Efficient Mixed-Potential Unsymmetrical Dimethylhydrazine Sensor Based on Yttria-Stabilized Zirconia (YSZ) and Co3O4 Sensing Electrodes.

Reliable detection of unsymmetrical dimethylhydrazine (UDMH), a volatile and highly toxic liquid propellant, is essential for aerospace safety and environmental monitoring. In this work, YSZ-based mixed-potential UDMH gas sensors were fabricated using Co3O4 sensing electrodes (SEs), representing, to our knowledge, the first attempt to apply this sensor platform to UDMH detection. The effect of calcination temperature on electrode microstructure, interfacial electrochemical behavior, and sensing performance was systematically investigated. Among the fabricated devices, the sensor based on Co3O4 calcined at 700 °C showed the strongest response to 10 ppm UDMH. This improvement is attributed mainly to its loosely packed nanoparticle structure and favorable interfacial electrochemical activity, which promote gas diffusion and increase the accessibility of active regions near the triple-phase boundary (TPB). The sensor exhibited a response of -38.8 mV toward 10 ppm UDMH at 410 °C, with response and recovery times of 15 and 29 s, respectively. It also produced a detectable response to 50 ppb UDMH and exhibited good selectivity against common interfering gases, repeatability, humidity tolerance, and 30-day stability. Oxygen partial pressure tests showed that the response remained relatively stable under different oxygen partial pressures, indicating adaptability to varying gas atmospheres. CV curves, polarization curves, and EIS spectra further indicated that Co3O4-700 had more active interfacial electrochemical reactions and lower charge-transfer resistance at the Co3O4/YSZ interface, consistent with its enhanced UDMH response. This work demonstrates the feasibility of YSZ-based mixed-potential gas sensors for hazardous UDMH vapor detection and provides a strategy for sensitive and reliable UDMH monitoring.