Study of the CO and humidity interference in La doped tin oxide CO2 gas sensor

The influence of lanthanum on SnO2 properties was studied using samples with different La over SnO2 content prepared by the impregnation method. Samples were structurally characterised by XRD, XPS and Raman spectroscopy in order to identify the location of the additive, its oxidation state, and its main phase. Thick film sensors fabricated by screen-printing were tested at concentrations of CO2 from 500 to 2500 ppm, at a wide range of relative humidities. CO was also analysed as main interfering molecule. DRIFTS studies were performed to explore the role of lanthanum in the sensing mechanisms. Finally, a two-sensor array is proposed to differentiate between the contributions of CO2 and its interferents.