Revealing long-lived electron–hole migration in core–shell α/γ-Fe2O3/FCP for efficient photoelectrochemical water oxidation

Abstract

The oxygen evolution reaction (OER) of Fe₂O₃ is limited by its low photocarrier separation efficiency in photoelectrochemical (PEC) water splitting. How to construct an effective photocarrier transmission route in Fe₂O₃ has become an important bottleneck for enhancing OER performance. Herein, we exploit a core–shell nanorod structure loaded with FeCo Prussian blue (FCP) to boost the water oxidation kinetics and charge transfer efficiency for the first time. As expected, the optimal γ-Fe₂O₃/α-Fe₂O₃ photoanode exhibits a remarkable photocurrent density of 2.4 mA cm⁻² at 1.23 V vs. RHE; when a cocatalyst FCP is introduced as a hole-transport layer, it shows a photocurrent density of 3.5 mA cm⁻² at 1.23 V vs. RHE, which is 8.7 times higher than that of the pure α-Fe₂O₃. The outstanding photochemical performance could be attributed to the highest separation efficiency. A further study on the carrier lifetime was performed and clarified that the photocarrier lifetime of the γ-Fe₂O₃/α-Fe₂O₃/FCP photoanode is prolonged (∼50.64 ps) as compared to that of the pure α-Fe₂O₃ photoanode (∼21.00 ps) using femtosecond time-resolved absorption spectroscopy (fs-TAS). This work successfully explains the photocatalytic water oxidation mechanism in the γ-Fe₂O₃/α-Fe₂O₃/FCP photoanode and provides an effective insight into designing a photocarrier delivery channel for the outstanding water oxidation.