong Gun Elsevier 2016 ELECTROCHIMICA ACTA Vol.193 No.-
<P><B>Abstract</B></P> <P>Precious metals such as platinum are commonly used in polymer-electrolyte membrane fuel cells (PEMFCs) to enhance sluggish oxygen-reduction reactions. However, agglomerations of the nano-sized platinum and corrosions of the carbon supports degrade the performance and durability of the PEMFC during the long-term operation. Here, we present a highly active and durable catalyst for the oxygen-reduction reactions by covering carbon-supported platinum with nitrogen-doped carbons as a protective layer. The PEMFC with the NC-protected Pt/C cathode shows a power density of 1.06Wcm<SUP>2</SUP> at 0.6V in H<SUB>2</SUB>-O<SUB>2</SUB>, comparable with 0.67Wcm<SUP>2</SUP> of the PEMFC with a commercial Pt/C cathode. Furthermore, the durability is remarkably enhanced over 50%, compared with the commercial carbon-supported platinum cathode. It suggests that the nitrogen-doped carbons as a protective layer are effective in enhancing the catalytic activity for oxygen-reduction reactions and durability of the PEMFCs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The Pt/C catalysts protected by N-doped carbons show high activity and durability for oxygen-reduction reactions. </LI> <LI> The optimum thickness of the N-doped carbon layers is 1nm. </LI> <LI> The Pt/C catalysts with 1 nm-thick N-doped carbon layers exhibit the best activity and durability in the PEMFC tests when annealed at 500°C. </LI> <LI> The pyridinic N in the NC layers may be strongly related to the enhancement of the PEMFC performances. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>The Pt/C catalysts covered with nitrogen-doped carbon layers improve both ORR activity and durability. When the catalysts are applied to the cathode of the PEMFCs, the cell performance and durability were significantly enhanced even at 120 °C with 40% of the relative humidity.</P> <P>[DISPLAY OMISSION]</P>