Short communicationFabrication of 3D CeVO4/graphene aerogels with efficient visible-light photocatalytic activity
Introduction
Nowadays, the growing population and industrial development have caused more and more serious underground and surface water pollution. For instance, dyes are often discharged with wastewater into the local environment without adequate treatment. Photocatalysis has been considered as an effective way to remove different pollutants in wastewater in the field of environmental remediation [1]. The preparation of highly efficient photocatalysts by combining advanced semiconductor materials and photocatalysis technology offers a green and energy saving technology for the degradation of harmful pollutants [2], [3]. Cerium vanadate (CeVO4), a wide (3.1–4.2 eV) band gap semiconductor, is of much interest due to its useful electronic and catalytic properties for applications in electrochromic materials and gas sensors [4]. However, the fast charge recombination at surfaces of CeVO4 leads to practical limitations [5].
The effective charge separation can be achieved by the construction of composite photocatalytic systems via loading the co-catalyst or a matrix into the semiconductor [6]. Graphene is an ideal material for forming photocatalytic nanocomposites, due to its fascinating properties such as large surface area, high electrical conductivity, stability and tunable surface properties [7]. Graphene acts as a substrate for the formation of composite materials on its surface, as well as an electrically conductive channel for the fast electron transfer to prevent the recombination [8], [9], [10]. However, graphene nanocomposites are difficult to separate and reclaim in the process of photocatalytic reaction, leading to the impossibility of industrialization [11]. Recent studies have shown that three-dimensional (3D) hybrid structures that are composed of semiconductor photocatalysts and chemically crosslinked graphene may be optimal candidates for removal of water pollutants due to 3D composites can be easily recovered [12]. This 3D structure has (i) effective adsorption afforded by a large surface area and strong interactions between the graphene and dye molecules and (ii) enhanced photocatalytic activity resulting from effective charge transfer from semiconductor photocatalysts to graphene network [12], [13], [14]. Thus, it is highly desirable to design and fabricate novel and well-defined 3D graphene-based composites for applications in water treatment and purification.
In this paper, we demonstrate a simple approach for synthesis of 3D self-assembled CeVO4/graphene composite aerogels. The formation mechanism for the 3D aerogels is proposed and the photocatalytic properties of CeVO4/graphene aerogels are investigated.
Section snippets
Preparation of CeVO4 powders
The raw materials (Ce(NO3)3·8H2O and NH4VO3) were analytical-grade reagents and purchased from Shanghai Chemical Reagent Corp. Firstly, appropriate amount of Ce(NO3)3·8H2O and NH4VO3 were dissolved with 50 mL deionized water, respectively. Then, the Ce3+ solution was added to the NH4VO3 solution under stirring, and yellow precipitation appeared. After substantial stirring, the slurry was transferred into a 200 mL sealed Teflon autoclave. The autoclave was kept at 180 °C for 15 h, and then cooled to
Results and discussion
Fabrication of 3D CeVO4/graphene hydrogels is illustrated schematically in Fig. 1. Firstly, CeVO4 particles were added to GO solution. When the reaction started, graphene sheets loading with CeVO4 particles self-assembled into a three-dimensional hydrogel. The resultant hydrogel exhibited negligible volume shrinkage in contrast with the initial GO solution. Water was removed from the CeVO4/graphene hydrogel after freeze-drying; finally, a dried and porous CeVO4/graphene aerogel was obtained.
Conclusions
In summary, 3D CeVO4/graphene composite hydrogels and aerogels were successfully prepared through a simple low-temperature method. In the 3D architecture, CeVO4 particles were anchored uniformly on the flexible graphene sheets, forming a porous network framework. CeVO4/graphene aerogel showed enhanced MB removal efficiency relative to that of CeVO4 particles due to the enhanced light absorption and effective charge transfer from CeVO4 to graphene sheets. Furthermore, the structure and
Acknowledgments
This work was financially supported by the National Natural Science Foundation of China (No. 51202093, 51302111 and 51272093), Natural Science Foundation of Jiangsu Province (No. BK20130523), Jiangsu University Development Foundation for Talents (No. 11JDG025), Jiangsu University Postdoctoral Science Foundation (No.1143002079), Jiangsu Province Postdoctoral Science Foundation (No.1101035C), China Postdoctoral Science Foundation (No. 20110491356).
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