A study of titanium oxynitride system for photocatalytic self-cleaning applications

Abstract

A study of titanium oxynitride system for self-cleaning applications was conducted. TiO2 has been studied extensively for its photocatalytic effects. N-doped TiO2 has significantly better photocatalytic activity over TiO2 under visible light. In this project, we explored ways of developing photocatalyst using TiN as the base material. Thin films and powders of TiN were oxidized at various temperatures followed by methylene blue tests to observe their photocatalytic performance. Furthermore, their crystallographic properties were studied through X-Ray Diffraction (XRD) analysis. Field-Emission Scanning Electron Microscope (FE-SEM) was used to observe the surface morphology. Lastly, their stoichiometry and surface chemical properties were analyzed by X-Ray Photoelectron Spectroscopy (XPS) while the bulk chemical properties were analyzed through SEM equipped with Energy-Dispersive X-ray (EDX). All these studies helped us to find out the optimum annealing temperature and atomic fractions of titanium, nitride and oxygen in the system. To improve the photocatalytic performance of titanium oxynitride system and make it more stable, a mill-down process of titanium powder as received was carried out. Overall, oxidized titanium nitride powder showed better photocatalytic performance than P25 under visible light while the photocatalytic reaction rate for annealed TiN sputtered thin films was very slow. The optimum annealing temperature for as bought TiN powders was found to be 350°C with a Ti : N : O atomic percent ratio of 35.1 : 3.86 : 61.0.