Discovery of New Multi-phase Photocatalysts

光催化剂是一种固体材料，能够利用光在其表面引发化学反应。它们目前被广泛用于商业产品的自清洁涂层（如自清洁窗户，自清洁织物），并消除废水或空气中的污染。根据BCC Research的数据，全球光催化行业预计到2014年将增长到17亿美元的价值。目前，有效的光催化剂只能使用紫外光。如果能找到一种能在可见光下工作的材料，可能会获得更高的效率，并开辟新的应用领域，因为在地球上，可见光的自然资源要丰富得多。一个重要的未来应用是通过光催化剂利用阳光分解水，形成氢；这有可能为可再生能源经济做出巨大贡献。本项目将研究光催化材料发现的新方向，旨在寻找新的可见光活性材料。该方法可以分为两部分，每一部分都解决了当前该领域研究中的一个关键问题：首先，在这个项目中，外延薄膜将被用作光催化材料发现的载体。其目的是解决广泛使用的定义不明确的样品，例如具有无法确定的相组成、掺杂物分布、表面形态和其他特性的纳米粉末，这些特性对材料的催化性能都有很大的影响。相反，外延薄膜作为模型样品，具有明确的取向、组成、表面和界面，使充分表征和发现有意义的结构-功能关系成为可能。各种新技术将被开发出来，以研究外延形式的光催化材料。其次，将研究仿生Z方案系统。它们使用与生物光合作用相同的原理，其中两个光系统耦合在一起进行整体反应。在本文研究的人工Z方案中，两种人工光催化剂材料将在固态下通过异质结耦合在一起，使用多种不同的途径来合成纳米复合材料。Z方案的关键优势在于它允许两个光子的能量结合。因此，两个低能量光子（可见光）可以用来代替一个高能量光子（紫外线）来进行光催化。由于地球上的可见光比紫外线丰富得多，这将意味着催化剂效能的显著提高。综上所述，这两个特征代表了光催化的一种重要的新方法，旨在克服该领域长期存在的问题，并产生可靠的、有充分根据的数据，作为真正合理的催化剂材料设计的基础。

Photocatalysts are solid materials capable of using light to initiate chemical reactions on their surfaces. They are currently used as self cleaning coatings in a wide range of commercial products (such as self cleaning windows, self cleaning fabrics) and to eliminate pollution in wastewater or the air. Globally the photocatalysis industry is predicted to grow to a value of US$1.7 billion by 2014, according to BCC Research. At present, effective photocatalysts can use only ultraviolet (UV) light. Far greater efficiency might be obtained, and new applications opened up, if a material could be found that works in visible light, as it is much more naturally abundant on Earth. One important future application is the use of sunlight by photocatalysts to split water, forming hydrogen; this has the possibility to contribute strongly to a renewable energy economy.The proposed project will study new directions in photocatalytic material discovery, with the aim of finding new visible light active materials. The approach can be divided into two strands, each of which addresses a key problem in current research in this area:Firstly, in this project epitaxial thin films will be used as vehicles for photocatalytic material discovery. The aim is to address the widespread use of poorly defined samples, such as nanopowders with inderterminable phase composition, dopant distribution, surface morphology and other properties that each contribute strongly to the catalytic properties of the material. In contrast epitaxial thin films act as model samples having well defined orientation, composition, surfaces and interfaces which make full characterisation and discovery of meaningful structure-function relationships possible. A variety of new techniques will be developed to study photocatalytic materials in epitaxial form.Secondly, biomimetic Z scheme systems will be investigated. These use the same principle as biological photosynthesis, where two photosystems are coupled together to perform an overall reaction. In the artificial Z schemes studied here, two artificial photocatalyst materials will be coupled together in the solid state across a heterojunction, using a variety of different routes to synthesise the nanocomposite materials. The key advantage of a Z scheme is that it allows the energy of two photons to be combined. Therefore two low energy (visible light) photons can be used in place of one high energy (ultraviolet) photon to perform photocatalysis. Since visible light is much more abundant than UV light on Earth, this would mean a significant increase in catalyst efficacy.Taken together, these two features represent a significantly novel approach to photocatlaysis, which aims to overcome long standing problems in the field, and generate reliable, well founded data as the basis for truly rational catalyst material design.