Diode-Type Hydrogen Sensor Employing Pd-coated Pt Electrodes and Anodized Titania under Gaseous Atmosphere and Its Application to Oil-Deterioration Monitoring

The H 2 -sensing properties of the diode-type sensor using Pd-coated Pt electrodes and an anodized titania film (Pd/Pt/TiO 2 sensor) were investigated in air and N 2 at 250°C. The current ( I )–voltage ( V ) characteristics of the Pd/Pt/TiO 2 sensor were largely dependent on the composition of the gaseous atmospheres, and the sensor showed a large H 2 response in wet air, which was comparable to that in wet N 2 . This indicates that the H 2 response are hardly dependent on the oxygen concentration under a wet gaseous atmosphere. In addition, the oil-deterioration monitoring properties of the Pd/Pt/TiO 2 sensor were also examined at 30°C. The sensor also exhibited nonlinear I–V characteristics in fresh and deteriorated oils, and the magnitudes of the current and resistance responses were largely dependent on the deterioration of the oils. These results clearly indicate that the Pd/Pt/TiO 2 sensor can monitor the deterioration of oils.