Polypyrene Cu Amidate Complexes on ITO Electrodes as Molecular Water Oxidation Anodes

Photoelectrochemical devices require solid anodes and cathodes for the easy assembly of the whole cell, and thus redox catalysts need to be deposited on solid surfaces. Molecular catalysts can be anchored on electrodes via simple drop casting, the formation of covalent bonds or supramolecular interactions, and the formation of polymeric structures. Here, we present the anchoring of water oxidation catalysts (WOCs) based on a molecular Cu complex containing a tetraamidate ligand. The molecular complex is functionalized with a pyrene moiety that, upon exposure to an oxidative potential, generates a polypyrene structure containing the molecular WOC, firmly attached at the surface of a variety of electrodes such as glassy carbon (GC), indium tin oxide (ITO), or nano-ITO. The new molecular hybrid materials have been characterized by electrochemical and spectroscopic techniques and tested with regard to their capacity to act as water oxidation electrocatalysts. Their best performance is obtained at pH 10, giving faradic efficiencies in the range of 65-74% with an onset potential of around 0.8 V vs normal hydrogen electrode (NHE).