Ag 2 SO 4 -Ag 2 S transformation in SnO 2 -based nanofibers for high selectivity and response H 2 S sensors.

Tin-based gas sensors have been developed for many years owing to their advantages of low price, high response and stability. However, selectivity remains a significant issue. Herein, Ag-SnO 2 nanofibers are synthesized using AgCl as the doping reagent. The 3%Ag-SnO 2 nanofibers sensors show a high response of 68 toward 1 ppm H 2 S at 90°C . Besides, the sensor with 3% AgCl possesses the shortest response time about 136 s at 150°C which is only 30% value of the sensor without AgCl doping. It is also demonstrated that the nanofibers show a high selectivity towards H 2 S. According to the ex-situ XPS and XRD results, AgCl was transferred to Ag 2 S after Ag-SnO 2 was exposed to H 2 S, and reversible transformation between Ag 2 SO 4 and Ag 2 S was the main mechanism for H 2 S detection. Compared with pure SnO 2 nanofiber sensors, the presence of Ag 2 S with high conductivity greatly affects the resistance to H 2 S, resulting in high selectivity and response. This mechanism differs from that of the transformation between Ag 2 O and Ag 2 SO 4 . This study may provide a new strategy for the design and investigation of sensors with high selectivity.