Ethanol gas sensing mechanisms of p-type NiO at room temperature

Conductometric gas sensors based on metal oxide semiconductors (MOS) usually require high temperature operation, increasing their energy consumption and limiting their applicability. However, room temperature operation with these devices still remains a challenge in many sensor-analyte systems due in part to the low or null response and recovery speeds obtained at this temperature. In this work, the conductometric response of ptype NiO ceramic samples to ethanol is studied under room temperature operation. An anomalous response consisting in an unexpected resistance decrease upon ethanol exposure is observed depending on sample texturing, which is tuned by changing the temperature at which the samples are synthesized. This anomalous response is characterized by fast response and recovery times. A model based on two competing mechanisms, consisting in either an electron transfer from NiO to the ethanol molecule or the catalytic decomposition of adsorbed ethanol, is proposed to explain the observed anomalous response. Extending this model to other MOS could pave the way for fast sensors operating at room temperature.

Automated summary

Conductometric gas sensors based on metal oxide semiconductors often require high temperature operation, but this study focuses on room temperature operation of p-type NiO ceramic samples in response to ethanol. An anomalous response with fast response and recovery times is observed when the samples are synthesized at different temperatures, and a model is proposed to explain this unexpected resistance decrease upon ethanol exposure. This model could potentially lead to the development of fast sensors operating at room temperature for other MOS systems.