UV-activated acetylene sensor based on WO₃/NiO-modified ZnO heterostructures with good stability in transformer oil

Dissolved gas analysis (DGA) is an effective method for diagnosing potential faults in oil-immersed power transformers. Metal oxide semiconductor (MOS) gas sensors exhibit excellent performance. However, high operating temperatures can accelerate device aging, thereby reducing the reliability of online monitoring. In this study, hierarchical porous pure ZnO and WO₃/NiO-ZnO heterojunction nanocomposites were synthesized via a facile hydrothermal method. The acetylene sensing characteristics of pure ZnO and heterojunction sensors were investigated in the absence and presence of UV irradiation. The results indicated that the NiO-ZnO sensor exhibited superior gas sensitivity compared to pure ZnO and WO₃-ZnO sensors. For the NiO-ZnO sensor, the optimal operating temperature under UV irradiation decreased to as low as 60 °C. Additionally, the performance decay of the sensor over 60 days of accelerated aging was documented. Notably, the long-term stability of sensors was significantly improved under UV irradiation. The enhanced properties were possibly attributed to the synergistic effect between photoelectrons excited by UV light and heterojunctions. Photo-activated free electrons could promote the adsorption of oxygen, leading to the formation of photoinduced oxygen ions.