Research Projects

Transition metal complexes of N-heterocyclic carbene ligands (NHCs) are widely used as catalysts in organic transformations and solar-energy conversion. Ruthenium complexes of C^N-type mixed NHC ligands show comparable efficiency to state-of-the-art N3 dyes in dye-sensitized solar cells. However, their ability in photovoltaic hydrogen generation is nearly forgotten. This project aims to combine functionalized ruthenium photosensitizers (PS) with ruthenium (II)-NHC-based water oxidation catalysts (WOC) and cobalt (II)-NHC-based hydrogen-evolving catalysts (HEC) to obtain the respective PS-WOC and PS-HEC dyads. Stable ruthenium complexes of NHC ligands as WOC fragments will propel the oxygen evolution reaction (OER). Ru-NHC-based WOCs stabilize key intermediates in homogenous electrocatalytic reactions and lower the overpotential of the OER. Increasing the number of NHC ligands in WOCs will also lower overpotentials in oxygen-evolving half-cell reactions. Using Co-NHC complexes at the HEC will lower the cost of traditionally used platinum-based cathodes. Tandem Dye-Sensitized Photoelectrochemical Cells (DSPECs) bearing photoanodes with PS-WOC dyads upon n-type semiconductor (TiO2) and photocathodes with PS-HEC dyads upon p-type semiconductor (NiO) can produce green hydrogen in a fully-sustainable manner. Robust NHC-based organometallic complexes in the WOC-PS and HEC-PS dyads can provide higher turnovers. However, DSPECs bearing these organometallic dyads anchored to electrode surfaces are scarcely studied.