Study of Detection Mechanism for Optically Readable Hydrogen Sensor

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To use hydrogen as a clean energy resource, it is essential to develop devices for detection of its leakage because hydrogen is explosive with wide range of concentration and low ignition energy. An optically readable hydrogen sensor is one of the most feasible candidates because of its excellent characteristics at room temperature and high safety. The sensor consists of a thin film of catalytic metal such as palladium(Pd) deposited on the glass substrate or the optical fiber end, and the change in optical properties of the film during hydrogenation is utilized for the hydrogen detection. This project was aimed at investigating the detection mechanism of the optically readable hydrogen sensor in order to improve the sensitivity, response/recovery property and the durability. The following results were obtained from the research.(1)The patterned Pd film on the glass substrate exhibited high sensitivity and durability. The sensitivity increased gradually with increasing hydrogen absorpti … More on-desorption cycle.(2)The Pd films on the polyethyleneterephthalate(PET) and polycarbonate(PC) substrates showed stable sensitivity compared to the film on glass substrate. The recovery time of the Pd/PET increased with increasing cycle. On the other hand, the Pd/PC sample had the stable repetition characteristic. From these results, it turned out that substrate material influenced the sensing characteristics.(3)The Pd/Y double-layered thin films had a great advantage of high sensitivity compared with the Pd film. The recovery time was controllable by controlling the thickness of Pd film.(4)The sensitivity of the Pd/Mg doubter-layered thin films was higher than that of Pd/Y films. From the optical measurement by spectroscopic ellipsometry, a considerable change in the dielectric function of the Pd/Mg film in hydrogen atmosphere was observed. The change suggested the decrease in the free electron density and the appearance of polarized electrons in hydrogen atmosphere.(5)The influence of Stearic Acid(SA) buffer layer on the durability and the sensitivity of an optically readable hydrogen sensor using Pd/SA/glass was investigated. The Pd/SA films showed high durability and sensitivity even after repeated hydrogen detection. Less