WO₃/Pt/PEG/SiO₂ porous film for hydrogen sensing by the sol-gel method

Tungsten oxide (W O ₃) has been widely used in hydrogen sensing due to its stable chemical properties and high oxygen vacancy diffusion coefficient. However, the response of pure W O ₃ to hydrogen is slow, and doping is an effective way to improve the hydrogen sensing performance of W O ₃ materials. In this paper, W O ₃/P t/P E G/S i O ₂ porous film was prepared by the sol-gel method using tungsten powder, H ₂ O ₂ and C ₂ H ₅ O H as precursors, polyethylene glycol (PEG) as the pore-forming agent, and tetraethyl orthosilicate (TEOS) as the S i O ₂ source material. The sensing properties of the W O ₃ composite for hydrogen were characterized by a transmission optical fiber hydrogen sensing system made at home. The process parameters such as water bath time, aging time, W:PEG ratio, and W:TEOS ratio were optimized to improve the sensitivity and response time of the sensing film. The experimental results indicate that the sensitivity is 15.68%, the average response time is 45 s, and the repeatability is up to 98.74% in 16 consecutive tests. The linearity index R ² is 0.9946 within the hydrogen concentration range of 5000 ppm to 50,000 ppm. The film responds only to H ₂ when the concentration of interfering gases (C H ₄, CO, C O ₂) is 2000 ppm. The hydrogen sensing performance of the optimized film is significantly improved compared with that of the undoped film.