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

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-Fe 2 O 3 and g-C 3 N 4 via aerosol-assisted chemical vapour deposition (AACVD) followed by spin coating and air annealing. Enhanced PEC performance and stability are observed for the α-Fe 2 O 3 /g-C 3 N 4 heterojunction photoanode in comparison to pristine α-Fe 2 O 3 and the reason is systematically discussed in this paper. Most importantly, the fabricated α-Fe 2 O 3 /g-C 3 N 4 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-Fe 2 O 3 induced by AACVD. This nanostructure promotes good adhesion with the g-C 3 N 4 particles, as the particles tend to be trapped within the α-Fe 2 O 3 valleys and eventually create strong and large interfacial contacts. This leads to improved separation of charge carriers at the α-Fe 2 O 3 /g-C 3 N 4 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. Modification of the nanostructural features of an α-Fe 2 O 3 /g-C 3 N 4 heterojunction photoanode contributes to a threefold stability enhancement in photoelectrochemical water splitting owing to the efficient charge transfer dynamics.