Sensing response of palladium nanoparticles and thin films to deuterium and hydrogen: Effect of gas atom diffusivity

In this study, the sensing behaviour of palladium nanoparticle layers and thin film samples has been investigated for hydrogen and deuterium at room temperature and pressures between 4 and 5 Torr. Deuterium has been synthesised using electrolysis of heavy water. Nanoparticle as well as thin film samples show higher sensitivity for deuterium gas, in comparison to hydrogen gas, at all the gas pressures investigated. Nanoparticle sample shows faster sensing response for deuterium in comparison to hydrogen. It is interesting to note that palladium thin films show different sensitivity towards deuterium and hydrogen in comparison to palladium nanoparticles. This may be attributed to the difference in diffusivities of the two gases (deuterium and hydrogen) in palladium thin films. The results of this study indicate that by using a hybrid gas sensor, employing comparison of electrical resistance change in palladium nanoparticles and thin film, it may be feasible to differentiate between hydrogen and deuterium. The proposed sensor is based on the higher palladium diffusivity of deuterium in comparison to hydrogen, when the two gases are below the respective solubility limits.