Nanostructure-assisted charge transfer in α-Fe₂O₃/g-C₃N₄ heterojunctions for efficient and highly stable photoelectrochemical water splitting

Abstract

The development of semiconductor heterojunctions is a promising and yet challenging strategy to boost the performance in photoelectrochemical (PEC) water splitting. This paper describes the fabrication of a heterojunction photoanode by coupling α-Fe₂O₃ and g-C₃N₄via aerosol-assisted chemical vapour deposition (AACVD) followed by spin coating and air annealing. Enhanced PEC performance and stability are observed for the α-Fe₂O₃/g-C₃N₄ heterojunction photoanode in comparison to pristine α-Fe₂O₃ and the reason is systematically discussed in this paper. Most importantly, the fabricated α-Fe₂O₃/g-C₃N₄ film shows impressive stability, retaining more than 90% of the initial current over 12 h operating time. The excellent stability of the heterojunction photoanode is achieved due to the unique nanoflake structure of α-Fe₂O₃ induced by AACVD. This nanostructure promotes good adhesion with the g-C₃N₄ particles, as the particles tend to be trapped within the α-Fe₂O₃ valleys and eventually create strong and large interfacial contacts. This leads to improved separation of charge carriers at the α-Fe₂O₃/g-C₃N₄ interface and suppression of charge recombination in the photoanode, which are confirmed by the transient decay time, charge transfer efficiency and electrochemical impedance analysis. Our findings demonstrate the importance of nanostructure engineering for developing heterojunction structures with efficient charge transfer dynamics.