Enhancement of Visible-Light Photocatalytic Efficiency of TiO2 Nanopowder by Anatase/Rutile Dual Phase Formation

Yi-Jia Chen,Tse-Shan Lin

doi:10.3390/app10186353

Yi-Jia Chen, Tse-Shan Lin

Open Access

https://doi.org/10.3390/app10186353

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Journal: Applied Sciences	Publication Date: Sep 12, 2020
Citations: 5	License type: CC BY 4.0

Affiliation: National Dong Hwa University

Abstract

Visible-light photocatalytically active titanium oxide (TiO2) nano-powder was synthesized by a flat-flame chemical vapor condensation method. The formation of TiO2 consisting of different ratios of anatase and rutile phases was controlled by two parameters: the acetylene flow rate (C2H2, 600 sccm and 800 sccm) and the acetylene/oxygen flow ratio (C2H2/O2, 1:3, 1:4, 1:5, and 1:6). The location of the photonic center was identified for visible-light absorption, which is in the anatase grains. The photonic center on the surface of anatase grains happens to be the nucleation site for rutile in an oxygen-deficient environment. The visible-light absorption could be attributed to the formation of defect levels related to the photonic center within the band gap of anatase. The major role of the mixed-phase structure of TiO2 in the enhancement of visible-light photocatalytic activity is in the enhancement of carrier separation and not of light harvest, for the powder produced in this study.

Highlights

Titanium dioxide has long been considered an excellent photocatalyst in many aspects
Pure anatase is inhibited for use under visible light by its wide bandgap of 3.2 eV, since it can only absorb the bandgap equivalent
The main rutile peaks appearing in spectra for samples from C2 H2 800 sccm, C2 H2 /O2 = 1:4 through C2 H2 800 sccm, C2 H2 /O2 = 1:6 have the same characteristics in terms of narrow rutile peak shape at 27.5◦

Summary

Introduction

Titanium dioxide has long been considered an excellent photocatalyst in many aspects. It has many advantages, such as insolubility in acid and alkali, nonoccurrence of light corrosion under sunlight, chemical stability, non-toxicity for humans, and the abundance of its elements in the Earth’s crust [1]. When TiO2 absorbs photons from the light, it generates electron–hole pairs [2,3,4]. Anatase is thought to be the best photocatalyst, among others [7,8]. Pure anatase is inhibited for use under visible light by its wide bandgap of 3.2 eV, since it can only absorb the bandgap equivalent

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