Nitrogen-doped SrTiO3/TiO2 composite photocatalysts for hydrogen production under visible light irradiation

doi:10.1016/j.jallcom.2008.04.078

Journal of Alloys and Compounds

Volume 472, Issues 1–2, 20 March 2009, Pages 429-433

https://doi.org/10.1016/j.jallcom.2008.04.078 Get rights and content

Abstract

Nitrogen-doped SrTiO₃ powders were prepared by solid phase method, and further combined with TiO₂ by sol–gel method. Then Pt particles were deposited to prepare Pt-loaded composite powders by hydrogen reduction method. These obtained powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectra, thermogravimetric–differential thermal, ultraviolet (UV)–vis diffuse reflectance spectra and fluorescence spectra techniques. Photocatalytic production of hydrogen from oxalic acid solution was used as the probe reaction to evaluate the photocatalytic activity of hydrogen production under visible light in detail from aspects of different calcination temperatures, and different contents of metal Pt. The result demonstrates that when the calcination temperature is 400 °C, the optimized photocatalytic activity of hydrogen production under visible light can be achieved. Pt depositing greatly improves the photocatalytic activity, and the average hydrogen production rate is up to 5.1 mmol g cat⁻¹ h⁻¹ with 2 wt.% loaded Pt.

Introduction

Energy and environment have become two important problems with the rapid development of industry. Photocatalytic reactions of semiconductor such as decomposition of water have been received great attention around the world [1], [2]. SrTiO₃, one of the important photocatalysts, has been used for water splitting and mineralization of organic pollutants under ultraviolet (UV) irradiation, whereas it is active only in the UV region because of its wide band gap (3.2 eV). Therefore, its photocatalytic properties in UV light range have been investigated for several decades [3], [4]. Nowadays, the research on photocatalysis in the field of visible light has attracted many people's attention [5], [6], [7], [8], [9], and it has become a target of researchers to improve the photocatalytic activity of SrTiO₃ and extend its optical absorption edge towards the visible light range. To our knowledge, researches of SrTiO₃ on the photocatalytic hydrogen production are still scarce. We have not found any report on nitrogen-doped SrTiO₃/TiO₂ photocatalyst under visible light irradiation.

In this paper, nitrogen-doped SrTiO₃ powders were prepared by solid phase method, and nitrogen-doped SrTiO₃/TiO₂ composite powders were prepared by sol–gel method and then Pt powders were further deposited to prepare Pt-loaded composite powders by hydrogen reduction method, whose photocatalytic activity for hydrogen production from oxalic acid solution was investigated under visible light irradiation. The effects of several factors such as the calcination temperatures of composite powders, and the contents of metal Pt on the rate of hydrogen production were studied.

Section snippets

Preparation of photocatalysts

According to our previous research [10], the nitrogen-doped SrTiO₃ powders were prepared as follows: hexamethylenetetramine (HMT) was mixed with a perovskite SrTiO₃ powder and grinded thoroughly in an agate mortar. The mass ratio of hexamethylenetetramine to SrTiO₃ powders was 3 to 1. The mixed powder was packed in a lidded double alumina crucible and calcined at 450 °C under aerated conditions for 1 h. Nitrogen-doped SrTiO₃ powders obtained was grinded in mortar after calcination.

Nitrogen-doped

Characterization of photocatalysts

XRD is used to investigate the phase structures of the samples. The XRD patterns of SrTiO₃, N–SrTiO₃, N–SrTiO₃/TiO₂ (350–600 °C) and Pt/N–SrTiO₃–TiO₂(400 °C, 2 wt.%) are shown, respectively in Fig. 1, Fig. 2. The average crystal size of SrTiO₃ was determined to be 38.8 nm and nitrogen-doped SrTiO₃ samples was 38.4 nm. The average crystal size of the TiO₂ single crystal in composite catalyst calcined at 350, 400, 450, 500 and 600 °C was determined to be 8.5, 9.1, 9.5, 11.8 and 12.6 nm, respectively.

Conclusions

No hydrogen was produced for single SrTiO₃ and TiO₂ under visible light irradiation. SrTiO₃ was doped nitrogen by solid phase method and further combined with TiO₂ by sol–gel method. The photocatalytic hydrogen production activity was greatly improved under visible light irradiation. When the temperature of calcination is 400 °C, the optimized photocatalytic activity of hydrogen production under visible light irradiation can be achieved. Pt depositing greatly improved the photocatalytic

Acknowledgement

This research was financially supported by National Nature Science Foundation of China (No. 20876039), and the Scientific Research Foundation of Hunan Provincial Education Deparment, China (No. 08A026).

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Nitrogen-doped SrTiO3/TiO2 composite photocatalysts for hydrogen production under visible light irradiation

Abstract

Introduction

Section snippets

Preparation of photocatalysts

Characterization of photocatalysts

Conclusions

Acknowledgement

Mater. Res. Bull.

J. Phys. Chem. Solids

Appl. Catal. A: Gen.

J. Photochem. Photobiol. A: Chem.

J. Photochem. Photobiol. A: Chem.

Sci. Technol. Adv. Mater.

J. Photochem. Photobiol. A: Chem.

Acta Chim. Sin.

Nature

Chem. Rev.

Nitrogen-doped SrTiO₃/TiO₂ composite photocatalysts for hydrogen production under visible light irradiation