Korea Institute Of Energy Technology Evaluation And Planning Research Articles

Bayesian Approach to Estimate Distribution of Relaxation Times for Lithium-Ion Batteries

Electrochemical impedance spectroscopy (EIS) has emerged as a powerful tool for analyzing the state of lithium-ion batteries due to its ability to provide rich electrochemical information. Traditionally, equivalent circuit and physical models have been utilized for interpreting EIS data. However, these methods possess inherent drawbacks: equivalent circuit models are non-unique, while physical models can be challenging to implement. As an alternative, the distribution of relaxation times (DRT) has garnered increasing attention in recent years. The DRT method enables the analysis of EIS data without predefining a model's shape, allowing for the decomposition of internal characteristics in complex systems, such as lithium-ion batteries. Despite its advantages, DRT estimation is an ill-posed inverse problem that often requires regularization or fine-tuning based on empirical choices, which can lead to the misinterpretation of EIS data.To address these challenges, we propose a Bayesian approach that enables the estimation of DRT while considering uncertainties, even in the presence of observational errors in EIS data. Moreover, the proposed method can assist in estimating the state of health (SOH) of the battery, which provides valuable insights into the battery's overall performance, longevity, and safety. To validate the efficacy of our proposed method, we apply it to synthetic EIS data and compare its performance with existing DRT estimation methods. The results show that the proposed Bayesian approach offers a more robust and accurate estimation of DRT. We also demonstrate the practical applicability of the proposed method by applying it to real lithium-ion battery EIS experimental data, where it successfully extracts meaningful information about the battery's internal state and SOH. In summary, the proposed DRT-based Bayesian method has the potential to enable a robust diagnosis of the internal state and SOH of lithium-ion batteries through EIS measurements. By incorporating this approach, researchers and industry practitioners can gain a deeper understanding of battery performance, facilitating the development of improved diagnostic techniques and battery management strategies to enhance the performance and reliability of lithium-ion batteries. This, in turn, could contribute to the broader adoption of sustainable energy solutions, such as electric vehicles and renewable energy storage systems.This work was supported by the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grants funded by the Ministry of Trade, Industry & Energy, Republic of Korea (No. 20214910100070). Figure 1

Performance of Solvent Substituted Ionomer Dispersions in Catalyst Layer for Hydrogen-Based Energy Conversion Devices

Catalyst inks for the preparation of porous catalyst layer for hydrogen-based energy conversion devices is composed of electrocatalyst, ionomer dispersion and additional solvents. Solvents have an important role in determining the size of ionomer aggregates, the properties of catalyst ink and the morphology of catalyst layer. It has been reported that the solvents for ionomer dispersions substantially influenced the size of ionomer aggregates and finally resulted in the performance and durability. To understand a deep insight into solvent-ionomer molecular interaction, solvation energy obtained by molecular design modeling for a measurement of the relative solubility of ionomers in solvents was studied in this study. In this study, we investigated the solvent-ionomer molecular interaction using molecular design modeling simulation and experimental validation in proton exchange membrane fuel cell and water electrolysis. In addition, I-V polarization curves, cyclic voltammetry and electrochemical impedance spectroscopy were measured and analyzed in terms of solvent property and solvation energy. Acknowledgment This research was supported in part by the Hydrogen Energy Innovation Technology Development Program of the National Research Foundation (NRF) funded by the Ministry of Science, ICT & Future Planning(NRF-2019M3E6A1063677) and by the New and Renewable Energy of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) granted financial resource from the Ministry of Trade, Industry & Energy, Republic of Korea (No. 20213030040520).

Catalyst Layers with Blended Ionomer Using Short- and Long-Side Chain Dispersions

Hydrogen-based energy conversion technology is based on the membrane electrode assembly (MEA) comprising of an electrolyte and a pair of catalyst layers. It should have high efficiency and allow dynamic operation at low temperature. Electrochemical reactions for hydrogen oxidation reaction and oxygen reduction reaction occur in the catalyst layers in the MEA. Catalyst layers for MEA is prepared by catalyst inks comprising of electrocatalyst, ionomer dispersion and additional solvents. Ionomers plays an important roles for the formation of porous structure of catalyst layer for transportation of gas and reactant and for the ionic conduction. The ionomers are divided that long side chain (LSC) and short side chain (SSC) depending on the length of side chain. Long side chain (LSC) ionomers shows high performance at low temperatures and high humidity, while short side chain (SSC) ionomers shows high performance at high temperatures and low humidity. It has been reported that the properties of ionomer dispersions substantially influence the performance of catalyst layers due to the different interaction between electrocatalysts and ionomer. In this study, to investigate the effect of the properties of ionomer, various contents of blended ionomer dispersions were prepared. Properties of single and blended ionomers were characterized using catalysts layers in terms of I-V polarization, cyclic voltammetry, electrochemical impedance spectroscopy and microscopic evaluation such as porosimetry. Acknowledgment This research was supported in part by the Hydrogen Energy Innovation Technology Development Program of the National Research Foundation (NRF) funded by the Ministry of Science, ICT & Future Planning(NRF-2019M3E6A1063677) and by the New and Renewable Energy of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) granted financial resource from the Ministry of Trade, Industry & Energy, Republic of Korea (No. 20213030040520).

