Seong-Ju Hwang

Mesoporous layer-by-layer ordered nanohybrids highly active for visible light-induced O(2) generation are synthesized by self-assembly between oppositely charged 2D nanosheets of Zn-Cr-layered double hydroxide (Zn-Cr-LDH) and layered titanium oxide. The layer-by-layer ordering of two kinds of 2D nanosheets is evidenced by powder X-ray diffraction and cross-sectional high resolution-transmission electron microscopy. Upon the interstratification process, the original in-plane atomic arrangements a

Abstract Polynary transition‐metal atom catalysts are promising to supersede platinum (Pt)‐based catalysts for oxygen reduction reaction (ORR). Regulating the local configuration of atomic catalysts is the key to catalyst performance enhancement. Different from the previously reported single‐atom or dual‐atom configurations, a new type of ternary‐atom catalyst, which consists of atomically dispersed, nitrogen‐coordinated Co–Co dimers, and Fe single sites (i.e., Co 2 –N 6 and Fe–N 4 structures) t

Highly efficient photocatalysts for visible light-induced O2 generation are synthesized via an electrostatically derived self-assembly of Zn–Cr-LDH 2D nanoplates with graphene 2D nanosheets. In the obtained nanohybrids, the positively charged Zn–Cr-LDH nanoplates are immobilized on the surface of negatively charged graphene nanosheets with the formation of a highly porous stacked structure. A strong electronic coupling of the subnanometer-thick Zn–Cr-LDH nanoplates with reduced graphene oxide (R

Bifunctional 2D superlattice electrocatalysts of alternating layered double hydroxide (LDH)–transition metal dichalcogenide (TMD) heterolayers were synthesized by interstratification of the exfoliated nanosheets. Density functional theory calculations predict an increased interfacial charge transfer between interstratified LDH and TMD nanosheets, which would lead to enhanced electrocatalytic activity. The electrostatically driven self-assembly of oppositely charged 2D building blocks, i.e., exfo

We have achieved the synthesis of dual-metal single atoms and atomic clusters that co-anchor on a highly graphitic carbon support. The catalyst comprises Ni₄ (and Fe₄) nanoclusters located adjacent to the corresponding NiN₄ (and FeN₄) single-atom sites, which is verified by systematic X-ray absorption characterization and density functional theory calculations. A distinct cooperation between Fe₄ (Ni₄) nanoclusters and the correspo

The 2D nanosheets of layered inorganic solids prepared by soft-chemical exfoliation reaction can be used as effective building blocks for hybridization with inorganic, organic, bio-, and polymer molecules/nanostructures. In comparison with graphene nanosheets, the 2D inorganic nanosheets boast much higher tunability in their chemical composition and physicochemical properties, leading to the creation of unexpected novel functionalities upon hybridization. Despite such unique and intriguing advan

Strongly coupled nanocomposites of layered titanate and reduced graphene oxide (RGO) are synthesized by electrostatically derived self-assembly between negatively charged RGO nanosheets and positively charged TiO(2) nanosols, which is then followed by a phase transition of the anatase TiO(2) component into layered titanate. The resulting nanocomposite consists of thin 2D nanoplates of lepidocrocite-type layered titanate immobilized on the surface of RGO nanosheets. The composite formation with R

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 exfoliat

New phases of Zn–Co-layered double hydroxides (Zn–Co-LDHs) were synthesized for the first time via a co-precipitation reaction using hydrogen peroxide as an oxidant. According to powder X-ray diffraction and field emission-scanning electron microscopy, both nitrate- and sulfate-forms of the Zn–Co-LDHs crystallized with the brucite-type layer structure having interlayer nitrate and sulfate anions, respectively, and commonly showed plate-like morphology with a crystal size of several hundred nanom

An effective way to tailor the physicochemical properties of graphene film is developed by combining colloidal suspensions of reduced graphene oxide (rG‐O) nanosheets and exfoliated layered titanate nanosheets for the fabrication of freestanding hybrid films comprised of stacked and overlapped nanosheets. A flow‐directed filtration of such mixed colloidal suspensions yields freestanding hybrid films comprised of strongly‐coupled rG‐O and titanate nanosheets with tunable chemical composition. Thi

Despite the high energy densities, lithium–sulfur (Li–S) batteries suffer from insufficient cycle life originating from the shuttling process involving lithium polysulfides (LiPSs). Various approaches have been introduced to resolve the shuttling problem, but they are not usually effective for electrodes with high sulfur contents. Here, we report an exfoliated 2D lepidocrocite titanium oxide nanosheet as a component for sulfur cathodes to suppress polysulfide dissolution markedly. In particular,

Porously assembled 2D nanosheets of alkali metal manganese oxides were synthesized via the flocculation of exfoliated MnO 2 nanosheets with alkali metal cations. According to X-ray diffraction and electron microscopic analyses, the MnO 2 nanosheets were porously restacked with alkali metal cations, resulting in the mesoporous assembly of lamellar crystallites with surface expansion (∼50−70 m 2 g − 1 ). Mn K-edge X-ray absorption spectroscopy clearly demonstrated that manganese ions in the reasse

Mesoporous iron oxide-layered titanate nanohybrids have been synthesized through a reassembling reaction between exfoliated titanate nanosheets and iron hydroxide nanoclusters, in which an electrostatic attraction between both nanosized species could be achieved at low pH of 1.5. The formation of the layer-by-layer ordered heterostructure with the repeating unit of 1.33 nm was clearly evidenced by powder X-ray diffraction and transmission electron microscopic analysis. According to Fe K-edge X-r

Abstract An effective chemical way to optimize the oxygen electrocatalyst and Li‐O 2 electrode functionalities of metal oxide can be developed by the control of chemical bond nature with the surface anchoring of highly oxidized selenate (SeO 4 2− ) clusters. The bond competition between (Se 6+ −O) and (Mn−O) bonds is quite effective in stabilizing Jahn–Teller‐active Mn 3+ state and in increasing oxygen electron density of α‐MnO 2 nanowire (NW). The selenate‐anchored α‐MnO 2 NW shows excellent ox