Modification of a thin layer of α-Fe2O3 onto a largely voided TiO2 nanorod array as a photoanode to significantly improve the photoelectrochemical performance toward water oxidation

Abstract

A largely voided TiO₂ nanorod array was synthesized and further modified with a thin layer of α-Fe₂O₃ (Fe₂O₃@TiO₂), by the pyrolysis of an FeCl₃ ethanol solution, as a photoanode toward water oxidation, showing significantly improved photoelectrochemical performance over a TiO₂ nanorod array. Among all of the Fe₂O₃ decorated TiO₂-based photoanodes, the optimal voided Fe₂O₃@TiO₂ nanorod array photoanode delivered the largest photocurrent density of 3.39 mA cm⁻² at 1.23 V (vs. RHE) and the highest applied bias photon-to-current efficiency (ABPE) (1.153%) under 100 mW cm⁻² UV-vis light illumination. In particular, the ABPE for the as-prepared photoanode was ∼3.3 times higher than that of the plain TiO₂ nanorod array (0.35%), ∼11.3 times higher than that of the Fe₂O₃-modified randomly arranged TiO₂ nanorods and ∼6.2 times higher than that of a Fe₂O₃-modified densely arranged TiO₂ nanotube array. The significant enhancement mainly originates from the large voids in the nanorod array allowing a thin layer of Fe₂O₃ to fully modify the TiO₂ nanorods, which improves the absorption of UV light, boosts the charge interface transfer rate, reduces the charge diffusion length and suppresses the charge recombination process. This work demonstrates a feasible route to improving the photoelectrochemical catalytic performance of TiO₂ semiconductors toward water splitting.