Heterostructural (Sr0.6Bi0.305)2Bi2O7/ZnO for novel high-performance H2S sensor operating at low temperature

Fig. 1. (a) The XRD patterns and (b) Bi 4f XPS spectra of SBO. it is detected by XRD and XPS.Fig. 2. SEM images of (a) ZnO, (b) SBO and (c) SBO/ZnO composite. (d) TEM and HRTEM (e, f) images of heterostructural SBO/ZnO. (g) XRD patterns of heterostructural SBO/ZnO(h) SAED image of heterostructural SBO/ZnO. (i-n) HAADF-STEM image and EDS elemental mappings for the heterostructural SBO/ZnO it is displayed by XRD，SEM, TEM。Fig. 3. (a) Responses of all sensors to 10 ppm H2S versus the operation temperature, (b) successive response curves of all sensors to 1–10 ppm H2S at 75 ◦C, (c) subppm response and recovery curves to H2S at 75 ◦C and (d) concentration dependent sensitivity curves of SBO, ZnO and 10% SBO/ZnO sensors. it is detected by four channel gas sensitive test system.Fig. 4. (a) Response characteristics of all sensors to 10 ppm various gases at fixed operation temperature of 75 ◦C. (b) PCA analysis of 9 kinds of vapors (colored online) at 75 ◦C. (c) Response characteristics of all sensors to 10 ppm gases at fixed operation temperature of 200 ◦C, H2S is measured at 75 ◦C. (d) PCA analysis of 9 kinds of vapors (colored online) at 200 ◦C. it is detected by four channel gas sensitive test system and PCA analysis.Fig. 5. (a) Repeatability of 10% SBO/ZnO sensor to 10 ppm H2S for 9 cycles at 75 ◦C. (b) Long-term stability of SBO, ZnO and 10% SBO/ZnO sensors to 10 ppm H2S at 75 ◦C. it is detected by four channel gas sensitive test system.Fig. 6. (a) The resistance and (b) normalized response of the 10% SBO/ZnO heterojunction sensor to 10 ppm H2S gas at different relative humidity at 75 ◦C (the normalized response is response at x% humidity/response at 0% humidity), the insets are the images of a water droplet before and after being dropped on the surface of the ZnO, SBO and 10% SBO/ZnO heterojunction sensor. it is detected by four channel gas sensitive test system and water contact angle insrtument.Table 1 Sensing performance of H2S sensors in previous works and current work (where SR is gas response defined as Ra/Rg or Rg/Ra). Fig. 7. Response (R = Ra/Rg or R = Rg/Ra for homogenous and heterojunction materials) versus temperature using various MOS cited in Table 1 (Yang et al., 2016, 2017, 2018; Yu et al., 2012). T2 – T6 refers to the IEC explosion-proof grade of combustible gas, corresponding to the highest surface temperature of 300, 200, 135, 100 and 85 ◦C, respectively. it is detected by four channel gas sensitive test system and compared with lietratures.Fig. 8. OV defect characterizations by EPR and (b) photoluminescence (PL) spectra of ZnO, SBO and 10% SBO/ZnO. (c) PL spectra Gaussian fitting of ZnO and 10% ZnO/SBO. it is detected by EPR and PL.Table 2 Center wavelength, full-width-half-maximum (FWHM), area ratio and origin of the deconvoluted PL peak. it is detected by PL.Fig. 9. (a− c) S 2p and (d− f) O 1s XPS spectra of ZnO, SBO and 10% SBO/ZnO sensing layer taken on different stages, respectively. it is detected by XPS.Fig. 10. Schematic illustration of the band diagram of heterostructural SBO/ ZnO sensor. it is detected by DRS and UPS.