Design of SnO2-based CH4 sensors with reactive anti-poisoning layers: excellent stability and high resistance to hexamethyldisiloxane.

CH₄ sensors based on metal oxide semiconductors (MOS) provide high sensitivity and fast response, but the sensitivity will be lost when they are poisoned by silicone. Therefore, there is an urgent need to address the poisoning deactivation of MOS gas sensors caused by silicone. Here, the unique strategy of coating a reactive anti-poisoning material onto the surface of the sensing material is proposed to effectively improve the anti-poisoning ability without degrading the gas sensing performance. As an experimental verification, SnO₂/α-Al₂O₃ is designed as the anti-poisoning layer and SnO₂ loaded with precious metals (Pt and Pd) as the sensing layer. Owing to the protection of the anti-poisoning layer, the response (R_a/R_g = 24.69) and the response/recovery time (1/24 s) of the sensor to CH₄ remained undiminished at 364 °C after being poisoned under an air/hexamethyldisiloxane (HMDSO) (10 ppm) environment for 40 min, which meets the requirements of the Chinese National Standard (GB 15322.2-2019). The mechanism analysis shows that HMDSO can be decomposed with the adsorbed oxygen on the surface of SnO₂ in the anti-poisoning layer, and CH₄ can diffuse into the sensing layer to be detected. The unique anti-poisoning strategies can provide a promising insight for improving the poisoning tolerance of MOS gas sensors. [ABSTRACT FROM AUTHOR]