Scholar Hub Community:https://yscholarhub.yonsei.ac.kr/handle/2021.sw.yonsei/40212024-03-29T10:02:27Z2024-03-29T10:02:27ZHydrogel protection strategy to stabilize water-splitting photoelectrodesJEIWAN TANByungJun KangKyungmin KimDONYOUNG KANGHyungsoo Leesunihl magyumin JangHyungsuk LeeJoo Ho Moonhttps://yscholarhub.yonsei.ac.kr/handle/2021.sw.yonsei/63012024-03-08T14:31:04Z2022-06-01T00:00:00ZTitle: Hydrogel protection strategy to stabilize water-splitting photoelectrodes
Authors: JEIWAN TAN; ByungJun Kang; Kyungmin Kim; DONYOUNG KANG; Hyungsoo Lee; sunihl ma; gyumin Jang; Hyungsuk Lee; Joo Ho Moon
Abstract: Photoelectrochemical water splitting is an attractive solar-to-hydrogen pathway. However, the lifetime of photoelectrochemical devices is hampered by severe photocorrosion of semiconductors and instability of co-catalysts. Here we report a strategy for stabilizing photoelectrochemical devices that use a polyacrylamide hydrogel as a highly permeable and transparent device-on-top protector. A hydrogel-protected Sb2Se3 photocathode exhibits stability over 100?h, maintaining ~70% of the initial photocurrent, and the degradation rate gradually decreases to the saturation level. The structural stability of a Pt/TiO2/Sb2Se3 photocathode remains unchanged beyond this duration, and effective bubble escape is ensured through the micro gas tunnel formed in the hydrogel to achieve a mechanically stable protector. We demonstrate the versatility of the device-on-top hydrogel protector under a wide electrolyte pH range and by using a SnS photocathode and a BiVO4 photoanode with ~500?h of lifetime.2022-06-01T00:00:00ZStrong enhancement of room-temperature thermoelectric properties of Cu-doped Bi2Te2.7Se0.3Kim, GwansikLee, KyungmiShin, HyunjunKim, JeongminChang, JoonyeonRoh, Jong WookLee, Wooyounghttps://yscholarhub.yonsei.ac.kr/handle/2021.sw.yonsei/65802024-03-08T15:26:11Z2022-01-01T00:00:00ZTitle: Strong enhancement of room-temperature thermoelectric properties of Cu-doped Bi2Te2.7Se0.3
Authors: Kim, Gwansik; Lee, Kyungmi; Shin, Hyunjun; Kim, Jeongmin; Chang, Joonyeon; Roh, Jong Wook; Lee, Wooyoung
Abstract: We investigate thermoelectric properties of Cu-doped Bi2Te2.7Se0.3 fabricated using a simple doping process and spark plasma sintering. Through precise control of Cu doping, it is found that Cu atoms preferentially occupied Bi sites and then intercalated into the van der Waals gap with an increasing Cu content. Electrical transport properties of Cu-doped samples were systemically controlled using this mechanism. At the same time, thermal conductivities of the Cu-doped samples were reduced by the enhancement of point defect phonon scattering due to the Cu atoms. Compared to that of pristine samples, the dimensionless thermoelectric figure of merit ( "ZT ") of 0.98 at 323 K for the Cu-doped sample was increased by more than 92% owing to these synergetic effects. Furthermore, the shift of maximum ZT to room temperature provides advantages for enlarging the applications of thermoelectric effects at room temperature.2022-01-01T00:00:00ZTunable Curie temperature in Mn1.15Fe0.85P0.55Si0.45 via lattice engineering by Al additionKim S.Shin H.Chu I.Lee K.KYUHYUNG LEEWooyoung Leehttps://yscholarhub.yonsei.ac.kr/handle/2021.sw.yonsei/64642024-03-08T15:26:11Z2022-01-01T00:00:00ZTitle: Tunable Curie temperature in Mn1.15Fe0.85P0.55Si0.45 via lattice engineering by Al addition
Authors: Kim S.; Shin H.; Chu I.; Lee K.; KYUHYUNG LEE; Wooyoung Lee
Abstract: Bulk polycrystalline samples of hexagonal Fe2P-type Al-added Mn1.15Fe0.85P0.55Si0.45 were prepared via a solid-state reaction under controlled heat treatment, and their magnetocaloric properties, including magnetization and entropy change, were investigated. Notably, the Curie temperature, which is directly related to the operating temperature of magnetocaloric materials, could be systematically tuned through Al substitution at Si sites owing to the lattice engineering effect. We found an inverse relationship between the Curie temperature and the ratio of the c-axis lattice constant to a-axis lattice constant, which enables the design of magnetocaloric materials for high-performance magnetic cooling systems.2022-01-01T00:00:00ZA Review on Silicide-Based Materials: Thermoelectric and Mechanical PropertiesKim, GwansikShin, HyunjunLee, JihyunLee, Wooyounghttps://yscholarhub.yonsei.ac.kr/handle/2021.sw.yonsei/65862024-03-08T15:26:40Z2021-07-01T00:00:00ZTitle: A Review on Silicide-Based Materials: Thermoelectric and Mechanical Properties
Authors: Kim, Gwansik; Shin, Hyunjun; Lee, Jihyun; Lee, Wooyoung
Abstract: Silicide-based thermoelectric (TE) materials are promising candidates for automotive TE generators, which can collect wasted heat and convert it into electricity. Adequate strategies should be used to manufacture highly efficient silicide-based TE devices. This review summarizes novel strategies for obtaining materials that feature excellent TE properties and mechanical reliability. Controlling the carrier concentration and band structure could increase their electronic transport properties, while nanostructure engineering could effectively reduce their lattice thermal conductivity. Moreover, well designed microstructures are required to obtain mechanically reliable TE materials, which indicates that precisely controlling their nanostructure is essential for the improved trade-off relationship between TE and mechanical properties. While many challenges should still be overcome, the development of highly efficient TE materials and devices could represent new solutions for the global energy crisis. Graphic2021-07-01T00:00:00Z