Electron photo-accumulation in Ir(III) photosensitizers for proton and CO2 reduction

Abstract

In view of developing novel sustainable energy supply as an alternative or complement to fossil fuels, different technologies have been explored for the conversion of sunlight into useful energy sources. Among them, the sunlight-triggered hydrogen evolution reaction (HER) represents a promising solution to worldwide consumption of fossil fuels as hydrogen is an energy-dense and carbon-free fuel. This HER usually operates via a photoinduced electron transfer (PET) from a photosensitizer (PS) to a catalytic centre, where hydrogen is produced. Current challenges in the field are related to the development of more robust hydrogen evolving catalysts and photosensitizers that absorb a wider range of the solar spectrum as well as a deeper engagement of researchers towards the development of active repair strategies. In here, we focused on the development of novel Ir(III) photosensitizers that are capable of storing multiple electrons on one ligand for catalysis applications. These novel photosensitizers were evaluated for proton reduction and CO2 reduction using well-established catalysts and compared our results to prototypical iridium(III) photosensitizers unable to photo-accumulate electrons. These results were complemented by nanosecond transient absorption experiments as well as pump-pump-probe experiments