Structural Stability and Performance of Noble Metal-Free SnO₂-Based Gas Sensors

Abstract: The structural stability of pure SnO₂ nanoparticles and highly sensitive SnO₂-SiO₂ nanocomposites (0–15 SiO₂ wt%) has been investigated for conditions relevant to their utilization as chemoresistive gas sensors. Thermal stabilization by SiO₂ co-synthesis has been investigated at up to 600 °C determining regimes of crystal size stability as a function of SiO₂-content. For operation up to 400 °C, thermally stable crystal sizes of ca. 24 and 11 nm were identified for SnO₂ nanoparticles and 1.4 wt% SnO₂-SiO₂ nanocomposites, respectively. The effect of crystal growth during operation (T_O = 320 °C) on the sensor response to ethanol has been reported, revealing possible long-term destabilization mechanisms. In particular, crystal growth and sintering-neck formation were discussed with respect to their potential to change the sensor response and calibration. Furthermore, the effect of SiO₂ cosynthesis on the cross-sensitivity to humidity of these noble metal-free SnO₂-based gas sensors was assessed.