Photoanode with multilayered nanostructure developed for efficient photoelectrochemical water splitting

Hematite (α-Fe₂O₃) is considered one of the most promising materials for photoelectrochemical (PEC) water splitting under solar light. However, the drawbacks of lower charge transfer efficiency and slow oxygen evolution reaction (OER) kinetics limit the practical application of α-Fe₂O₃ photoanodes. Therefore, efforts have been made to promote the PEC properties of α-Fe₂O₃, such as elemental doping, morphology modulation, and construction of heterojunctions.

In a study published in International Journal of Hydrogen Energy, the research group led by Prof. Lu Canzhong from the Fujian Institute of Research on the Structure of Matter of the Chinese Academy of Sciences reported a novel α-Fe₂O₃ photoanode with multilayered In₂O₃/Co-Mn nanostructure for efficient photoelectrochemical water splitting.

The researchers synthesized α-Fe₂O₃ nanorod arrays using classic hydrothermal methods, followed by a layer of In₂O₃ nanolayers covered on the α-Fe₂O₃ using wet chemical deposition, and ultimately covered with a layer of nanosheet combining ultrathin non-crystalline Co(OH)_x and Mn₃O₄ nanocrystals (Co-Mn nanosheet coating) using electrodeposition.

By linear sweep voltammetry (LSV) testing, the researchers found that the high photocurrent density of In₂O₃/Co-Mn modified α-Fe₂O₃ photoanode is 13.8 times that of ordinary α-Fe₂O₃ materials. They also tested the efficiency of incident photons photocurrent(IPCE), and found that the IPCE value of pristine α-Fe₂O₃ at an incident light wavelength of 400 nm is only 9.5 %, and the IPCE value of In₂O₃/Co-Mn modified α-Fe₂O₃ photoanode is 57.9 %.

In addition, they evaluated the H₂ production rate. The In₂O₃/Co-Mn modified α-Fe₂O₃ photoanode production reached 74.10 mmol/cm²/h, which was 13.12 times higher than the α-Fe₂O₃ photoanode.

The researchers also revealed that the loading of In₂O₃ nanolayers significantly improves the photoelectrochemical water oxidation activity of α-Fe₂O₃ nanorods. The heterojunction formed by the In₂O₃ passivation layer and α-Fe₂O₃ effectively promotes charge separation, increasing photocurrent density.

The Co-Mn nanosheet coating loading helps improve the water oxidation performance of α-Fe₂O₃, and this multi-layer structure enables efficient photoelectrochemical water decomposition of α-Fe₂O₃ nanorods.