Ag nanoclusters on anatase single crystal TiO2 surfaces: the role of electronic structure in the enhanced photoactivity of Ag dosed TiO2 nanoparticles

二氧化钛(二氧化钛)通常以白色粉末的形式使用。它以三种不同的结构存在，即金红石、锐钛矿和板蓝石。它的用途广泛，从白色颜料(用于蛋黄酱、牙膏和油漆)到从阳光中产生电力，在阳光下它被一种染料激活。它的主要优点是无毒，而且大规模生产成本低廉。20世纪70年代，S发现，在紫外光存在下，二氧化钛也可以用来将水分解成氢和氧，然后这些氢和氧可能被用作燃料。然而，尽管进行了许多积极的研究，但这一领域的全部潜力尚未实现。然而，与这种光催化性能相关的是，二氧化钛已被用于分解有机化学品，还可以杀灭废水中的细菌。这也是用于自清洁窗户的这种特性，在窗户上有一层薄薄的二氧化钛。其中许多应用使用了由几十纳米或数百纳米大小的颗粒组成的二氧化钛，这迫使二氧化钛采用锐钛矿型结构。最近发现，在二氧化钛纳米颗粒中添加纳米级的银团簇可以显著提高其光催化活性。然而，目前还不知道为什么会出现这种情况。钛和氧之间的键(价带)中的电子结构(即电子所处的状态)被认为是二氧化钛光催化活性的关键。在这项工作中，我们想要使用瑞典的同步辐射光源详细地观察这些价电子。同步辐射允许我们调整我们探测样品的能量，这反过来又允许我们将各种元素的贡献映射到价带。这项工作需要相对较低的能量光，这在英国目前是不可用的。其目的是了解银如何改变二氧化钛的电子结构，并将其与光催化活性的提高相关联。通过了解这个系统的工作原理，我们可以使用最少量的银来提高催化剂的活性，从而降低开发这些催化剂的成本。我们还可以帮助其他研究人员寻找其他金属或材料，以进一步提高催化剂的效率。

Titanium dioxide (Titania/TiO2) is usually used in the form of a white powder. It exists in three different structures, rutile, anatase and brookite. It has uses which range from a white pigment (used in mayonnaise and toothpaste as well as paints) to generating electricity from sunlight where it is "activated" with a dye. Its main advantages are that it is not toxic and cheap to produce on a large scale. In the 1970's it was found that titania in the presence of ultra violet light could also be used to split water into hydrogen and oxygen, which could then potentially be used as fuels. However despite much active research the full potential in this area has not been realised. Related to this photocatalytic property however, titania has been used to breakdown organic chemicals and also kill bacteria in waste water. It is also this property which is used in self-cleaning windows which have a thin film of titania on them. Many of these applications use the titania consisting of particles a few tens or hundreds of nanometres in size, which forces the titania to adopt the anatase structure.Recently it was found that adding nanometre sized clusters of silver to the nanoparticles of titania dramatically improved their photocatalytic activity. However it is not known why this is the case. The electronic structure (i.e. the states where electrons are located) in the bonds between the titanium and oxygen (the valence band) is thought to be key to the photocatalytic activity of titania. In this work we want to look in detail at these valence electrons using a synchrotron radiation source in Sweden. Synchrotron radiation allows us to tune the energy with which we probe our samples, which in turn allows us to map the contributions of the various elements to the valence band. The work requires relatively low energy light which is not currently available in the UK. The aim is to understand how silver modifies the electronic structure of the titania and correlate this to the increased photocatalytic activity. By understanding how this system works we can use the minimum amount of silver to enhance the activity of the catalyst and therefore keep the costs of developing these catalysts down. We may also help other researchers identify other metals or materials which can increase the efficiency of the catalysts further.