金奈米樹枝晶叢林應用於可見光增強甲醇氧化反應

Gold Dendritic Nano-Forests for Visible-Light-Enhanced Methanol Oxidation Reaction

光增強甲醇氧化反應為近年來光──燃料電池的重要研究課題。先前技術對於光增強甲醇氧化反應觸媒的研究多聚焦於金屬──半導體複合材料。本研究提出利用三維金奈米樹枝晶叢林做為光電極，在可見光照射下增強甲醇氧化反應。此純金屬奈米結構同時具有觸媒及光觸媒之功效。本研究使用氟離子輔助加凡尼取代反應（fluoride assisted galvanic replacement reaction），於室溫條件下，在矽（Si）基材上快速成長了三維金奈米樹枝晶叢林結構，同時研究其材料特性及光觸媒效果。在Au奈米樹枝晶上，甲醇氧化電流在寬頻可見光照射下（69 mW·cm-2；l > 400 nm）提升了28%。我們更進一步比較了不同波長入射光對於甲醇氧化電流增強效果之差異，並且引入局部表面電漿子共振（localized surface plasmon resonance）模型解釋此隨波長改變的光增強現象。此外，本研究提出的低成本、快速且可室溫操作的矽基金屬奈米樹枝晶製造方法，也為未來製造大面積自站立三維金屬奈米結構提供了新的思維方向。 Photo-enhanced methanol oxidation reaction(PEMOR) is a crucial issue in the development of photo-fuel cells. In the study of catalysts for the PEMOR, efforts have been focused on metal-semiconductor composites in the prior arts. In this study, we utilized metal dendritic nanoforests(DNFs) as the photo-elecrodes to boost methanol oxidation reaction under irradiation. These pure metallic nanostructures can serve as catalysts and photo-catalysts simultaneously. Besides, a facile fl uoride assisted galvanic replacement reaction was developed to prepare threedimensional Au DNFs under ambient conditions. The material characteristics and photo-enhancement toward methanol oxidation reaction were studied. The oxidation current of methanol was boosted by 28% under broadband visible light illumination(69 mW－cm-2；l ＞ 400 nm) .We further compared the photo-enhancements under various irradiation wavelengths. Localized surface plasmon resonance was introduced to explain the wavelengthdependent enhancement. Moreover, the cost-effective and facile process suitable for room-temperature preparation of Si-based metallic DNFs provides a new direction for preparing large-scale free-standing metallic nanostructures.