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Jung, Namgee,Chung, Young-Hoon,Chung, Dong Young,Choi, Kwang-Hyun,Park, Hee-Young,Ryu, Jaeyune,Lee, Sang-Young,Kim, Mansu,Sung, Yung-Eun,Yoo, Sung Jong The Royal Society of Chemistry 2013 Physical chemistry chemical physics Vol.15 No.40
<P>Pt-skin surfaces were successfully fabricated by the chemical deposition of additional Pt on corrugated Pt–Ni nanoparticles with Pt-skeleton surfaces. Compared to the Pt-skin formed by heat annealing, the chemically-tuned Pt-skin had a higher Pt coordination number and surface crystallinity, which resulted in superior ORR activity and durability.</P> <P>Graphic Abstract</P><P>A highly ordered and compact Pt-skin catalyst with superior ORR activity and durability was developed through chemical tuning of Pt-skeleton surfaces. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c3cp52807c'> </P>
Jung, Namgee,Kim, Sang Moon,Kang, Do Hyun,Chung, Dong Young,Kang, Yun Sik,Chung, Young-Hoon,Choi, Yong Whan,Pang, Changhyun,Suh, Kahp-Yang,Sung, Yung-Eun American Chemical Society 2013 Chemistry of materials Vol.25 No.9
<P>Carbon-supported Pt (Pt/C) catalyst was selectively functionalized with thermally responsive poly(<I>N</I>-isopropylacrylamide) (PNIPAM) to improve water transport in the cathode of proton exchange membrane fuel cell (PEMFC). Amine-terminated PNIPAM selectively reacted with the functional group of −COOH on carbon surfaces of Pt/C via the amide reaction by 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) as a catalyst. Pt surfaces of Pt/C were intact throughout the carbon surface functionalization, and the carbon surface property could be thermally changed. The PNIPAM-functionalized Pt/C was well-dispersed, because of its hydrophilic surface property at room temperature during the catalyst ink preparation. In sharp contrast, when PEMFC was operated at 70 °C, PNIPAM-coated carbon surface of Pt/C became hydrophobic, which resulted in a decrease in water flooding in the cathode electrode. Because of the switched wetting property of the carbon surface, PEMFC with PNIPAM-functionalized Pt/C catalyst in the cathode showed high performance in the high current density region. To explain the enhanced water transport, we proposed a simple index as the ratio of systematic pressure (driving force) and retention force. The synthetic method presented here will provide a new insight into various energy device applications using organic and inorganic composite materials and functional polymers.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/cmatex/2013/cmatex.2013.25.issue-9/cm303691e/production/images/medium/cm-2012-03691e_0009.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/cm303691e'>ACS Electronic Supporting Info</A></P>
Hyeon, Yuhwan,Jung, Su-Ho,Jang, Wonseok,Kim, Mansu,Kim, Byung-Sung,Lee, Jae-Hyun,Nandanapalli, Koteeswara Reddy,Jung, Namgee,Whang, Dongmok American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.5
<P>In MoS<SUB>2</SUB>-carbon composite catalysts for hydrogen evolution reaction (HER), the carbon materials generally act as supports to enhance the catalytic activity of MoS<SUB>2</SUB> nanosheets. The carbon support provides a large surface area for increasing the MoS<SUB>2</SUB> edge site density, and its physical structure can affect the electron transport rate in the composite catalysts. However, despite the importance of the carbon materials, direct observation of the effects of the physical properties of the carbon supports on the HER activity of MoS<SUB>2</SUB>-carbon composite catalysts has been hardly reported. In this work, we conduct an experimental model study to find the fundamental and important understanding of the correlation between the structural characteristics of carbon supports and the HER performance of MoS<SUB>2</SUB>-carbon composite catalysts using surface-modified graphitic carbon shell (GCS)-encapsulated SiO<SUB>2</SUB> nanowires (GCS@SiO<SUB>2</SUB> NWs) as support materials for MoS<SUB>2</SUB> nanosheets. The surface defect density and the electrical resistance of GCS@SiO<SUB>2</SUB> NWs are systematically modulated by control of H<SUB>2</SUB> gas flow rates during the carbon shell growth on the SiO<SUB>2</SUB> NWs. From in-depth characterization of the model catalysts, it is confirmed that the intrinsic catalytic activity of MoS<SUB>2</SUB>-carbon composites for the HER is improved linearly with the conductance of the carbon supports regardless of the MoS<SUB>2</SUB> edge site density. However, in the HER polarization curve, the apparent current density increases in proportion to the product of the number of MoS<SUB>2</SUB> edge sites and the conductance of GCS@SiO<SUB>2</SUB> NWs.</P> [FIG OMISSION]</BR>
Ryu, Jaeyune,Jung, Namgee,Lim, Dong-Hee,Shin, Dong Yun,Park, Sae Hume,Ham, Hyung Chul,Jang, Jong Hyun,Kim, Hyoung-Juhn,Yoo, Sung Jong The Royal Society of Chemistry 2014 Chemical communications Vol.50 No.100
<P>Described herein is the development of a novel Co-based oxygen electrode catalyst coupled with unique carbon structures. The present carbon shell coated Co nanoparticles of which the surface composites are modified by phosphorus incorporation, exhibit efficient oxygen reduction activities as well as oxygen evolving properties.</P> <P>Graphic Abstract</P><P>The present carbon shell coated Co nanoparticles of which the surface composites are modified by phosphorus incorporation, exhibit efficient and durable oxygen reduction activities in alkaline medium. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c4cc07143c'> </P>
Sharma, Monika,Jung, Namgee,Yoo, Sung Jong American Chemical Society 2018 Chemistry of materials Vol.30 No.1
