Improved Water Oxidation of Fe₂O₃/Fe₂TiO₅ Photoanode by Functionalizing with a Hydrophilic Organic Hole Storage Overlayer

Abstract

The integration of inorganic and organic materials has been demonstrated as an effective route for photoanodes to yield enhanced photoelectrochemical (PEC) water oxidation performance. In this study, we report the preparation of an inorganic/organic composite photoanode by depositing 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) onto the surface of an Fe2O3/Fe2TiO5 heterostructure. It is found that the HEDP overlayer as an efficient and highly hydrophilic hole storage layer can effectively promote the surface charge dynamics by facilitating charge transfer and meanwhile by suppressing charge recombination. Consequently, the as-fabricated HEDP-Fe2O3/Fe2TiO5 photoanode exhibits an increased photocurrent density of 3.10 mA cm–2 at 1.23 V versus reversible hydrogen electrode (RHE) and a significant cathodic shift in the onset potential (∼120 mV). Furthermore, after the loading of FeNiOOH cocatalyst, a comparable photocurrent density of 3.40 mA cm–2 at 1.23 V versus RHE accompanied with a lowered onset potential are obtained. This work demonstrates an effective route to synthesize highly active hematite photoanodes via organic semiconductor integration.