Identifying the Active Oxygen Species in SnO₂ Based Gas Sensing Materials: An Operando IR Spectrsocopy Study

Abstract

This work demonstrates that it is possible to follow the surface chemistry of oxygen on SnO 2 based gas sensing materials using operando Diffuse Reflectance Infrared Fourier-Transform Spectroscopy (DRIFTS). The inherent difficulties, due to the intrinsic properties of the studied oxide and the limitations of the method, were overcome by comparing the results obtained for two different materials and by using of isotopically labeled gases together with the simultaneous measurement of the sensor signals. In spite of the differences in the surface composition and reactivity between the different materials, the experimental results show that the reactive oxygen species are similar in nature and the gas recognition takes place by the interplay of surface reduction and (re-)oxidation.

A Self-doping Surface Effect and its Influence on the Sensor Performance of Undoped SnO2 Based Gas Sensors

“…This indicates that the surface is much more reduced for the former, when compared to the latter, most probably because of a higher concentration of defects, which are very likely oxygen vacancies. The reduction of the surface for both materials was recently demonstrated by DRIFTs in [9]. New simultaneous DC electrical resistance and work function changes measurements performed on IPC450w (see Fig.…”

Structure and chemistry of surface-doped Pt:SnO2 gas sensing materials

“…13 While the pristine SnO 2 surface is deactivated by water vapour, 45 the Pt-OSn sites on Pt:SnO 2 remain active maintaining the sensing activity (Fig. 1).…”

Operando Investigations of Differently Prepared In2O3-Gas Sensors

“…It is important to note that the chemistry of water is different for the different sensitive materials because the nature and the relative weight of the different water related surface species differ: the rooted hydroxyl groups seem not to be present in the case of SA while for IC1 they seem to be dominant. It is also very interesting that there does not seem to be any carbonates in the case of SA but a lot of them for IC1 and IC2; in future experiments we will have to find out if those carbonates are reaction intermediates from CO to CO2 or are due to the adsorption of the resulting CO2 like in the case of SnO2 [7]. Anyways, in the presence of humidity their concentration decreases.…”