Investigation of the performance of an Fe2O3/g-C3N4 heterojunction photoanode in the photoelectrocatalytic oxygen evolution reaction

Abstract

Photoelectrochemical water splitting for hydrogen production has become a research hotspot owing to its potential to directly convert solar energy into clean hydrogen fuel. In the photoelectrochemical water splitting process, the oxygen evolution reaction (OER) at the photoanode is the rate-determining step. The poor OER kinetics of a pure Fe₂O₃ photoanode is caused by its low photogenic carrier mobility. Hence, we constructed a heterojunction structure by combining Fe₂O₃ with g-C₃N₄ through a straightforward hydrothermal synthesis and high-temperature calcination, aiming to adjust the band structure and create an internal electric field. Furthermore, we investigated the impact of g-C₃N₄ loading on the photoelectrocatalytic water-splitting performance of Fe₂O₃. With the increase in g-C₃N₄ loading, the photocurrent density initially increases and then decreases. Moreover, Fe₂O₃/g-C₃N₄-2 achieves the highest photocurrent density of 1.02 mA cm⁻² at 1.23 V vs. RHE, which is 5.2 times that of pure Fe₂O₃. The Mott–Schottky (M–S) curve and electrochemical impedance spectroscopy (EIS) demonstrated that the heterojunction structure between Fe₂O₃ and g-C₃N₄ could significantly enhance separation efficiency and increase the migration rate of photogenerated charges in the Fe₂O₃ photoanode, thereby improving the performance in Fe₂O₃ photoelectrocatalytic water decomposition. This indicates that the Fe₂O₃/g-C₃N₄ heterostructure has considerable potential in enhancing the performance of photoelectrocatalytic water decomposition.