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

This work demonstrates that it is possible to follow the surface chemistry of oxygen on SnO2 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 use 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.