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Eom, KwangSup,Kim, MinJoong,Oh, SeKwon,Cho, EunAe,Kwon, HyukSang Elsevier 2011 International journal of hydrogen energy Vol.36 No.18
<P><B>Abstract</B></P><P>An Al–Sn–Fe alloy is designed to increase the hydrogen generation rate even in weak alkaline water through the effective removal of Al oxide. Al-1wt.%Sn-1wt.%Fe alloy exhibits the hydrogen generation rate about 6 times higher than pure Al and 1.6 times higher than Al-1wt.%Fe alloy. Increases in exchange current density of Al alloys are in good accordance with increases in hydrogen generation rate. The addition of Sn in Al–Fe alloy can increase the hydrolysis rate by accelerating the breakdown of passive film (Al(OH)<SUB>3</SUB> and Al<SUB>2</SUB>O<SUB>3</SUB>) in an alkaline solution. Hence, the Al-1wt.%Sn-1wt%Fe alloy shows a much higher hydrogen generation rate than pure Al and Al-1wt.%Fe alloy in relatively weak alkaline water. In the hydrolysis of Al-1wt.%Sn-1wt%Fe, Fe accelerates the hydrogen production by inducing simultaneously both inter-granular and galvanic corrosion, whereas Sn increases the hydrogen generation rate by breaking the Al oxide down effectively. Based on the increase in the hydrogen generation rate of Al-1wt.%Fe and Al-1wt.%Sn-1wt%Fe alloys over pure Al, the contribution to the increase of Fe and Sn are calculated to be 63% and 27%, respectively. Because the same amount of power is obtained by PEMFC using 6 times less Al–Sn–Fe alloy than pure Al, the weight and volume of on-board hydrogen production reactor can be reduced significantly by alloying Al with a small amount of Fe and Sn.</P> <P><B>Highlights</B></P><P>► Al–1Fe–1Sn alloy exhibits the hydrogen generation rate about 6 times higher than pure Al. ► Fe accelerates the hydrogen production by inducing both inter-granular and galvanic corrosion. ► Sn increases the hydrogen generation rate by breaking the Al oxide down effectively. ► Same amount of power is obtained by PEMFC using 6 times less Al–1Sn–1Fe alloy than pure Al.</P>
Kim, GyeongHee,Eom, KwangSup,Kim, MinJoong,Yoo, Sung Jong,Jang, Jong Hyun,Kim, Hyoung-Juhn,Cho, EunAe American Chemical Society 2015 ACS APPLIED MATERIALS & INTERFACES Vol.7 No.50
<P>The membrane electrolyte assembly (MEA) designed in this study utilizes a double-layered cathode: an inner catalyst layer prepared by a conventional decal transfer method and an outer catalyst layer directly coated on a gas diffusion layer. The double-layered structure was used to improve the interfacial contact between the catalyst layer and membrane, to increase catalyst utilization and to modify the removal of product water from the cathode. Based on a series of MEAs with double-layered cathodes with an overall Pt loading fixed at 0.4 mg cm<SUP>–2</SUP> and different ratios of inner-to-outer Pt loading, the MEA with an inner layer of 0.3 mg Pt cm<SUP>–2</SUP> and an outer layer of 0.1 mg Pt cm<SUP>–2</SUP> exhibited the best performance. This performance was better than that of the conventional single-layered electrode by 13.5% at a current density of 1.4 A cm<SUP>–2</SUP>.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2015/aamick.2015.7.issue-50/acsami.5b07346/production/images/medium/am-2015-07346t_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am5b07346'>ACS Electronic Supporting Info</A></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>
Design of Mg-Cu alloys for fast hydrogen production, and its application to PEM fuel cell
Oh, SeKwon,Kim, HyoWon,Kim, MinJoong,Eom, KwangSup,Kyung, JoonSeok,Kim, DoHyang,Cho, EunAe,Kwon, HyukSang Elsevier 2018 Journal of Alloys and Compounds Vol.741 No.-
