Hongming Liu,Jingxin Wang,Hai Xiong,Yue Chen,Jianzhong Xiao,Chao Wang
Restricted by an insufficient understanding of the compositional and structural characteristics of the sensing materials that affect the sensing performances, the YSZ-based CO gas sensor remains in a dilemma in terms of further promoting sensitivity, selectivity and long-term stability. In this work, two bimetallic oxides with different crystal structures, perovskite SmMnO 3 and mullite SmMn 2 O 5 , were prepared and adopted to elucidate the roles of the Mn 3+ , Mn 4+ and surface oxygen vacancies . Compared with SmMnO 3 , the coexisting coordination modes of Mn 3+ and Mn 4+ in SmMn 2 O 5 is conducive to generating oxygen vacancies. Furthermore, a SmMn 2 O 5 -based sensor with more oxygen vacancies demonstrates a relatively faster response/recovery speed and enhanced sensitivity of 2.05 times that of SmMnO 3 under the same operation conditions. Such work may broaden insight into the development of efficient sensing materials that introduce oxygen vacancies through the construction of phase structures without complicated operations. Overall, the sensor attached to SmMn 2 O 5 exhibits a low detection limit (5 ppm), a feasible response/recovery speed (24 s/28 s toward 40 ppm CO operating at 450 °C), satisfactory CO selectivity and long-term stability, highlighting its potential for CO monitoring in harsh environments.
Graphical This paper selectes MBioFs with copper ions as the metal center to design an MBioFs/PANI composite suitable for CO gas sensors. The morphology and nanostructure of the prepared materials were thoroughly analyzed, followed by testing their gas-sensing properties. Subsequently, the gas sensing mechanism of composite materials was proposed and discussed in detail. In addressing the issue of poor gas sensitivity in semiconductor CO sensor materials used in mining, such as pure PANI. This study utilized an ice-water bath in combination with an in-situ polymerization method to synthesize a new composite material consisting of Cu(II)-racemic glutamate nanofibers and PANI. The morphology, structure, and chemical bonds of the composite material were analyzed using scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) and spectral analysis. The material's ability to detect CO (100–500 ppm) at room temperature was investigated, revealing a response value of up to 6.8 % for 400 ppm CO detection when the composite material was deposited on a ceramic interdigital electrode. The material exhibited good selectivity and responsiveness to CO detection at room temperature, attributed to the heterojunction formed between Cu(II)-racemic glutamate nanofibers and PANI, which enhanced carrier migration. Consequently, the Cu(II)-racemic glutamate nanofiber/PANI composite(Cu(II)-RGlu/PANI) material shows promise as a high-performance sensing material for CO detection at room temperature and as a low-power, integrable sensor material for underground coal mines. This research contributes to the development of a theoretical framework for such applications.
CO sensor is helpful to monitor the working state of combustion equipment, such as industrial boilers and engines, and to ensure the production process and human life safety. However, balancing fast response/recovery and high response value for metal oxide CO sensors remains a challenge. In this work, based on band gap engineering, porous TiO 2 /CeO 2 NSs with different TiO 2 coupling amounts were prepared by hydrothermal method combined with flame annealing. The heterojunction composed of TiO 2 and CeO 2 narrowed the energy band width of the composite system and made the electron transmission more efficient, which endowed TiO 2 /CeO 2 NSs with good gas sensing properties. The results indicated that the response value of TiO 2 /CeO 2 NSs is 9.78 time that of CeO 2 NSs. Its ultrafast response/recovery time (2 s/6 s), good CO selectivity and wide CO monitoring range (500 ppb-5000 ppm) are also impressive. The TiO 2 /CeO 2 NSs sensor has great potential for rapid CO monitoring.
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