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

Tungsten oxide (${{\rm WO}_3}$) has been widely used in hydrogen sensing due to its stable chemical properties and high oxygen vacancy diffusion coefficient. However, the response of pure ${{\rm WO}_3}$ to hydrogen is slow, and doping is an effective way to improve the hydrogen sensing performance of ${{\rm WO}_3}$ materials. In this paper, ${{\rm WO}_3}/{\rm Pt}/{\rm PEG}/{{\rm SiO}_2}$ porous film was prepared by the sol-gel method using tungsten powder, ${{\rm H}_2}{{\rm O}_2}$ and ${{\rm C}_2}{{\rm H}_5}{\rm OH}$ as precursors, polyethylene glycol (PEG) as the pore-forming agent, and tetraethyl orthosilicate (TEOS) as the ${{\rm SiO}_2}$ source material. The sensing properties of the ${{\rm WO}_3}$ 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 ${{\rm R}^2}$ is 0.9946 within the hydrogen concentration range of 5000 ppm to 50,000 ppm. The film responds only to ${{\rm H}_2}$ when the concentration of interfering gases (${{\rm CH}_4}$, CO, ${{\rm CO}_2}$) is 2000 ppm. The hydrogen sensing performance of the optimized film is significantly improved compared with that of the undoped film.