Design and development of highly H2-sensitive interfaces

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Diode-type gas sensors with an anodized TiO2 film on a Ti plate and noble-metal electrodes (Pd and/or Pt) have been fabricated, and the effects of the chemical state and composition of the Pd and Pt at the sensing-electrode surface on the H2-sensing properties have been investigated. The H2-sensing properties in air at 250C are largely dependent on the chemical state of the Pd-Pt electrode surface, and the H2 response and the response speed were improved by a decrease in the amount of Pt and the ratio of PdO to Pd on the electrode surface, respectively. The suitable coating of some polymers on the Pd-Pt sensing-electrode increased the H2 responses in wet air and N2 and reduced O2 concentration dependence of H2 responses. The modification of the small amount of Au on the sensing electrode (especially, Pt) drastically improved the H2 response at 250C, especially in dry air. In addition, the sensor with the Au/Pt electrode showed large and O2-independent H2 response under wet atmosphere.