Photochemistry of novel porphyrin-based photoelectrodes: towards solar fuel production

Abstract

Photoelectrochemical cells (PECs) provide a feasible strategy for the conversion ofsolar energy into chemical fuel. Central to the design of PECs is a photoelectrode which contains surface anchored dye molecules with the ability to 1) bind to a metal-oxide nanoparticle surface, 2) absorb light in the visible and ultraviolet spectra, 3) use the absorbed light energy to inject electrons into the semiconductor surface, and 4) use the excited state energy to oxidize a molecular catalyst. Designing PEC systems requires dye molecules with precisely chosen optical and electrochemical properties to meet the aforementioned criteria. Main-group porphyrin complexes are excellent candidates for use in these systems as they have high absorptivity of visible light, robust photoinduced redox chemistry, and the ability to readily modify their properties systematically via functionalization. Herein is reported the synthesis and photophysical characterization of numerous main-group porphyrin complexes. The complexes with the most ideal properties are then used to construct supramolecular model systems, allowing their photoinduced reactions to be studied in detail. Finally, these dyes are used to create prototype photoelectrodes for PECs. The final PEC designs are systematically evaluated to determine which dye designs have valuable properties for the large-scale construction of PECs for industrial scale solar fuel production.