Hydrothermal etching fabrication of TiO2@graphene hollow structures: mutually independent exposed {001} and {101} facets nanocrystals and its synergistic photocaltalytic effects.

Hui Liu,Tingting Liu,Shuang Liu,Xiaonan Dong,Zhiling Zhang

doi:10.1038/srep33839

Abstract

Highly exposed facets TiO2 attracts enormous attention due to its excellent separation effect of photogenerated electron-hole pairs and induced high performance of photocatalytic activity. Herein, a novel hydrothermal etching reaction was used to synthesize graphene-wrapped TiO2 hollow core-shell structures. Different with the reported co-exposed facets TiO2 single crystal nanoparticles, the present TiO2 core layer is composed by the mutually independent exposed {001} and {101} facets nanocrystals. Combined with the reduced graphene oxide shell layer, this graphene-wrapped TiO2 hollow core-shell structures formed a Z-scheme photocatalytic system, which possess simultaneously the high charge-separation efficiency and strong redox ability. Additionally, the as-prepared samples show a higher absorption property for organic molecules and visible light due to the presence of graphene. All of these unique properties ensure the excellent photocatalytic activity for the graphene-wrapped TiO2 hollow structures in the synergistic photo-oxidation of organic molecules and photo-reduced of Cr(VI) process. The TiO2 core composed with mutually independent exposed {001} and {101} facets nanocrystals is propose to play an important role in the fabrication of this Z-scheme photocatalytic system. Fabrication of Z-scheme photocatalytic system based on this unique exposed facets TiO2 nanocrystals will provides a new insight into the design and fabrication of advanced photocatalytic materials.

Highlights

Exposed facets TiO2 attracts enormous attention due to its excellent separation effect of photogenerated electron-hole pairs and induced high performance of photocatalytic activity
The synthesis steps for graphene-wrapped anatase TiO2 hollow core-shell microspheres are mainly as follows: firstly, the surface of amorphous TiO2 microspheres was directly wrapped with graphene oxide (GO) nanosheets via a chemical bonding reaction, which involved with dehydration condensation between TiO2 and GO without any modified agents[18], followed by a one-step GO reduction and TiO2 crystallization process via hydrothermal etching treatment in a HCl solution (Fig. 1a)
Different from that of the pure TiO2 microspheres, we found that the surface of the sample TiO2@GO core/shell microspheres present a wrinkle-like morphology (Fig. 1c) after GO wrapped process, which confirms that graphene oxide sheets have combined with the TiO2 microspheres

Summary

Introduction

Exposed facets TiO2 attracts enormous attention due to its excellent separation effect of photogenerated electron-hole pairs and induced high performance of photocatalytic activity. The photocatalytic activity of the as-prepared graphene-wrapped TiO2 hollow core-shell structures were evaluated for synergistic removal effect of organic molecules and Cr(VI) co-exist system in aqueous solution under simulated solar light irradiation, and the possible photocatalytic mechanism of this photocatalyst was briefly discussed.

Results

Conclusion