A New Frontier in CO2 Sensing: A Comparative Study of Thermal and Light Activation in Na:In2O3 Nanostructured Materials

Carbon dioxide emissions are a major contributor to climate change. To effectively map these levels and restrict carbon footprint, we need reliable and affordable CO 2 sensors that address main limitations of conventional technologies developed until now. Our recent research has demonstrated the highly CO 2 sensing capabilities of a new chemoresistive gas sensor based on sodium-doped indium oxide operating at 250 °C. The present work aimed to further exploit the properties of this semiconductor in order to make it even more sustainable and effective. One promising approach involves using UV or visible light for sensor activation at room temperature. Then, this study explored the chemoresistive properties of sodium-doped indium oxide nanostructured films towards CO 2 under both thermal and light activation (using 385 nm UV-LED). Three different sodium-doped samples were prepared and comprehensively characterized. These films exhibited a high sensitivity and selectivity to CO 2 over a very broad concentration range (250-5000 ppm), which covers most indoor and outdoor applications, further with a negligible influence of environmental humidity variations. Advanced operando diffuse reflectance infrared Fourier transform spectroscopy was exploited to achieve a deeper understanding on the sensing mechanism in thermo- and UV-light activated conditions.