The concentration of acetylene (C2H2) is a key parameter to monitor the status of oil-immersed transformers. When the transformer is operated at 330 kV, the transformer oil dissolving 1 ppm of C2H2 is considered as red flag. Therefore, low detection limit of C2H2 is very necessary for transformer monitoring systems. In this work, a freeze-dry assisted sol-gel method is proposed to synthesize rich surface oxygen vacancies SmFeO3. Compared to the traditional sol-gel method, the freeze-dry synthesized SmFeO3 exhibits the increased oxygen vacancies and a higher proportion of larger pores (>100 nm). The response of the sensor based on above SmFeO3 (SFO-F) to C2H2 is higher than that of the sensor based on SmFeO3 synthesized by traditionally sol-gel method (SFO-S), and the SFO-F exhibits the low detection limit of 200 ppb C2H2. In addition, the response time for 200 ppb C2H2 of the SFO-F is relatively smaller than that of the SFO-S. Moreover, the sensors exhibit a high selectivity towards C2H2 in comparison to other gases (C2H4, CH4, NO, CO, H2), and five consecutive test cycles demonstrate the high stability of the sensors. The SmFeO3 prepared through freeze-drying may provide a viable approach to enhance the performance of C2H2 sensors and presenting a fresh perspective to fabricating oxygen-rich vacancy materials.
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