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<p>There are several advantages to using metal-oxide semiconductor (MOS) gas sensors, including their high sensitivity, short response–recovery time, and long-term stability. However, the poor selectivity is a severe challenge in the applications of MOS gas sensors. For instance, it can be difficult for MOS sensors to differentiate between carbon monoxide (CO) and hydrogen (H<sub>2</sub>) due to their similar gas-sensing behaviors. In this paper, a series of n-<i>x</i>ZnO/p-<i>y</i>Cr<sub>2</sub>O<sub>3</sub> nanocomposites (Zn<sub><i>x</i></sub>Cr<sub><i>y</i></sub> NPs, <i>x</i>:<i>y</i> represents the molar ratio of Zn:Cr) were prepared using a simple sol–gel method. The structural, composition, and the surface physicochemical states of the Zn<sub><i>x</i></sub>Cr<sub><i>y</i></sub> material were studied via X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The characterization results demonstrate that p-n heterojunctions of Zn<sub>x</sub>Cr<sub>y</sub> NPs have been prepared. Gas-sensing results showed that the Zn<sub>x</sub>Cr<sub>y</sub> NPs' gas-sensing behavior was influenced by the Zn:Cr molar ratio. Interestingly, Zn<sub>8</sub>Cr<sub>2</sub> NPs sensors showed <i>n</i>-type responses to H<sub>2</sub> but opposite responses (<i>p</i>-type) to CO, demonstrating that the low selectivity of MOS gas sensors can be addressed by modulating the <i>n</i>- or <i>p</i>-type semiconductor concentration in ZnxCry NPs. This paper offered an effective way to address the problem of poor selectivity of MOS sensors to CO and H<sub>2</sub>. The gas-sensing mechanism of Zn<sub>x</sub>Cr<sub>y</sub> NPs-based sensors is experimentally studied in details.</p>

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Opposite gas-sensing behavior of n-xZnO/p-yCr2O3 nanocomposites to H2 against CO and its selectivity mechanism

  • 期刊论文

  • 发表日期：

    2025年3月21日

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  • Wen-Dong Zhou,
  • Hong-Xia Liu,
  • Qi Wang,
  • Davoud Dastan,
  • Hong-Bo Zhang,
  • Hanieh Helli

摘要

There are several advantages to using metal-oxide semiconductor (MOS) gas sensors, including their high sensitivity, short response–recovery time, and long-term stability. However, the poor selectivity is a severe challenge in the applications of MOS gas sensors. For instance, it can be difficult for MOS sensors to differentiate between carbon monoxide (CO) and hydrogen (H2) due to their similar gas-sensing behaviors. In this paper, a series of n-xZnO/p-yCr2O3 nanocomposites (ZnxCry NPs, x:y represents the molar ratio of Zn:Cr) were prepared using a simple sol–gel method. The structural, composition, and the surface physicochemical states of the ZnxCry material were studied via X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The characterization results demonstrate that p-n heterojunctions of ZnxCry NPs have been prepared. Gas-sensing results showed that the ZnxCry NPs' gas-sensing behavior was influenced by the Zn:Cr molar ratio. Interestingly, Zn8Cr2 NPs sensors showed n-type responses to H2 but opposite responses (p-type) to CO, demonstrating that the low selectivity of MOS gas sensors can be addressed by modulating the n- or p-type semiconductor concentration in ZnxCry NPs. This paper offered an effective way to address the problem of poor selectivity of MOS sensors to CO and H2. The gas-sensing mechanism of ZnxCry NPs-based sensors is experimentally studied in details.