A green and facile strategy for preparation of novel and stable Cr-doped SrTiO3/g-C3N4 hybrid nanocomposites with enhanced visible light photocatalytic activity

doi:10.1016/j.jallcom.2015.06.056

Journal of Alloys and Compounds

Volume 647, 25 October 2015, Pages 456-462

https://doi.org/10.1016/j.jallcom.2015.06.056 Get rights and content

Highlights

•
We synthesized the CrSTO/g-CN nanocomposites via a green and facile method.
•
CrSTO/g-CN nanocomposites showed an enhanced visible light photocatalytic activity than CrSTO and g-C₃N₄.
•
A possible Z-scheme charge transfer mechanism was proposed in our paper.

Abstract

Herein, a green and facile strategy to prepare graphite carbon nitride hybridized chromium doping strontium titanate spheres (CrSTO/g-CN) nanocomposites was reported in this study. The structure characterization clearly indicated that the CrSTO spheres were successfully loaded on the g-C₃N₄ nano-sheets forming the CrSTO/g-CN heterojunction. Furthermore, the measurement of photocatalytic activity revealed that the as-prepared CrSTO/g-CN hybrid nanocomposites exhibit the considerable stability and significantly enhanced photocatalytic activity for the degradation of rhodamine B under visible light irradiation. Especially the photocatalytic activity of CrSTO/g-CN-70% was almost 4.5 times higher than that of pure g-C₃N₄ and 3.5 times higher than that of pure Cr-doped SrTiO₃ respectively. The enhanced photocatalytic activity of the CrSTO/g-CN hybrid nanocomposites was due to a synergistic effect following the Z-scheme charge transfer mechanism to enhanced charge-separation ability. Therefore, the CrSTO/g-CN hybrid nanocomposites could be of potential interest for water splitting, new fuels synthesis and environmental remediation under natural sunlight.

Graphical abstract

Introduction

With the development of the global economy, energy crisis and environment problem have been increasingly apparent, so water splitting, new fuels synthesis and environmental remediation through semiconductor photocatalysts have attracted much attention [1], [2], [3], [4], [5], [6]. Titanium dioxide (TiO₂) has been considered as one of the most promising semiconductor materials in hydrogen generation since it was founded by Fujishima and Honda in 1972 [7]. However TiO₂ is limited to a great extent for it could only respond to UV-light irradiation [8], [9]. Furthermore, lots of semiconductor materials like SnO₂, ZnO, CdS have been developed in recent years [10], [11], [12], [13], [14]. It is a pity that most of them could keep active under UV-light irradiation like TiO₂[15]. As we all know, the solar spectrum only include 4–5% of the UV-light. Therefore seeking significantly efficient, stable, inexpensive, visible light photocatalyst has been a worldwide continuing endeavor.

Recently, graphite carbon nitride (g-C₃N₄) is found to be a typical metal-free visible light active semiconductor material which could respond to visible light irradiation [4], [16], [17], [18], [19]. Meanwhile, compared with many other organic semiconductor, g-C₃N₄ has high thermal and chemical stability, it can maintain the structural stability under the atmosphere of 550 °C and redox reaction [20], [21]. However g-C₃N₄ also has some deficiencies in the limited capacity of visible light absorption due to its 2.7 eV electronic band gap and the high recombination rate of the electron–hole pairs for the defects in the surface [22], which could decrease its photocatalytic efficiency. In order to overcome these drawbacks, some strategies were developed in previous studies. Such as constructing semiconductor/g-C₃N₄ nanocomposites [23], [24], [25], [26], [27], [28], [29], loading some noblemetal nanoparticles on the surface of g-C₃N₄[30], doping some elements to g-C₃N₄[31], [32], [33], and controlling morphology of g-C₃N₄[20], [34], [35].

On the other hand, strontium titanate (SrTiO₃) with perovskite structure has attracted considerable attentions in photocatalytic technology because of its interesting physical, chemical and structural properties. But, band gap of SrTiO₃ is 3.2 eV [36], [37], [38], which only induce photoinduced electron–hole pair under UV-light. Fortunately, for its special electronic structure and crystal structure, SrTiO₃ would easily adjust band edge by doping with a cation of a different valence state [39], [40], [41]. Especially, preparation of Cr-doped SrTiO₃ (CrSTO) through hydrothermal could immensely improve photocatalytic activity under visible light for the valance band could adjust to more negative and less phase impurity introduced [42]. Therefore, the strategies for making the SrTiO₃ as valuable visible light active photocatalyst have been continuously pursued.

