Hyoyoung Lee
Sungkyunkwan University
South Korea
Title: Crystalline/amorphous low energy bandgap TiO2 materials prepared in solution and their industrial applications
Biography
Biography: Hyoyoung Lee
Abstract
Recently, surface-disordered TiO2, referred to as black TiO2, which can absorb both visible and near-infrared solar light that has triggered an explosion of interest in many important applications. Here, we demonstrate a selective reduction of commercialized degussa P-25 TiO2 nanoparticles using simple room-temperature solution processing, which maintains the unique three-phase interfaces composed of ordered white-anatase and disordered black-rutile with open structures for easy electrolyte access. The strong reducing agent in superbase, which consists of lithium ion ethylenediamine (Li-EDA), can disorder only the white-rutile phase of P-25. Single P-25 TiO2 nanoparticles with this engineered surface made immediate contact with the electrolyte. This contact is called white-black-electrolyte three-phase interfaces and can not only efficiently internally separate electrons/holes through type-II bandgap alignment but also induce a strong hydrogen (H2) evolution surface reaction. The white-black-electrolyte three-phase interfaces exhibited outstanding H2 production rates of 13.89 mmol/h/g using 0.5 wt.% Pt (co-catalyst) and 3.46 mmol/h/g without using any co-catalyst. These values are the highest recorded in the world to date. In addition, our newly developed crystalline/amorphous reduced TiO2 (rTiO2) that has low energy bandgap can effectively generate reactive oxygen species (ROS) under solar light and successfully remove a bloom of algae. Only reduced TiO2 materials can generate ROS under solar light, which was confirmed by electron spin resonance. Among the three different types of Li-EDA treated TiO2 (anatase, rutile and both phased TiO2), the both phased rTiO2 showed the best performance to produce ROS. The generated ROS effectively removed the common green algae Chlamydomonas. This is the first report on algae degradation under solar light, proving the feasibility of commercially available products for disinfection. Finally, we like to introduce transition metal chalcogenide materials for the hydrogen evolution reaction and energy storage with grapheme flakes.