Chan Ho Jung

Surface Plasmon-Driven Hot Electron Flow Probed with Metal-Semiconductor Nanodiodes

A continuous flow of hot electrons that are not at thermal equilibrium with the surrounding metal atoms is generated by the absorption of photons. Here we show that hot electron flow generated on a gold thin film by photon absorption (or internal photoemission) is amplified by localized surface plasmon resonance. This was achieved by direct measurement of photocurrent on a chemically modified gold thin film of metal-semiconductor (TiO(2)) Schottky diodes. The short-circuit photocurrent obtained with low-energy photons is consistent with Fowlers law, confirming the presence of hot electron flows. The morphology of the metal thin film was modified to a connected gold island structure after heating such that it exhibits surface plasmon. Photocurrent and optical measurements on the connected island structures revealed the presence of a localized surface plasmon at 550 ± 20 nm. The results indicate an intrinsic correlation between the hot electron flow generated by internal photoemission and localized surface plasmon resonance.

Ultrathin titania coating for high-temperature stable SiO2/Pt nanocatalysts

The facile synthesis of silica supported platinum nanoparticles with ultrathin titania coating to enhance metal-support interactions suitable for high temperature reactions is reported, as thermal and structure stability of metal nanoparticles is important for catalytic reactions.

Effect of the metal-support interaction on the activity and selectivity of methanol oxidation over Au supported on mesoporous oxides

To elucidate the factors affecting the catalytic properties of supported Au catalysts on the metal oxide support we investigated Au NPs deposited on crystallized mesoporous transition-metal oxides (m-oxides: Co3O4, NiO, and α-Fe2O3) prepared using the nanocasting method. The metal-oxide interaction in Au/mesoporous oxides resulted in higher catalytic activity for converting methanol to CO2 as a full oxidation product than pure m-oxides. Au/m-Fe2O3 exhibited high activity and low selectivity for methyl formate as a partial oxidative coupling product. We correlate the change in activity and selectivity with the interface between the Au and m-oxides.

Pt/oxide nanocatalysts synthesized via the ultrasonic spray pyrolysis process: engineering metal–oxide interfaces for enhanced catalytic activity

We show that Pt nanoparticles synthesized on oxide nanocatalysts exhibit catalytic activity enhancement depending on the type of the oxide support. To synthesize the Pt/oxide nanocatalysts, we employed a versatile synthesis method using Pt nanoparticles (NPs) supported on various metal oxides (i.e., SiO2, CeO2, Al2O3, and FeAl2O4) utilizing ultrasonic spray pyrolysis. Catalytic CO oxidation was carried out on these catalysts, and it was found that the catalytic activity of the Pt NPs varied depending on the supporting oxide. While Pt/CeO2 exhibited the highest metal dispersion and active surface area, Pt/FeAl2O4 exhibited the lowest active surface area. Among the Pt/oxide nanocatalysts, Pt NPs supported on CeO2 showed the highest catalytic activity. We ascribe the enhancement in turnover frequency of the Pt/CeO2 nanocatalysts to strong metal–support interactions due to charge transport between the metal catalysts and the oxide support. Such Pt/oxide nanocatalysts synthesized via spray pyrolysis offer potential possibilities for large-scale synthesis of tailored catalytic systems for technologically relevant applications.