Photoelectrochemical Behavior of a Molecular Ru-Based Water Oxidation Catalyst Bound to TiO2-Protected Si Photoanodes

A hybrid photoanode based on a molecular water oxidation precatalyst was prepared from TiO2-protected n-or p(+)-Si coated with multiwalled carbon nanotubes (CNT) and the ruthenium-based water oxidation precatalyst [Ru-IV(tda)(py-pyr)(2)(O)], 1(0) (tda(2)-is [2,2':6',2 ''-terpyridine]-6,6 ''-dicarboxylato and py-pir is 4-(pyren-1-y1)-N-(pyridin-4-ylmethyl)butanamide). The Ru complex was immobilized by pi-pi stacking onto CNTs that had been deposited by drop casting onto Si electrodes coated with 60 nm of amorphous TiO2 and 20 nm of a layer of sputtered C. At pH = 7 with 3 Sun illumination, the n-Si/TiO2/C/CNT/ [1+1(0)] electrodes exhibited current densities of 1 mA cm(-2) at 1.07 V vs NHE. The current density was maintained for >200 min at a constant potential while intermittently collecting voltammograms that indicated that over half of the Ru was still in molecular form after O-2 evolution.