Acetylene- and Ethylene-Sensing Mechanism for LaFeO₃‑Based Gas Sensors: Operando Insights

We recently demonstrated acetylene and ethylene selectivity for LaFeO₃ (LFO)-based gas sensors. To understand the origin of sensing, we combined catalytic conversion measurements with simultaneously performed operando diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy and DC resistance measurements. We applied our operando investigation technique to the relevant analytes, CO₂, C₂H₄, and C₂H₂, in order to identify the type and role of different adsorbates. DRIFT spectra revealed that at 150 °C, the reaction with both acetylene and ethylene resulted in surface formate species; at higher temperatures, this was the case only for acetylene. Accordingly, LFO responds to both gases at 150 °C but only to acetylene at 250 °C. Finally, we could identify the mechanism by which the formate species are responsible for the sensor response and the essential role played by Pt electrodes in the detection of ethylene and the temperature-dependent selectivity.