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Steam activation of Fe-N-C catalyst for advanced power performance of alkaline hydrazine fuel cells

Journal of Energy Chemistry 2022年第1期31卷 276-285,I0008页

作者： Sooan Bae jihyeon park Yuna Hwang Jin-Soo park Jaeyoung Lee Beomgyun Jeong Research Center for Materials Analysis Korea Basic Science Institute169-14&Gwahak-roDaejeon 34133Republic of Korea School of Earth Sciences and Environmental Engineering Gwangju Institute of Science and Technology123 Cheomdangwagi-ro.Buk-guGwangju 61005Republic of Korea Department of Green Chemical Engineering Sangmyung University31 Sangmyungdae-gilDongnam-gu.CheonanChungnam Province 31066Republic of Korea Ertl Center for Electrochemistry and Catalysis Gwangju Institute of Science and Technology123 Cheomdangwagi-roBuk-giiGwangju 61005Republic of Korea

Alkaline hydrazine liquid fuel cells(AHFC) have been highlighted in terms of high power performance with non-precious metal catalysts.Although Fe-N-C is a promising non-Pt electrocatalyst for oxygen reduction reaction(ORR),the surface density of the active site is very low and the catalyst layer should be thick to acquire the necessary number of catalytic active sites.With this thick catalyst layer,it is important to have an optimum pore structure for effective reactant conveyance to active sites and an interface structure for faster charge transfer.Herein,we prepare a Fe-N-C catalyst with magnetite particles and hierarchical pore structure by steam activation.The steam activation process significantly improves the power performance of the AHFC as indicated by the lower IR and activation voltage losses.Based on a systematic characterization,we found that hierarchical pore structures improve the catalyst utilization efficiency of the AHFCs,and magnetite nanoparticles act as surface modifiers to reduce the interracial resistance between the electrode and the ion-exchange membrane.

关键词： Alkaline hydrazine fuel cell Oxygen reduction reaction Electrocatalyst Steam activation Ohmic loss Interfacial resistance Surface modifier

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Rapid determination of lithium-ion battery degradation: High C-rate LAM and calculated limiting LLI

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Journal of Energy Chemistry 2022年第4期31卷 663-671页

作者： Gyuwon Seo Jaeyun Ha Moonsu Kim jihyeon park Jaewon Lee Eunoak park Sungyool Bong Kiyoung Lee Soon Jong Kwon Seung-pil Moon Jinsub Choi Jaeyoung Lee Electrochemical Reaction and Technology Laboratory School of Earth Sciences and Environmental EngineeringGwangju Institute of Science and Technology(GIST)Gwangju 61005South Korea Department of Chemistry and Chemical Engineering Inha UniversityIncheon 22212South Korea Ertl Center for Electrochemistry and Catalysis GISTGwangju 61005South Korea Korea Electric Power Corporation Research Institute Daejeon 34056South Korea International Future Research Center of Chemical Energy Storage and Conversion Processes(ifRC-CHESS) GISTGwangju 61005South Korea

Herein,incremental capacity-differential voltage (IC-DV) at a high C-rate (HC) is used as a non-invasive diagnostic tool in lithium-ion batteries,which inevitably exhibit capacity fading caused by multiple mechanisms during charge/discharge cycling.Because battery degradation modes are complex,the simple output of capacity fading does not yield any useful data in that respect.Although IC and DV curves obtained under restricted conditions (<0.1C,25℃) were applied in non-invasive analysis for accurate observation of degradation symptoms,a facile,rapid diagnostic approach without intricate,complex calculations is critical in on-board applications.Herein,Li Ni_(0.5)Mn_(0.3)Co_(0.2)O_(2)(NMC532)/graphite pouch cells were cycled at 4 and 6C and the degradation characteristics,i.e.,loss of active materials (LAM) and loss of lithium inventory (LLI),were parameterized using the IC-DV curves.During the incremental current cycling,the initial steep LAM and LLI slopes underwent gradual transitions to gentle states and revealed the gap between low-and high-current measurements.A quantitative comparison of LAM at high and low C-rate showed that a IC;revealed the relative amount of available reaction region limited by cell polarization.However,this did not provide a direct relationship for estimating the LAM at a low C-rate.Conversely,the limiting LLI,which is calculated at a C-rate approaching 0,was obtained by extrapolating the LLI through more than two points measured at high C-rate,and therefore,the LLI at 0.1C was accurately determined using rapid cycling.

