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

Abstract

Understanding the mode of operation of metal-oxide gas sensors (e.g., SnO2, In2O3) is of great scientific and economic interest. [...]

Application of Raman Spectroscopy to Working Gas Sensors: From in situ to operando Studies

“…To explore the state of silver origin during working conditions, we have recently exploited the potential of operando SERS, for the first time in the context of metal-oxide gas sensors [35]. Figure 11 depicts 514.5 nm Raman spectra for Ag/In 2 O 3 , when switching between air (spectra 1, 3, 5) and 250 ppm EtOH/air (spectra 2, 4) at 190 °C.…”

“…Despite the potential of Raman spectroscopy for studying gas sensors, only a small number of studies have been published, compared with other characterization techniques (e.g., IR spectroscopy). Previous work published in the context of metal-oxide gas sensors ranges from the (ex situ) use of Raman characterization [13,14,15,16,17,18,19,20] to In situ Raman studies [21,22,23,24,25,26,27,28,29,30,31,32] and operando Raman studies [5,6,33,34,35,36], part of which were done in combination with operando UV-Vis spectroscopy [6,35]. In these studies typical gas sensor materials, such as SnO 2 , WO 3 , and In 2 O 3 were investigated towards a variety of target gases, e.g., H 2 S, CH 4 , H 2 , CO, NH 3 , NO 2 , ethanol (EtOH), and acetaldehyde (acetald.).…”