Abstract: The honeycomb-like porous WO₃ assembled by nanowires was synthesized by a solvothermal method. After mixing and grinding with 1% molar ratio of CuO or CuCl₂, the CuO-WO₃ andCu²⁺-WO₃composites were obtained. The morphology, composition, valence state and energy band structure etc. of the WO3, CuO-WO₃ and Cu²⁺-WO₃ samples were characterized systematically and their gas sensing performances to H₂S were studied. It was found that the response value of the pure WO₃ was rather low, only 2.8, while the sensitivities of the two composite sensors were significantly increased. Among the three sensors, the Cu²⁺-WO₃ sensor had the highest response value to H₂S, 67.6, which is 24.1 times that of the pure WO₃ sensor. Moreover, the Cu²⁺-WO₃ sensor can effectively detect extremely low concentration of H₂S gas, 20 ppb, indicating its superior sensitivity for H₂S detection. This might be due to (1) copper ion doping enhancing the charge transfer efficiency/separation, (2) narrowed band gap and (3) the redox reactions between the Cu²⁺ and H₂S, leading significantly improving the gas sensing performance.

Key words: WO₃ composite, Cu²⁺ ion doping, H₂S, Gas sensing, Sensing mechanism