S-Doped FeOOH Layers as Efficient Hole Transport Channels for the Enhanced Photoelectrochemical Performance of Fe2O3.

Hematite (Fe₂O₃) has been accepted as a promising and potential photo(electro)catalyst. However, its poor carrier separation and transfer efficiency has limited its application for photoelectrocatalytic (PEC) water oxidation. Herein, a S-doped FeOOH (S:FeOOH) layer was rationally designed and grown on Fe₂O₃ to construct a S:FeOOH/Fe₂O₃ composite photoanode. The obtained S:FeOOH/Fe₂O₃ photoanodes were fully characterized. The surface injection efficiency for Fe₂O₃ was then significantly increased with a high η_surface value of 92.8%, which increases to 2.98 times for Fe₂O₃ and 2.16 times for FeOOH/Fe₂O₃, respectively. With 2.43 mA cm^‒2 at 1.23 V, the optimized S:FeOOH/Fe₂O₃ photoanode was entrusted with a higher photocurrent density. The onset potential for S:FeOOH/Fe₂O₃ cathodically shifts 70 mV over Fe₂O₃. The improved PEC performance suggests that the S:FeOOH layer acts as ultrafast transport channels for holes at the photoanode/electrolyte interface, suppressing surface charge recombination. A Z-scheme band alignment between Fe₂O₃ and S:FeOOH was deduced from the UV-Vis and UPS spectra to promote charge transfer. This method provides an alternative for the construction of photoanodes with enhanced PEC water splitting performance.