An Enhanced YSZ Gas Sensor through Optimizing Electrode Thickness for ppb-level H2S Detection

Abstract

Nowadays, there is uncertainty regarding the impact of sensing electrode thickness on the gas sensing performance of mixed potential gas sensors due to simultaneous competitive heterogeneous catalytic reaction and electrochemical reaction. In this study, yttrium oxide doped zirconia gas sensors with varying thickness of NiFe2O4 sensing electrode have been fabricated for H2S gas detection. The operating temperature of yttrium oxide doped zirconia gas sensors have been firstly optimized, followed by a systematic study of the effects of NiFe2O4 sensing electrode thickness on H2S sensing performance. The best sensing performance have been achieved for the yttrium oxide doped zirconia gas sensor with a 10 μm-thick sensing electrode (S-10 sensor). Sensitivities of −8.7 and −44.6 mV/decade have been attained for 10–100 ppb and 100–10000 ppb, respectively, with a lower limit of detection as low as 10 ppb at 510 °C for the S-10 sensor. Furthermore, the potential application of the S-10 sensor in halitosis detection was further evaluated using simulated exhaled breath from patient with halitosis and healthy volunteers. The significant change in human exhaled gas response values detect by the S-10 sensor at different times provide additional support for the prospect of diagnosing halitosis.