Synthesis of highly-ordered TiO2 nanotubes for a hydrogen sensor

Abstract Highly-ordered, vertically oriented TiO 2 nanotubes are synthesized, and their hydrogen sensing properties are investigated. Self-organized TiO 2 nanotube arrays are grown by anodic oxidation of a titanium foil in an aqueous solution that contains 1 wt% hydrofluoric acid at 20 °C. We use a potential ramp at a rate of 100 mV s −1 , increasing from the initial open-circuit potential (OCP) to 20 V, and this final potential of 20 V is then held constant during the anodization process. The fabricated TiO 2 nanotubes are approximately 1 μm in length and 90 nm in diameter. For the sensor measurements, two platinum pads are used as electrodes on the TiO 2 nanotube arrays. The hydrogen sensing characteristics of the sensor are analyzed by measuring the sensor responses (( I  −  I 0 )/ I 0 ) in the temperature interval of 20–150 °C. We find that the sensitivity of the sensor is approximately 20 for 1000 ppm H 2 exposure at room temperature, and increases with increasing temperature. The sensing mechanism of the TiO 2 nanotube sensor could be explained with chemisorption of H 2 on the highly active nanotube surface.

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