Elsevier

Applied Surface Science

Volume 256, Issue 16, 1 June 2010, Pages 5051-5055
Applied Surface Science

H2S-sensing properties of Pt-doped mesoporous indium oxide

https://doi.org/10.1016/j.apsusc.2010.03.055Get rights and content

Abstract

Pt-doped mesoporous indium oxide (In2O3) has been successfully obtained by a simple and effective in situ nanocasting method. The resultant samples were characterized by XRD, FE-SEM, TEM, N2 physisorption, XPS and EDX. The gas sensing properties for hydrogen sulfide (H2S) of the Pt-doped mesoporous In2O3 specimens were also examined. The results exhibit those In2O3 specimens possess much higher response to H2S even at low concentration of 2 ppm and a lower optimum working temperature of 150 °C. A possible mechanism was also provided to explain the improvement of the sensing properties.

Introduction

Semiconductor-based gas sensors have attracted much attention due to their applications in medical diagnosis, environmental monitoring, personal safety, and national security [1], [2], [3], [4], [5]. Up to now, extensive foundational and technological efforts have been dedicated to fabricate perfect gas sensors based various semiconducting metal oxides. Among of them, indium oxide (In2O3), as an n-type semiconductor, has been considered as a promising sensing material for both reducing and oxidizing gases, such as HCHO, C2H5OH, and NO2 [6], [7].

Recently, mesoporous metal oxide materials have attracted increasing focus for gas sensing applications owing to their increased specific surface area, pore volume, and the density of surface activity sites [8], [9], [10]. Varieties of techniques and methods have been employed to synthesize such materials [11], [12], [13], [14]. Among of them, nanocasting, as a simple and versatile method, has stimulated greatest interest because it can withstand the higher temperature processing, which is in favor of the crystallization of metal oxides [15], [16], [17]. However, to the best of our knowledge, few investigations on the hydrogen sulfide (H2S) sensing properties of mesoporous oxides synthesized by nanocasting have been reported.

Herein, we reported a simple and effective method for Pt-doped mesoporous In2O3, which was successfully controlled in both nanometer (meso-structure) and micrometer (morphology) scale. And the H2S sensor based on Pt-doped mesoporous In2O3 was also investigated, which exhibited excellent sensing properties, and could respond to 2 ppm H2S at reduced working temperature.

Section snippets

Pt-doped mesoporous indium oxide

Mesoporous silica KIT-6 was synthesized according to the prior papers with the difference in surfactant removing method [18], [19]. The detailed procedure was as follow: 1.0 g of triblock copolymer P123 (Aldrich) was dissolved in a mixture of 30 g distilled water and 3.5 g hydrochloric acid (36%), then 1.0 g n-butanol was added and the solution was stirred for 1 h. To this mixture, 2.0 g of tetraethylorthosilicate (TEOS) was added and stirred for 24 h at 35 °C. The resulting gel was transferred to a

Results and discussion

The small-angle XRD pattern of KIT-6 and Pt-doped mesoporous In2O3 are given in Fig. 1. KIT-6 showed at least three well-resolved diffraction peaks, indicating an excellent ordered mesoporous structure (Ia3d) of the material [18]. After nanocasting, Pt-doped mesoporous In2O3 features one high-intensity Bragg peak, a shoulder peak, and a broad diffraction peak. The 1/d(hkl) value ratios of the first two peaks are exactly 1.18, which implies that these two peaks can be indexed as (2 1 1) and (2 2 0)

Conclusions

Pt-doped mesoporous indium oxide was successfully obtained through a simple and effective in situ nanocasting method. The gas sensor based on Pt-doped mesoporous indium oxide exhibit excellent H2S-sensing properties with high sensitivity, good selectivity and low optimum working temperature. And it could be seen as a promising candidate of detecting low concentration of H2S at low temperature. Similar method could be applied to the preparation of other noble metal doped mesoporous metal oxides

Acknowledgement

This research was supported by the National Science Foundation (20903046).

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