In the Swedish Consortium for Artificial Photosynthesis, we build on principles from the natural enzymes Photosystem II and FeFe-hydrogenases to construct synthetic molecular systems for Solar Fuel production. Despite intense research on FeFe-hydrogenase mimics and many demonstrations of electrochemical H2 production, photochemical production of H2 with such complexes has only recently been realized. We reported the first system where a FeFe-complex showed catalytic performance of the same order as the best Co-complexes, with a TON = 200. In photosynthesis each absorbed photon leads to charge separation on a single-electron level only, while catalytic water splitting and hydrogen production are multi-electron processes. Artificial molecular systems have therefore shown light-driven water oxidation and fuel production as half reactions only, using sacrificial agents to accumulate redox equivalents on only one side. In order instead use the energy of reversible photogenerated charge separated states, it is important to learn to control accumulative electron transfer on molecular components. We have now designed the first molecular system that shows light-induced accumulative charge separation without sacrificial agents. Water splitting and proton reduction at the catalysts requires management of proton release and/or uptake, which control the electron transfer processes by proton-coupled electron transfer (PCET). We have demonstrated light-driven, proton-coupled oxidations at catalytic sites, and also analyzed in detail the intramolecular PCET reactions and effects of hydrogen bonds in model systems.
ASJC Scopus subject areas
- Chemical Engineering(all)