Alkaline-Stable Anion Conducting Ionomers for Anion Exchange Membrane Water Electrolyzers

Water electrolysis is a process that uses renewable energy to decompose water into oxygen and hydrogen. It is one of the most promising alternatives to produce and store new energy from renewable energy resources. In this study, pore-filled anion exchange membranes (PFAEMs) were prepared by using quaternary ammonia groups along with various cross-linker groups with different chain lengths and using porous polyethylene substrates which were pretreated from hydrophobic into hydrophilic using surfactants. The conductivity of the anion exchange membranes was measured by the in-plane cell and through-plane at room temperature or 60 ℃. In addition, the characterizations of anion exchange membranes such as water uptake, swelling ratio, mechanical strength, contact angle and TGA were carried out. As a result, the PFAEM exhibited remarkably high ion conductivity at extremely low areal swelling ratio and excellent chemical stability in a NaOH solution for 500 h. As an essential component of anion exchange membrane water electrolyzers, catalyst layers prepared by the catalyst inks comprising of ionomer binder and electrocatalysts are sandwiched between the anion exchange membrane to form a membrane electrode assembly in order to evaluate its impedance and I-V polarization curves. Acknowledgment This research was supported in part by the New and Renewable Energy of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) granted financial resource from the Ministry of Trade, Industry & Energy, Republic of Korea (No. 20213030040520) and by 2021 Green Convergence Professional Manpower Training Program of the Korea Environmental Industry and Technology Institute funded by the Ministry of Environment.

효율적인 탄소저감을 위한 CCUS와 배출권거래제와의 관계 구축에 대한 연구

This work was supported by the Korea Institute of Energy Technology Evaluation and Planning(KETEP) and the Ministry of Trade, Industry & Energy(MOTIE) of the Republic of Korea (20214710100040,CCUS 법률안 정비 및 수용성을 포함한 제도적 기반 구축). Many problems are appearing due to climate disasters or global warming. Therefore, many countries are moving towards ‘net zero’ policy by setting greenhouse gas reduction targets. Korea is also responding to the climate crisis by enacting the Carbon Neutral and Green Growth Framework Act (so called the Carbon Neutral Framework Act). Korea, like other countries, recognizes that CCUS technology is indispensable to achieve ‘zero carbon’ by 2050. Therefore, in Article 34 of the Framework Act on Carbon Neutrality, there was a provision on the promotion of carbon capture, use and storage technology to prepare policies to support the development of “carbon capture, use, and storage technology.” Special regulations for the demonstration of technology are to be separately stipulated by law. In order to apply CCUS technology, the CCUS single bill is being revised. Meanwhile, in Korea, the “Act on Allocation and Trade of Greenhouse Gas Emission Permits” is in effect. However, in the EU Emissions Trading Act, which implemented the emission trading system earlier than Korea, and the EU CCS Directive was enacted in 2009 and the EU Emissions Trading Directive was also revised. According to the amendments, the EU ETS provides the important incentive for CCS, and according to the EU legal framework, CO2 captured and safely stored is considered “not released” by the ETS. In addition, the 2018 Directive (EU) 2018/410, which amended 2003/87/EC, made amendments in relation to CCUS. That is, the 325 million allowance in quantities that can be allocated free of charge and 75 million allowances in quantities that can be auctioned under Article 10 can be used to support innovation in low-carbon technologies and processes. contributing to environmentally safe carbon capture and utilization (“CCUS”). Based on the lessons learned from the EU's Emissions Trading Act, we investigated what regulations should be stipulated in the Emissions Trading Act when Korea enacts the single CCUS Act. In addition, the CCUS Act suggested what contents should be stipulated to reflect the emission trading system. This work was supported by the Korea Institute of Energy Technology Evaluation and Planning(KETEP) and the Ministry of Trade, Industry & Energy(MOTIE) of the Republic of Korea (20214710100040,CCUS 법률안 정비 및 수용성을 포함한 제도적 기반 구축). Many problems are appearing due to climate disasters or global warming. Therefore, many countries are moving towards ‘net zero’ policy by setting greenhouse gas reduction targets. Korea is also responding to the climate crisis by enacting the Carbon Neutral and Green Growth Framework Act (so called the Carbon Neutral Framework Act). Korea, like other countries, recognizes that CCUS technology is indispensable to achieve ‘zero carbon’ by 2050. Therefore, in Article 34 of the Framework Act on Carbon Neutrality, there was a provision on the promotion of carbon capture, use and storage technology to prepare policies to support the development of “carbon capture, use, and storage technology.” Special regulations for the demonstration of technology are to be separately stipulated by law. In order to apply CCUS technology, the CCUS single bill is being revised. Meanwhile, in Korea, the “Act on Allocation and Trade of Greenhouse Gas Emission Permits” is in effect. However, in the EU Emissions Trading Act, which implemented the emission trading system earlier than Korea, and the EU CCS Directive was enacted in 2009 and the EU Emissions Trading Directive was also revised. According to the amendments, the EU ETS provides the important incentive for CCS, and according to the EU legal framework, CO2 capt

