In Situ Construction of a MgSn(OH)6 Perovskite/SnO2 Type-II Heterojunction: A Highly Efficient Photocatalyst towards Photodegradation of Tetracycline.

Yuanyuan Li,Qimei Yang,Bin Zhang,Yue Diao,Xiaofang Tian,Dingfeng Yang,Yaoqiong Wang

doi:10.3390/nano10010053

Abstract

Using solar energy to remove antibiotics from aqueous environments via photocatalysis is highly desirable. In this work, a novel type-II heterojunction photocatalyst, MgSn(OH)6/SnO2, was successfully prepared via a facile one-pot in situ hydrothermal method at 220 °C for 24 h. The obtained heterojunctions were characterized via powder X-ray diffraction, Fourier-transform infrared spectroscopy, transmission electron microscopy, and ultraviolet-visible diffuse reflectance spectroscopy. The photocatalytic performance was evaluated for photodegradation of tetracycline solution under ultraviolet irradiation. The initial concentration of tetracycline solution was set to be 20 mg/L. The prepared heterojunctions exhibited superior photocatalytic activity compared with the parent MgSn(OH)6 and SnO2 compounds. Among them, the obtained MgSn(OH)6/SnO2 heterojunction with MgCl2·6H2O:SnCl4·5H2O = 4:5.2 (mmol) displayed the highest photocatalytic performance and the photodegradation efficiency conversion of 91% could be reached after 60 min under ultraviolet irradiation. The prepared heterojunction maintained its performance after four successive cycles of use. Active species trapping experiments demonstrated that holes were the dominant active species. Hydroxyl radicals and superoxide ions had minor effects on the photocatalytic oxidation of tetracycline. Photoelectrochemical measurements were used to investigate the photocatalytic mechanism. The enhancement of photocatalytic activity could be assigned to the formation of a type-II junction photocatalytic system, which was beneficial for efficient transfer and separation of photogenerated electrons and holes. This research provides an in situ growth strategy for the design of highly efficient photocatalysts for environmental restoration.

Highlights

Pharmaceutical residues in wastewater are a severe threat to the ecological environment
Photocatalysts synthesized from SnO2, MgSn(OH)6, and the MSOH-SO heterojunction were characterized by Powder X-ray diffraction (PXRD) (Figure 1)
On the basis of the PXRD and Fourier transform infrared (FT-IR) observations, we concluded that both SnO2 and MgSn(OH)6 existed in the heterojunctions

Summary

Introduction

Pharmaceutical residues in wastewater are a severe threat to the ecological environment. Misuse and overuse of antibiotics can lead to high antibiotic resistance and multi-resistant strains of microorganisms [1,2,3,4]. As a broad-spectrum antibiotic, tetracycline (TC) is widely used for disease treatment in humans, and it is frequently detected in various bodies of water owing to its high solubility. Removal of TC from wastewater is important. Semiconductor-based photocatalysis, an advanced oxidation method, is the most promising technique for harvesting solar energy to alleviate environmental problems [5,6]. The discovery and design of photocatalysts that are stable, efficient, inexpensive, and ecofriendly is of importance [7,8]. Among the numerous photocatalytic materials, perovskite-based materials have excellent stability, crystalline structures with high symmetry, and diverse chemical and physical properties [9,10]

Methods

Results

Conclusion