CO gas sensors based on p-type CuO nanotubes and CuO nanocubes: Morphology and surface structure effects on the sensing performance

Metal oxide nanomaterials have been widely applied in the high-performance gas sensors. For metal oxide semiconductors, high surface-to-volume ratio and the exposed crystal facets are the two key factors for determining their gas sensing performances. In order to study the effect of surface structure on the gas sensing properties, in this work, two types of copper oxide (CuO) nanostructures, CuO nanotubes (CuO NTs) with exposed surface plane of (111) and CuO nanocubes (CuO NCs) with exposed surface plane of (110), were obtained from Cu nanowires (Cu NWs) and Cu2O nanocubes (Cu2O NCs), respectively. The morphologies, crystal and surface structures were characterized by high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The gas-sensing performances of CuO NTs and CuO NCs for CO gas detection were then studied. The results demonstrated that compared to CuO NCs, the CuO NTs exhibited lower optimum working temperature and higher sensitivity for CO gas detection. At the operating temperature of 175 °C, the prepared CuO NTs exhibited high sensitivity, good selectivity, fast response and recovery times to CO gas. The present study indicates that for the same semiconductor sensing material, the surface crystal structure has significant influence on the sensing performance.