Effects of surface modification of noble-metal sensing electrodes with Au on the hydrogen-sensing properties of diode-type gas sensors employing an anodized titania film

SENSORS AND ACTUATORS B-CHEMICAL

卷:207

Article

Hyodo, Takeo¹  Yamashita, Tomoki¹  Shimizu, Yasuhiro¹ 

[1] Nagasaki Univ, Grad Sch Engn, Nagasaki 8528521, Japan

关键词: Diode-type gas sensor;    Surface modification;    Gold;    Platinum;    Hydrogen;   

DOI  :  10.1016/j.snb.2014.10.005

来源: Elsevier

【 摘 要 】

Diode-type gas sensors employing an anodized TiO2 film and noble-metal (Pt, Pd and Pd-Pt) sensing electrodes modified with and without a small amount of Au (Au/M/TiO2 and M/TiO2, respectively, M = Pt, Pd, Pd-Pt (Pd:Pt = 58:42 in weight)) have been fabricated, and the effects of surface modification of the electrodes with Au on their H-2-sensing properties have been investigated at 250 degrees C in both air and N-2 under dry and wet atmospheres. H-2 response of all the M/TiO2 sensors in N-2 was much larger than that in air under both dry and wet atmospheres. The Pt/TiO2 sensor showed the smallest H-2 response in air among them, but the surface modification of the Pt electrode with Au was quite effective in enhancing the H-2 response of the Pt/TiO2 sensor in air. Therefore, the response of the Au/Pt/TiO2 sensor to 8000 ppm H-2 in air was comparable to that in N-2, especially under wet atmosphere, and thus the response of the Au/Pt/TiO2 sensor to 8000 ppm H-2 was almost independent of oxygen concentration under wet atmosphere. In addition, the annealing of the sensor at 600 degrees C did not affect the response of the Au/Pt/TiO2 sensor to 8000 ppm H-2. The homogeneous mixing of Au into the Pt electrode also improved the H-2 response of the Pt/TiO2 sensor, but the effectiveness was much lower than that of the surface modification of the Pt electrode with Au. On the other hand, the response of the as-fabricated Au/Pd/TiO(2)and Au/Pd-Pt/TiO2 sensors to 8000 ppm H-2 in air was much larger than that of the Au/Pd/TiO2 and Au/Pd-Pt/TiO2 sensors annealed at 600 degrees C, especially under wet atmosphere. The large H-2 response observed with the Au/Pt/TiO2 sensor and the as-fabricated Au/Pd/TiO2 and Au/Pd-Pt/TiO2 sensors can be explained by large suppression of H-2 oxidation by Au components remained at the surface of their sensing electrodes and then increased amount of dissociatively adsorbed hydrogen species at the sensing electrode surface. (C) 2014 Elsevier B.V. All rights reserved.

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