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Kim, Kwiyong,Lee, Seung Jong,Kim, Dong-Yeon,Yoo, Chung-Yul,Choi, Jang Wook,Kim, Jong-Nam,Woo, Youngmin,Yoon, Hyung Chul,Han, Jong-In Wiley (John WileySons) 2018 CHEM SUS CHEM Vol.11 No.1
<P>Lithium-mediated reduction of dinitrogen is a promising method to evade electron-stealing hydrogen evolution, a critical challenge which limits faradaic efficiency (FE) and thus hinders the success of traditional protic-solvent-based ammonia electro-synthesis. A viable implementation of the lithium-mediated pathway using lithium-ion conducting glass ceramics involves i)lithium deposition, ii)nitridation, and iii)ammonia formation. Ammonia was successfully synthesized from molecular nitrogen and water, yielding a maximum FE of 52.3%. With an ammonia synthesis rate comparable to previously reported approaches, the fairly high FE demonstrates the possibility of using this nitrogen fixation strategy as a substitute for firmly established, yet exceedingly complicated and expensive technology, and in so doing represents a next-generation energy storage system.</P>
Kim, Kwiyong,Han, Jong-In Elsevier 2015 International journal of hydrogen energy Vol.40 No.13
<P><B>Abstract</B></P> <P>In this study, carbon supported Pd and Pd–Co alloys were synthesized and investigated as anode catalysts for the practical application of a promising sulfide-fed fuel cell, named direct alkaline sulfide fuel cell (DASFC). Physical and electrochemical properties of the Pd/C and Pd–Co/C catalysts were evaluated using X-ray diffraction (XRD), transmission electron microscope (TEM), energy dispersive X-ray (EDX), inductively coupled plasma optical emission spectroscopy (ICP-OES), cyclic voltammetry (CV), linear sweep voltammetry (LSV), I–V analysis and electrochemical impedance spectroscopy (EIS). Among all the Pd-based catalysts tested, Pd<SUB>8</SUB>Co<SUB>2</SUB>/C showed the highest sulfide oxidation activity in terms of the lowest onset potential and the highest current density, mass activity, and specific activity at −0.2 V (vs. Ag/AgCl). The maximum power density of DASFC with Pd<SUB>8</SUB>Co<SUB>2</SUB>/C anode catalyst was 46.82 mW cm<SUP>−2</SUP> at 70 °C, which is 26% higher than that with Pd/C. It is speculated that the incorporation of Co into Pd facilitated the adsorption of OH<SUB>ads</SUB> at a lower potential, and Pd<SUB>8</SUB>Co<SUB>2</SUB>/C provided the optimal coverage of OH<SUB>ads</SUB> that played a catalytic role and thus led to the highest performance.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Pd and Pd–Co were used as anode catalysts in direct alkaline sulfide fuel cell. </LI> <LI> Incorporation of Co into Pd facilitated the adsorption of OH<SUB>ads</SUB> at a lower potential. </LI> <LI> Pd<SUB>8</SUB>Co<SUB>2</SUB>/C provided the optimal coverage of OH<SUB>ads</SUB> that played a catalytic role. </LI> <LI> Pd<SUB>8</SUB>Co<SUB>2</SUB>/C exhibited the highest OCV and maximum power density in a single cell. </LI> </UL> </P>
Kim, Kwiyong,Lee, Nara,Yoo, Chung-Yul,Kim, Jong-Nam,Yoon, Hyung Chul,Han, Jong-In The Electrochemical Society 2016 Journal of the Electrochemical Society Vol.163 No.7
<P>Selection of an appropriate electrolyte medium is essential for successful NH3 electro-synthesis at low temperature and pressure. In this study, 2-propanol was employed as an electrolyte medium and its effectiveness in the electro-reduction of N-2 to NH3 under ambient conditions was evaluated. NH3 synthesis and faradaic efficiency using a mixture of 2-propanol/water (9:1, v/v) surpassed those when electrosynthesis was carried out using solely water. The concentration of H2SO4 and the applied current density influenced NH3 synthesis in this 2-propanol-based system, and the optimal conditions led to maximized N-2 reduction, indicating that the competing and electron-losing reaction of H-2 evolution was relatively well suppressed. (C) 2016 The Electrochemical Society. All rights reserved.</P>
Kim, Kwiyong,Yoo, Chung-Yul,Kim, Jong-Nam,Yoon, Hyung Chul,Han, Jong-In The Electrochemical Society 2016 Journal of the Electrochemical Society Vol.163 No.14
<P>In this study, a novel electrolysis cell based on ethylenediamine (EDA) as a cathodic solvent was developed for NH3 electro-synthesis. The NH3-generating cathode chamber was filled with 0.1 M LiCl/EDA and separated by a cation exchange membrane from the anodic compartment, which was filled with 0.05 M H2SO4 aqueous solution. It appeared that EDA was cathodically stable, and thus electron-stealing medium destruction was substantially avoided. The faradaic efficiency for NH3 synthesis was 17.2%, producing 7.73 x 10(-7) mol NH3 for 1 h electrolysis at a cell voltage of 1.8 V with the charge consumption of 1.3 C. (C) 2016 The Electrochemical Society. All rights reserved.</P>
Kim, Kwiyong,Cho, Hoon,Jeon, Seok Hwan,Lee, Seung Jong,Yoo, Chung-Yul,Kim, Jong-Nam,Choi, Jang Wook,Yoon, Hyung Chul,Han, Jong-In The Electrochemical Society 2018 Journal of the Electrochemical Society Vol.165 No.13
<P>Electro-reduction of nitrogen aided by lithium offers a new route for ammonia synthesis. In this novel approach, the first step of lithium plating plays a determining role in faradaic efficiency (FE) of the electro-synthesis process. It was found that the simple addition of cesium salt in a conventional organic electrolyte enhanced Li plating performance (FE of 82.3% for ammonia synthesis) to a substantial extent. This improvement appeared to have a lot to do with a Cs-caused change in morphology of Li deposit, which brought about the suppression of parasitic side reactions between metallic Li and propylene carbonate. This study proves that FE enhancement can be made possible via a simple change in electrolyte composition, an approach that is collectively called electrolyte engineering, and this approach can serve as effective means for making the best of Li-mediated ammonia synthesis. (C) 2018 The Electrochemical Society.</P>
윤형철,Jong-In Han,Kwiyong Kim,유충열,Jong Nam Kim 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.6
Nano-Fe2O3 and CoFe2O4 were suspended in molten salt of alkali-metal chloride (LiCl-KCl-CsCl) and their catalytic activity in electrochemical ammonia synthesis was evaluated from potentiostatic electrolysis at 600 K. The presence of nanoparticle suspension in the molten chloride resulted in improved production of NH3, recording NH3 synthesis rate of 1.78×10−10 mol s−1 cm−2 and 3.00×10−10 mol s−1 cm−2 with CoFe2O4 and Fe2O3, which are 102% and 240% higher than that without the use of a nanocatalyst, respectively. We speculated that the nanoparticles triggered both the electrochemical reduction of nitrogen and also chemical reaction between nitrogen and hydrogen that was produced from water electro-reduction on cathode. The use of nanocatalysts in the form of suspension offers an effective way to overcome the sluggish nature of nitrogen reduction in the molten chloride electrolyte.