Mechanistic insight into unusual humidity resistance enhancement in metal oxide semiconductor hydrogen sensors via crystalline ceria decoration

CeO 2 was often incorporated into metal oxide semiconductor (MOS) based gas sensors to improve their humidity resistance for real-world gas detection applications. However, the traditional intrinsic anti-humidity mechanism of crystalline CeO 2 materials often faces challenge to high-humidity environment. In this work, CeO 2 decoration layers with varying degrees of crystallinity were designed to explore their impact on the humidity resistance of Tb-SnO 2 @CeO 2 core-shell composite nanofibers for hydrogen (H 2 ) sensing. Gas sensing tests revealed that the sensor based on Tb-SnO 2 NFs decorated with crystalline CeO 2 particles (Tb-SnO 2 @CeO 2 -P) exhibited a 2.43-fold improvement in response compared to the undecorated Tb-SnO 2 sensor when detecting 10-ppm H 2 at 280℃ & 40 % RH. Moreover, the Tb-SnO 2 @CeO 2 -P NF sensor retained ∼83 % of its sensing performance as ambient humidity increased from 25 % to 85 % RH. The sensor also demonstrated ultra-short response/recovery times (< 1 s), a low limit of detection (20 ppb), and an excellent linearity in response over a wide H 2 concentration range. Additionally, series of analysis indicated that the crystallinity degree of CeO 2 coating significantly affects the formation of a hydroxyl crystal-like layer on its surface, further governing the anti-humidity property of the sensors. Furthermore, the mechanisms discussion indicated that the electron sensitization effect from CeO₂ component greatly reduce the interface resistance, thereby greatly improved the gas sensing performances of Tb-SnO₂@CeO₂-P sensors.