Markedly Enhanced Surface Hydroxyl Groups of TiO₂ Nanoparticles with Superior Water-Dispersibility for Photocatalysis.

Chung-Yi Wu,Jin-Pei Deng,Chien-Hou Wu,Yu-Shiu Lo,Kuan-Ju Tu

doi:10.3390/ma10050566

Chung-Yi Wu, Jin-Pei Deng + Show 3 more

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https://doi.org/10.3390/ma10050566

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Abstract

The benefits of increasing the number of surface hydroxyls on TiO2 nanoparticles (NPs) are known for environmental and energy applications; however, the roles of the hydroxyl groups have not been characterized and distinguished. Herein, TiO2 NPs with abundant surface hydroxyl groups were prepared using commercial titanium dioxide (ST-01) powder pretreated with alkaline hydrogen peroxide. Through this simple treatment, the pure anatase phase was retained with an average crystallite size of 5 nm and the surface hydroxyl group density was enhanced to 12.0 OH/nm2, estimated by thermogravimetric analysis, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. Especially, this treatment increased the amounts of terminal hydroxyls five- to six-fold, which could raise the isoelectric point and the positive charges on the TiO2 surface in water. The photocatalytic efficiency of the obtained TiO2 NPs was investigated by the photodegradation of sulforhodamine B under visible light irradiation as a function of TiO2 content, pH of solution, and initial dye concentration. The high surface hydroxyl group density of TiO2 NPs can not only enhance water-dispersibility but also promote dye sensitization by generating more hydroxyl radicals.

Highlights

Nano-sized titania has emerged as one of the most fascinating materials in the fields of environmental remediation and energy conversion [1,2]
Several investigations have demonstrated that the additional hydroxyl groups on the TiO2 surface can improve the adsorption capacity, the formation of mesoporous structure, and the catalytic efficiency [9,10,11]
We have shown that alkaline hydrogen peroxide (AHP) treatment is a simple and green way to improve the

Summary

Introduction

Nano-sized titania has emerged as one of the most fascinating materials in the fields of environmental remediation and energy conversion [1,2]. Several investigations have demonstrated that the additional hydroxyl groups on the TiO2 surface can improve the adsorption capacity, the formation of mesoporous structure, and the catalytic efficiency [9,10,11]. Most preparation methods for TiO2 with increased surface hydroxyl groups have complicated surface modification and are based on a sol-gel process from a precursor in special reaction conditions [12,13,14,15,16,17,18]. Each modification method may cause a more complex system, which is difficult to be generalized and each sol-gel process usually causes inconsistent results, which can hardly be used for industrial production

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