효율적인 탄소저감을 위한 CCUS와 배출권거래제와의 관계 구축에 대한 연구

This work was supported by the Korea Institute of Energy Technology Evaluation and Planning(KETEP) and the Ministry of Trade, Industry & Energy(MOTIE) of the Republic of Korea (20214710100040,CCUS 법률안 정비 및 수용성을 포함한 제도적 기반 구축). Many problems are appearing due to climate disasters or global warming. Therefore, many countries are moving towards ‘net zero’ policy by setting greenhouse gas reduction targets. Korea is also responding to the climate crisis by enacting the Carbon Neutral and Green Growth Framework Act (so called the Carbon Neutral Framework Act). Korea, like other countries, recognizes that CCUS technology is indispensable to achieve ‘zero carbon’ by 2050. Therefore, in Article 34 of the Framework Act on Carbon Neutrality, there was a provision on the promotion of carbon capture, use and storage technology to prepare policies to support the development of “carbon capture, use, and storage technology.” Special regulations for the demonstration of technology are to be separately stipulated by law. In order to apply CCUS technology, the CCUS single bill is being revised. Meanwhile, in Korea, the “Act on Allocation and Trade of Greenhouse Gas Emission Permits” is in effect. However, in the EU Emissions Trading Act, which implemented the emission trading system earlier than Korea, and the EU CCS Directive was enacted in 2009 and the EU Emissions Trading Directive was also revised. According to the amendments, the EU ETS provides the important incentive for CCS, and according to the EU legal framework, CO2 captured and safely stored is considered “not released” by the ETS. In addition, the 2018 Directive (EU) 2018/410, which amended 2003/87/EC, made amendments in relation to CCUS. That is, the 325 million allowance in quantities that can be allocated free of charge and 75 million allowances in quantities that can be auctioned under Article 10 can be used to support innovation in low-carbon technologies and processes. contributing to environmentally safe carbon capture and utilization (“CCUS”). Based on the lessons learned from the EU's Emissions Trading Act, we investigated what regulations should be stipulated in the Emissions Trading Act when Korea enacts the single CCUS Act. In addition, the CCUS Act suggested what contents should be stipulated to reflect the emission trading system. This work was supported by the Korea Institute of Energy Technology Evaluation and Planning(KETEP) and the Ministry of Trade, Industry & Energy(MOTIE) of the Republic of Korea (20214710100040,CCUS 법률안 정비 및 수용성을 포함한 제도적 기반 구축). Many problems are appearing due to climate disasters or global warming. Therefore, many countries are moving towards ‘net zero’ policy by setting greenhouse gas reduction targets. Korea is also responding to the climate crisis by enacting the Carbon Neutral and Green Growth Framework Act (so called the Carbon Neutral Framework Act). Korea, like other countries, recognizes that CCUS technology is indispensable to achieve ‘zero carbon’ by 2050. Therefore, in Article 34 of the Framework Act on Carbon Neutrality, there was a provision on the promotion of carbon capture, use and storage technology to prepare policies to support the development of “carbon capture, use, and storage technology.” Special regulations for the demonstration of technology are to be separately stipulated by law. In order to apply CCUS technology, the CCUS single bill is being revised. Meanwhile, in Korea, the “Act on Allocation and Trade of Greenhouse Gas Emission Permits” is in effect. However, in the EU Emissions Trading Act, which implemented the emission trading system earlier than Korea, and the EU CCS Directive was enacted in 2009 and the EU Emissions Trading Directive was also revised. According to the amendments, the EU ETS provides the important incentive for CCS, and according to the EU legal framework, CO2 capt

Development of Pore-Filling Anion Exchange Membranes for Anion Exchange Membrane Water Electrolysis: Enhancement of Alkaline Stability

Water electrolysis is a process that uses electricity to decompose water into oxygen and hydrogen. There are several types of ion exchange membrane can be used, anion exchange membrane, proton exchange membrane and bipolar membrane for water electrolysis. Alkaline based water electrolysis has several advantages to use non-precious electrocatalysts. However, the development of low resistance and durable anion-exchange membranes is of importance. In this study, several anion-exchange membranes were developed to enhance alkaline stability. Pore-filling anion exchange composite membranes with different contents of cross-linkers were prepared by mixing an electrolyte having good anion conducting ability. The mixture of monomers into a porous polyethylene (PE) substrate were polymerized by UV curing. The pore-filling reinforced composite membranes have been investigated in terms of good chemical stability properties, in particular, the variation of conductivity and mechanical strength in 1 M KOH at 60 oC. Characterization in terms of ion exchange capacity, water uptake, swelling ratio, and mechanical strength were also investigated. Acknowledgments This research was supported in part by "Cooperative Research Program for Agriculture Science and Technology Development (Project No. PJ016253)" Rural Development Administration, Republic of Korea, by the New and Renewable Energy of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) granted financial resource from the Ministry of Trade, Industry & Energy, Republic of Korea (No. 20213030040520) and by 2022 Green Convergence Professional Manpower Training Program of the Korea Environmental Industry and Technology Institute funded by the Ministry of Environment.

