Studies on Sensing Properties and Mechanism of CuO Nanoparticles to H₂S Gas

In this work, the high crystalline copper oxide (CuO) nanoparticles were fabricated by a hydrothermal method, and their structural properties were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The sensing results show that CuO nanoparticles exhibit enhanced sensitivity and good selectivity for hydrogen sulfide (H₂S) gas at a low temperature. There are two working mechanisms involved in the H₂S sensing based on CuO nanoparticle sensors. They are the H₂S oxidation mechanism and the copper sulphide (CuS) formation mechanism, respectively. The two sensing mechanisms collectively enhance the sensor's response in the H₂S sensing process. The Cu-S bonding is stable and cannot break spontaneously at a low temperature. Therefore, the CuS formation inhibits the sensor's recovery process. Such inhibition gradually enhances as the gas concentration increases from 0.2 ppm to 5 ppm, and it becomes weaker as the operating temperature rises from 40 °C to 250 °C. The XPS results confirmed the CuS formation phenomenon, and the micro Raman spectra demonstrated that the formation of CuS bonding and its decomposition can be effectively triggered by a thermal effect. Gas-sensing mechanism analysis supplied abundant cognition for the H₂S sensing phenomena based on CuO materials.