Improved photoelectrochemical water splitting of hematite nanorods thermally grown on Fe–Ti alloys

•Hematite nanorods are formed on FeTi alloys using a simple thermal treatment.•The use of FeTi alloys suppresses the formation of thick suboxide underlayers.•A remarkable cathodic shift of the water splitting onset potential is obtained.

Here we show that hematite (α-Fe2O3) nanostructures with a high water splitting performance can be formed on Fe–Ti alloys using the most simple thermal treatment in air and Ar. The use of the Fe–Ti alloy suppresses the formation of thick suboxide underlayers that are strongly detrimental for the photoconversion efficiency. The formed nanorod structures show an onset potential of up to 0.6–0.7 VRHE. This beneficial effect is attributed to the combination of suppression of a thick suboxide and the nature of the α-Fe2O3 nanorods after Ar annealing.