关键词： Battery degradation Rapid degradation diagnosis Loss of active materials(LAM) Loss of lithium inventory(LLI) Incremental capacity(IC) Differential voltage(DV)

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Ultra-low concentration of total organic carbon in ultrapure water using ion-exchange resin embedding silanized magnetic nanoparticles

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Journal of Environmental Sciences 2020年第6期32卷 11-17页

作者： Jung Joon Lee jihyeon park Bo-Hyun Kim Sunjong Lee Department of Advanced Materials Science and Engineering Sungkyunkwan UniversitySuwon 16419South Korea Korea Institute of Industrial Technology 89 Yangdaegiro-gilIpjang-myeonCheonan-si 31056South Korea

Regeneration of pure water is an important issue not only for the healthy life but also for the fine control of precise processes in various industries.One important issue in ultrahigh purified water is to reduce the amount of total organic carbon(TOC).Herein,we introduce a new approach to reduce the TOC using the surface silanized nanoparticles,in which the magnetic nanoparticles(mNPs)are silanized and then complexed with ion exchange resin(IER)beads.The Fe3O4 mNPs are surface modified by using high concentrated vinyltrimethoxysilane(VTMS)and then adhered on the surface of IER beads.The surface modified mNPs have a thick-shell of polysiloxane layer varying from 5 to 22 nm depending on the amount of VTMS used,which leads the significant increase of specific surface area.The IER beads embedding VTMS-silanized mNPs achieves about 7μg/L of the TOC level in ultrapure water system,which is two orders less than 228μg/L of the feeding water and one order less than 96μg/L from the system using pristine IER beads.This result is mainly attributed to the polysiloxane layer forming broccoli-like surface structure and some part by the vinyl group of VTMS exposed to the amines in the water.

关键词： Total organic carbon Ultrapure water Magnetic nanoparticle Ion-exchange resin Hybrid structure

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A systematic correlation between morphology of porous carbon cathode and electrolyte in lithium-sulfur battery

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Journal of Energy Chemistry 2021年第10期30卷 561-573,I0014页

作者： jihyeon park Seoyoung Yoon Seoyeah Oh Jiyoon Kim Dongjun Kim Geonho Kim Jiyeon Lee Myeong Jun Song Ilto Kim Kwonnam Sohn Jiwon Kim School of Integrated Technology College of EngineeringYonsei University85 Songdogwahak-roYeonsu-guIncheon 21983Republic of Korea Integrated Science and Engineering Division Underwood International CollegeYonsei University85 Songdogwahak-roYeonsu-guIncheon 21983Republic of Korea Integrated Biotechnology and Translational Medicine Graduate SchoolYonsei University85 Songdogwahak-roYeonsu-guIncheon 21983Republic of Korea LG Chem. LG Science Park30 Magokjungang 10-roGangseo-guSeoul 07796Republic of Korea

Porous carbon has been applied for lithium-sulfur battery cathodes,and carbonized metal-organic framework(MOF)is advantageous in tuning the morphology.Herein,we have systematically synthesized water-distorted MOF(WDM)derived porous carbon via controlling the proportion of both water in a mixed solvent(dimethylformamide and water)and ligand in MOF-5 precursors(metal and ligand),which is categorized by its morphology(i.e.Cracked stone(closed),Tassel(open)and Intermediate(semi-open)).For example,decrease in water and increase in ligand content induce Cracked stone WDMs which showed the highest specific surface area(2742-2990 m^(2)/g)and pore volume(2.81-3.28 cm^(3)/g)after carbonization.Morphological effect of carbonized WDMs(CWDMs)on battery performance was examined by introducing electrolytes with different sulfur reduction mechanisms(i.e.DOL/DME and ACN_(2) LiTFSITTE):Closed framework effectively confines polysulfide,whereas open framework enhances electrolyte accessibility.The initial capacities of the batteries were in the following order:Cracked stone>Intermediate>Tassel for DOL/DME and Intermediate>Tassel>Cracked stone for ACN_(2) LiTFSI-TTE.To note,Intermediate CWDM exhibited the highest initial capacity and retained capacity after 100 cycles(1398 and 747 mAh/g)in ACN_(2) LiTFSI-TTE electrolyte having advantages from both open and closed frameworks.In sum,we could correlate cathode morphology(openness and pore structure)and electrolyte type(i.***.polysulfide solubility)with lithium-sulfur battery performance.

关键词： Lithium-sulfur battery Metal-organic framework Hierarchical porous carbon cathode Morphology control Electrolyte Lithium polysulfide solubility

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