Increased Active Sites on Irregular Morphological α-Fe₂O₃ Nanorods for Enhanced Photoelectrochemical Performance

Uniform rectangular α-Fe₂O₃ nanorods (R-Fe₂O₃) and irregular α-Fe₂O₃ nanorods (D-Fe₂O₃) with a random size vertically aligned on fluorine-doped tin oxide were prepared with a facile one-step hydrothermal procedure. X-ray diffraction (XRD) measurements and Raman spectra confirm that the obtained samples are α-Fe₂O₃, and XRD patterns show that D-Fe₂O₃ has two extra (012) and (104) planes of hematite in addition to the identical peaks to R-Fe₂O₃. The carrier density of the D-Fe₂O₃ sample is four times larger than that of R-Fe₂O₃. Finally, the D-Fe₂O₃ photoelectrode exhibited a better photoelectrochemical (PEC) performance under visible illumination than that of R-Fe₂O₃, achieving the photocurrent density of 0.15 mA cm^-2 at 1.23 V versus reversible hydrogen electrode. In addition, incident photo-to-current conversion efficiency of D-Fe₂O₃ is nearly three times larger than that of R-Fe₂O₃. Hence, the improved PEC performance of D-Fe₂O₃ can be ascribed to higher carrier density resulting from the amount of oxygen vacancies and more activated exposed surface facets.