Carrier Transfer and Capture Kinetics of the TiO2/Ag2V4O11 Photocatalyst.

Yun Zhou,Lixin Liu,Yuan Wang,Bing Wang,Xiaoping Ouyang,Junyu Li,Qiujie Ding

doi:10.3390/nano10050828

Abstract

In this paper, TiO2/Ag2V4O11 nanoheterojunctions have been synthesized by hydrothermal methods, which show enhanced photocatalytic activity compared to TiO2 under visible light. Moreover, the TiO2/Ag2V4O11 nanoheterojunction with set molar ratio of 2:1, referred to as TA2, show the highest visible light photocatalytic activity, which could decompose about 100% RhB molecules within 80 min of irradiation with visible light. Specially, the time-resolved photoluminescence spectrum of TA2 demonstrates that the free exciton recombination occurs in approximately 1.7 ns, and the time scale for Shockley–Read–Hall recombination of photogenerated electrons and holes is prolonged to 6.84 ns. The prolonged timescale of TA2 compared to TiO2 and Ag2V4O11 can be attributed to the carrier separation between nanojunctions and the carrier capture by interfacial defects. Furthermore, the enhanced photocatalytic activity of TiO2/Ag2V4O11 nanoheterojunctions also benefits from the synergistic effect of the broadened absorption region, higher photocarrier generation, longer carrier lifetime, and quicker collection dynamics.

Highlights

As is known, photocatalysis technology is considered as the most promising way to solve energy shortage and environmental pollution issues [1,2]
TiO2/Ag2V4O11 nanoheterojunctions are constructed in the paper to promote the separation of photogenerated carriers and reduce the carrier recombination
The XPS results reveal the co-existence of the Ag and Ag+ in the sample; these are entirely consistent with the XRD results

Summary

Introduction

Photocatalysis technology is considered as the most promising way to solve energy shortage and environmental pollution issues [1,2]. Appropriate heterojunctions are important structures for effectively promoting the separation of photogenerated electron–hole pairs [5,6,7]. The photogenerated electrons and holes can transfer in separate directions across the heterojunction boundary owing to the energy ladder between the band structure. It is confirmed that constructing a nanoheterostucture can effectively broaden the visible light absorption ability, inhibit the photogenerated carrier recombination, and enhance the photocatalytic activity. Ag2V4O11 is an ideal choice for constructing an effective nanoheterostructure with TiO2 to improve the photocatalytic activity under visible light. TiO2/Ag2V4O11 nanoheterojunctions are constructed in the paper to promote the separation of photogenerated carriers and reduce the carrier recombination. In competition to the transfer and separation, photogenerated electrons and holes may quench by a direct band-to-band transition or Shockley–Read–Hall (SRH) recombination in the heterostructure. Tracking the transportation and quenching kinetics of photogenerated carriers in heterojunctions is a critical are of research that must be investigated in depth

Methods

Results

Conclusion