Development of Pore-Filling Anion Exchange Membranes for Anion Exchange Membrane Water Electrolysis: Enhancement of Resistance

Water electrolysis is a process that uses electricity to decompose water into oxygen and hydrogen. There are several types of ion exchange membrane can be used, anion exchange membrane, proton exchange membrane and bipolar membrane for water electrolysis. Alkaline based water electrolysis has several advantages to use non-precious electrocatalysts. However, the development of low resistance and durable anion-exchange membranes is of importance. In this study, several anion-exchange membranes were developed to enhance areal resistance, in other words, to minimize areal resistance. Pore-filling anion exchange composite membranes with different contents of cross-linkers were prepared by mixing an electrolyte having good anion conducting ability. The mixture of monomers into a porous polyethylene (PE) substrate were polymerized by UV curing. The pore-filling reinforced composite membranes have been investigated in terms of good electrochemical properties, in particular, areal resistance. The conductivity and areal specific resistance were measured in both in-plane cell and through-plane cell at 80 ℃ and at room temperature, respectively. Characterization in terms of ion exchange capacity, water uptake, swelling ratio, and mechanical strength were also investigated. Acknowledgments This research was supported in part by "Cooperative Research Program for Agriculture Science and Technology Development (Project No. PJ016253)" Rural Development Administration, Republic of Korea, by the New and Renewable Energy of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) granted financial resource from the Ministry of Trade, Industry & Energy, Republic of Korea (No. 20213030040520) and by 2022 Green Convergence Professional Manpower Training Program of the Korea Environmental Industry and Technology Institute funded by the Ministry of Environment.

MnO2-Modified 3D-Printed Lattice Photo-Bioelectrode for Photosynthetic Energy Conversion from Spinach Thylakoids

Photosynthetic bio-solar energy conversion has been widely investigated as a promising potential in the field of renewable energy due to its high internal quantum efficiency. Thylakoid membranes (TMs) are organelles in chloroplasts where photosynthesis occurs. Once photosynthesis begins photosynthetic electrons (PEs) were generated, and they were transferred via proteins embedded in TMs by sequential redox reactions. To efficiently collect PEs, several approaches were reported to improve electrical connections such as carbon nanotube modified electrode [1], graphene oxide (GO)/TMs composites [2], or ruthenium oxide (RuO2) modified electrode [3]. As another approach, TM-alginate films were electrosprayed on SU-8 micro-pillar electrode to enlarge the electrochemical surface area between TMs and electrode [4]. However, the previous works were still limited in using two-dimensional electrodes with a marginal increase of electrode surface area.In this study, we aimed to maximize the electrochemically-active surface of TM-decorated bioelectrodes using 3D-printed polymeric lattices. We designed an octet-truss lattice structure with a high specific surface area. For the large surface area of the electrode with a high volume fraction, a strut diameter of the lattice was set to be 0.4 mm in the unit cell of an octet-truss lattice with a total length of 2.5 mm. To maximize light transmission, the octet-truss lattice was 3D-printed with a clear resin using stereolithography (SLA). To grant electrical conductivity on the hydrophobic nature of poly(urethane dimethacrylate) resin, poly(dopamine) (PDA) was polymerized as a binder on SLA-printed lattices followed by immersion in the 1.3 wt% of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) solution for 30 min. After immersion in PEDOT:PSS solution, PEDOT:PSS coated lattice was gently dried to remove the remaining solution with N2 gun and annealed in a vacuum oven at 120 ℃ for 15 min. On the other hand, the intrinsic electrical conductivity of PEDOT:PSS is lower than 1 S/cm. Therefore, to enhance the conductivity of annealed PEDOT:PSS layer, PEDOT:PSS coated lattice was immersed 5 wt% of ethylene glycol (EG) solution. Then, EG-treated PEDOT:PSS coated lattice was annealed in a vacuum oven as above described. Due to the removal of surplus insulating PSS chains and reorientation of PEDOT chains, the resistance of EG-treated PEDOT:PSS coated lattice was measured thousands of times lower than no treated lattice. A manganese oxide (MnO2) was electrochemically deposited for improved attachment to TMs at 0.5 V vs Ag/AgCl for 2 min. Then, TMs of 1 mg chl/ml were drop-cast on MnO2/PEDOT:PSS/PDA octet-truss lattice electrode. Each intermediate product was carefully analyzed using SEM, optical microscopy, and fluorescence spectroscopy. The PE currents from TM/MnO2/PEDOT:PSS/PDA octet-truss lattice electrode were measured and compared to a flat electrode and with different layers of lattice structures. With 2 layers of TM/MnO2/PEDOT:PSS/PDA octet-truss lattice electrode, the PE currents were increased 4 times compared to PE currents of the flat electrode. Acknowledgement This work was supported by the National Research Foundation of Korea(NRF) Grant funded by the Korean Government(MSIT) (No. 2020R1A2C3013158), and the Human Resources Development program (No.20204030200110) of the Korea Institute of Energy Technology Evaluation and Planning(KETEP) grant funded by the Korea government Ministry of Trade, Industry and Energy.

