The impacts of the surface modification of Pt-sensing electrodes with Au on the H₂-sensing properties and mechanism of diode-type gas sensors based on anodized titania (TiO₂) were discussed in this study. The sensors using Pt electrodes modified with and without Au (Au(n)/Pt/TiO₂ (n: sputtering time (s)) and Pt/TiO₂ sensors, respectively) were fabricated by employing an anodized TiO₂ film on a Ti plate. The surface modification of the Pt electrodes with Au(20) having a thickness of ca. 10 nm was the most drastically enhanced H₂ response of the Pt/TiO₂ sensor especially in air. The oxidation activity of H₂ over the Pt and typical Au(n)/Pt electrodes was investigated to clarify the H₂-sensing mechanism, together with analyses of crystal structure and chemical state of these electrodes by X-ray diffraction and X-ray photoelectron spectroscopy, respectively. The oxidation activity of H₂ over the Pt electrode decreased with an increase in the amount of the surface-modified Au. Besides, the addition of moisture into the gaseous atmosphere reduced the oxidation activity of H₂ in air. The alloying of Pt with Au was confirmed after annealing of the Au(n)/Pt electrodes at 600 °C in air, and the number of oxygen adsorbates on the surface increased with an increase in the amount of the surface-modified Au. On the basis of these results, we can suggest that the large H₂ response of the Au(n)/Pt/TiO₂ sensors arises from both a decrease in the number of highly active oxygen adsorbates and an increase in dissociatively adsorbed hydrogen species on the surface. The water molecules and/or hydroxy groups adsorbed on the surface by the addition of moisture into the gaseous atmosphere seem to have a crucial role in increasing the dissociatively adsorbed hydrogen species on the surface, to enhance the H₂ response.

#	Concept	H-Index	Publications	Citations
1	Engineering	1	1	87
2	Chemistry	1	1	87
3	Materials Science	1	1	87
4	Optical Sensors	1	1	87
5	Sensors	1	1	87

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