Hydrogen Sensing and Theoretical Understanding of Absorption Phenomena for Materials

This report introduces hydrogen sensing with Membrane-type Surface stress Sensor (MSS) coated with two kinds of hydrogen adsorbent materials : Pd and PdCuSi. The equilibrium hydrogen pressure can be measured by detecting surface stress associated with a volume change of the material caused by hydrogen absorption. For Pd on MSS, it takes a long time for the hydrogen absorption reaction to reach saturation. However, it is possible to shorten the determination time by using the initial absorption rate as an index. As for PdCuSi on MSS, it needs a short time to reach saturation. We show that the relationship between the hydrogen concentration and the respective index of the absorption rate or the saturation value of the absorption can be well explained by using a 2-step reaction kinetic model for hydrogen absorption into bulk via adsorption on surface.