Elsevier

Applied Surface Science

Volume 351, 1 October 2015, Pages 1025-1033
Applied Surface Science

A high performance hydrogen sulfide gas sensor based on porous α-Fe2O3 operates at room-temperature

https://doi.org/10.1016/j.apsusc.2015.06.053Get rights and content

Highlights

  • Novel porous α-Fe2O3 nanoparticles were prepared by a facile hydrothermal method.

  • The sensor based on porous α-Fe2O3 exhibits high sensitivity towards H2S gas.

  • The detection limit towards H2S gas was as low as 50 ppb at room temperature.

  • The sensor exhibits excellent selectivity against other toxic and noxious gases.

Abstract

Porous α-Fe2O3 nanoparticles were synthesized by simple annealing of β-FeOOH precursor derived from a facile hydrothermal route, the structures and morphologies of the as-prepared product were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results showed that the average crystallite size of the obtained porous α-Fe2O3 was 34 nm and exits numerous irregularly distributed pores with a diameter varying from 2 nm to 10 nm on the particle surface. The gas-sensing properties of the sensor based on porous α-Fe2O3 nanoparticles were investigated, and the result showed that the sensor exhibited a high performance in hydrogen sulfide (H2S) detection at room temperature. The highest sensitivity reached 38.4 for 100 ppm H2S, and the detection limit was as low as 50 ppb. In addition, the response of the sensor towards other gases including C2H5OH, CO, H2 and NH3 indicates the sensor has an excellent selectivity to detection H2S gas. Finally, the sensing mechanism of the sensor towards H2S was also discussed.

Introduction

Hydrogen sulfide (H2S), as a commonly-used chemical gas is extensively utilized in metallurgy, medicine, pesticide and catalyst fields. However, H2S also is an inflammable and malodorous toxic gas, which is harmful to the human nerve and respiratory system even at low concentration. As generally reported, the short term (10 min) and long term (8 h) exposure limit of H2S has been set to 15 ppm and 10 ppm, respectively. When the concentration reaches over 15 ppm, the human olfactory nerve would be paralyzed and the ability to sense H2S declines [1], [2], which could result in lethal consequences. Hence, it is urgent to develop a high-performance H2S gas sensor with high-efficiency, high-reliability, high sensitivity, low cost, low detection limits, and low operation temperature for environmental protection and personal safety during industrial production process.

In recent years, numerous materials including metal oxide semiconductor materials, such as In2O3 [3], [4], WO3 [5], [6], ZnO [7], [8], [9], SnO2 [10], and novel functional materials, such as graphene [11], carbon nanotube [12] have been exploited as H2S gas sensor due to their superior sensing performance towards H2S gas. Among them, the metal oxide semiconductor (MOS) based gas sensors have gained special focus because of their low manufacturing cost, low operation power consumption, simple design, and ease of incorporation into microelectronic devices with possible high device integration density. Of various metal oxide based H2S gas sensors, the α-Fe2O3 based sensors have been proven to be promising due to their high sensitivity, high selectivity and non-toxicity.

Hematite (α-Fe2O3), which is the most stable iron oxide, possesses n-type semiconducting properties with a band gap of 2.1 eV under ambient conditions [13]. As an important and promising functional material, α-Fe2O3 has been widely applied in various areas including photo-catalyst, magnetic materials, waste-water treatment, anode material of lithium batteries [14], [15], [16], [17], [18]. Additionally, it is considered as a good candidate in the gas sensing field. It is well known that the gas sensing properties of α-Fe2O3 dependent strongly on its morphologies, such as aspect ratio, size, orientation and crystal density [19]. Thus, over the past decades, considerable efforts have been made to improve the sensor's sensitivity and selectivity, stability and reproducibility by controllable synthesis of various α-Fe2O3 nanostructures, such as nanospindles [20], nanorings [21], nanospheres [22], nanorods [23], nanowires [24] etc., Moreover, α-Fe2O3 with porous structure has been demonstrated to be an favorable architecture for boosting gas sensing performance due to the porous structures’ significantly enhanced the surface-area-to-volume ratio and material's active sites, which would make the gas diffusion or mass transport onto the surface of materials much more convenient and effective in comparison to the solid ones [25], [26], [27]. For example, Wang et al. synthesized porous α-Fe2O3 nanorods by a facile solution approach, and then utilized the material as a gas sensor for ethanol detection [23]. Deng et al. reported a high-performance H2S gas sensor based on porous α-Fe2O3 nanospheres by microwave-assisted a hydrothermal process [28]. However, it is a disadvantage that most porous α-Fe2O3 based gas sensors reported previously operate at high temperature (200–500 °C), which severely restricted its practical application. Therefore, reducing working temperature or operating at room-temperature would be of great significance.

