Sol-gel derived Pt/WO₃ films for hydrogen sensing in natural gas

Recently hydrogen has been used for the decarbonization of heat, as it can serve as a direct substitute for natural gas in the existing gas grid. Pilot projects have already begun to implement hydrogen into natural gas pipelines at concentrations up to 20 % by volume. In this work, an optical sensor for detecting hydrogen in methane was developed. A sol-gel tungsten oxide thin film decorated with platinum nanoparticles was employed as sensitive material for the fabrication of a gasochromic sensor. The sensing response was evaluated by monitoring the absorbance change at 850 nm upon exposure to hydrogen at concentrations ranging from 0.5 % to 20 % v/v in methane, at different operating temperatures ranging from 20 to 250°C. Several tests adapted from the ISO standard 26142:2010 were performed to characterize the sensor performance in terms of response/recovery times, stability, cyclability, effect of gas flow rate. The sensor displayed excellent hydrogen sensing performances in methane with high accuracy, repeatability and long-term stability. The best performances were found at 200–250°C, with a response time of 11 s. Regarding cross-sensitivity, it was demonstrated that the sensor’s performances are maintained in presence of natural gas constituents like alkanes and CO₂, while further investigations are necessary for evaluating the effect of contaminants such as CO, H2S.