Preparation and Characterization of Developed Cu_xSn_1-xO₂ Nanocomposite and Its Promising Methane Gas Sensing Properties

Novel materials with nanostructures are effective in controlling the physical properties needed for specific applications. The use of active and sensing materials is increasing in many applications, such as gas sensing. In the present work, we attempted to synthesize incorporated Cu²⁺ into the SnO₂ matrix as Cu_xSn_1-xO₂ nanocomposite using a cost-effective precursor and method. It was observed that, at low concentrations of copper precursor, only SnO₂ phase could be detected by X-ray diffraction (XRD)_. The distribution of Cu in the SnO₂ matrix was further measured by elemental analysis of energy-dispersive X-ray (EDX) mapping and X-ray fluorescence (XRF). At high copper concentration, a separated monoclinic phase of CuO was formed (noted here as CuO/SnO₂). The average crystallite size was slightly reduced from 5.9 nm to 4.7 nm with low doping of 0.00-5.00% Cu but increased up to 15.0 nm at high doping of 10.00% Cu upon the formation of separated SnO₂ and CuO phases. The formation of Cu-SnO₂ or CuO phases at low and high concentrations was also observed by photoluminescent spectra. Here, only the emission peak of SnO₂ with a slight blueshift was recorded at low concentrations, while only the CuO emission peak was recorded at high concentration. The effect of Cu concentration on the sensing properties of SnO₂ toward methane (CH₄) gas was also investigated. It was found that the sensor embedded with 2.00% Cu exhibited an excellent sensitivity of 69.0 at 350 °C and a short response-recovery time compared with the other sensors reported here. The sensing mechanism of Cu_xSn_1-xO₂ and CuO/SnO₂ is thus proposed based on Cu incorporation.