Functionalization of Indium Oxide for Empowered Detection of CO2 over an Extra-Wide Range of Concentrations

Carbon capture, storage, and utilization have becomefamiliar termswhen discussing climate change mitigation actions. Such endeavorsdemand the availability of smart and inexpensive devices for CO2 monitoring. To date, CO2 detection relies on opticalproperties and there is a lack of devices based on solid-state gassensors, which can be miniaturized and easily made compatible withInternet of Things platforms. With this purpose, we present an innovativesemiconductor as a functional material for CO2 detection.A nanostructured In2O3 film, functionalizedby Na, proves to enhance the surface reactivity of pristine oxideand promote the chemisorption of even rather an inert molecule asCO(2). An advanced operando equipment basedon surface-sensitive diffuse infrared Fourier transform is used toinvestigate its improved surface reactivity. The role of sodium isto increase the concentration of active sites such as oxygen vacanciesand, in turn, to strengthen CO2 adsorption and reactionat the surface. It results in a change in film conductivity, i.e.,in transduction of a concentration of CO2. The films exhibitexcellent sensitivity and selectivity to CO2 over an extra-widerange of concentrations (250-5000 ppm), which covers most indoorand outdoor applications due to the marginal influence by environmentalhumidity.