Preparation and characterization of nitrogen-doped highly ordered titanium dioxide nanotubes (N-doped-HOTN): How far it will improve toward the visible light response and why?

• Main Authors: Pangestuti, A. D., Gunlazuardi, J.
• Format: Conference Proceeding
• Language: English
• Subjects: Anatase; Band gap; Crystal structure; Crystallinity; Earth surface; Electrochemical oxidation; Electronic structure; Energy gap; Ethylene glycol; Fourier transforms; Light; Morphology; Nanotubes; Nitrogen; Phase transitions; Photoelectric effect; Photoelectric emission; Plates (structural members); Solar energy conversion; Titanium; Titanium dioxide; Ultraviolet radiation
• ISSN: 0094-243X; 1551-7616
• DOI: 10.1063/1.5064106

Titanium dioxide (TiO2), a semiconductor having a band gap of 3.0 - 3.2 eV, can be an active photo anode under UV light (wave length < 410 nm). Since that light region only presents in a small fraction of the solar light reached the earth surface, the TiO2, as it is, is less useful for solar energy conversion. Abundant efforts have been conducting by researcher to improve its activity toward solar light. The improvement of its morphology, to obtain a high surface area, and its electronic structure, to shorten the band gap have been a main task reported, regularly. Recently, our group developed a simple way to prepare the highly ordered TiO2 nanotubes (HOTN), by the mean of anodization process, followed by calcinations. In the course of the development, we find another possible easy way to dope nitrogen during the anodization and calcinations processes. The HOTN was prepared by electrochemical oxidation (at certain voltage) of Ti plate in an electrolyte containing ethylene glycol, NH4F, urea, and water, to obtain amorphous HOTN. The fresh HOTN was then calcinated at certain condition (typically 4500C) for a phase transition and nitrogen incorporation (replacing some of oxygen in the anatase phase). The obtained crystalline phase of HOTN film was then characterized by the mean of spectroscopic (UV-DRS, FTIR, XRD, SEM) and photoelectrochemical methods. The results revealed that by the mentioned process a HOTN film having a band gap as low as 2.9 eV can be obtained, designed as N doped HOTN. The nitrogen doped HOTN showed a characteristic of IR peak related to –Ti-N- and –Ti-O-N as well, indicating mixture nitrogen doped which lead to shorten the band gap and the one is not. So far, the anatase crystalline phase was not disturbed by the presence of nitrogen. The obtained nitrogen doped HOTN showed a higher photocurrent under visible light compared to those of bare HOTN.