Dr. Hyoyoung Lee, Professor, Department of Energy Science, Sungkyunkwan University, Korea.

Speech Title: Low energy bandgap semiconducting materials for energy and environmental

Abstract: Here, we demonstrate a selective reduction of only rutile phase TiO₂ from commercialized Degussa P-25 TiO₂ nanoparticles to give new blue-TiO₂ by using simple solution processing under room-temperature and atmosphere, which maintains an ordered white-anatase and disordered black-rutile TiO₂ (crystalline anatase/amorphous rutile TiO₂ (rTiO₂, call blue-TiO₂)). The strong reducing agent in superbase, which consists of lithium in ethylenediamine (Li-EDA), can disorder only the white-rutile phase of P-25. The resulting amorphous rutile TiO₂ surface has a super-hydrophilic property and also very stable even at oxygen atmosphere. Our newly developed rTiO₂ that has low energy bandgap can effectively generate reactive oxygen species (ROS) under solar light, which can generate hydrogen/oxygen gas from water (called water splitting) and successfully remove a bloom of algae. In addition, the super-hydrophilic blue TiO₂ materials can decompose particulate matters and remove the bacterial, which is now applying for industry applications.

In addition, we like to report new layered ternary transition metal chalcogenides (TTMCs) material to overcome to the limitation of active sites which is challenging in binary transition metal chalcogenides (BTMC) such as MoS₂ towards electrochemical hydrogen production. The TTMC, Cu₂MoS₄ has been successfully synthesized by a facile solution-processed method. Moreover, by anion doping such as Se in as the synthesized Cu₂MoS₄, it has been found that TTMC can be exfoliated into single layer nanosheets and the single layered TTMC exhibits the highest electrocatalytic activity towards hydrogen evolution reaction.