Synthesis and photoelectrochemical properties of nanoporous iron (III) oxide by potentiostatic anodization

We report the synthesis of self-organized nanoporous iron (III) oxide (haematite) via potentiostatic anodization of iron foil. Dependent upon the applied potential and electrolytic composition, the pore diameters range from 50 to 250 nm with a pore depth of approximately 500 nm. We examine the effect of electrolytic composition, anodization bath temperature and applied potential on the dimensions of the as-synthesized nanoporous structure. Crystallization and structural retention of the synthesized structure are achieved upon annealing the initial amorphous sample in a nitrogen atmosphere at 400 °C. The crystallized nanoporous film, having a 2.2 eV bandgap, exhibited a net photocurrent density of 0.51 mA cm−2 in 0.5 M H2O2+1 M NaOH at 0.6 V versus Ag/AgCl under simulated AM 1.5 sunlight. Factors limiting the photoresponse and strategies of improvement are discussed.

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