Hematite‐Based Solar Water Splitting in Acidic Solutions: Functionalization by Mono‐ and Multilayers of Iridium Oxygen‐Evolution Catalysts

Abstract

AbstractSolar water splitting in acidic solutions has important technological implications, but has not been demonstrated to date in a dual absorber photoelectrochemical cell. The lack of functionally stable water‐oxidation catalysts (WOCs) in acids is a key reason for this slow development. The only WOCs that are stable at low pH are Ir‐based systems, which are typically too expensive to be implemented broadly. It is now shown that this deficiency may be corrected by applying an ultra‐thin monolayer of a molecular Ir WOC to hematite for solar water splitting in acidic solutions. The turn‐on voltage is observed to shift cathodically by 250 mV upon the application of a monolayer of the molecular Ir WOC. When the molecular WOC is replaced by a heterogeneous multilayer derivative, stable solar water splitting for over 5 h is achieved with near‐unity Faradaic efficiency.