Herein, a green and facile strategy to prepare graphite carbon nitride hybridized chromium doping strontium titanate (CrSTO/g-C₃N₄) nanocomposites was rationally designed and reported in this paper. We investigated the structural and optical properties of CrSTO/g-CN hybrid nanocomposites with different mass ratios. Importantly, the photocatalytic activity of CrSTO/g-CN hybrid nanocomposites under visible light irradiation was studied systematically, and attempted to present a clear portrait of the key factor in determining the photocatalytic efficiency. Moreover, a possible photocatalytic mechanism was also proposed based on experimental results.

Section snippets

Hybrid nanocomposites preparation

All chemicals were analytical pure reagent and purchased commercially without further purification. Pure g-C₃N₄ nano-sheets were prepared by direct heating of melamine at 550 °C in a muffle furnace for 4 h at a heating rate of 2.3 °C/min. The Cr-doped SrTiO₃ sphere was synthesized by a sol–gel hydrothermal route. Firstly, Sr(NO₃)₂ and Cr(NO₃)₃•9H₂O were dissolved in 20 mL EG, which was heated to 105 °C under continuous stirring. Then Ti(C₄H₉O)₄ was added into the solution drop by drop, with the

Results and discussion

The XRD patterns of pure SrTiO₃ and CrSTO were given in Fig. 1a in order to account for the phase and structural parameters. The observed diffraction peaks of pure SrTiO₃ were identified for pure perovskite cubic crystalline structure. Furthermore, the observed diffraction peaks of CrSTO were the same as pure SrTiO₃, which indicated that the crystal structure of CrSTO did not change after Cr cations doped in SrTiO₃. However, the peak position of (110) shifted slightly toward a higher 2θ value

Conclusions

In summary, novel CrSTO/g-CN hybrid nanocomposites have been successfully prepared by a green and facile method. The structural characterizations show that Cr-doped SrTiO₃ spheres have been successfully loaded on the g-C₃N₄ nano-sheets. Furthermore, the as-prepared CrSTO/g-CN hybrid nanocomposites exhibit the considerable stability and significantly enhanced photocatalytic activity for the degradation of RhB under visible light irradiation. In addition, the photocatalytic activity of

Acknowledgments

We gratefully acknowledge financial support by the National Science Foundation of China (51302325), Science Fund for Distinguished Young Scholars of Hunan Province(2015JJ1016), Program for New Century Excellent Talents in University (NECT-12-0553), the fund of the State Key Laboratory of Advanced Technologies for Comprehensive Utilization of Platinum Metals (SKL-SPM- 201507), the Scientific Research Foundation for the Returned Oversea China Scholars, the Hunan Youth Innovation Platform and

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A green and facile strategy for preparation of novel and stable Cr-doped SrTiO3/g-C3N4 hybrid nanocomposites with enhanced visible light photocatalytic activity

Highlights

Abstract

Graphical abstract

Introduction

Section snippets

Hybrid nanocomposites preparation

Results and discussion

Conclusions

Acknowledgments

J. Photochem. Photobiol. C Photochem. Rev.

Appl. Catal. B Environ.

J. Alloys Compd.

Mater. Sci. Eng. R Rep.

J. Alloys Compd.

J. Alloys Compd.

Appl. Catal. B Environ.

J. Alloys Compd.

J. Alloys Compd.

J. Alloys Compd.

J. Alloys Compd.

Appl. Catal. B Environ.

Appl. Catal. B Environ.

J. Alloys Compd.

J. Alloys Compd.

Electrochim. Acta

J. Alloys Compd.

Appl. Catal. B Environ.

Mater. Chem. Phys.

Chem. Soc. Rev.

Chem. Rev.

Angew. Chem.

ACS Catal.

Nature

J. Phys. Chem. B

Nano Lett.

Nanoscale

J. Phys. Chem. C

A green and facile strategy for preparation of novel and stable Cr-doped SrTiO₃/g-C₃N₄ hybrid nanocomposites with enhanced visible light photocatalytic activity