FeS as hole transport pathway regulating charge transfer for efficient photoelectrochemical water splitting of hematite photoanodes

[Display omitted] •This study first identifies FeS as an efficient hole transport layer in Fe2O3 photoanodes.•The FeS layer enhances PEC performance by improving charge carrier utilization.•Strong S-Fe-O bonds reduce interfacial defects between FeS and Fe2O3 phases.•The Ti-Fe2O3/FeS/FeOOH photoanode achieves 4.24 mA/cm2 at 1.23 V vs. RHE, with 4.7 % STH efficiency. An efficient charge transport layer that enhances charge separation is crucial for achieving high solar-to-hydrogen (STH) conversion efficiencies in photoelectrochemical (PEC) water splitting. This study investigates the potential of FeS as a hole-transporting layer (HTL) in hematite (Fe2O3) photoanodes to enhance PEC water splitting performance. The integration of p-type FeS onto the Fe2O3 surface formed a p-n heterojunction, providing an additional driving force for the transfer of photogenerated holes from Ti-Fe2O3 to the oxygen-evolution co-catalyst (OEC) FeOOH, while also inhibiting the diffusion of photogenerated electrons. Additionally, the formation of S-Fe-O bonds at the Ti-Fe2O3/FeS interface significantly reduced interfacial defects, thereby improving charge separation. As a result, the optimal photoanode reached a high photocurrent density of 4.24 mA/cm2 at 1.23 V vs. RHE. Furthermore, a tandem device combining Ti-Fe2O3/FeS/FeOOH photoanodes with a Si solar cell demonstrated unbiased solar water splitting under parallel illumination mode, achieving an STH conversion efficiency of 4.7 %. This study underscores the effectiveness of FeS as a medium for hole extraction and transport medium in photoanodes, addressing the inherent recombination challenges of hematite and enabling efficient and stable water splitting.