Hence, in this paper, we report a high-performance room-temperature H2S gas sensor based on porous α-Fe2O3, prepared by the annealing of β-FeOOH precursor derived from a facile hydrothermal method. The sensing characteristics including sensitivity, selectivity, stability, response time and recovery time are investigated. In addition, the H2S sensing mechanism of porous α-Fe2O3 based sensors is also discussed.

Section snippets

Experimental procedure

All the reagents were of analytical grade and used without any further purification, purchased from Sinopharm Chemical Reagents Co., Ltd. (Shanghai, china). Besides, all the water used throughout the experiment was deionized water with a resistivity of 18.3  cm.

The preparation of the porous α-Fe2O3 nanoparticles consists of two steps including the formation of β-FeOOH precursor prepared by hydrothermal reaction and the further annealing of the as-prepared β-FeOOH precursor. In a typical

Structural and morphology characterization

Fig. 3 shows the XRD patterns of the obtained precursor and the final product by annealing the precursor at 500 °C for 2 h. As is shown in Fig. 3a, all of the diffraction peaks correspond well to the tetragonal β-FeOOH (JCPDS NO.34-1266) and no impurities peaks can be observed in the patterns, indicates the high purity of the product. Fig. 3b displays the XRD pattern of the final product. It can be seen that all the diffraction peaks are well matched with the standard hexagonal structure of

Conclusions

In summary, a novel porous α-Fe2O3 nanoparticles based gas sensor was reported in this work. The fabrication process involves the formation of β-FeOOH as a precursor and thermal conversion β-FeOOH to porous α-Fe2O3 by annealing treatment. As a gas sensor, it showed a high-performance in H2S detection, the response to 100 ppm H2S gas reached 38.4 at room temperature and the detection limit was as low as 50 ppb. Moreover, the sensor also exhibited an excellent selectivity, reproducibility and

Acknowledgments

This work was supported by the Fundamental Research Funds for the Central Universities (ZYGX2012J047), the Joint Fund of the National Natural Science Foundation of China and the China Academy of Engineering Physics (U1330108).

References (38)

  • V. Balouria et al.

    Nano-crystalline Fe2O3 thin films for ppm level detection of H2S

    Sens. Actuators B

    (2013)
  • C. Balamurugan et al.

    A selective NH3gas sensor based on mesoporous p-type NiV2O6semiconducting nanorods synthesized using solution method

    Sens. Actuator

    (2014)
  • Y. Wang et al.

    H2S sensing characteristics of Pt-doped -Fe2O3 thick film sensors

    Sens. Actuator B

    (2007)
  • R.H. Bari et al.

    Detection of H2S gas at lower operating temperature using sprayed nanostructured In2O3 thin films

    Bull. Mater. Sci.

    (2013)
  • R. Lonescu et al.

    Low-level detection of ethanol and H2S with temperature modulated WO3 nanoparticle gas sensors

    Sens. Actuators B

    (2009)
  • K.J. Iversen et al.

    Effect of ZnO nanostructure morphology on the sensing of H2S gas

    J. Phys. Chem. C

    (2013)
  • A. Fattah et al.

    Selective H2S gas sensing with a graphene/n-Si schottky diode

    IEEE Sens. J.

    (2014)
  • H.Y. Jung et al.

    High-performance H2S detection by redox reactions in semiconducting carbon nanotube-based devices

    Analyst

    (2013)
  • W. Peng et al.

    Biomimetic fabrication of α-Fe2O3 with hierarchical structures as H2S sensor

    J. Mater. Sci.

    (2013)
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