利用XAS研究鉬改質氧化釩薄膜於氣致變色反應的特性

Abstract

本研究利用無機溶膠凝膠法(Sol-gel)與旋轉塗佈技術製備一系列不同濃度的鉬(Mo)改質氧化釩薄膜(VOx)。利用吸收光譜(X-ray Absorption Spectroscopy, XAS)分析薄膜之氧化態與電子結構及氣致變色(Gasochromism)特性。結果顯示在鉬(Mo)改質氧化釩薄膜(VOx)中具有良好的層狀結構，並且釩以V5+氧化態存在。鉬(Mo)的摻入導致電子結構的轉變，並增加了氧原子八面體的對稱性，對稱性的增加是影響氣致變色速率的關鍵。通氫氣使其氣致變色反應後，釩由V5+下降至V3.7+氧化態，並伴隨著晶體結構的變化。於In situ XAS實驗結果顯示，鉬(Mo)改質氧化釩薄膜(VOx)與氧化釩薄膜(VOx)相較之下，具有較佳的變色速率與還原效果，在於鉬(Mo)改質氧化釩薄膜(VOx)具有較對稱之氧原子八面體。根據本研究結果，鉬(Mo)改質氧化釩薄膜(VOx)具備良好的氫氣感測器的應用層面。

A series of Mo-modified VOx thin films with different concentrations were fabricated using sol-gel solution by spin coating method. X-ray absorption spectroscopy (XAS) was used to investigate the modification of both oxidation state and electronic structures of these thin films when they were exposed to dihydrogrn. Analytical results indicate that the prepared thin films are amorphous with V5+ valance. The addition of Mo alters the electronic structures and increases the structural symmetry. These facts are crucial for gasochromic properties in these hydric films. Additionally, these thin films reduce the vanadium valence from V5+ to V3.7+ accompanied by lattice structural distortion upon adsorption of dihydrogen. In situ XAS results show a better coloration rate and reduction effect of Mo-modified VOx than those of pristine VOx can be ascribed to the increase of the interlayer space in the Mo-modified VOx thin films. Based on the results of this study, Mo-modified VOx thin film is recommended for use in H2 gas sensors.