Nanocrystalline Water Splitting Photodiodes II: Device Engineering, Integration and Scale-up

化石燃料是大多数工业化国家的主要能源来源，全球储量正在迅速枯竭，促使人们对替代能源的兴趣日益浓厚。近年来，随着越来越多的政治和社会接受的观察结果，这种浓厚的兴趣大大增强，燃烧化石燃料发电是全球变暖的一个主要因素，如果不是，每年释放到大气中的二氧化碳约为8.0千吨，即目前大气水平的约10%。在可能替代化石燃料的可再生能源中，只有阳光或太阳能有能力满足当前的全球能源需求。事实上，落在地球上的太阳能超过了人类目前能源需求的5000倍。不幸的是，它不是一种可以随时使用的形式，而是需要转化为电能或作为化学燃料储存。利用光电器件，如硅太阳能电池或染料敏化太阳能电池，将太阳能转化为电能的方法已经确立。然而，电能不容易大量储存，太阳能是昼夜间断的，在我们最需要它的时候，也就是冬天的晚上，太阳能是最少的。因此，真正需要的是一种高效（10%）、廉价（每平方米< 5英镑）的太阳能转换装置，它能产生一种易于利用的化学燃料。直接由太阳能驱动的水分解系统的优势在于，它将太阳能转化为一种化学形式，即氢，这种化学形式可以很容易地以最低的能源成本储存或运输，并在需要时使用，并且作为燃料使用时无污染，因为产品是水。在该项目的第一阶段，研究人员能够研究基本特性并开发小型实验室水分裂二极管原型。特别是，研究表明，半导体-金属支撑界面的精心设计对高活性至关重要，因为需要获得尽可能高的表面积、孔隙率和光触媒层的组成。为了进一步提高光触媒膜的附着力，需要可行的规模化生产方法来创造实际的原型，使其在现实生活条件下高效运行。这种装置还需要与某种类型的燃料电池集成，以便作为一种能源解决方案得到广泛应用。因此，本建议项目（第二阶段）的最终目标是制作一份有效的、按比例放大的建议原始形式文件。第3页10打印日期：12/10/2010 10:48:54TS/I002855/1保存日期：能够收集太阳能的商业演示器(i)将水分解成氢气和氧气过程流，达到或接近家庭规模，（ii）有一个最终的，廉价的优化设计，在生命周期分析和综合材料选择方面是可持续的，（iii）在设备集成到家庭利用模型方面获得重要和足够的知识；最值得注意的是，它解决了氢气储存和随后通过商业燃料电池或燃烧器使用的问题。第二阶段的终点将提供一个可行的设备，使用优化的催化剂和光催化剂以及最合适的涂层方法，在(i)高活性、稳健性和可扩展性（ii）经济影响方面；（三）环境、道德和社会方面的考虑。

Summary Fossil fuels are the primary source of energy for most industrialised countries and global stocks are being rapidly depleted, prompting a growing interest in alternative energy sources. In recent years this keen interest has sharpened considerably with the increasingly politically and socially accepted observation that burning fossil fuels to create electricity is a, if not the, major contributor to global warming, releasing into the atmosphere every year ca. 8.0 Gig tonnes of carbon dioxide, CO2, i.e. ca. 10% of present atmospheric levels. Of the renewable energy resources that might substitute for the fossil fuels, only sunlight, or solar energy, has the capability to satisfy current global energy demands. Indeed, the amount of solar energy falling on the Earth is exceeding humankind's present energy requirements by > 5000 times. Unfortunately it is not in a form that can be always readily utilised but, instead, needs to be converted into electricity or stored as a chemical fuel. The conversion of solar to electrical energy using photovoltaic devices, such as the silicon solar cell or using dye-sensitised solar cells, is well-established. However, electrical energy is not easily stored in large amounts and solar energy is diurnal and intermittent and there is least of it when we most need it, i.e. at night in winter. As a consequence, there is a real need for an efficient (> 10%), inexpensive (< £5 per m2) solar energy conversion device that generates a readily utilised chemical fuel. The advantage of a direct solar-driven, water-splitting system is that it converts the sun's energy into a chemical form, i.e. hydrogen, that can be readily stored or transported at minimal energy cost and used when needed and is non-polluting when used as a fuel, since the product is water. In stage 1 of this project, the researchers were able to investigate the fundamental properties and develop small laboratory prototype water splitting diodes. In particular, it was shown that careful engineering of the semiconductor-metal support interface was critical to high activity, as was the need to obtain a high as possible surface area, porosity and composition of the photocatalyst layer. Further improvements with regard to photocatalyst film adhesion, viable scale-up production methods are required to create practical prototypes which would run efficiently and effectively under real life conditions. This device will also require integration with a fuel cell of some kind in order to be of broad use as an energy solution. Therefore, the target at the end-point of this proposed project (Stage 2) is the fabrication of an efficient, scaled up, Proposal original proforma documentPage 3 of 10 Date printed: 12/10/2010 10:48:54TS/I002855/1 Date saved: 12/10/2010 10:39:12commercial demonstrator capable of harvesting solar energy to (i) split water into hydrogen and oxygen process streams on or near to domestic scale, (ii) have a final, inexpensive optimised design, which is sustainable in terms of life cycle analysis and comprehensive materials selection and (iii) gain significant and sufficient know how in terms of device integration into domestic utilisation model; most notably addressing the issues of hydrogen storage and subsequent usage via a commercial fuel cell or burner. The end point of Stage 2 will deliver a viable device, using optimised catalyst(s) and photocatalysts and the most suitable coating method in terms of (i) high activity and robustness and scalability (ii) economic impact; and (iii) environmental, ethical and societal considerations.