Ultra-sensitive sensor for hydrogen detection in transformer oil based on TiO2 quantum dots-modified spindle-shaped multilateral CeO2 rods

Hydrogen (H 2 ) is one of the most critical gases in transformer oil. In this paper, an H 2 sensor based on spindle-shaped multilateral CeO 2 rods in micron size and TiO 2 quantum dots (QDs) with an average size of 3.09 nm was designed. The sensor based on CeO 2 with 1 wt%TiO 2 has the best performance and is labeled as Ce–Ti1 sensor. The Ce–Ti1 sensor operates at 250 °C and has the better response value of 52.51% to H 2 of 1000 ppm. The response time is less than 1 s for 2000 ppm H 2 and the response time is 1 s. The Ce–Ti1 sensor has low response values for several dissolved gases in transformer oils (5.78 times than 1000 ppm C 2 H 6 , 9.28 times than 50 ppm CO, and 18.04 times than 1000 ppm CH 4 ). The response of the Ce–Ti1 sensor is affected by humidity, while it shows good long-term stability and repeatability. The response intensity can decrease by 50.21% in RH = 85% compared with sensing performance in RH = 33%. First-principle calculations are used to analyze the H 2 -sensing properties of TiO 2 , CeO 2 , and their composite heterostructures from a microscopic perspective. The adsorption mechanism between the Ce–Ti1 heterojunction and H 2 molecules is analyzed by the adsorbed oxygen mechanism. The construction of DFT calculations and H 2 -sensitive mechanism models can provide guidance for the subsequent construction of high-performance CeO 2 -based gas sensors.