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2023. 07. 09

Electrocatalysis on Atom-Precise Metal Nanoclusters

  Electrocatalysis on Atom-Precise Metal Nanoclusters   Dongil Lee   Yonsei University, Seoul 03722, Republic of Korea  dongil@yonsei.ac.kr   Accurate identification of active sites is critical for elucidating catalytic reaction mechanisms and developing highly efficient and selective electrocatalysts. In the first part of my presentation, I will talk about atomic-level identification of active sites for the electrochemical CO2 reduction reaction (CO2RR) using atomically well-defined metal nanoclusters (NCs) Au25(SR)18 and Ag25(SR)18 (SR = thiolate). While both NCs produced CO as a main CO2RR product, the Au25 NC exhibited a significantly higher CO2RR activity than the Ag25 NC. Theoretical and operando studies revealed that the CO2RR limiting potential for the Au25 NC was significantly smaller than that for the Ag25 NC, while both NCs contained the partially dethiolated metal sites as the active sites. Active-site engineering was performed by replacing the Ag12(SR)18 shell of the Ag25(SR)18 NC with the Au12(SR)18 shell to generate a core-shell AuAg12@Au12(SR)18 NC, which exhibited stable CO2-to-CO electroreduction at a commercially relevant current density of 200 mA/cm2 and a full-cell potential of 2.1 V in a zero-gap CO2 electrolyzer. In the second part, I will discuss the effects of metal doping and ligand engineering on the hydrogen evolution reaction (HER) activities of gold and silver NCs. Studies of electrocatalysis by the rationally engineered NCs provide many important design principles for the development of electrocatalysts with tailored structure and adsorption energy. These principles are illustrated with NC-based electrocatalysts for water splitting and CO2 conversion.  ...

2023. 07. 18

Observing atmospheric chemical components from the space: applications to air pollution and climate studies

Observing atmospheric chemical components from space: applications to air pollution and climate studies   Rokjin Park School of Earth and Environmental Sciences, Seoul National University   Observing the earth’s radiances from space can be an effective approach to monitoring atmospheric chemical composition, which changes cause various environmental issues, including local air pollution and global climate changes. Low-orbiting satellites have been widely used to provide global-scale information and are often limited by their infrequent overpass times, which could be hampered by clouds. Since the first geostationary environmental monitoring spectrometer (GEMS) has been successfully launched by the Korean Ministry of Environment, we are in a new era of satellite observations. This talk mainly focuses on developing GEMS retrieval algorithms to observe volatile organic compounds (VOCs) column concentrations in East Asia and the first evaluation of GEMS VOCs observations. Furthermore, I will talk about some issues related to greenhouse gas concentrations whose emissions are highly uncertain, which are diagnosed by satellite observations....

2023. 03. 13

Atomically thin 3D semiconductors

Atomically thin 3D semiconductors   Jong-Hoon Kang   Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Republic of Korea​   3D architecture design and process with thin and lightweight components is promising for high-speed and low-power operation towards next generation electronics and optoelectronics. However,...

2023. 05. 08

Recent developments in multi-scale and non-linear topology optimization problems

Recent developments in multi-scale and non-linear topology optimization problems By Ole Sigmund, Villum Investigator, Dept. of Mechanical Engineering, Technical University of Denmark Topology optimization was introduced as a multi-scale approach in the seminal paper by Bendsøe and Kikuchi from 1988. However, simpler isotropic density interpolation schemes soon substituted the original homogenization-based approach. With advances in additive manufacturing technologies that may realize complex lattice and infill structures, needs for efficient...

2023. 07. 09

Bioinspired Artificial Cameras: Optic Components and Imaging Sensors

Bioinspired Artificial Cameras: Optic Components and Imaging Sensors   Young Min Song*,1    1School of Electrical Engineering and Computer Science, Gwangju Institute of Science and Technology, Gwangju 61005, Korea e-mail corresponding author: ymsong@gist.ac.kr   Key words: Bioinspired Optical Sensors, Bioinspired Photonics, Imaging Systems, Digital Cameras, Optic Components   Abstract   The diverse vision systems in nature can provide attractive design inspiration for imaging devices, ranging from optical subcomponents to digital cameras and visual prostheses, with more desirable optical characteristics than conventional imagers. The advantages of natural vision systems include high visual acuity, wide field of view, wavelength-free imaging, improved aberration correction and depth of field, and high motion sensitivity. Recent advances in soft materials, ultrathin electronics, and deformable optoelectronics have facilitated the realization of novel processes and device designs that mimic biological vision systems. This tutorial introduces recent progress and continued efforts in the research and development of bioinspired artificial eyes. At first, the configuration of two representative eyes found in nature: a single-chambered eye and a compound eye, is explained [1, 2]. Then, recent advances in bioinspired optic components and image sensors are discussed regarding materials, optical/mechanical designs, and integration schemes [3-6]....