Hyung‐Kyu Lim

Lithium-oxygen chemistry offers the highest energy density for a rechargeable system as a "lithium-air battery". Most studies of lithium-air batteries have focused on demonstrating battery operations in pure oxygen conditions; such a battery should technically be described as a "lithium-dioxygen battery". Consequently, the next step for the lithium-"air" battery is to understand how the reaction chemistry is affected by the constituents of ambient air. Among the components of air, CO2 is of part

CO2 conversion is an essential technology to develop a sustainable carbon economy for the present and the future. Many studies have focused extensively on the electrochemical conversion of CO2 into various useful chemicals. However, there is not yet a solution of sufficiently high enough efficiency and stability to demonstrate practical applicability. In this work, we use first-principles-based high-throughput screening to propose silver-based catalysts for efficient electrochemical reduction of

The free energy of H adsorption (<i>ΔG</i>_H) on a metallic catalyst has been taken as a descriptor to predict the hydrogen evolution reaction (HER) kinetics but has not been well applied in alkaline media. To assess this, we prepare Pd@Pt and PdH@Pt core-shell octahedra enclosed by Pt(111) facets as model catalysts for controlling the <i>ΔG</i>_H affected by the ligand, the strain, and their ensemble effects. The Pt shell thickness is adjusted from 1 to 5 atomic layers by va

Ni₂Mo₃N catalyst is synthesized directly on Ni foam by a simple and economical method, which shows excellent hydrogen evolution performance in alkaline electrolyte.

Recently, many experimental and theoretical efforts are being intensified to develop high-performance catalysts for electrochemical CO2 conversion. Beyond the catalyst material screening, it is also critical to optimize the surrounding reaction medium. From vast experiments, inclusion of room-temperature ionic liquid (RTIL) in the electrolyte is found to be beneficial for CO2 conversion; however, there is no unified picture of the role of RTIL, prohibiting further optimization of the reaction me

Developing effective anode materials for sodium-ion batteries (SIBs) remains challenging. Although FeS2 has a high theoretical capacity, it suffers from significant volume changes during charge/discharge and forms soluble polysulfides at lower potentials (below 0.8 V vs. Na/Na+), making practical application difficult. We have developed an effective strategy to synthesize N-doped carbon-coated FeS2 nanorattles encapsulated in N/S dual-doped graphene/single-walled carbon nanotubes (G/SWCNTs) via

Electrochemical CO₂ conversion technology is becoming indispensable in the development of a sustainable carbon-based economy. While various types of electrocatalytic systems have been designed, those based on room-temperature ionic liquids (RTILs) have attracted considerable attention because of their high efficiencies and selectivities. Furthermore, it should be possible to develop more advanced electrocatalytic systems for commercial use because target-specific characteristics can be fine-tune

Among various models that incorporate solvation effects into first-principles-based electronic structure theory such as density functional theory (DFT), the average solvent electrostatic potential/molecular dynamics (ASEP/MD) method is particularly advantageous. This method explicitly includes the nature of complicated solvent structures that is absent in implicit solvation methods. Because the ASEP/MD method treats only solvent molecule dynamics, it requires less computational cost than the con

The transient overshoot in drain current that occurs in thin-film SOI (Si-on-SiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> ) MOSFET's because of the floating body in analyzed, and the benefit it can provide to propagation delay (speed) in SOI CMOS digital circuits is assessed. The analysis accounts for the charge coupling between the front and back gates, and hence describes the dependence of the transient drain (saturation) current an

A charge-based large-signal model for thin-film SOI (Si-on-SiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> ) MOSFET's, intended for computer simulation of transient characteristics of SOI and 3-D circuits, is developed emphasizing the structural uniqueness of the devices. Closed-form expressions for the quasi-static terminal charges, simpler than those for the bulk MOSFET because of the thin-film structure, are derived in terms of termin

Although metastable crystal structures have received much attention owing to their utilization in various fields, their phase-transition to a thermodynamic structure has attracted comparably little interest. In the case of nanoscale crystals, such an exothermic phase-transition releases high energy within a confined surface area and reconstructs surface atomic arrangement in a short time. Thus, this high-energy nanosurface may create novel crystal structures when some elements are supplied. In t

We report gas-phase photocatalytic CO2 reduction with Cu2O/TiO2 photocatalysts of varying surface passivation. With taurine adsorbed on the photocatalyst surface, the CH4 production rate increases and CO production rate decreases compared to photocatalysts with no ligand treatment. When ethylenediamine is present on Cu2O/TiO2 photocatalysts, CO selectivity enhances significantly. In situ Fourier transform infrared spectroscopy and density functional theory calculation reveal that the surface lig