Solar water splitting is desirable for generating hydrogen from non-fossil-fuel sources. The major challenge to realizing solar water splitting is the slow four-electron water oxidation half-reaction. Molecular water oxidation catalysts (WOCs) can help overcome the kinetic limitations of water oxidation and typically generate oxygen faster than semiconductor photoelectrocatalysts. However, molecular WOCs typically require sacrificial oxidants (e.g.�Ce4+ or S2O82-), and they only operate in the dark unless a separate photosensitizing component is added. To address these drawbacks, a molecular iron WOC, Fe(tebppmcn)Cl2 (1  , tebppmcn = tetraethyl N,N'-bis(2-methylpyridyl-4-phosphonate)-N,N'-dimethyl-cyclohexyldiamine) has been tethered to semiconducting WO3 through its phosphonate linker to generate a solar-responsive oxygen-evolving system (1  -WO3). The photocurrent density in 1  -WO3 is 50% higher than that of WO3. In addition, the 1  -WO3 electrode exhibits a 61% increase in selectivity for water oxidation in acidic sulfate solution. Finally, varying the anchor and the oxide semiconductor allows for electron transfer between the molecular catalyst and the photosensitizer to be optimized. These efforts present a new avenue toward simultaneously photosensitizing molecular catalysts and removing sacrificial oxidants specifically for effecting solar water oxidation.

Photosensitization of a molecular iron catalyst for water oxidation using semiconductor electrodes

247th National Meeting (2014)

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