Elucidation of durability of carbon-supported PdIr alloy catalyst by experimental and theoretical approaches in polymer electrolyte membrane fuel cell

권경중,Kang Hee Lee,엄동호,Seon-ah Jin,Hyun S. Park,Jinwon Cho,현진호,함형철,박찬호 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.97 No.-

PdIr nanoparticles supported on carbon support are synthesized and their oxygen reduction reaction(ORR) activity and durability in a half cell or membrane-electrode assembly (MEA) configuration forpolymer electrolyte membrane fuel cell are examined. A synergistic effect of the combination of Pdpossessing the effective ORR catalytic activity and Ir as one of the most stable elements in acidic medialeads to a decrease in particle size, a higher particle dispersion, and a better ORR activity than Pdmonometallic catalysts. It is expected that PdIr alloys would form phase-separated nanoalloys that havePd-rich surface owing to the higher surface energy of Ir. The addition of Ir to Pd in PdIr/C increases themetallic Pd portion. Meanwhile, the Pd5Ir/C is the most durable compared to Pd/C and Pt/C over 3000 h ofMEA operation. The ORR activity of PdIr alloy is expected to increase by reducing the oxygen bindingenergy of Pd in the presence of Ir from thefirst-principle calculation, and each contribution ofcompressive strain and ligand effects is quantified. The cohesive energy and the kinetic segregationenergy are also calculated to support the improved stability of PdIr compared to Pd and Pt in the ORRcondition.

고체 고분자 연료전지용 비백금계 산소환원촉매 조성 조사 및 분석

권경중,Kwon, Kyung-Jung 한국전기화학회 2012 한국전기화학회지 Vol.15 No.1

다양한 응용분야에서 활용될 수 있는 고체고분자연료전지의 경우 현재 상용화에 가장 큰 걸림돌이 되고 있는 것이 고가의 백금 촉매이다. 따라서 특히 최근 들어 산소환원반응에서 백금을 대체하는 물질을 개발하기 위한 연구가 전세계적으로 확산되고 있다. 그러나 촉매 개발 시 경제성 관점 외에 내구성도 고려해야 하는데, 이런 관점에서 백금과 유사한 물성과 활성이 기대되는 백금족 원소들이 한 대안이 될 것이다. 가장 백금과 유사한 물성, 활성을 나타내는 팔라듐과 칼코겐화물 형태의 루테늄이 지금까지 가장 많이 연구가 되었으며 상대적으로 이리듐, 로듐, 오스뮴은 산소환원 촉매로 많은 연구가 되지 않았다. RDE (rotating disk electrode)를 이용한 반쪽전지 실험이나 연료전지 MEA (membrane electrode assembly) 운전을 통하여 백금과 활성을 비교해보면 팔라듐 계열의 비백금 촉매가 가장 백금에 가까운 활성을 나타내고 있음을 알 수 있다. 이 논문에서는 각 백금족 원소들 기반의, 현재까지 문헌상으로 보고된 촉매조성들을 분석하여 비백금 산소환원 촉매 개발에 도움이 되고자 한다. The prohibitively high cost of Pt catalyst might be the biggest barrier for the commercialization of proton exchange membrane fuel cells (PEMFC) of which wide application is expected. Worldwide research efforts for the development of alternative to Pt oxygen reduction reaction (ORR) catalyst are made recently. One of the important considerations in the catalyst development is durability issue as well as economic aspect. From this point of view, platinum group metals (PGM) except Pt can be a candidate for replacing Pt catalyst because the material properties and the catalytic activity of PGM are expected to be similar to Pt. In contrast to Ir, Rh and Os to which not so much attention has been paid as an ORR catalyst, Pd that is most similar to Pt in terms of material properties and catalytic activity and Ru that is in the form of chalcogenide have been studied intensively. Activity comparison between non-Pt and Pt oxygen reduction catalysts by half cell test using RDE (rotating disk electrode) or PEMFC MEA (membrane electrode assembly) operation indicates that Pd-based catalysts show the most similar activity to Pt. In this paper we analyze the composition of PGM ORR catalyst in literature to promote the development of non-Pt ORR catalyst.

