Advances in understanding the gas sensing mechanisms by in situ and operando spectroscopy

Abstract

Comprehensive knowledge of the gas sensor mechanisms demands a detailed command of the physicochemical properties and features of the active sensing materials and their interaction with the analyte gas molecules. Based on the observations from different in situ and operando spectroscopic investigations, experimental and theoretical studies, ionosorption, oxygen vacancy, and charge transfer models are proposed for the understanding of the chemiresitive gas sensing mechanisms. In situ and operando spectroscopic techniques are considered as the methodologies to gain insights into the fundamental working principles and mechanisms of the gas sensor devices. In this review, we have provided brief information about different models, sensing mechanisms, and sensor evaluation parameters of the chemiresitive gas sensors in the initial sections. Recent developments and future perspectives on different in situ and spectroscopic techniques such as optical, vibrational, X-ray, scanning probe, and electron-based techniques were employed to gain insights into the electronic structure and the surface chemistry associated with the adsorption of gas molecules are summarized. Observations from the in situ and operando spectroscopic studies of the gas sensors demonstrate that the combination of spectroscopic and electrical characterization methods give key bits of knowledge into the gas sensing systems, which are useful for the design of superior gas sensor devices.