Research Projects

Solar energy is widely considered to be one of the most promising avenues towards the development of new environmentally friendly energy sources of the future. Its energy source is virtually unlimited and solar irradiation provides an average global energy of about 4.93 MJ m-2 (1.37 kW h m-2).[2] This translates into a usable energy of circa 3×1024 J per year, more than 10 000 times the current annual world energy demand. Methods for harvesting the energy of the sun have been investigated for several decades. Investigations on the potential of molecular photocatalysts for hydrogen generation have been taking place since the late 1970s and since then there has been increasing interest in the use of molecular components as solar dyes absorbing in the visible part of the spectrum. In these early studies, the intermolecular approach was taken where mixtures of a light absorbing moiety and a catalytic center were utilized to produce solar fuels. In this approach the photosensitizer was irradiated and electron transfer from the excited state of the sensitizer to the catalytic center occurred. Sacrificial electron donors (S) such as triethylamine (TEA) were added to regenerate the dye. The development of intramolecular photochemical molecular devices (PMDs) is inspired by natural photosynthesis where a chain of carefully chosen porphyrin-type components fulfils tasks such as light absorption in the visible part of the spectrum, vectorial electron transfer from the light absorber to the catalytic center and most importantly, charge separation. Since 2006, the intramolecular option has been considered and this has led to the development of a wide range of bimetallic complexes that act as intramolecular photocatalytic centers. However, the design of such assemblies is not without difficulty and much research has been devoted towards varying the bridging and peripheral ligands, or the catalytic centers and their effects on turn-over numbers (TONs) or turn-over frequency (TOF). Both TONs and TOF are usually used to report the amount of hydrogen produced. During this project, several new organic ligands will be developed and these ligands will be used to construct new transition metal photosensitizers (dyes). These new ligands will connect the photosensitizer with the hydrogen evolving catalysts made up of abundant metals such as cobalt and iron. The bottom-up homogeneous synthetic approach allow fine tuning intrinsic properties necessary to develop efficient heterogeneous PMDS.