Constructing an S-Scheme Heterojunction of Hematite with an Oxygen-Deficient Double Perovskite Co-Catalyst for Photoelectrochemical Water Splitting.

Abstract

Hematite (αFe₂O₃) photoanodes, when integrated with an oxygen evolution co-catalyst (OEC), offer several advantages for sustainable green hydrogen production via photoelectrochemical cells (PECs). However, intrinsic limitations such as restricted surface charge transfer and sluggish oxygen evolution reaction (OER) kinetics in OEC-decorated hematite photoanodes pose significant challenges for practical PEC water splitting applications. This study presents an innovative strategy to overcome these drawbacks by decorating the hematite surface with an oxygen-deficient double perovskite oxide layer, PrBa_0.5Sr_0.5Co_1.5Fe_0.5O_6- _δ (PBSCF), serving as an OEC, with the goal of simultaneously enhancing surface charge transfer and OER kinetics. Notably, an S-scheme heterojunction is formed between the PBSCF layer and doped hematite, and theoretical calculations confirm efficient electron transfer within the heterostructure. Leveraging these advantageous features, the Si:Ti-Fe₂O₃/PBSCF photoanode exhibits a significant increase in photocurrent density, ≈1.4 times higher, reaching 3.70 mA cm^-2 at 1.23 V_RHE, along with a noticeable shift in the onset potential. Furthermore, the photoanode demonstrates exceptional PEC operational stability for 120 h, attributed to the uniform contact provided by the PBSCF layer. Overall, this work highlights the potential of perovskite oxide-based materials to enhance PEC water splitting systems and paves the way for their broader application in the pursuit of a sustainable energy future.