리튬2차전지에서 Ni 기판에 화학흡착된 기체에 의한 리튬의 표면개질

조수익,권경중,장영철,손헌준 ( S . I . Jo,K . J . Kwon,Y . C . Chang,H . J . Sohn ) 한국공업화학회 1996 한국공업화학회 심포지엄 Vol.1 No.-

Electrodeposition of Some Selective Metals Belonging to Light, Refractory and Noble Metals from Ionic Liquid Electrolytes

Bonita Dilasari,권경중,이철경,김한수 한국전기화학회 2012 한국전기화학회지 Vol.15 No.3

Ionic liquids are steadily attracting interests throughout a recent decade and their application is expanding into various fields including electrochemistry due to their unique properties such as non-volatility, inflammability, low toxicity, good ionic conductivity, wide electrochemical potential window and so on. These features make ionic liquids become an alternative solution for electrodeposition of metals that cannot be electroplated in aqueous electrolytes. In this review, we classify investigated metals into three categories, which are light (Li, Mg), refractory (Ti, Ta) and noble (Pd, Pt, Au) metals, rather than covering the exhaustive list of metals and try to update the recent development in this area. In electrodeposition of light metals, granular fine Li particles were successfully obtained while the passivation of electrodeposited Mg layers is an obstacle to reversible deposition-dissolution process of Mg. In the case of refractory metals, the quality of Ta and Ti deposit particles was effectively improved with addition of LiF and pyrrole, respectively. In noble metal category, EMIM TFSA ionic liquid as an electrolyte for Au electrodeposition was proven to be effective and BMP TFSA ionic liquid developed a smooth Pd deposit. Pt nanoparticle production from ionic liquid droplet in aqueous solution can be cost-effective and display an excellent electrocatalytic activity.

콩고산 코발트 정광으로부터 제조한 매트의 고온고압침출

김건하,강가희,김수경,손정수,권경중,Kim, Gunha,Kang, Ga-hee,Kim, Sookyung,Sohn, Jeongsoo,Kwon, Kyungjung 한국자원리싸이클링학회 2015 資源 리싸이클링 Vol.24 No.4

이차전지 재료 등으로 사용되는 코발트는 콩고 민주공화국 등 일부 국가에 편중되어 있다. 국내 코발트의 안정적인 공급을 위한 해외 코발트광과 코발트 제련 기술의 확보는 필수적이다. 이에 본 실험에서는 콩고산 코발트 정광(Co ~ 8 wt%, Cu ~ 19 wt%, Fe ~ 3 wt%)을 용융환원시켜 얻어지는 합금상에 매트 내 황의 비율을 달리해 만든 2가지 조성의 매트를 제조했으며, 주된 원소는 19 ~ 21wt% Co, 39 ~ 41wt% Cu, 7 ~ 9wt% Fe이다. 매트 분쇄산물을 autoclave를 이용한 고온고압침출법으로 3가지의 영향(산화제 유무, 침출제인 황산 농도, 매트 제조 시 투입되는 황 함량)을 고려해 실험을 진행했다. 먼저 산화제(산소)의 존재는 Co 침출률 향상을 위해 필수적이며 낮은 농도의 황산을 사용하더라도 Co를 전량 침출시킬 수 있다. 둘째 산소 분위기에서 높은 황산농도는 Cu와 Fe의 침출률을 증가시켜 선택적인 Co 침출을 방해한다. 마지막으로 매트 내 황 함량은 Co의 침출률에는 영향이 크지 않음을 알 수 있었다. Cobalt is abundant only in some countries including Democratic Republic of the Congo. It would be necessary to secure overseas Co ores and Co extraction technology. Two kinds of matte varying the sulfur content were manufactured by smelting reduction of Co concentrate containing ~8 wt% Co, ~19 wt% Cu, and ~3 wt% Fe. The amount of Co, Cu and Fe was concentrated to 19~21 wt%, 39~41 wt%, and 7~9 wt% respectively in the resulting matte. High-pressure leaching of matte was performed in an autoclave with considering the effect of oxidizing agent, $H_2SO_4$ concentration as a lixiviant, and the amount of sulfur added to the matte. An oxidizing agent (oxygen) is necessary to improve Co leaching efficiency enabling usage of a dilute $H_2SO_4$ leaching agent. An increase in $H_2SO_4$ concentration prevents selective leaching of Co, and the sulfur content in matte has a minor influence on the Co leaching efficiency.