Detection Condition to Improve the Reliabilty of Coating Flaw Detection on Pipes Buried in the Soil

Generally, indirect assessment of external corrosion of pipe has been undertaken as a 2 step process using a close interval potential survey (CIPS) performed to determine the level of cathodic polarization and a direct current voltage gradient (DCVG) survey to determine the location of coating defects on the pipes buried in the soil. Usually, two techniques are used separately, but there are several advantages to undertaking a combined CIPS and DCVG survey. However, since detection conditions depend upon the experience skill of the experts, the reliability to detect the coating flaw on pipes buried in the soil was low level. This work focused on the deduction of detection voltage to get 100% reliabilty of coating flaw detection on pipes buried in the soil. Test bed with 3 layered pipelines was constructed, and cathodic protection system was real-time monitored. The material of buried pipe was one kind of ‘polyken coated steel pipe’. The burial depths of pipes were from 1 to 3 meters and coating flaws on the pipes were intentionally formed. The effect of applied voltage on the detection reliability of coating flaw on buried pipe in soil was elucidated. The applied voltage to detect the coating flaws is dependent upon the amount of buried pipes and soil condition etc. The detection potential to get 100 % detection reliability can be calculated using the newly proposed equation. (This work was supported by the Nuclear Power Core Technology Development Program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) granted financial resource from the Ministry of Trade, Industry & Energy, Republic of Korea (No. 20171520000350))

Surfactant Free-Ir/IrOX Catalysts with Improved Activity and Stability for Polymer Electrolyte Membrane Water Electrolyzer

As renewable energy technologies have advanced, their power generation capacity has improved commensurately. However, since they often experience intermittent power generation problems, it has been suggested that a solution, which is to use water electrolysis (WE) technology to convert electric power into hydrogen energy. One option to accomplish this is polymer electrolyte membrane water electrolysis (PEMWE). This technique is attractive because it produces high purity H2, has a rapid response rate, and supports high current density operation, among other features [1]. However, before PEMWE can be properly commercialized, challenges of efficiency and stability must be addressed. PEMWE involves both the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER). However, the kinetics of the OER is much more sluggish than those of the HER, which decreases the overall WE efficiency. Furthermore, as the OER takes place in harsh environments (e.g., high voltage and low pH), the stability of the materials used in PEMWE is of concern. In an effort to overcome this huddle, researchers have focused on the development of OER catalysts [2-4].Compared to the previous study [5, 6], the Ir/IrOX catalyst is prepared by using formic acid and polyol as the reducing agent and solvent, respectively, absence of any surfactant assistance in this study. It is worth in terms that the mass production of catalysts could be possible through this process. In half cell test (Fig. 1(a)), although the Tafel slopes of Ir/IrOX and state-of-art IrO2 (TKK, Tanaka Kikinzoku Kogyo) for the OER is similar, the catalytic activity of the former is more excellent until 1.45 VRHE (IR-free). To reveal an enhanced catalyst activity and stability towards OER, we fabricated MEAs using Ir/IrOX catalysts and TKK-IrO2 as anode catalysts, and commercial Pt/C at a cathode catalyst, respectively. As shown in Fig. 1(b), the performance of single-cell was compared at 2 A cm-2 geo. under the 353 K condition and is of Ir/IrOX (2.04 V), and TKK-IrO2 (2.32 V), respectively. This result indicates that the energy efficiency of the MEA using the Ir/IrOX catalyst is higher 13.72 % than that of TKK-IrO2. The obtained results are expected to decrease the amount of precious metals required to develop a cost-effective water electrolysis system for renewable hydrogen production.This work was supported by the Korea Institute of Energy Technology Evaluation and Planning (KETEP) and the Ministry of Trade, Industry & Energy (MOTIE) of the Republic of Korea (No. 20183010032380), and GIST.

