FeOCl as a bifunctional co-catalyst on hematite: Heterojunction and charge transfer acceleration

The photoelectrochemical water splitting performance of hematite photoanodes is limited by both poor charge separation and sluggish surface reaction kinetics. Herein, FeOCl is in situ deposited on Ti-doped Fe 2 O 3 (Ti-Fe 2 O 3 ) as an efficient co-catalyst with a bifunctional role. FeOCl forms a type-II heterojunction with Ti-Fe 2 O 3 that enhances bulk charge separation and accelerates charge transfer, potentially due to the activation of the lattice oxygen-mediated mechanism (LOM) to accelerate oxygen evolution reaction kinetics. Furthermore, an AlOOH interlayer introduced between FeOCl and Ti-Fe 2 O 3 reinforces the built-in electric field and works synergistically with FeOCl to further improve charge separation. The FeOCl/Al/Ti-Fe 2 O 3 photoanode delivers an optimized photocurrent density of 2.85 mA cm −2 at 1.23 V vs. RHE and 3.88 mA cm −2 at 1.50 V vs. RHE, outperforming both single-modifier photoanodes. This work demonstrates a dual-function design strategy that couples heterojunction formation with LOM activation, guiding the development of multi-component photoanodes.