{0 0 1}-Facet-Exposed Ag4V2O7 Nanoplates: Additive-Free Hydrothermal Synthesis and Enhanced Photocatalytic Activity

Nguyen Duc Van,Ngo Thi Hong Le

doi:10.1155/2018/8462764

Abstract

The synthesis of silver pyrovanadate, Ag4V2O7, nanoplates with exposed {0 0 1}-facets by a facile, additive-free hydrothermal method was described in this paper. The photocatalytic activity of rhodamine B over Ag4V2O7 samples under solar light irradiation was also evaluated. By using an equimolar mixture of NH4VO3 and AgNO3 with the presence of a suitable amount of ammonia, Ag4V2O7 nanoplates were obtained readily and purely at temperatures from 100 to 140°C for 4 h. In particular, the c-axis orientation growth of Ag4V2O7 nanoplates occurred and increased monotonously with temperatures in the range of over 100 up to 140°C. Further increase in hydrothermal temperature up to 220°C, the Ag4V2O7 phase no longer existed and the β-AgVO3 phase was formed instead. The photocatalytic activity of the optimized Ag4V2O7 sample comprising {0 0 1}-facet-exposed nanoplates with the highest degree of orientation was significantly higher than that of the random-oriented sample. The effects of using ammonia as a complexing agent on the structure, microstructure, texture, exposed facet, and photocatalytic activity of Ag4V2O7 samples were also investigated for the first time.

Highlights

Novel ternary oxide-based photocatalysts including silver vanadates as alternatives to traditional TiO2 have been recently attracted a lot of attention in both basic research and applications [1,2,3,4]
Current research activities focus on enhancing their photocatalytic performances via morphological controlling, crystal facet engineering, and reducing band gap by elemental doping separately or simultaneously [5,6,7,8,9]
By applying crystal facet engineering, in another approach, the surface energy of textured grains of obtained photocatalytic samples with certain exposed facet is higher than that of randomoriented ones [10,11,12]. This originated from the fact that the photocatalytic reactivity and efficiency of a photocatalyst are strongly affected by their surface energy and chemisorption properties

Summary

Introduction

Novel ternary oxide-based photocatalysts including silver vanadates as alternatives to traditional TiO2 have been recently attracted a lot of attention in both basic research and applications [1,2,3,4] For these photocatalytic systems, current research activities focus on enhancing their photocatalytic performances via morphological controlling, crystal facet engineering, and reducing band gap by elemental doping separately or simultaneously [5,6,7,8,9]. Comparing to the case of randomly oriented samples, the photocatalytic process is more accelerated with these textured grains because the adsorption-desorption rates of available species existed on the surface become faster Due to their thermodynamic instability with higher surface energy, these highly reactive facets tend to be eliminated during the crystal growth process [13].

Methods

Results

Conclusion