Innovative Optimized Design of CeO ₂ /SnO ₂ Composites for Power Equipment Oil Achieving Breakthrough in High-Performance H ₂ Gas Sensing

Monitoring changes in the dissolved gas compositional within transformer oil, particularly hydrogen (H₂), is vital for early fault diagnosis. Among various sensing materials, SnO₂ shows promise for H₂ gas detection but faces challenges, such as high operating temperatures, poor selectivity, and slow response/recovery kinetics. This study successfully synthesizes a series of CeO₂/SnO₂ composite materials with varying Ce/Sn molar ratios using a hydrothermal method, followed by calcination. The impact of the composite ratio on its microstructure, surface chemistry, and H₂ gas-sensing performance has been systematically explored. The strategic incorporation of CeO₂ significantly boosts the surface oxygen vacancy concentration of SnO₂. These vacancies serve as active sites, which enhance the adsorption and reactivity of gas molecules. Additionally, the addition of CeO₂ synergistically enhances surface oxygen vacancy concentration (62.27%) and forms a mesoporous structure, which collectively accelerate gas diffusion and electron transfer at the heterojunction interface. The CeO₂/SnO₂ composite with a 3:7 Ce/Sn molar ratio shows a high response value of 35.69 to 20 ppm H₂ at 175 °C, nearly three times higher than pure SnO₂. The corresponding response and recovery times are reduced to 116.4 and 168.6 s, respectively. Moreover, the composite also displays excellent linearity (<i>R</i> ² = 0.997), long-term stability (>30 days), and selectivity. Energy band analysis reveals a type-II band alignment and work function difference in the CeO₂/SnO₂ heterojunction, promoting efficient charge transfer at the interface and enhancing electrical conductivity and gas-sensing response. This work provides crucial theoretical insights and material optimization strategies for developing high-performance semiconductor gas sensors and advancing gas-sensing technologies toward H₂.