Construction of ultra-fast hydrogen sensor for dissolved gas detection in oil-immersed transformers based on titanium dioxide quantum dots modified tin dioxide nanosheets

Hydrogen (H2) is a typical product dissolved in transformer oil and a typical fault diagnosis gas for oil-immersed transformer equipment. The large concentration range and fast detection of H2 gas sensors have certain engineering significance. In this paper, TiO2 quantum dots (QDs) with particle size of about 5 nm were prepared by solvothermal reaction, and SnO2 nanosheets modified by TiO2 QDs was successfully prepared. The gas sensing performance of TiO2-SnO2 to H2 was systematically explored. The optimal operating temperature of the sensors is 400 °C. At the optimal operating temperature of 400 °C, the TiO2 (1 %)-SnO2 sensor demonstrated the most excellent gas sensing performance to H2, such as the short response and recovery time (2 s and 5 s to 200 ppm H2), excellent stability, outstanding selectivity and large detection range of 4.8–5000 ppm. The first-principles calculations were carried out and the gas sensing mechanism was further elaborated, which show that the improvement of the TiO2(1 %)-SnO2 is mainly ascribed to the sensitization and homojunction effect of TiO2 QDs. The TiO2 (1 %)-SnO2 gas sensor is expected to provide a choice for the dissolved gas analysis (DGA) method in transformer oil analysis.