KAIST · Materials Science
Sang Woo Han 교수의 연구실은 주로 나노구조 재료의 합성과 그 응용에 중점을 두고 있으며, 특히 이종 금속 나노소재(예: Pd-Pt-Ag, Au-Pd 등)의 이국적 구조적 특성과 원자 배치가 촉매 성능에 미치는 영향을 깊이 있게 연구하고 있습니다. 고도로 제어된 2차원 나노시트, 허브 구조, 코어-쉘 나노입자 등 다양한 나노구조를 설계하여 전기화학적 반응(예: 에탄올 산화, 산소 환원, 포름산 산화)에서 뛰어난 촉매 성능을 발휘하는 물질을 개발하고 있습니다. 또한 표면 화학 및 표면 분석 기법을 활용해 나노입자와 기질 간의 상호작용 메커니즘을 규명함으로써, 기초 과학적 이해를 바탕으로 한 실용적 응용 기술을 추구합니다.
표시된 성과는 수집된 데이터 기준으로 산출되며, 일부 차이가 있을 수 있습니다.
Abstract Hollow tin dioxide (SnO 2 ) microspheres were synthesized by the simple heat treatment of a mixture composed of tin( IV ) tetrachloride pentahydrate (SnCl 4 ·5H 2 O) and resorcinol–formaldehyde gel (RF gel). Because hollow structures were formed during the heat treatment, the pre‐formation of template and the adsorption of target precursor on template are unnecessary in the current method, leading to simplified synthetic procedures and facilitating mass production. Field‐emission scanni
A synthesis strategy for the preparation of ultrathin free-standing ternary-alloy nanosheets is reported. Ultrathin Pd-Pt-Ag nanosheets with a thickness of approximately 3 nm were successfully prepared by co-reduction of the metal precursors in an appropriate molar ratio in the presence of CO. Both the presence of CO and the interplay between the constituent metals provide fine control over the anisotropic two-dimensional growth of the ternary-alloy nanostructure. The prepared Pd-Pt-Ag nanosheet
Die Mischung macht's: Au-Pd-Legierungs-, Au@Pd-Kern-Schale-, Pd- und Au-Nanokristalle (NCs) mit identischer Oktaederform und ähnlicher Größe wurden hergestellt, um speziell die Auswirkung der Atomverteilung auf die Leistungsfähigkeit von NC-Katalysatoren zu studieren. Für die Oxidation von Ameisensäure wurde eine starke Abhängigkeit der Aktivitäten und Stabilitäten dieser NCs gefunden: Au–Pd (Legierung) > Au@Pd (Kern-Schale) > Pd ≫ Au. Detailed facts of importance to specialist readers are publi
In the mix: Au–Pd alloy, Au@Pd core–shell, Pd, and Au nanocrystals (NCs) with an identical octahedral shape and with similar NC size were prepared to examine exclusively the effect of atomic distribution on the catalytic performance of NCs (see picture). The catalytic activities and stabilities toward formic acid oxidation highly depend on the atomic distribution in the NCs: Au–Pd alloy > Au@Pd core–shell > Pd ≫ Au NCs.
The core of the matter: The catalytic activities of [email protected] heteronanostructures (see scheme; CTAB: cetyltrimethylammonium bromide, NPs: nanoparticles) toward oxygen reduction are highly dependent on the shape of the cores, thus revealing the importance of the core structure for enhancing the activity of core–shell-type nanocatalysts. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or ty
We have investigated comparative adsorptivities and relative stabilities of self-assembled monolayers of thiol (benzenethiol, BT) vs selenol (benzeneselenol, BSe) on a silver surface by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy and surface-enhanced Raman spectroscopy (SERS). BT and BSe are chemisorbed on silver as benzenethiolate and benzeneselenolate, respectively, after deprotonation with a tilted orientation with respect to the substrate surface; the benzene rings of
The many faces of noble metals: Through the simultaneous reduction of Au and Pd ions in the presence of octahedral Au nanocrystal (NC) seeds, hexoctahedron-like convex Au@Pd core–shell NCs, enclosed predominantly by high-index {12 5 3} facets, were synthesized under aqueous room-temperature conditions (see picture). The convex Au@Pd NCs showed much higher electrocatalytic properties toward ethanol oxidation than other types of Au@Pd NCs. Detailed facts of importance to specialist readers are pub
To develop high-performance bimetallic catalysts, fine control over both the ligand and strain effects of secondary elements on the catalytic function of primary elements is crucial. Here we introduce an approach to produce Pd–Ag bimetallic core–shell nanocatalysts with synergistic regulation of the ligand and strain effects of Ag. Through precise core–shell engineering, (PdAg alloy core)@(ultrathin Pd shell) nanocrystals with controlled core compositions and shell thicknesses in addition to a w
In place of functional groups that impose different inductive effects, we immobilize molecules carrying thiol groups on a gold electrode. By applying different voltages, the properties of the immobilized molecules can be tuned. The base-catalyzed saponification of benzoic esters is fully inhibited by applying a mildly negative voltage of -0.25 volt versus open circuit potential. Furthermore, the rate of a Suzuki-Miyaura cross-coupling reaction can be changed by applying a voltage when the arylha
{110}-faceted alloy nanocrystals: Rhombic dodecahedral Au–Pd alloy nanocrystals (NCs) enclosed exclusively by 12 {110} facets were prepared by a simple one-pot aqueous synthetic method. The picture shows an SEM image of the NCs (inset: ideal RD structure). The NCs exhibit higher surface-enhanced Raman scattering and electrocatalytic activities than {111}-faceted nanoparticles. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-re
The adsorption of anthraquinone-2-carboxylic acid (AQ-2-COOH) on a gold surface has been investigated by reflection−absorption infrared (RAIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), surface-enhanced Raman scattering (SERS), quartz crystal microbalance (QCM), and ab initio quantum mechanical calculation. The RAIR spectral data clearly showed that the molecule was chemisorbed on gold as carboxylate, after deprotonation, with its two oxygen atoms bound symmet
ConspectusLocalized surface plasmon resonance is a unique property appearing in certain metal nanostructures, which can generate hot carriers (electrons and holes) and bring about an intense electromagnetic field localized near the surface of nanostructures. Specific locations, such as the rough surfaces and gaps in nanostructures, where a strong electromagnetic field is formed are referred to as hot spots. Hot-spot-containing plasmonic nanostructures have shown great promise in molecular sensin
Improving the electrocatalytic activity and durability of Pt-based catalysts with low Pt content toward the oxygen reduction reaction (ORR) is one of the main challenges in advancing the performance of polymer electrolyte membrane fuel cells (PEMFCs). Herein, a designed synthesis of well-defined Pd@Pt core-shell nanoparticles (NPs) with a controlled Pt shell thickness of 0.4-1.2 nm by a facile wet chemical method and their electrocatalytic performances for ORR as a function of shell thickness ar
