Surface engineering of hematite nanorods photoanode towards optimized photoelectrochemical water splitting

Rapid charge recombination in hematite (Fe₂O₃) during photoelectrochemical water splitting is a major obstacle to achieving high-efficiency photoelectrodes. Surface defect engineering is considered as a viable strategy for enhancing photoelectrochemical activity of oxide photoanodes. Herein, a one-dimensional (1D) defective γ-Fe₂O₃ nanorods (DFNRs) photoanode is prepared using solvothermal and high-temperature hydrogenation strategies. The as-prepared DFNRs possess superior visible-light absorption capacity and exhibit excellent photoelectrochemical performance (0.98 mA cm^-2), with approximately three-fold higher photocurrent density than that of pristine Fe₂O₃ (FNRs, 0.32 mA cm^-2). The enhanced activity of the DFNRs results from the moderate formation of oxygen vacancy defects, which promotes spatial charge separation and transfer at the DFNRs/electrolyte interface, as well as the 1D nanorod structure, which favors rapid charge transfer. The surface of γ-Fe₂O₃ with hydroxyl (OH) groups provides sufficient surface-active sites. This result suggests that surface-oxygen deficiency of γ-Fe₂O₃ can not only expand the light absorption range but also facilitating photo-generated charge carriers separation. This surface engineering strategy provides an alternative method for preparing stable and highly active metal oxide photoanodes for photoelectrochemical water splitting.