Seung Jae Baek

Microporous Carbon Nanoplates from Regenerated Silk Proteins for Supercapacitors

Novel carbon-based microporous nanoplates containing numerous heteroatoms (H-CMNs) are fabricated from regenerated silk fibroin by the carbonization and activation of KOH. The H-CMNs exhibit superior electrochemical performance, displaying a specific capacitance of 264 F/g in aqueous electrolytes, a specific energy of 133 Wh/kg, a specific power of 217 kW/kg, and a stable cycle life over 10000 cycles.

N-type graphene induced by dissociative H2 adsorption at room temperature

Studies of the interaction between hydrogen and graphene have been increasingly required due to the indispensable modulation of the electronic structure of graphene for device applications and the possibility of using graphene as a hydrogen storage material. Here, we report on the behaviour of molecular hydrogen on graphene using the gate voltage-dependent resistance of single-, bi-, and multi-layer graphene sheets as a function of H2 gas pressure up to 24 bar from 300 K to 345 K. Upon H2 exposure, the charge neutrality point shifts toward the negative gate voltage region, indicating n-type doping, and distinct Raman signature changes, increases in the interlayer distance of multi-layer graphene, and a decrease in the d-spacing occur, as determined by TEM. These results demonstrate the occurrence of dissociative H2 adsorption due to the existence of vacancy defects on graphene.

Macroscopic single-walled-carbon-nanotube fiber self-assembled by dip-coating method.

Pure macroscopic single-walled-carbon-nanotube (SWNT) fibers are fabricated by using a dip-coating method without any additive or additional electrical equipment or complex apparatus. The present method only utilizes microfluidics, which includes capillary condensation, capillary flow, and surface tension, and results in the self-assembly and self-alignment of SWNT colloids.

The dependence of the Schottky barrier height on carbon nanotube diameter for Pd?carbon nanotube contacts

Direct measurements are presented of the Schottky barrier (SB) heights of carbon nanotube devices contacted with Pd electrodes. The SB barrier heights were determined from the activation energy of the temperature-dependent thermionic emission current in the off-state of the devices. The barrier heights generally decrease with increasing diameter of the nanotubes and they are in agreement with the values expected when assuming little or no influence of Fermi level pinning.

Effect of sulphur vacancy on geometric and electronic structure of MoS2 induced by molecular hydrogen treatment at room temperature

Investigations into the interaction between molecular hydrogen and molybdenum disulphide have been in increasing demand to improve the understanding of the hydrodesulphurisation process, especially the creation of sulphur vacancies which result in coordinatively unsaturated sites in MoS2. Here we present comprehensive studies of the structural and electronic modulation caused by exposure of MoS2 to H2 over a low temperature range, which may be helpful for industrial applications. Detail investigations were conducted with Raman spectroscopy, high resolution transmission electron microscopy (HRTEM), and electrical transport properties as a function of H2 gas pressure up to 24 bar from 295 K to 350 K. Upon exposure to H2, we observed bond-softening using Raman spectroscopy, a decrease in d-spacing from the TEM results, and an increase in conductance, all of which are consistent with the first-principles calculations. The results demonstrate the formation of sulphur vacancies even under low H2 pressure at low temperature.

N-type carbon nanotube by alkaline-earth metal Sr doping

Alkaline-earth metal, Sr, was doped on multiwalled carbon nanotubes (MWNTs) by vapor phase reaction method. The tunneling electron microscopy, energy dispersive x ray, and Raman spectroscopy were studied for verifying the Sr doping on MWNT. The temperature-dependent resistivity [ρ(T)] and thermoelectric power [S(T)] were also performed for both pristine MWNT and Sr-doped MWNT (Sr-MWNT). ρ(T) of Sr-MWNT did not significantly change compared to pristine MWNT. However, S(T) of Sr-MWNT considerably changes, i.e., it shows n-type behavior in contrast to pristine MWNT.