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Molecular Photoelectrode for Water Oxidation Inspired by Photosystem II
- Wang, Degao, Sampaio, Renato N., Troian-Gautier, Ludovic, Marquard, Seth L., Farnum, Byron H., Sherman, Benjamin D., Sheridan, Matthew V., Dares, Christopher J., Meyer, Gerald J., Meyer, Thomas J.
- Journal of the American Chemical Society 2019 v.141 no.19 pp. 7926-7933
- aqueous solutions, carbon, carbon dioxide, catalysts, electrodes, hydrogen, lighting, oxidation, oxygen, photosystem II
- In artificial photosynthesis, the sun drives water splitting into H₂ and O₂ or converts CO₂ into a useful form of carbon. In most schemes, water oxidation is typically the limiting half-reaction. Here, we introduce a molecular approach to the design of a photoanode that incorporates an electron acceptor, a sensitizer, an electron donor, and a water oxidation catalyst in a single molecular assembly. The strategy mimics the key elements in Photosystem II by initiating light-driven water oxidation with integration of a light absorber, an electron acceptor, an electron donor, and a catalyst in a controlled molecular environment on the surface of a conducting oxide electrode. Visible excitation of the assembly results in the appearance of reductive equivalents at the electrode and oxidative equivalents at a catalyst that persist for seconds in aqueous solutions. Steady-state illumination of the assembly with 440 nm light with an applied bias results in photoelectrochemical water oxidation with a per-photon absorbed efficiency of 2.3%. The results are notable in demonstrating that light-driven water oxidation can be carried out at a conductive electrode in a structure with the functional elements of Photosystem II including charge separation and water oxidation.