Sung Hyeon Baeck

A catalytic and efficient route for reduction of graphene oxide by hydrogen spillover

In this paper, an efficient catalytic route for the reduction of graphene oxide (GO) is described using hydrogen spillovered platinum (Pt) nanoparticles at room temperature. Pt nanoparticles were decorated on GO sheets using a hydrogen reduction of chloroplatinic acid. The Pt nanoparticles served as a catalyst for the process of hydrogen disassociation to atomic hydrogen, which spillovered onto the GO sheets which acted as a strong reducing agent for the reduction of GO. Reduced graphene oxide (RGO) obtained in this manner has a C/O atomic ratio as high as 22, which is one of the highest values ever reported for chemically converted graphenes. The electrical conductivity was greater than 8000 S m−1. Electrochemical studies revealed that the RGO–Pt hybrid exhibits excellent electrocatalytic activity toward the methanol oxidation reaction, with high CO tolerance and long-term stability.

Effect of surface treatment of graphene nanoplatelets for improvement of thermal and electrical properties of epoxy composites

In this study, in order to improve the thermal and electrical properties of epoxy/graphene nanoplatelets (GNPs), surface modifications of GNPs are conducted using silane coupling agents. Three silane coupling agents, i.e. 2-(3,4-epoxycyclohexyl)-ethyltrimethoxysilane (ETMOS), 3-glycidoxypropyltriethoxysilane (GPTS), and 3-glycidoxypropyltrimethoxysilane (GPTMS), were used. Among theses, GPTMS exhibits the best modification performance for fabricating GNP-incorporated epoxy composites. The effect of the silanization is evaluated using transmission electron microscopy (TEM), scanning electron microscopy, thermogravimetric analysis, and energy dispersive X-ray spectroscopy. The electrical and thermal conductivities are characterized. The epoxy/silanized GNPs exhibits higher thermal and electrical properties than the epoxy/raw GNPs due to the improved dispersion state of the GNPs in the epoxy matrix. The TEM microphotographs and Turbiscan data demonstrate that the silane molecules grafted onto the GNP surface improve the GNP dispersion in the epoxy.

Synthesis of Dimethyl Carbonate from Methanol and Carbon Dioxide by Heteropolyacid/Metal Oxide Catalysts

CexTi1-xO2 and H3PW12O40/CexTi1-xO2 catalysts were prepared by sol-gel method, and they were applied to the direct synthesis of dimethyl carbonate (DMC) from methanol and carbon dioxide in a batch reactor. The reaction was carried out in an autoclave reactor at 170oC and 5 MPa. It was found that CexTi1-xO2 exhibited a higher catalytic performance than pure CeO2 and TiO2. The catalytic performance of CexTi1-xO2 was the maximum when x=0.1. It was also revealed that H3PW12O40/CexTi1-xO2 catalysts showed a remarkably enhanced catalytic performance than the corresponding CexTi1-xO2 catalysts. The amount of DMC produced by 15 wt% H3PW12O40/ Ce0.1Ti0.9O2 catalyst was six times higher than that produced by Ce0.1Ti0.9O2 catalyst. It is concluded that both Brönsted acid sites provided by H3PW12O40 and base sites in CexTi1-xO2 played an important role in improving the catalytic performance of H3PW12O40/CexTi1-xO2.

Synthesis of Au nanoparticles supported on metal oxides (H3PMo12O40 and TiO2) by PS-PVP block copolymer encapsulation method

Au supported on metal oxides (P-25, HPA) was successfully synthesized by PS-PVP block copolymer encapsulation method. The size of nanoparticles was strongly dependent on calcination conditions (time and temperature). The particle size was also controlled by selection of the appropriate length of PVP part in block copolymer. When particulate gold was doped on the surface of P-25, it strongly improved visible light absorption by plasma resonance. Compared with pure TiO2, Au supported on P-25 demonstrated much higher photocatalytic activity for acetaldehyde decomposition under visible light illumination. The enhanced photocatalytic activity could be attributed to the increase of visible light absorption and catalytic activity of nanoparticulate Au.

Influence of graphene nanoplatelets content on the structure and properties of macroporous carbon foams prepared by organic colloidal templates

Graphene nanoplatelets (GNPs)-reinforced carbon foams have been fabricated by polycondensation of resorcinol–formaldehyde resin as a carbon precursor and GNPs as a reinforcing material. The pore structure, mechanical properties, and electrical conductivity were investigated in terms of the amount of the GNPs. The results show that the amount of GNPs has a considerable influence on compressive strength, electrical conductivity, and specific capacitance. Although the amount of GNPs added does not influence the pore structure, the mechanical properties, electrical conductivity, and specific capacitance of carbon foams were improved with increasing the GNPs content. With 5xa0wt% addition of GNPs, the compressive strength, electrical conductivity, and specific capacitance increased by 75.2, 240.26, and 53.36xa0%, respectively.

Fabrication of Nanoparticles Supported on Metal Oxides by PS-PVP Block Copolymer Encapsulation Method

Nanoparticles (Au, Pt, Ru) supported on metal oxides (TiO2, Heteropoly Acid) were prepared by PS-PVP block copolymer encapsulation method. It was confirmed by XPS analysis that the oxidation state of metal is 0 after calcination, which indicates the complete removal of polymer. Synthesized catalysts were characterized by TEM, SEM-EDS, and UV-VIS spectroscopy and it was observed that synthesis and calcination conditions, and the interaction between nanoparticle and metal oxide affected significantly the particle size of metal on the surface of metal oxide. When two different metal precursors were diffused into the core of inversed micelles, nano alloy could be synthesized and the composition of nano alloy was controlled by varying the ratio between the two metal precursors.