MagnéLi-Phase Ti4O7-Supported Irru-Based Catalysts for Reversal Tolerant Anode of Automotive Polymer Electrolyte Membrane Fuel Cell

During the operation of a polymer electrolyte membrane fuel cell electric vehicle, various transient conditions may trigger hydrogen fuel starvation, which results in fatal degradation of anode caused by the reversal of the cell voltage in the anode. The reversal-tolerant anode (RTA) strategy has been introduced to mitigate the influence of hydrogen starvation. The RTA employs a catalyst for the oxygen evolution reaction (OER), thereby boosting the electrolysis of water and reducing the rate of the carbon oxidation reaction (COR). Many previous studies for fuel starvation phenomena suggest that the COR and MEA deterioration can be suppressed by IrO2 as an RTA catalyst. However, since the surface properties of Pt/C are different from those of IrO2, the uniform dispersion of the IrO2 in the catalyst slurry to obtain a homogeneous electrode remains a challenge. Also, the utilization efficiency of both catalysts (Pt/C and IrO2) may be decreased [1]. In view of this, we have proposed the multifunctional IrRu-based catalysts with hydrogen oxidation reaction (HOR) and OER activity [2, 3]. Ultimately, to realize a durable catalyst layer in MEA, it needs to replace from carbon materials, which is usually used as active materials support, to metal oxide. However, there are challenges to use metal oxide as catalysts support as follows: (1) low specific surface area (SSA) (2) poor electric conductivity.To resolve these problems, meso-ATO [4], and Ti4O7 [5], which is well-known conductive metal oxide, have been investigated. In this study, commercial Ti4O7 (SSA = ~38 m2 g-1) was utilized as support and Ti4O7-supported IrRu-based catalysts were prepared by using a polyol that acts as both the solvent and reducing agent under acidic conditions.In the electrochemical test, kinetics current for HOR of 20 wt.% IrRu4/Ti4O7 at 80 mV cm-2 is 23 mA cm-2, which is similar to the that (~ 23.04 mA cm-2) of state-of-art commercial 20 wt.% Pt/C catalyst. To confirm the catalytic effect, MEAs were fabricated by using Ti4O7-supported IrRu-based catalysts as anode catalysts and commercial PtCo/C as a cathode catalyst. Single-cell performance was evaluated at 0.6 V under 338 K and 50% relative humidity (RH), and is showed 0.645 A cm−2 for IrRu4/Ti4O7 and 0.642A cm−2 for Pt/C, respectively. Thus, the performances of MEAs comprising IrRu4/Ti4O7 is similar to the commercial Pt/C anode catalyst. Fuel starvation simulation test [3] to estimate the RTA durability reveals that the MEA with IrRu4/Ti4O7 resulted in excellent RTA durability (~5 h), which was much superior to that of Pt/C (~5 min). The obtained results are expected to promote the application of multifunctional IrRu alloy catalysts for RTA of automotive PEMFC, allowing one to replace the conventional Pt/C catalysts.This work was supported by the Hyundai Mobis, Korea Institute of Energy Technology Evaluation and Planning (KETEP) and the Ministry of Trade, Industry & Energy(MOTIE) of the Republic of Korea (No. 20183010032380), and GRI funded by GIST in 2019.

Flexible Cu2znsn(S, Se)4 Solar Cells over 7% Power Conversion Efficiency

The development of flexible solar cells is necessary for achieving market competitiveness through the implementation of low cost solar cells and for applying customized business models, such as Building Integrated Photovoltaics (BIPV). Cu2ZnSn(S,Se)S4 (CZTSSe) thin films have attracted attention as low-cost absorber materials for solar cells; however, further studies are required to develop flexible solar cells from this material and to achieve a high power conversion efficiency. In this work, the carrier separation characteristics of flexible CZTSSe thin-film solar cells on Mo foil substrates were identified. The surface electrical characteristics of the CZTSSe absorber layer indicate that the topography, surface potential, and local current are proportional to one another, in contrast to the characteristics exhibited by CIGS cells. For the CZTSSe absorber layer, an upward band bending-like band structure formed at and near the GBs, and a current path formed along the IGs as holes collected toward the GBs, and electrons collected toward the IGs. In contrast to that in CIGS cells, the carrier separation induced by the formation of the upward band bending-like band structure at the GBs is crucial in CZTSSe thin-film solar cells. Furthermore, the positive potential distribution at the IGs and average potential difference showed a proportional relationship to the local current and PCE. Through the implementation of these carrier separation characteristics, a flexible CZTSSe thin-film solar cell on a Mo foil substrate achieved a PCE of over 7%. Acknowledge: This work was supported by the Korea Institute of Energy Technology Evaluation and Planning (KETEP) and the Ministry of Trade, Industry & Energy (MOTIE) (No. 20173010012980) and by the DGIST R&D Programs of the Ministry of Science, ICT & Future Planning of Korea (19-BD-05).

