Enhancing performance of FSP SnO2-based gas sensors through Sb-doping and Pd-functionalization

Via flame spray pyrolysis (FSP), SnO2 gas sensing layers have been doped with 0.01–4 wt% Sb as well as 0.01 wt% Pd in combination with 1 wt% Sb. Characterization of these materials through X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface analysis, and transmission electron microscopy (TEM) revealed particle grain sizes and crystallinity unchanged by the presence of Sb and/or Pd. The addition of Sb to SnO2 resulted in the significant decrease in baseline resistance; up to two orders of magnitude in dry air at 300 °C and three orders of magnitude in humid air at 300 °C, which is significant for FSP-prepared gas sensors with high porosity and low particle coordination number since they typically suffer from high baseline resistance. While the baseline resistance was improved with Sb-doping, the sensor signal (R0/Rgas) remained constant over all concentrations explored. Moreover, regarding the surface functionalization of SnO2 with Pd in combination with Sb-doping, the reduction of baseline resistance was preserved without influencing sensor signal.