Mechano-synthesized orange TiO2 shows significant photocatalysis under visible light

Ken-Ichi Saitow,Yufeng Wang,Shintaro Takahashi

doi:10.1038/s41598-018-33772-6

Abstract

Nitrogen and carbon co-doped TiO2 particles with a brilliant yellow-orange color were produced mechanochemically by high-energy ball milling as one-pot synthesis. This facile synthesis required only grinding TiO2 with melamine at room temperature. Using monochoromatic lights with the same intensity in visible and UV, the photocatalytic activity of the TiO2 particles was accurately evaluated with respect to the degradation of an aqueous dye (methylene blue) solution. The activities under visible light (450 and 500 nm) were, respectively, 4 and 2 times higher than that of the unmilled TiO2 under UV light (377 nm), corresponding to 9 and 5 times higher than the UV under the solar light condition. The properties and structure of the co-doped TiO2 particles before and after milling were analyzed using eight experimental methods. As a result, it was found that the nitrogen replaced as an oxygen site in milled TiO2 has the highest concertation (2.3%) in the past studies and the structure of milled TiO2 is composed of a polymorphism of four different solid phases of TiO2, gives significant higher photocatalytic activity at visible light than that of UV light. A good repeatability of the photocatalyst was investigated by the number of cycles for the decomposition reaction of the aquesous dye solution.

Highlights

Titanium dioxide (TiO2) is the most popular photocatalyst and is used for self-cleaning and self-sterilization applications, water and air purification, and as a water-splitting catalyst[1,2]
There have been only a few systems that exhibit higher activity under visible light than that under UV light, such as N-doped TiO2 prepared by sputtering with N2 gas[15], S-doped TiO2 prepared by annealing TiS216 and Ag-TiO2 prepared by sol-gel and calcination processes[17]
As a sample preparation method, ball milling has attracted considerable attention as a physical synthesis method because a large number of particles can be obtained by grinding solid materials in a milling vessel with milling balls, i.e., one-pot facile synthesis at room temperature[25]

Summary

Introduction

Titanium dioxide (TiO2) is the most popular photocatalyst and is used for self-cleaning and self-sterilization applications, water and air purification, and as a water-splitting catalyst[1,2]. Nitrogen (N) and carbon (C) co-doped TiO2 particles were synthesized by high-energy ball milling as one-pot synthesis at room temperature.

Results

Conclusion