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

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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.