Feasibility of Hydrothermal Nitrogen Doping Process for Enhancing Visible Light Photocatalytic Activity of Metatitanic Acid Powder

Abstract

Wide band-gap photocatalyst is active only under UV light irradiation. Nitrogen doping into photocatalyst is able to extend the light absorption to the visible light region, allowing more solar energy to be utilized in photocatalytic applications. The hydrothermal process is widely applied for the preparation of nitrogen-doped TiO2. The hydrothermal method is attractive for its simplicity and environment friendly conditions. Metatitanic acid (MTA) is an industrially available intermediate product in sulfate process for TiO2production, which is mesoporous material with large specific surface area and pore volume. In this work, MTA powder was hydrothermally treated with three types of nitrogen sources (urea, hexamethylenetetramine, and ammonium hydroxide) and subsequently heat-treated in N2flow. The results of UV-Vis diffuse reflection spectra and XPS show that it is possible to dope the nitrogen dopant into MTA by the hydrothermal process and the post-heat treatment. Higher photocatalytic activity in photodegrading rhodamine B dye under visible light was obtained when processed in ammonium hydroxide (MTA-A), but weaker in the samples of urea (MTA-U) and hexamethylenetetramine (MTA-H).