Photoactivities of Nanostructured α-Fe2O3 Anodes Prepared by Pulsed Electrodeposition

Ferric oxide (-Fe 2 O 3 , hematite) is an n-type semiconductor; due to its narrow band gap (E g = 2.1 eV), it is a highly attractive and desirable material for use in solar hydrogenation by water oxidation. However, the actual conversion efficiency achieved with Fe 2 O 3 is considerably lower than the theoretical values because the considerably short diffusion length (2-4 nm) of holes in Fe 2 O 3 induces excessive charge recombination and low absorption. This is a significant hurdle that must be overcome in order to obtain high solar-to-hydrogen conversion efficiency. In consideration of this, it is thought that elemental doping, which may make it possible to enhance the charge transfer at the interface, will have a marked effect in terms of improving the photoactivities of -Fe 2 O 3 photoanodes. Herein, we report on the synthesis by pulsed electrodeposition of -Fe 2 O 3 -based anodes; we also report on the resulting photoelectrochemical (PEC) properties. We attempted Ti-doping to enhance the PEC properties of -Fe 2 O 3 anodes. It is revealed that the photocurrent density of a bare -Fe 2 O 3 anode can be dramatically changed by controlling the condition of the electrodeposition and the concentration of TiCl 3 . Under optimum conditions, a modified -Fe 2 O 3 anode exhibits a maximum photocurrent density of 0.4 mA/cm 2 at 1.23 V vs. reversible hydrogen electrode (RHE) under 1.5 G simulated sunlight illumination; this photocurrent density value is about 3 times greater than that of unmodified -Fe 2 O 3 anodes.