Development of Hydrogen Leak Sensors for Fuel Cell Transportation

Hydrogen is the most promising clean fuel for the new transportation scenario based on fuel cells. In this contest, detection of hydrogen leak is an important issue for safety reasons [1]. Indeed, hydrogen is an explosive gas (Lower Explosive Level - LEL in ambient air is ∼ 4 vol %), then safe operation of fuel cells will require inexpensive sensors to detect the presence of hydrogen leaks in air. These sensors can also find applications in the petroleum industry, chemical production, cryogenic cooling and semiconductor manufacturing processes among the others. Inexpensive hydrogen sensors are then indispensable for the future hydrogen fuel economy. A series of sensors based on different principles have been proposed for in-situ monitoring of hydrogen leak [2,3]. To date, the most sensitive hydrogen sensors rely on the resistance variations of titania nanotube arrays in the presence of hydrogen in air [3]. Earlier works highlighted the fundamental role of the metal oxide nanostructure, modifier (e.g. noble metals) or UV irradiation in the sensing mechanism and performance enhancement. In this regard, in this paper we describe the design and operation of a solid state hydrogen sensor based on thick films of Pt-doped TiO2 nanotubes. The growth of Pt-doped titania nanotube arrays prepared by anodic oxidation, as well as the morphological and microstructural characteristics as a function of the process parameters, anodization potential, reaction time and the electrolyte concentration, were widely investigated. To fabricate the hydrogen sensing device, a thick sensing layer of Pt-doped TiO2 nanotubes was deposited on a ceramic substrate provided with interdigited Pt electrodes, so the variation of the film resistance can be monitored in real time. The sensor is approximately 3x6 mm2 with 150 μm wide gap between the electrode contacts. A planar Pt heater on the opposite side is able to maintain constant the temperature within 0.1°C at operating temperature between 50-300 °C. As a comparison, a sensor based on mesoporous In2O3 has been also fabricated and tested in the same conditions, both in dark and under UV irradiation. Results obtained are discussed, with the final aim to help us in the development of a prototype hydrogen leak sensor for applications in fuel cells. REFERENCES [1] M. Arndt, I. Simon, Hydrogen sensor for application in fuel cell vehicles, in: Proceeding of Sensor 2001, Nürnberg, May 2001, pp. 541-545. [2] G. Neri, A. Bonavita, G. Micali, N. Donato, Development of a self-calibrating hydrogen leak sensor, 7th IEEE Conference on Sensors, Lecce, June 2008. [3] O. K. Varghese, D. Gong, M. Paulose, K. G. Ong, C. A. Grimes, Hydrogen sensing using titania nanotubes, Sensors and Actuators B 93 (2003) 338–344.