Effect of Ambient Oxygen Partial Pressure on the Hydrogen Response of SnO2 Semiconductor Gas Sensors

In this study, the influence of the oxygen partial pressures (P O2 ) on the sensor response to H 2 of SnO 2 resistive-type gas sensors was evaluated under various humid atmospheres. SnO 2 nanoparticles of 8–15 nm in diameter were synthesized using a hydrothermal technique followed by calcination at 600°C. Additionally, a large amount of pores with diameters greater than 10 nm was confirmed in the nanoparticles. The electrical resistance at 350°C was decreased with decreasing the P O2 , and the electrical resistance in the presence of 10 ppm H 2 was much smaller than that in the absence of H 2 in both dry and humid atmospheres regardless of the P O2 . Furthermore, the sensor response to 10 ppm H 2 at 350°C increased with decreasing P O2 in both dry and humid atmospheres. Thus, decreasing the amount of oxygen adsorption enhanced the effect of rooted hydroxyl formation on the SnO 2 surface through a combustion reaction between H 2 and adsorbed oxygen and improved the sensor response to H 2 . These results are important for understanding the fundamental mechanisms of gas detection and for the material surface design of highly sensitive resistive-type semiconductor gas sensors.