<P>Pt-based multistructured nanocatalysts such as alloy, core–shell, and surface Pt-rich nanoparticles have been extensively studied for hydrogen fuel cell applications, and their catalytic performances for oxygen reduction reactions have been significantly upgraded for decades. Due to these technical enhancements, Pt-based nanoarchitectures have turned out to be compatible with commercially accessible fuel cell systems. In addition, based on physical and electrochemical backgrounds for the basic catalyst nanoarchitectures, novel catalyst designs with organic–inorganic hybrid concepts have been recently developed to more effectively improve the electrochemical reaction activities and durabilities. In this review, the typical class of Pt-based nanocatalysts are systematically explained according to their compositions and structures, and the emerging class of organic–inorganic hybrid catalyst designs are then thoroughly introduced. It is expected that the most recent improvements of Pt-based nanoarchitectures will have great effects on the future works for the commercialization of fuel cell catalysts.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/cmatex/2018/cmatex.2018.30.issue-1/acs.chemmater.7b03422/production/images/medium/cm-2017-034226_0037.gif'></P>
Effects of anode flooding on the performance degradation of polymer electrolyte membrane fuel cells
Kim, Mansu,Jung, Namgee,Eom, KwangSup,Yoo, Sung Jong,Kim, Jin Young,Jang, Jong Hyun,Kim, Hyoung-Juhn,Hong, Bo Ki,Cho, EunAe Elsevier 2014 Journal of Power Sources Vol.266 No.-
<P><B>Abstract</B></P> <P>Polymer electrolyte membrane fuel cell (PEMFC) stacks in a fuel cell vehicle can be inevitably exposed to harsh environments such as cold weather in winter, causing water flooding by the direct flow of condensed water to the electrodes. In this study, anode flooding was experimentally investigated with condensed water generated by cooling the anode gas line during a long-term operation (∼1600 h). The results showed that the performance of the PEMFC was considerably degraded. After the long-term experiment, the thickness of the anode decreased, and the ratio of Pt to carbon in the anode increased. Moreover, repeated fuel starvation of the half-cell severely oxidized the carbon surface due to the high induced potential (>1.5 V<SUB>RHE</SUB>). The cyclic voltammogram of the anode in the half-cell experiments indicated that the characteristic feature of the oxidized carbon surface was similar to that of the anode in the single cell under anode flooding conditions during the long-term experiment. Therefore, repeated fuel starvation by anode flooding caused severe carbon corrosion in the anode because the electrode potential locally increased to >1.0 V<SUB>RHE</SUB>. Consequently, the density of the tri-phase boundary decreased due to the corrosion of carbons supporting the Pt nanoparticles in the anode.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Anode flooding can occur by direct flow of condensed water in humidified fuel. </LI> <LI> Anode flooding induces local fuel starvation and high potential in the anode. </LI> <LI> High potential locally present in the anode results in anode carbon corrosion. </LI> <LI> Anode carbon corrosion plays a key role in MEA degradation by anode flooding. </LI> </UL> </P>
Lee, Sang-Young,Jung, Namgee,Shin, Dong Yun,Park, Hee-Young,Ahn, Docheon,Kim, Hyoung-Juhn,Jang, Jong Hyun,Lim, Dong-Hee,Yoo, Sung Jong Elsevier 2017 Applied Catalysis B Vol.206 No.-
<P><B>Abstract</B></P> <P>Pt shells were synthesized on Pd-based alloy-cores <I>via</I> the chemical reduction method. Pt shells containing 1, 2, or 3 layers were prepared by controlling the amounts of Pt precursor used during synthesis. The thicknesses of Pt shell layers were calculated using the difference in the particle size between core and core-shell nanocatalysts, as determined from Cs-corrected scanning transmission electron microscopy (Cs-STEM) data. The shape and elemental distribution in the core-shell structured nanoparticles were analyzed using line profiles and elemental mapping from Cs-STEM. High-resolution X-ray diffraction and X-ray photoelectron spectroscopy analyses suggested that the structural and electronic properties of core-shell nanocatalysts were dependent on the number of shell layers. The activity and durability of the core-shell nanocatalysts were analyzed by the electrochemical method. Accelerated durability tests (ADT) were conducted in the potential range of 0.6–1V for 10000 cycles, and the mass and specific activities of ADT were shown to be stable for the carbon-supported core-shell nanocatalyst with two Pt shell layers (core@Pt[2](*)/C). In addition, excellent electrochemical performance was observed for the core@Pt[2]/C sample before and after the ADT compared to the commercial samples as well as other samples prepared in this study. Importantly, the optimized Pt usage demonstrated in this study would significantly contribute to the commercialization of proton exchange membrane fuel cells.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Formation of various Pt shell layers on alloy-core <I>via</I> chemical reduction method. </LI> <LI> Investigations of changed relation between core and shell after acceleration durability test. </LI> <LI> Relationship between the electrocatalytic activities and durability in ADT and DFT calculations. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
A compact BrFAFC (Bio-reformed Formic Acid Fuel Cell) converting formate to power
Shin, Jong-Hwan,Jung, Namgee,Yoo, Sung Jong,Cho, Yong-Hun,Sung, Yung-Eun,Park, Tai Hyun Royal Society of Chemistry 2011 Chemical communications Vol.47 No.13
<P>A compact BrFAFC can directly convert formate to power without hydrogen storage and poisoning effect by CO at mild temperature. We are the first to establish the performance of the BrFAFC with high power density. Furthermore, this BrFAFC can be manufactured in a simple design for use in portable fuel cells.</P> <P>Graphic Abstract</P><P>A compact BrFAFC (Bio-reformed Formic Acid Fuel Cell) directly converts formate to power without hydrogen storage. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c0cc05225f'> </P>