Effects of methanesulfonic acid on electrolyte for vanadium redox flow batteries

김건하,김영권,김태은,권경중 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.99 No.-

Methanesulfonic acid (MSA) is investigated as an additive for improving the thermal stability andelectrochemical property of the vanadium redoxflow battery (VRFB) electrolyte. The effect of MSA on thethermal stability of the electrolyte is estimated by a storage test, inductively coupled plasma massspectrometry, and ultraviolet–visible spectrometry. Thermal stability tests show that MSA delays theformation of precipitates. The precipitates formed from the electrolyte are analyzed by X-ray diffraction,scanning electron microscopy, and energy-dispersive spectroscopy. The precipitates gained from the V(II)electrolyte at5 C and the V(V) electrolyte at 40 C have different physicochemical properties. Theinfluence of MSA on the electrochemical property is examined by cyclic voltammetry, linear polarization,and electrochemical impedance spectroscopy. According to the electrochemical analysis, MSA enhancesthe diffusion of the V(III) and V(IV) ions and the redox reaction rate of the V ions. Additionally, nuclearmagnetic resonance analysis is performed to understand the positive effect of MSA on the electrolyte. AVRFB full cell employing the electrolyte with MSA shows enhanced energy efficiency as well as highenergy density by improving electrolyte utilization.

Effect of water on the stability of zinc in 1-butyl-1- methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ionic liquid

Bonita Dilasari,정여진,권경중 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.45 No.-

Ionic liquids are considered as a potential electrolyte for rechargeable zinc–air battery due to nonvolatility,high ionic conductivity, and so on. Electrochemical measurements are conducted to investigatethe redox behavior of zinc electrode in 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide([BMPyr] [NTf2]) ionic liquid and the effect of water in the ionic liquid is also studied. Cyclic voltammetryof zinc electrode in [BMPyr] [NTf2] shows a reversible redox peak, and the presence of water givessignificant effects particularly on the cathodic current of zinc electrode. Different surface reactionmechanism on zinc electrode depending on the presence of water in ionic liquid is suggested.

리튬이차전지 양극활물질의 암모니아 침출액에서 공침법에 의한 활물질 전구체의 합성에 대한 암모니아 농도의 영향

박상혁,구희숙,이경준,송준호,김수경,손정수,권경중,Park, Sanghyuk,Ku, Heesuk,Lee, Kyoung-Joon,Song, Jun Ho,Kim, Sookyung,Sohn, Jeongsoo,Kwon, Kyungjung 한국자원리싸이클링학회 2015 資源 리싸이클링 Vol.24 No.6

