Photocatalytic and thermoelectric properties of hollow titanium oxynitride nanoparticle

다국어 초록 (Multilingual Abstract)

Environmental problems due to the improvement of science and technologies have become major concern. Photocatalysis is one of the solutions for these problems. Photocatalytic reaction removes harmful substances, like organic compounds or nearby bacteria, by oxidation and reduction. Among the photocatalytic materials, TiO2 is a promising material but photocatalytic reactions rarely occur in the visible range due to a wide band gap.
In this thesis, hollow rock-salt titanium oxynitride nanoparticles were synthesized by a simple reduction process for the first time. To confirm the structural properties, XRD, XPS, TEM and neutron scattering were conducted. The mechanism for formation of hollow structures is presented. Compared to P25 (TiO2), titanium oxynitride nanoparticles exhibit improvement of photocatalytic performance in visible light.
Hollow rock-salt titanium oxynitride nanoparticles were fabricated by reduction under NH3/N2 flow at 800 oC. A hollow structure was generated by direct reduction. During the reduction, oxygen vacancies were generated and then diffused and merged inside particles. The titanium oxynitride nanoparticles had a rock-salt structure which is observed above a transition temperature of 1250 oC. Incorporation of N was related to the structural properties and stability. The composition of particles was metal deficient Ti0.7O0.7N0.3.
Photocatalytic reaction of titanium oynitride and P25 were characterized by photodegradation of MB and phenol. Hollow TiO1-xNx particles were composed 90% of MB but P25 was composed of 45% of MB in the UV-visible range. That is because the band gap of the hollow TiO1-xNx particles was decreased by N incorporation. Furthermore, after the photodegradation experiment, TiO1-xNx particles preserved their structure. Therefore, hollow rock-salt TiO1-xNx particles are a new promising photocatalyst.