Self-Assembled Chromophore–Catalyst Bilayer for Water Oxidation in a Dye-Sensitized Photoelectrosynthesis Cell

A new approach is described here for the preparation of water-oxidation photoanodes in a dye-sensitized photoelectrosynthesis cell for water splitting. It is based on a chromophore (C)–catalyst (Cat) assembly prepared by a self-assembled bilayer on a mesoporous SnO₂/TiO₂ core/shell electrode, FTO|SnO₂/TiO₂|-C–Cat. A key feature in the resulting assembly is the in situ “synthesis” by utilization of noncovalent interactions between long alkyl substituents of the chromophore and catalyst components. The photoanode carries out photoelectrochemical water oxidation for more than 3 h with ∼86% faradaic efficiency for oxygen generation. At pH 7 under 1 sun illumination, the photoanode reaches a photocurrent density of ∼2.2 mA/cm² with an incident photon to current efficiency of 29% at 450 nm. With an injection yield of only ∼42%, the efficiency of the cell, excluding the losses at the core/shell interface, is a remarkable 67%.