Oxygenated Molybdenum Carbide Nanowires for Enhanced Sensing of Characteristic SF₆ Decomposition Species

SF 6 equipment internal insulation faults generate trace amounts of characteristic gases, mainly SO 2 and SO 2 F 2 . Accurately tracing such small amounts of gas at a low temperature is rather necessary for SF 6 equipment status monitoring and fault diagnosis to ensure safe and stable operation of the power system. In this work, we present a gas sensor with ultrahigh sensitivity, excellent low-temperature performance, low detection limits, fast response, and superior recovery performance for detecting SO 2 and SO 2 F 2, employing molybdenum carbide nanowires with an oxygen content of 13.60% (Mo 2 C-500) as the sensing material. Gas-sensing test results show that the sensing performance of Mo 2 C enhances with the increase of the oxygen content, and that Mo 2 C-500 shows the most outstanding sensing performance for SO 2 and SO 2 F 2 among all three oxygenated Mo 2 C (oxygen contents of 0, 5.80, and 13.60%). In addition, at the optimum operating temperatures of 250 °C (SO 2 ) and 150 °C (SO 2 F 2 ), the response value (response time) of Mo 2 C-500 is 2.75(24 s) and 3.61(26 s) toward 300 ppm of SO 2 and SO 2 F 2, and the detection limits for SO 2 and SO 2 F 2 are 0.83 and 1.01 ppm, respectively. Moreover, the potential adsorption mechanism upon SO 2 and SO 2 F 2 by oxygenated Mo 2 C nanowires is further explored by density functional theory (DFT) calculations that the introduction of oxygen promotes the generation of more free electrons and the formation of a deeper electron depletion layer, giving rise to the enhanced sensing response to SO 2 and SO 2 F 2 . This study demonstrates that the Mo 2 C-500 gas sensor with excellent performance and low cost has superior application prospects in detecting SF 6 decomposition species, which serves as a basis for the development of nanogas sensors.