(502g) P-n Junction Based Gas Sensor for High Temperature Hydrocarbon Detection With Improved Selectivity

A novel high temperature gas sensor was fabricated based on the mixture of p-type and n-type metal oxides. Two different metal oxide nanofibers were prepared by a facile procedure consisting of electrospinning and following calcination process. The morphologies, structures and high temperature stability of the as-prepared metal oxides nanofibers were investigated by SEM, TEM and XRD. The pure p-type and n-type metal oxide nanofibers-based gas sensors were first tested to detect different concentrations of CO, C₃H₈, O₂ and NO₂ at high temperature (800 ^oC), showing opposite response directions of reducing gas on p-type and n-type metal oxide-based sensors, and also for oxidizing gas. Then, a series of p-type and n-type metal oxide nanofibers mixtures with different weight ratio were employed as sensing materials to detect different gases. By tuning the weight ratio from p-type metal oxide dominated to n-type metal oxide dominated mixture, the sensor showed a sensing performance transition from p-type to n-type behavior. At a specific ratio, the sensor can almost eliminate the response from oxidizing gas (O₂ and NO₂) and improve the selectivity towards C₃H₈ over CO, suggesting that the p-n junction based sensor is a promising approach to improve selectivity of gas sensors for the harsh environment applications.