In a recycling scheme of spent lithium ion batteries, a co-precipitation process for the re-synthesis of precursor is essential after the leaching of lithium ion battery scraps. In this study, the effect of ammonia as impurity during the co-precipitation process was investigated in order to re-synthesize a precursor of Ni-rich cathode active material $LiNi_{0.6}Co_{0.2}Mn_{0.2}O_2$ (NCM 622). As ammonia concentration increases from 1 M (the optimum condition for synthesis of the precursors based on 2 M of metal salt solution) to 4 M, the composition of obtained precursors deviates from the designed composition, most notably for Ni. The Ni co-precipitation efficiency gradually decreases from 100% to 87% when the concentration of ammonia solution increases from 1 M to 4 M. Meanwhile, the morphological properties of the obtained precursors such as sphericity, homogeneity and size distribution of particles were also investigated. 폐리튬이차전지 양극재 재활용기술에 있어 침출과정을 통해 회수된 유가금속을 다시 원하는 조성의 전구체로 재합성하는 공침공정은 필수적이다. 본 연구에서는 고용량 특성의 Ni-rich 조성인 $LiNi_{0.6}Co_{0.2}Mn_{0.2}O_2$ (NCM 622) 양극재의 전구체 재합성 시 암모니아가 불순물로서 미치는 영향을 확인하는 공침실험을 수행하였다. SEM 및 EDS 분석결과 양극재 전구체 최적 합성조건(금속염 용액 농도 2 M 기준 암모니아수 농도 1 M)에서 암모니아 농도가 증가할수록 원하는 조성의 전구체가 제조되지 않음을 확인하였다. Ni의 설계함량인 60 mol%를 기준하여 암모니아수 농도 1 M ~ 4 M 조건에서 각각 100%, 98%, 95%, 87%에 해당하는 공침효율을 보여주었다. 또한 제조된 전구체 입자들의 구형화도, 균일도 및 크기분포특성 등의 형상학적 특징을 확인하였다.

Phytic Acid-Doped Cross-linked Polyaniline Nanofibers for Electrochemical Supercapacitor Electrode Applications

임성진,김형진,신구,정후영,홍원기,권경중,홍영준 한국물리학회 2019 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.74 No.2

Electrochemical energy storage characteristics of chlorine- and phytic acid-doped polyaniline nanobers (Cl- and Ph-PAni NFs), which were synthesized via radical polymerization in a hy- drochloric acid and a Ph solution, respectively, were comparatively investigated. The Ph-PAni NFs showed a specic capacitance of 227 F g1, which was two times higher than the value of 105 F g1 for Cl-PAni NFs at 30 A g1, due to the enhanced electrical conductivity caused by Ph doping. Moreover, the Ph-PAni NFs presented superior supercapacitor electrode performances in terms of charge-discharge cycle life, specic power, and electrochemical impedance. Diverse spectroscopic analyses revealed that the Ph doping contributed to formation of crosslinks between PAni back- bones, which eventually provided many eective electrical conducting paths in the NFs. Thus, the high conductivity is responsible for the high electrochemical activity of Ph-PAni NFs. This ap- proach to increase the electrochemical performances is expected to be applied to other conducting polymeric supercapacitor electrodes for more practical device applications.

Corrosion Behavior of Stainless Steel 304, Titanium, Nickel and Aluminium in Non-Aqueous Electrolytes

Bonita Dilasari,박제식,Priyandi Kusumah,권경중,이철경 한국전기화학회 2014 한국전기화학회지 Vol.17 No.1

The corrosion behavior of stainless steel 304 (SS 304), titanium, nickel and aluminiumis studied by immersion and anodic polarization tests in non-aqueous electrolytes. Tetraethylammonium tetrafluoroborate is used as a supporting electrolyte in the three kinds ofsolvents. The immersion test shows that chemical corrosion rate in propylene carbonate-basedelectrolyte is lower than those in acetonitrile- or γ-butyrolactone-based electrolytes. Surfaceanalyses do not reveal any corrosion product formed after the immersion test. In the anodicpolarization tests, a higher concentration of supporting electrolyte gives a higher current density. In addition, a higher temperature increases the current density in the active region and reducesthe potential range in the passive region. SS 304 shows the highest corrosion potential whileAl shows the lowest corrosion potential and the highest current density in all studied conditions. Based on the conducted corrosion tests, the corrosion resistance of metal substrates in theorganic solvents can be sorted in descending order as follows: SS 304 - Ti - Ni - Al.