Enhanced photoelectrochemical performance of electrodeposited hematite films decorated with nanostructured NiMnOx

Abstract

In the present work, we report a novel nickel-manganese oxide (NiMnO_x) decorated hematite (α-Fe₂O₃) photoanode for efficient water splitting in a photoelectrochemical (PEC) cell. The photoanodes are prepared by a two step electrodeposition process. NiMnO_x loading on the hematite surface is varied by changing the electrodeposition time. The NiMnO_x loaded α-Fe₂O₃ photoanodes are characterized by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, UV-Vis absorption and photoluminescence spectroscopy. The results demonstrate that the NiMnO_x decorated α-Fe₂O₃ photoanode exhibits excellent photoelectrochemical activity. The α-Fe₂O₃/NiMnO_x photoanode, where NiMnO_x was coated for 200 s, shows a maximum photocurrent of 2.35 mA cm⁻² at an applied potential of 0.23 V vs. the Ag/AgCl reference electrode. There is a large shift in the onset potential towards the cathodic region also observed. The photoconversion efficiency is calculated which is around 0.85% at 0.23 V vs. Ag/AgCl. The superior PEC performance of NiMnO_x decorated α-Fe₂O₃ photoanodes can be explained by a combined effect of better water oxidation on the hematite surface and efficient separation of photogenerated electron–hole pairs on its surface due to NiMnO_x modification.