Orchestrating electron transfer for solar-powered water photolysis using iridium(III) photosensitizers.

摘要

The growing demands of the human civilization will ultimately require the increased use of alternative energy sources in order to sustain our growing current population and improving median quality of life. As the Sun is Earth's most plentiful energy source, the development of technologies that convert the supplied radiant energy into a more convenient fuel is logical. Such an approach, being analogous to photosynthesis, allows for the decoupling of energy use from supply. The majority of radiant energy provided by the Sun is thermodynamically capable of powering the photolysis of water to produce molecular hydrogen and oxygen, and therefore, dihydrogen has been considered a potential photosynthetic target that could be combusted, used in a fuel cell, or converted into liquid fuel through the hydrogenation of various substrates. However, the absorption of sunlight by water is negligible, and more importantly, contemporary catalysts operate at potentials that greatly exceed the thermodynamic requirement. As a result, there is a great need to develop new catalytic systems that are capable of both water reduction and oxidation. The work presented herein is aimed at understanding and developing photocatalytic water reduction systems that use an iridium(III) chromophore and a colloidal catalyst. The described system provides the study of decomposition products, while the parameter space of the reaction is probed using a high-throughput photoreactor. Furthermore, observing the modes of photosensitizer decomposition allowed for the design of an iridium complex with a novel architecture that demonstrates superior stability and photochemical properties. Finally, photosensitizing species were covalently attached to a polymer matrix in an effort to develop a polymer film that could compartmentalize water oxidation from reduction.