Essential role of electrode materials in ethylene and acetylene sensing selectivity for LaFeO3 based gas sensors

LaFeO3 (LFO) thick film gas sensors were obtained by depositing the same sensitive material on alumina substrates provided with electrodes made out of different noble metals, namely platinum and gold. Their acetylene and ethylene sensing properties were investigated in dry and humid conditions at different operating temperatures. The main finding is that the nature of the electrode materials has an impact on the sensor performance: in the case of Pt electrodes good responses to both ethylene and acetylene were recorded at 150 degrees C; in the same conditions, in the case of Au electrodes a good response was recorded only for acetylene. In order to understand the underlying reasons, we investigated the surface chemistry changes associated with the nature of electrodes by operando Diffuse Reflectance Infrared Fourier Transformed (DRIFT). We found that regardless of the electrode material, the surface reaction responsible for the sensor signals takes place for acetylene. However, in the case of ethylene, platinum is required for the reaction to occur.