Main content area

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.