Fabrication of CZTSSe Thin Film Solar Cell By Single Step Sulfo-Selenization of Stacked Metal Precursors

The Cu2ZnSn(S,Se)4 (CZTSSe) thin films are the most promising photovoltaic absorber to replace CIGS, because it is comprised of abundant and inexpensive elements, and have a very high absorption coefficient of over 104 cm−1 with a direct bandgap energy. The theoretical solar conversion efficiency of CZTS-based thin film solar cells is as high as 32.2%. However, the maximum conversion efficiencies reported for electrical characteristics of devices based on these materials are still far from those accomplished more grown CIGS technologies. In order to achieve the efficiency of 20 % or more required for commercial technology, it is necessary to understand the limiting factors of the CZTSSe thin film. A parameter impacting the performance of increasing photovoltaic efficiencies in CZTSSe solar cells is band gap control of absorber through the control of S/(S+Se) ratio of CZTSSe thin films. Most of reported synthesized CZTSSe with high efficiency, the chalcogen composition of the absorption layer was controlled to optimize the characteristics. Most of them explain only the role of S in controlling the band gap in the CZTSSe thin film. It also only describes the characteristics of CZTSSe thin films and devices with different S ratios. However, S element plays another important role in CZTSSe crystal growth process. In this work, we have discussed the different effects of S in the CZTSSe thin film synthesis process. We fabricated CZTSSe thin films using optimized SLG-Mo/Zn/Cu/Sn (MZCT) as a stack structure and described the volatilization phenomenon of Zn element using MZCT stack structure. In addition, we have introduced H2S gas to effectively control the S/(S+Se) of the film in the sulfo-selenization process and to suppress the volatilization of Zn. The S injection process using H2S gas is more uniform and reproducible than any other processes. Unlike the pure selenization process, it was confirmed that a stable ZnSSe thin film was formed on the surface of the precursor during the sulfo-selenization process. The formation of ZnSSe thin film inhibited the volatilization of Zn, which facilitated the control of thin-film stoichiometry and also played an important role in crystal growth. Finally, the characteristics of thin films and devices fabricated through the optimization process are discussed. Acknowledge: This work was supported by the DGIST R&D Program of the Ministry of Science and ICT (19-BD-05) and the Korea Institute of Energy Technology Evaluation and Planning (KETEP) and the Ministry of Trade, Industry & Energy(MOTIE) of the Republic of Korea (No. 20173010012980).

Effect of Ionomer Binder on Performance and Durability of Catalyst Layers

Energy conversion devices often needs movement of ions between two electrodes, i.e., anode and cathode. Ions reached in front of electrodes should be transported within electrodes to participate in anodic and cathodic reactions. Pathway for ions is normally in an aqueous phase. Regardless, the introduction of any aqueous phase in energy conversion devices causes many problems during fabrication, operation, maintenance, and so on. Thus, much efforts have been devoted to develop quasi-solid electrolytes such as gel polymer, ion exchangeable polymers, impregnation of ions in porous matrix and so on. Among the candidates, ion exchangeable polymers are quite often chosen as ion conducting media for energy conversion devices. The technique to introduce ion exchangeable polymers within electrodes for oxidation and reduction reactions is to solidify catalyst inks consisting of electrocatalyst, dispersion of ion exchangeable polymers, controlling solvents and additives by evaporation of all solvents in catalyst inks. Ion exchangeable polymers could be dispersed in various solvents. It causes different shapes of ion exchangeable polymers in solvents, for instance, cylindrical rods, a less-defined large particles, coils and so on. Such different types of ion exchangeable polymers form distinguished structure catalyst layers. In this study, the effect of solvents dispersing ion exchangeable polymers on the performance and durability of catalyst layers was investigated. Electrochemical characterization such as I-V polarization, cyclic voltammetry, impedance and so on and microscopic characterization such as SEM and TEM were carried out to evaluate the performance and durability of catalyst layers. Acknowledgement This work was supported by the New and Renewable Energy of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) granted financial resource from the Ministry of Trade, Industry & Energy, Republic of Korea (No. 20173010032100).

Influence of nano silica on the fresh, hardened and durability properties of self-cleaning white Portland cement mortars

Authors are thankful to Korea Institute of Energy Technology Evaluation and Planning (KETEP) and the Ministry of Trade, Industry & Energy (MOTIE) of the Republic of Korea (No. 20183010025510) for their support for this research work. The authors are also thankful to Charlie Sangho Lee, Senior Sales representative, Asia Pacific region of Cristal Corporates for providing free titanium dioxide (CristalACTiV™ PC105) for this research study.

First Principles Investigation of Grain Boundary Effects in Perovskite-Type Lithium Lanthanum Titanate Solid Electrolyte

Lithium lanthanum titanate (LLTO) is considered a particularly promising candidate for use as an electrolyte in all-solid-state lithium ion batteries due its good electrochemical stability and high ionic conductivity. However, measured values for the ionic conductivity of LLTO fall far below theoretical predictions, an incongruity which has been attributed to the presence of grain boundaries. Furthermore, recent experimental work has shown that lithium dendrite growth occurs along the grain boundaries in LLTO. While experimental studies have been able to reveal the detailed microstructure of polycrystalline LLTO, but little effort has been made to identify the fundamental mechanisms at work within the grain boundaries which lead to to suppressed ionic conductivity and Li dendrite growth. Using ab-initio calculations, we examine the electronic character of LLTO grain boundaries and investigate the impact of the defect states on ion transport and dendrite formation. Based on a fundamental understanding of the atomic and electronic character of LLTO grain boundaries, material design approaches are proposed to mitigate the impact of grain boundary behavior and improve the viability of LLTO as a practical solid electrolyte. This work was supported by the International Energy Joint R&D Program (No. 20168510011350) of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Ministry of Knowledge Economy, Korean government. This work is also supported by the L&F Co.’s World Class 300 Project of the Korea Institute of Advancement of Technology (KIAT) funded by the Ministry of Trade, industry and Energy (No.S2483103).

