Simple synthesis of Cu/Cu₂O/CuO composites with dual adsorption capacity for conductometric NO₂ detection

Starting from improving the sensing performance of sensing materials to NO₂, it is still a challenge to synthesize a material that can simultaneously enhance the adsorption capacity of NO₂ and the surface adsorbed oxygen content. In this paper, nano-sized octahedral HKUST-1 precursor was prepared by one-step hydrothermal method. After subsequent sintering treatment at different temperatures, a series of CuO-based composites with oxygen vacancies and pores were obtained. Among them, Cu/Cu₂O/CuO composite shows the best response for 1 ppm NO₂ at 50 °C (S =14.4), and excellent selectivity, moisture resistance and reproducibility. The minimum detection limit is as low as 50 ppb. In addition, XPS, PL, NO₂-TPD analyses and DFT calculations were used to study the reasons in detail for the excellent NO₂ gas sensing performance of Cu/Cu₂O/CuO. The presence of Cu in the composite improves the ability of material to adsorb NO₂, while the presence of Cu₂O and oxygen vacancies make the material have more surface adsorbed oxygen. The combined effect of the two makes the material have good NO₂ gas sensing performance. The synthesis of this composite material provides new ideas for improving the detection ability of toxic and harmful gases.