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-SnO₂nanofibers are synthesized using AgCl as the doping reagent. The 3%Ag-SnO₂nanofibers sensors show a high response of 68 toward 1 ppm H₂S 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 H₂S. According to theex situx-ray photoelectron spectrum and x-ray diffraction results, AgCl was transferred to Ag₂S after Ag-SnO₂was exposed to H₂S, and reversible transformation between Ag₂SO₄and Ag₂S was the main mechanism for H₂S detection. Compared with pure SnO₂nanofiber 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.