Development in Two-Dimensional Nanomaterials for Wearable Health Monitoring Systems

By virtue of the technology in ubiquitous computing and smart textile, gas sensor with wearability has been developed to play an imperative role in improving future healthcare. [1] The sensor revolution can significantly impact on outpatient care and management of chronical diseases by offering real-time condition monitoring. The combination of many technology is on the verge of producing this dramatic advance, and the significance placed on the development of sensor performance. [2] Recently, two-dimensional (2D) nanostructured materials have been regarded as instrumental sensing materials due to their working ability at low temperature. One attractive approach to enhance performance of 2D materials-based sensor is to hybridize with metal oxide. By grafting two nanostructured materials, sensing performance can be highly advanced by hybridization effects. [3] Another innovative strategy is to adapt newly discovered 2D materials. 2D transition metal carbides and/or carbonitrides (called MXenes) have recently shown excellent properties particularly in energy storage, and water purification applications. [4] Boundless combination of constituent elements and ordered structure in MXenes provides many opportunities to tailor its properties for different applications. In this study, 2D nanostructured nanomaterials and their hybrids were explored to develop wearable chemical sensor for precise health monitoring systems. Graphene oxide (GO) and molybdenum disulfide (MoS2) were studied to understand the effect of surface dangling bonds on gas sensing properties. To enhance sensing performance, 2D nanomaterials was combined with metal oxides. The gas sensing performance of the GO/TiO2 hybrid was improved by decorating titanium dioxide (TiO2). [5] After photo-reduction, the gas sensing behavior was converted from n-type to p-type with extended long-term stability. Moreover, 2D MXene was introduced as a promising room-temperature sensing material with their intriguing surface chemistry. The capability of titanium carbide (Ti3C2Tx) to sense an array of VOC gases was demonstrated, and its possible sensing mechanism was proposed in terms of the interaction between sensing species and the oxygen terminated surface of MXene. Another MXene material, vanadium carbide (V2CTx), was also investigated. 2D V2CTx gas sensors showed outstanding gas sensing performance including high sensitivity toward non-polar gases such as hydrogen and methane. Transformation of ordered structure and constituent elements of MXenes largely influenced on interaction between analyte and MXenes showing outstanding selectivity and limit of detection to non-polar gases. References Gravina, Raffaele, et al. "Multi-sensor fusion in body sensor networks: State-of-the-art and research challenges." Information Fusion 35 (2017): 68-80.Yao, Shanshan, Puchakayala Swetha, and Yong Zhu. "Nanomaterial‐Enabled Wearable Sensors for Healthcare." Advanced healthcare materials 7.1 (2018): 1700889.Chatterjee, Shyamasree Gupta, et al. "Graphene–metal oxide nanohybrids for toxic gas sensor: a review." Sensors and Actuators B: Chemical 221 (2015): 1170-1181.Anasori, Babak, Maria R. Lukatskaya, and Yury Gogotsi. "2D metal carbides and nitrides (MXenes) for energy storage." Nature Reviews Materials 2 (2017): 16098.Lee, Eunji, et al. "Enhanced Gas-Sensing Performance of GO/TiO2 Composite by Photocatalysis." Sensors 18.10 (2018): 3334. Acknowledgement This research was partially supported by the Korea Institute of Energy Technology Evaluation and Planning (KETEP), grant funded by the Korea Government Ministry of Trade, Industry and Energy (20158520000210), and Agency for Defense Development (ADD) as global cooperative research for high performance and light weight bio-urine based fuel cell (UD160050BD).

Design and analysis of an axial flux dual stator flux modulating synchronous reluctance machine

This work was supported in part by the Human Resources Program in Energy Technology of the Korea Institute of Energy Technology Evaluation and Planning (KETEP), granted financial resource from the Ministry of Trade, Industry & Energy, Republic of Korea, and in part by the BK21PLUS Program through the National Research Foundation of Korea within the Ministry of Education.

A pole changing vernier machine with consequent pole rotor

This work was supported in part by the Human Resources Program in Energy Technology of the Korea Institute of Energy Technology Evaluation and Planning (KETEP), granted financial resource from the Ministry of Trade, Industry & Energy, Republic of Korea, and in part by the BK21PLUS Program through the National Research Foundation of Korea within the Ministry of Education.