Cu3N-derived hydrophobic porous CuO hollow nanospheres for NO2 detection at room temperature

Good humidity resistance property are crucial for gas sensors to achieve high-performance sensing characteristics at room temperature. In this work, porous raspberry-like CuO hollow nanospheres were produced by calcining the Cu3N nanosphere precursors through a solid-gas displacement reaction involving the Kirkendall effect. The raspberry-like CuO hollow nanospheres had spherelike microstructure with nanoparticle-built rough surface, thereby showing a hydrophobic characteristic with a high static contact angle (143.0°). The CuO hollow nanospheres exhibited a high response of 26.2 to 300 ppb NO2 even under a high relative humidity of 80% at room temperature, 18.7 times greater than the commercial CuO powder. In addition, the response/recovery times of CuO hollow nanospheres were shorter than those of the CuO powder, with 1.9-fold/3.2-fold improvements in response/recovery kinetic coefficients. CuO hollow nanospheres also displayed good NO2 selectivity and cycling repeatability. The improved NO2 sensing characteristics of the CuO hollow nanospheres were primarily attributable to their increased specific surface area and porosity, increased response/recovery kinetics, and hydrophobic surface.