N-Doped Titania Thin Films Prepared by Atmospheric Pressure CVD using t -Butylamine as the Nitrogen Source: Enhanced Photocatalytic Activity under Visible Light
N-Doped Titania Thin Films Prepared by Atmospheric Pressure CVD using t -Butylamine as the Nitrogen Source: Enhanced Photocatalytic Activity under Visible Light
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以叔丁胺为氮源通过常压 CVD 制备氮掺杂二氧化钛薄膜：增强可见光下的光催化活性
DOI：
10.1002/cvde.200806274
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发表时间：
2009
影响因子：
--
通讯作者：
Dunnill C
中科院分区：
文献类型：
--
作者：
Dunnill C
二氧化钛（TiO2）膜已被用作光催化剂涂层，并应用于诸如自清洁玻璃等技术中。[1]这些涂层使用UV光（<385 nm）光催化降解窗户外表面上的有机物质。[1，2]虽然非常成功和商业化，但人们对改善这些第一代自清洁TiO 2涂层的活性和应用非常感兴趣。一种改进TiO2的方法是将带隙从紫外线转移到光谱的可见光区域，从而收集更大比例的太阳能，并允许薄膜在室内照明条件下工作。事实上，这是一个“圣杯”。将二氧化钛的带起始移动到可见光中，即使只有40 - 50 nm，也将使可用于发射的光子数增加10倍。实现这一点的一种方法是通过掺杂剂，并且已经尝试了许多元素，最流行的一种是氮以形成N掺杂的TiO 2。[3-9]用于掺杂的氮源通常是氨、肼、氮等离子体或一氧化二氮。这些路线中的许多路线在合成过程中具有缺点，并且由于预反应而无法放大到工业过程中。[10此外，关于活性的文献报道有时是矛盾的。[12]二氧化钛中N掺杂的位置至关重要，迄今尚未完全了解。例如，Yates等人通过CVD制备了一系列N掺杂的二氧化钛膜，其是比二氧化钛膜差的光催化剂;值得注意的是，在这些膜中，氮掺杂剂具有约396 eV的主要X射线光电子能谱（XPS）位移，表明在钛金属处氮化物取代氧化物。[13]一些作者声称，这是一个替代掺杂[3，7，9，14]，这是必要的可见光的掺杂，而其他人则声称，这是间隙掺杂。[3，4]在这里，我们报告了对使用叔丁胺作为氮源制备的氮掺杂膜的第一次研究。我们的研究表明，光活性，N-掺杂的TiO 2薄膜没有观察到的峰值在396 eV，并与观察到的峰值在400 eV，为N 1s峰，表明氮的间隙掺杂（与峰在400 eV）是优先在搜索增强的电致伸缩。该方法产生可再现的薄膜，其是可再现的光催化剂。这种新方法可以允许容易地结合到目前在浮法玻璃工业中使用的现有技术中，并且用于涂覆用于其他应用的各种表面。TiCl 4、乙酸乙酯和叔丁胺在500 ℃下的APCVD形成黄绿色膜，当从角度观察时可见干涉条纹。掺杂和未掺杂的二氧化钛膜都是耐刮擦的，其程度为仅具有足以使玻璃基材碎裂的硬度的物品可以标记膜。含氮和不含氮的薄膜在基板的相同区域具有相同的厚度，在约200 nm处的中心区域最大化（Swanepole方法[16]）。厚度梯度是与所使用的CVD反应器相关的固有因素，并且是由于温度和工艺条件的轻微变化（从中心到边缘的25 ° C的差异）导致的反应物在表面上的不均匀沉积的结果。因此，沉积过程受到表面反应速率的限制。为了防止厚度和材料的影响，分析主要在均匀厚度的中心区域进行;然而，通过分析膜的厚度的其他区域，发现功能特性不随厚度变化。吸收曲线（图1a）显示400 nm以下的强吸收和...
Titanium dioxide (TiO2) films have been utilized as photocatalyst coatings with applications in technologies such as self-cleaning glass.[1] These coatings photocatalytically degrade the organic species on the outer surface of windows, using UV light (< 385 nm).[1, 2] While highly successful and commercialized, there is significant interest in improving the activity and application of these first generation self cleaning TiO2 coatings. One such approach to improve on TiO2 is to shift the band-gap from UV into the visible region of the spectrum, thus harvesting a greater proportion of solar energy and allowing the films to work under room-lighting conditions. In fact this is the ‘holy-grail’of photocatalysis. Shifting the band onset of titania into the visible even by only 40–50 nm will enable a ten fold increase in the number of photons available for photocatalysis. One method of doing this is through dopants, and many elements have been tried, one of the most popular being nitrogen to form N-doped TiO2.[3–9] The nitrogen source for the doping is usually ammonia, hydrazine, a nitrogen plasma, or nitrous oxide. Many of these routes have drawbacks in synthetic procedure as well as scale-up into an industrial process due to pre-reaction.[10, 11] Furthermore, literature reports about activity are sometimes contradictory.[12] The site of N-doping within the titania is of key importance, and hitherto not fully understood. For example Yates et al. made a series of N-doped titania films by CVD that were inferior photocatalysts to titania films; notably in these films the nitrogen dopant had a predominant X-ray photoelectron spectroscopy (XPS) shift of ca 396 eV, indicative of a nitride for oxide substitution at the titanium metal.[13] Some authors claim that it is a substitutional doping [3, 7, 9, 14] that is necessary for visible light photocatalysis while others claim that it is the interstitial doping.[3, 4] Here we report the first investigation into a nitrogen-doped film prepared using t-butylamine as a nitrogen source. Our investigations show photoactive, N-doped TiO2 films without a peak observed at 396eV, and with a peak observed at 400eV, for the N 1s peak, indicating that the interstitial doping of nitrogen (associated with a peak at 400eV) is preferential in the search for enhanced photocatalysis. This method produces reproducible films which are visiblelight photocatalysts. This new method may allow ready incorporation into existing technology currently being used in the ffoat glass industry, and for use in coating a wide range of surfaces for other applications. The APCVD of TiCl4, ethylacetate, and t-butylamine at 500 8C forms a yellow-green film, with interference fringes visible when viewed off angle. Both doped and undoped titania films were scratch resistant to the extent that only items of sufficient hardness to chip the glass substrate could mark the films. The films with and without N were of the same thickness at the same areas of the substrate, maximized in the central region at ca 200 nm (Swanepole method [16]). The thickness gradient is an inherent factor associated with the CVD reactor used, and comes about as a result of nonuniform deposition of reactants on the surface due to slight variations in temperature and process conditions (25 8C difference from centre to edge). The deposition process is thus surface reaction rate-limited. To prevent thickness and material effects, analysis was primarily carried out on the central region of uniform thickness; however, by analyzing other regions of thickness of the film, it was found that the functional properties were unchanged with thickness. The absorption profile (Fig. 1a) shows a strong absorbance below 400 nm and a small feature at …