Global energy consumption is rising day by day. One answer for the increased energy demand is photocatalytic water splitting for hydrogen production. In water splitting solar energy is stored to chemical bonds between oxygen and hydrogen molecules. Stored energy can be released by burning hydrogen in presence of oxygen.
The literature review of this thesis briefly discusses heterogeneous semiconductors. The main focus of the work has been on homogeneous catalysis. Data describing their catalytic properties in oxygen production was gathered for such transition metals as Ru, Co, Ir, Fe and Mn. In the section dealing with hydrogen production, main focus has been on transition metals such as Co, Fe and Ni.
The aim of the study was to produce homogeneous catalyst for water splitting which can do both gases simultaneously. So far the literature has only reported catalysts which require three-component system (catalyst + photosensitizer + sacrificial reagent) and that produce only either of the gases (hydrogen or oxygen). The idea behind the work was to combine oxygen producing catalyst and hydrogen producing catalyst to one system where transition metal complexes act both as electron acceptors and donors. Thus, the sacrificial reagent is not needed.
In the experimental part of the work, combination of hydrogen forming Co-catalyst (S 12) and oxygen forming Ru-catalyst (ORu 5) with Ru-photosensitizer (PS 1) was able to split water photocatalytically in the absence of sacrificial reagents. Recorded turnover numbers were low (about 1 for oxygen and 2 for hydrogen) because of the fast deactivation of catalytic species. The deactivation is likely caused by direct electron interaction between Co-catalyst and Ru-catalyst.
