Publications by authors named "Yun Kyung Jo"

Although progress has been made to improve photocatalytic CO reduction under visible light (λ>400 nm), the development of photocatalysts that can work under a longer wavelength (λ>600 nm) remains a challenge. Now, a heterogeneous photocatalyst system consisting of a ruthenium complex and a monolayer nickel-alumina layered double hydroxide (NiAl-LDH), which act as light-harvesting and catalytic units for selective photoreduction of CO and H O into CH and CO under irradiation with λ>400 nm. By precisely tuning the irradiation wavelength, the selectivity of CH can be improved to 70.

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A scalable organic intercalant-free liquid exfoliation route to 2D nanosheets (NSs) of layered transition-metal oxides (TMOs) is developed by employing hydronium-intercalated derivatives as precursors. The replacement of interlayer alkali metal ions with larger hydronium ions via acid treatment makes possible the efficient liquid exfoliation of TMOs without any assistance of organic intercalant cations. Not only a weakening of interlayer electrostatic interaction upon hydronium intercalation but also an efficient solvation of deintercalated hydronium ions via hydrogen bonding with polar solvents is mainly responsible for the high efficacy of hydronium-intercalated TMOs as precursors for liquid exfoliation.

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The chemical environments of the interlayer Na sites of layered titanate are finely controlled by the intercalation of n-alkylamine with various alkyl chain lengths to explore an effective way to improve its electrode functionality for sodium-ion batteries (SIBs). The n-alkylamine intercalation via ion-exchange and exfoliation-restacking routes allows the modification of in-plane structures of layered titanate to be tuned. Among the present n-alkylamine-intercalates, the n-pentylamine-intercalated titanate shows the largest discharge capacity with the best rate characteristics, underscoring the critical role of optimized intracrystalline structure in improving the SIB electrode performance of layered titanate.

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Efficient visible light active hybrid photocatalysts for H production can be synthesized by the intercalative hybridization of Zn-Cr-layered double hydroxide (Zn-Cr-LDH) with a mesoporous g-CN lattice. Small Zn-Cr-LDH nanocrystals with a size of ∼6 nm are immobilized in the mesopores of g-CN. Beyond an optimal LDH/g-CN molar ratio of 0.

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An efficient chemical way to finely control the layer-by-layer stacking of inorganic nanosheets (NS) is developed by tuning the type and composition of intercalant ion, and the reaction temperature for restacking process. The finely controlled stacking of NS relies on a kinetic control of the self-assembly of NS in the presence of coordinating organic cations. A critical role of organic cations in this assembly highlights the importance of the appropriate activation energy.

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The photocatalytic activity and photostability of CdS quantum dot (QD) can be remarkably enhanced by hybridization with Rh-substituted layered titanate nanosheet even at very low Rh substitution rate (<1%). Mesoporous CdS-Ti(5.2-x)/6 Rhx/2O2 nanohybrids are synthesized by a self-assembly of exfoliated Ti(5.

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Hybridization with exfoliated two-dimensional (2D) nanosheets provides a very effective and powerful way not only to control the physicochemical properties of hybridized species but also to explore nanocomposites with novel functionalities. Deliberate coupling between the hybridized species is critically important in maximizing the effect of hybridization on the physicochemical properties and functionality of hybridized components. The very small thickness and extremely large surface of exfoliated 2D nanosheets render these materials ideal candidates for achieving a strong coupling with diverse guest species.

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In comparison with the hybridization with 0D TiO2 nanoparticle, 2D layered TiO2 nanosheets are much more effective in the improvement of the photocatalytic activity and photostability of semiconducting compounds. The 2D TiO2-Ag3PO4 nanohybrid described in this paper shows a greater decrease in the electron-hole recombination upon hybridization and a stronger chemical interaction between the components than the 0D homologue. This result confirms the benefits of 2D layered TiO2 nanosheets as a building block for efficient hybrid-type photocatalyst materials.

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Multicomponent Ag2CO3/Ag-layered Ti5NbO14 nanohybrids are synthesized by the crystal growth of silver carbonate on the surface of exfoliated layered titanoniobate 2D nanosheets. In the obtained nanohybrids, the spherical Ag2CO3 nanoparticles with a size of 5-10 nm are immobilized on the surface of the titanoniobate nanosheets with partial formation of neutral Ag metal caused by electron transfer from anionic titanoniobate nanosheets to silver cations. An electronic coupling between Ag2CO3/Ag and Ti5NbO14 nanosheets leads to a remarkable enhancement of visible light absorption and a significant depression of electron-hole recombination.

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Solid polymer electrolytes (SPEs) are an excellent alternative to liquid electrolytes due to their non-volatility, low toxicity, and high energy density. In this study, a SPE having the ion transport mechanism decoupled from segmental motion of a polymer based on poly(vinyl alcohol) (PVA) containing the salt lithium trifluoromethane sulfonate (LiCF3SO3, LiTf) has been prepared to overcome the low ionic conductivity of traditional SPEs at room temperature. PVA has a high glass transition temperature (358 K) and good mechanical properties, and despite being atactic, it can crystallize, especially if highly hydrolyzed.

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