Shining Light on Indium Oxide Gas Sensors at Work: A Combined Operando Raman/UV-Vis/FT-IR Spectroscopic Study

Understanding the mode of operation of metal-oxide gas sensors (e.g., SnO₂, In₂O₃) is of great scientific and economic interest. Such a knowledge based approach requires the development and application of spectroscopic tools to monitor the relevant surface and bulk processes under working conditions (operando approach) [1,2] In previous studies on In₂O₃ sensors, we applied combined operando Raman/gas-phase FT-IR spectroscopy to ethanol gas sensing [2,3] In this contribution, we will present recent results on ethanol and CO detection using undoped and Ag doped In₂O₃ gas sensors, demonstrating the advantages of (i) operando Surface Enhanced Raman Spectroscopy (SERS) to monitor the metal oxidation state, and (ii) extending the operando Raman/FT-IR setup by UV-Vis spectroscopy to reveal the degree of In₂O₃ reduction.