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 on the surface 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 PSII including charge separation and water oxidation.
Wang, D.; Sampaio, R. N.; Troian-Gautier, L.; Marquard, S. L.; Farnum, B. H.; Sherman, B. D.; Sheridan, M. V.; Dares, C. J.; Meyer, G. J.; Meyer, T. J. A Molecular Photoelectrode for Water Oxidation Inspired by Photosystem II. J. Am. Chem. Soc. 2019, 141 (19), 7926–7933. http://dx.doi.org/10.1021/jacs.9b02548