Moving towards the low cost Solar Generation of H2 fuel - How Metal Oxide Heterojunctions can make this a reality

化石燃料燃烧释放的二氧化碳是全球变暖的主要原因，对地球的气候和生态系统造成了广泛而持久的破坏。为了减轻气候变化的潜在灾难性影响，必须立即广泛地减少二氧化碳的排放。阳光是人类最大的能源，如果我们要减少二氧化碳的排放，尽量减少全球变暖，我们必须利用它。自然光合作用是利用阳光生产可再生燃料的完美例子。生物启发的方法——人工光合作用——已经显示出巨大的希望。一个特别有前途的方法是太阳能驱动的水的光解——水分裂——它产生氢燃料；这是一种燃料，可以干净地燃烧回水，不会释放任何二氧化碳。然而，一种经济可行的水分解装置仍然难以捉摸。许多金属氧化物半导体都能分解水。金属氧化物具有耐用性、低毒性和低成本的制备方法。它们也有潜力稳定不太耐用的材料，但有很好的电子性能。这个博士研究项目试图解决由廉价的富含地球元素组成的金属氧化物水分解装置是否可以通过工业上可扩展的方法（即化学气相沉积）生产，并显示出具有竞争力的效率和寿命。许多提高金属氧化物器件性能的策略将被解决，包括堆叠金属氧化物层（即形成异质结）和使用催化剂，也由富土元素制成。此外，金属氧化物异质结在光激发下的电子行为很少被研究。因此，一种可以监测金属氧化物异质结结构电子行为的激光闪光光谱（瞬态吸收光谱）也将被使用。这不仅是理解金属氧化物异质结如何发挥作用的必要条件，而且也是为了认识到它们的局限性，从而形成改进它们的设计策略。

The release of CO2 from the combustion of fossil fuels is the primary cause of Global Warming, causing pervasive and lasting damage to the earth's climate and ecosystems. To mitigate the potentially catastrophic effects of climate change an immediate and extensive reduction in CO2 emission must occur.Sunlight is mankind's largest energy source, which we must exploit if we are to reduce CO2 emissions and minimise Global Warming. Natural photosynthesis is the perfect example how sunlight can be used to produce renewable fuel. Bio-inspired approaches - artificial photosynthesis - have shown great promise. One particularly promising approach is the solar driven photolysis of water - water splitting - which produces hydrogen fuel; a fuel that burns cleanly back to water without any CO2 release. However, an economically viable water splitting device remains elusive. Many metal oxide semiconductors are capable of water splitting. Metal oxides can be durable, possess low toxicity and can be grown by low cost methodologies. They also have the potential to stabilise less durable materials with promising electronic properties. This PhD research project tries to address whether or not metal oxide based water splitting devices, composed of inexpensive earth abundant elements, can be produced by an industrially up-scalable method (namely chemical vapour deposition) and show competitive efficiencies and lifetimes. Many strategies for improving the performance of metal oxide devices will be addressed, which include stacking metal oxide layers (i.e. forming heterojunctions) and using catalysts, also made of earth abundant elements. Furthermore, the electronic behaviour upon light excitation of metal oxide heterojunctions have rarely been studied. Therefore, a form of laser flash spectroscopy (transient absorption spectroscopy) that can monitor the electronic behaviour of metal oxide heterojunction structures will also be used. Not only is this imperative for understanding how metal oxide heterojunctions function, but also to realise their limitations so that design strategies can be formed for improving them.