We study conceptually new catalytic approaches for solar fuel-forming reactions. The mainstream research in this area explores transition metal oxides and complexes to catalyze O2 and H2 evolution. These catalysts are often made of rare and toxic metals, which disables their wide usage. To provide less expensive and more environmentally friendly alternatives for catalytic water splitting, we aim to discover earth-abundant catalytic motifs that utilize solely organic compounds made of C, H, N and O. Two projects that are currently under investigation in our labs will be presented: (i) Electrocatalytic water oxidation by N-containing heteroaromatic cations. We investigated a number of nitrogen and oxygen-containing functional groups incorporated into conjugated organic frameworks as models for electrocatalytic oxygen evolution. The role of proton-coupled electron transfer in these model catalysts will be discussed. (ii) Photochemical reductions using biomimetic NAD+/NADH analogs. The organic molecular framework serves both as a dye sensitizer (NAD+ analog) and as the fuel-forming electrocatalyst (NADH analog). Our preliminary kinetic studies using ultrafast pump-probe spectroscopy on a series of NAD+ analogs suggest that the hole injection into the inorganic semiconductor (GaP) occurs efficiently with dyes that have sufficiently long excited-state lifetimes. In addition, the hydricities of a series of NADH analogs were evaluated, showing that some of the model compounds investigated are excellent hydride donors.

In search for metal-free catalytic motifs for solar fuels

255th National Meeting (2018)

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