Ag2SO4-Ag2S transformation in SnO2-based nanofibers for high selectivity and response H2S 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-SnO2 nanofibers are synthesized using AgCl as the doping reagent. The 3%Ag-SnO2 nanofibers sensors show a high response of 68 toward 1 ppm H2S at 90 degrees C. Besides, the sensor with 3% AgCl possesses the shortest response time about 136 s at 150 degrees C which is only 30% value of the sensor without AgCl doping. It is also demonstrated that the nanofibers show a high selectivity towards H2S. According to the ex situ x-ray photoelectron spectrum and x-ray diffraction results, AgCl was transferred to Ag2S after Ag-SnO2 was exposed to H2S, and reversible transformation between Ag2SO4 and Ag2S was the main mechanism for H2S detection. Compared with pure SnO2 nanofiber sensors, the presence of Ag2S with high conductivity greatly affects the resistance to H2S, resulting in high selectivity and response. This mechanism differs from that of the transformation between Ag2O and Ag2SO4. This study may provide a new strategy for the design and investigation of sensors with high selectivity.