Rapid and Stable Detection of Carbon Monoxide in Changing Humidity Atmospheres Using Clustered In₂O₃/CuO Nanospheres

Clustered indium oxide/copper oxide (In₂O₃/CuO) nanospheres with different CuO amounts were successfully synthesized as sensing materials for the carbon monoxide (CO) detection. Component and morphological characterizations were performed by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Sensing performance for CO of the clustered In₂O₃ and In₂O₃/CuO nanospheres were investigated under different temperatures and humidity conditions. The results show that the sensors based on 2 mol % In₂O₃/CuO (InCu2) exhibit about threefold improvement in response to CO compared to that of In₂O₃ with quick response and recovery time, wide linearity, and low detection limit at 200 °C under 25% relative humidity (RH). Moreover, it shows tiny resistance and response declines despite the wide range of humidity variation from 25 to 95% RH. Meanwhile, the mechanism of enhanced gas-sensing performances and antihumidity properties of InCu2 were systematically investigated. We speculated that most of the water-driven species are predominantly adsorbed by CuO due to its high affinity to the hydroxyl group, which suppresses the interaction between moisture and In₂O₃. InCu2 is a new and promising material to sense CO in a highly sensitive and fast manner with negligible interference from ambient humidity.