Hyeong Jin Yun

Preparation and characterization of Fe-doped TiO2 nanoparticles as a support for a high performance CO oxidation catalyst

A simple method is described for the preparation of Fe-doped TiO2 nanoparticles (Ti1−xFexO2) that can be used as a high performance support material for a CO oxidation catalyst. The method allows one to fabricate Ti1−xFexO2 with uniform sizes and shapes. Microstructural studies using XRD, Raman spectroscopy and EPR analyses indicate that the Fe dopant is substitutionally incorporated by replacing Ti4+ cations. Electrochemical results indicate that, when a small amount of Fe molecules (less than 8 atomic%) are incorporated into a TiO2 structure, the support material has greatly improved redox characteristics. This suggests that an Fe-doped TiO2 support enhances both the release and uptake of oxygen atoms from the catalysts, thus resulting in a high catalytic activity in CO oxidation reactions. The results confirmed that a Au catalyst supported on Fe-doped TiO2 containing a 6 atom% Fe dopant showed an outstanding oxidation performance. The findings reported herein represent an innovative route to designing high performance catalysts for oxidation reactions.

Mesoporous Siliconiobium Phosphate as a Pure Brønsted Acid Catalyst with Excellent Performance for the Dehydration of Glycerol to Acrolein

The development of solid acid catalysts that contain a high density of Brønsted acid sites with suitable acidity, as well as a long lifetime, is one of great challenges for the efficient dehydration of glycerol to acrolein. Herein, we report on a mesoporous siliconiobium phosphate (NbPSi-0.5) composite, which is a promising solid Brønsted acid that is a potential candidate for such a high-performance catalyst. A variety of characterization results confirm that NbPSi-0.5 contains nearly pure Brønsted acid sites and has well-defined large mesopores. In addition, NbPSi-0.5 contains a similar amount of acid sites and exhibits weaker acidity than that of the highly acidic niobium phosphate and HZSM-5 zeolite. NbPSi-0.5 is quite stable and has a high activity for the dehydration of glycerol. The stability of NbPSi-0.5 is about three times higher than that of the reported catalyst. The significantly enhanced catalytic performance of NbPSi-0.5 can be attributed to 1) nearly pure Brønsted acidity, which suppresses side reactions that lead to coke formation; 2) a significant reduction of pore blocking due to the mesopores; and 3) a decrease in the amount and oxidation temperature of coke.

Tuning the oxidation states of nanostructured amorphous Mn oxides for electrochemical applications

A simple precipitation method is proposed in order to maximize the electrochemical performance of nanostructured amorphous Mn oxide via the tuning of the oxidation states using various n-alcohol solvents with different lengths of alkyl chain.