Nanohybrid Material Research Group
Department of Materials Science and Engineering, Kookmin Univ.
RESEARCH
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Energy Harvesting
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With running out of fossil fuels, the research for development of renewable and eco-friendly energy power generation has been required. This group has been working on developing materials and devices related to the renewable energy especially focusing on solar cells and thermoelectrics. Solar cell is a device which receive solar energy to convert it to electric current. Among many types of solar cells, we studied dye-sensitized solar cell (DSSC) using nanostructured and porous TiO2 films such as an inverse opal film as a photoelectrode. Another topic of my research on new & renewable energy device is thermoelectric device using nanostructured carbon materials. Thermoelectric device utilizes Peltier-Seebeck effect which implies the direct conversion of temperature differences to electric voltage. My research focus regarding thermoelectric device is to chemically modify carbon nanotube (CNT) or graphene oxide to achieve an improved conversion efficiency, and to develop wearable thermoelectric devices utilizing body temperature. Our current research interests expand into the energy storage system such as lithium or sodium ion battery.
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Thermoelectric generator Thermoelectric generator converts thermal energy to electrical power. When temperature gradient (ΔT) is generated in the end of both hot side and cold side of thermoelectric material, charge carrier transports from hot side to cold side, producing an electrical potential (ΔV) which is known as Seebeck effect (S= ΔV /ΔT). Because it can use waste heat from vehicle, body heat and so on as a resource of temperature, they have been regarded as promising energy harvesting devices. Thermoelectric efficiency is determined by the figure of merit (ZT) with the achievement of high electrical conductivity (σ), high Seebeck coefficient (S), and low thermal conductivity (k) for high performance thermoelectric devices. ZT=(S^2 σ)/k T In our group, thermoelectric performance of various low dimensional nanomaterials has been researched with chemical doping, tuning the energy states or control of structure by using various low dimensional nanomaterials for enhanced thermoelectric performance. These accomplishments provide the basis of wearable electric power generator for healthcare devices and smart fashion items. The human body maintains its temperature constantly at around 37°C regardless of the wide variation of ambient temperature, which ranges from −40°C to 50°C. The temperature difference between the human body and surrounding environment is a good source for thermoelectric (TE) conversion because electrical generation in a TE device is based on a temperature difference. Therefore, thermoelectricity will be the most suitable energy source for developing wearable power generators. |
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Secondary ion battery
Lithium-ion batteries (LIBs) have been extensively investigated for a wide range of fields including electric and hybrid vehicles, information technology, aerospace, etc. as the most commonly used potential energy conversion and storage devices. Considering attractive properties such as long cycle life, high energy density, portable size, low weight, flexible body, few memory effects and low pollution, LIBs have been recognized as the most likely method to be used to store electrical power in the future as well as at present. This group demonstrates the utilization of various carbon-based nanomaterials as anode materials for Li-ion battery applications and challenges to formulate nanomaterials for Li-ion battery applications.
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Dye-sensitized solar cell (DSSC) As a solution to environmental pollution and energy problems, research on alternative energy devices has been constantly required. One of them, solar cell has been considered as a high efficient renewable energy device. As a kind of solar cell, dye-sensitive solar cell (DSSC) has a relatively simple, eco-friendly fabrication process compared to silicon solar cells. In addition, because it is translucent and relatively easy to realize flexible device, the application fields are wide. However, it has lower conversion efficiency than silicon solar cells. In this group, photonic crystal was applied in the photo-electrode as for efficient solar absorption. Also, in order to increase conversion efficiency, TiO2 structure was controlled for high surface area with various methods. |  |
Relevent Publication
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Hyunwoo Bark, Museok Ko, Mijung Lee, Wonmok Lee, Byunghee Hong, and Hyunjung Lee*, “Thermoelectric Properties of Thermally Reduced Graphene Oxide Observed by Tuning the Energy States”, ACS Sustainable Chem. Eng., 2018, 6(6), 7468–7474
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| 2 | Jongwook Kim, Jonghyun Kang, Uiyoung Jeong, Heesuk Kim, Hyunjung Lee* “Catalytic, Conductive, and Transparent Platinum Nanofiber Webs for FTO-Free Dye-Sensitized Solar Cells”, ACS Appl. Mater. Interfaces 2013, 5, 3176−3181 |
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Young Gon Seo, Kyoungja Woo, Junkyung Kim, Hyunjung Lee,* and Wonmok Lee*, “Rapid Fabrication of an Inverse Opal TiO2 Photoelectrode for DSSC using a Binary Mixture of TiO2 Nanoparticles and Polymer Microspheres”, Adv. Funct. Mater, 2011, 21, 3094-3103 (featured as a front cover) |
| 4 | Eun Sik Kwak, Won Mok Lee, Nam Gyu Park, Jun Kyung Kim and Hyunjung Lee*, “Compact inverse opal electrode using nonaggregated TiO2 nanoparticles for dye-sensitized solar cells”, Advanced Functional Materials, 2009, 19, 1093-1099 (Featured as an inner front conver) |
| 5 | Su-Chul Yang, Dae-Jin Yang, Junkyung Kim, Jae-Min Hong, Ho-Gi Kim, Il-Doo Kim*, Hyunjung Lee *, “Hollow TiO2 Hemispheres Obtained by Colloidal Templating for Application in Dye-Sensitized Solar Cells”, Adv. Mater, 2008, 20(5), 1059–1064 (Featured as on of the most accessed articles) |
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We applied five US patents as followings.
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