Hydrogen incorporation in gasochromic coloration of sol–gel WO₃ thin films

• Published in: Sensors and actuators. B, Chemical Vol. 157; no. 2; pp. 504 - 509
• Main Authors: Chan, Chih-Chieh, Hsu, Wen-Chia, Chang, Chung-Chieh, Hsu, Chao-Sheng
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 20.10.2011
• Subjects: air; Annealing; coatings; color; equations; hydrogen; Insertion; Nanostructure; Platinum; scanning electron microscopy; Sol gel process; Spin coating; temperature; Thin films; transmittance; tungsten; Tungsten oxides; X-ray diffraction
• ISSN: 0925-4005; 1873-3077
• DOI: 10.1016/j.snb.2011.05.008

In the present work, nanostructured WO₃ films were prepared by the sol–gel spin coating method. The as-prepared films were annealed at different temperatures and their structures were characterized by field-emission scanning electron microscopy and X-ray diffraction. A layer of platinum (Pt) was then sputtered onto the surface of WO₃ films. The gasochromic properties of the prepared Pt/WO₃ thin films were examined by use of optical transmittance under alternate exposures to various H₂–N₂ gas mixture and air. The results indicated that the sol–gel derived WO₃ films with amorphous structure exhibited excellent gasochromic performance with good coloration change and fast response rate under ambient condition. The coloration kinetics was well fitted by exponential equation, indicating the coloration was a surface reaction-controlled process. A new model based on double-injection concept is proposed. According to the model, it is found that the hydrogen insertion coefficient (x) in the gasochromic colored tungsten bronze state (HₓWO₃) of the studied sol–gel WO₃ films is about 0.29, which is similar to the reported gasochromic and electrochromic studies.