Cu₂O/CuO Hollow Nanospheres/Carbon Composites for NO₂ Detection at Room Temperature

Designing low-energy consumption, highly sensitive, and stable room temperature (RT) gas sensors based on green and renewable materials is both significant and attractive. Cellulose nanocrystals (CNC), eco-friendly materials extracted from the most abundant natural polymer, cellulose, possess unique characteristics, including one-dimensional nanorod structures, abundant functional groups, large specific surface area, a high aspect ratio, and a point-to-point conductive network structure. These characteristics have shown great potential in the development of high-performance gas sensors. Herein, a magnificent C–Cu 2 O/CuO nanocomposite is facilely synthesized from a CNC/Cu 2+ aerogel freeze-drying method followed by subsequent heat treatment. By adjusting the degree of annealing, the material forms a heterogeneous structure that is conducive to enhancing its sensing properties. Structural characterization confirms that the heterostructured Cu 2 O/CuO hollow nanospheres are formed and embedded within the CNC-derived carbon, providing abundant active sites for gas molecule adsorption, thereby ensuring high performance. The as-prepared sensor exhibits high sensitivity (∼1801 toward 10 ppm), excellent linearity, and selectivity to NO 2 at 25 °C. Intriguingly, the calculated limit of detection (LOD) of the sensor, which integrates the merits of CNC and heterostructured Cu 2 O/CuO, is as low as 0.15 ppb. Therefore, it is believed that the proposed idea of constructing nanostructures provides a universal strategy for developing other types of carbon-supported porous metal oxide nanocomposites.