The decreasing costs of solar and wind power have enabled a substantial growth in renewable electricity supply, however electricity makes up less than 25% of the world's energy demand. The major global energy demand is for fuels, and this demand is still predominantly met by fossil sources, because renewable fuel production is currently not competitive on price.

Clean H2 fuel can be sustainably generated by photochemically splitting water into H2 and O2, but the inevitable formation of O2 is limiting the overall efficiency of this process. Unless H2 and O2 production are spatially separated, the generated O2 suppresses H2 production. While such a separation is possible for electrolytic water splitting using ion-exchange membranes, albeit at added cost and complexity, there is no simple solution for photochemical H2 production, which is believed to offer the highest market potential for commercial solar fuel production.

This work aims to overcome these efficiency limitations through the design of novel reaction media. Water splitting is currently done in water as the solvent, but the high O2 solubility in water is problematic. Here, tailor-made non-aqueous reaction media will be developed to minimise O2 solubility, in order to suppress its detrimental effects and enable simple and robust solar fuel production at high efficiency. A range of organic solvents will be screened for their O2 solubility to establish structure-property relationships. The most promising solvents will be studied as reaction media for photocatalytic H2 generation in the presence of O2.

This project strongly aligns with the 'Hydrogen and alternative energy vectors' area of the EPSRC remit. By developing efficient ways to produce renewable H2 fuel at low cost using solar energy, this work directly addresses the National Renewable Energy Action Plan aiming to supply 10% of the UK's transportation fuel from renewable sources by 2020. It is also well aligned with the 'Sustainable Development' challenge of the UKRI global challenges fund, specifically aiming to provide 'equitable access to affordable, reliable, sustainable energy' through efficient low-cost generation of renewable fuels.