<P><B>Abstract</B></P> <P>Mg-Cu alloys are designed for fast hydrogen generation by precipitating an electrochemically noble phase (Mg<SUB>2</SUB>Cu) at the grain boundaries. The noble precipitates accelerate the hydrolysis kinetics of the alloy by synergetic action of galvanic and intergranular corrosion. The Mg-3Cu alloy exhibits a hydrogen generation rate of 5.23 ml min<SUP>−1</SUP> g<SUP>−1</SUP>, which is 307 times faster than that of pure Mg (0.017 ml min<SUP>−1</SUP> g<SUP>−1</SUP>). Furthermore, the effects of annealing of the alloy on the hydrogen generation rate and the feasibility of the production of power via hydrolysis of Mg-3Cu alloy are also confirmed. The annealing of the alloy reduces the hydrogen generation rate through the decrease of precipitates, and 10 g of Mg-3Cu alloy can produce power of 7.25 W for 37 min by operation of a single cell PEMFC.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Mg-Cu (1∼3 wt %) alloys were specially designed for fast H<SUB>2</SUB> generation. </LI> <LI> Electrochemically noble phase (Mg<SUB>2</SUB>Cu) was precipitated along the grain boundary. </LI> <LI> H<SUB>2</SUB> generation rate of Mg-3Cu alloy was 307 times faster than that of pure Mg in seawater. </LI> <LI> Enhanced performance is originated from the galvanic, intergranular corrosion. </LI> <LI> Just 10g of Mg-3Cu alloy can produce 7.25 W for 37 min stably via PEMFC operation. </LI> </UL> </P>
Lee, Byeongyong,Lee, Chongmin,Liu, Tianyuan,Eom, Kwangsup,Chen, Zhongming,Noda, Suguru,Fuller, Thomas F.,Jang, Hee Dong,Lee, Seung Woo Royal Society of Chemistry 2016 Nanoscale Vol.8 No.24
<P>Crumpled graphene is known to have a strong aggregation-resistive property due to its unique 3D morphology, providing a promising solution to prevent the restacking issue of graphene based electrode materials. Here, we demonstrate the utilization of redox-active oxygen functional groups on the partially reduced crumpled graphene oxide (r-CGO) for electrochemical energy storage applications. To effectively utilize the surface redox reactions of the functional groups, hierarchical networks of electrodes including r-CGO and functionalized few-walled carbon nanotubes (f-FWNTs) are assembled via a vacuum-filtration process, resulting in a 3D porous structure. These composite electrodes are employed as positive electrodes in Li-cells, delivering high gravimetric capacities of up to similar to 170 mA h g(-1) with significantly enhanced rate-capability compared to the electrodes consisting of conventional 2D reduced graphene oxide and f-FWNTs. These results highlight the importance of microstructure design coupled with oxygen chemistry control, to maximize the surface redox reactions on functionalized graphene based electrodes.</P>
Fabrication of Mg–Ni–Sn alloys for fast hydrogen generation in seawater
Oh, SeKwon,Cho, TaeHee,Kim, MinJoong,Lim, JeongHoon,Eom, KwangSup,Kim, DoHyang,Cho, EunAe,Kwon, HyukSang Pergamon Press 2017 International journal of hydrogen energy Vol.42 No.12
<P><B>Abstract</B></P> <P>Mg-2.7Ni-x wt.% Sn(x = 0–2) alloys were fabricated to promote hydrogen generation kinetics of Mg-2.7Ni alloy. The Sn in Mg-2.7Ni-Sn alloys exists as Mg<SUB>2</SUB>Sn phase at the grain boundary and solid solution at the Mg matrix. The Mg<SUB>2</SUB>Sn at the grain boundary acts as the initiation site for pitting corrosion and the dissolved Sn in the alloy causes pitting corrosion by locally breaking the surface oxide film in the Mg matrix in seawater. The Mg-2.7Ni-1Sn alloy showed an excellent hydrogen generation rate of 28.71 ml min<SUP>−1</SUP> g<SUP>−1</SUP>, which is 1700 times faster than that of pure Mg due to the combined action of galvanic and intergranular corrosion as well as pitting corrosion in seawater. As the solution temperature was increased from 30 to 70 °C, the hydrogen generation rate from the hydrolysis of the Mg-2.7Ni-1Sn alloy was dramatically increased from 34 to 257.3 ml min<SUP>−1</SUP> g<SUP>−1</SUP>. The activation energy for the hydrolysis of Mg was calculated to be 43.13 kJ mol<SUP>−1</SUP>.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The Mg–Ni–Sn alloys were specially designed to fast generate H<SUB>2</SUB> in seawater. </LI> <LI> The Mg<SUB>2</SUB>Sn at the grain boundary acts as the initiation site for pitting corrosion. </LI> <LI> The dissolved Sn causes pitting corrosion by locally breaking the surface oxide film. </LI> <LI> H<SUB>2</SUB> generation rate of Mg-2.7Ni-1Sn was 1700 times faster than that of pure Mg in seawater. </LI> <LI> Enhanced performance was attributed to pitting, galvanic and intergranular corrosion. </LI> </UL> </P>