A Facile Surface Passivation of Hematite Photoanodes with Iron Titanate Cocatalyst for Enhanced Water Splitting

The surface modification of semiconductor photoelectrodes with passivation overlayers has attracted great attention as an effective strategy to improve the charge separation and charge transfer processes across the semiconductor‐electrolyte interface. In this work, a thin Fe2TiO5 layer was decorated on nanostructured hematite nanoflake and nanocoral photoanodes (by thermal oxidation of iron foils) by a facile water‐based solution method. Photoelectrochemical measurements show that the Fe2O3/Fe2TiO5 heterostructure exhibits an obvious enhancement in photoelectrochemical water oxidation performance compared to the pristine hematite. For example, at 1.23 V versus the reversible hydrogen electrode (VRHE) in 1 m KOH under AM 1.5 G (100 mW cm−2) illumination, a 4–8× increase in the water oxidation photocurrent is achieved for Fe2O3/Fe2TiO5, and a considerable cathodic shift of the onset potential up to 0.53–0.62 VRHE is obtained. Moreover, the performance of the Fe2O3/Fe2TiO5 heterostructure can be further improved by decoration with a SnOx layer. The enhancement in photocurrent can be attributed to the synergistic effect of Fe2TiO5/SnOx overlayers passivating surface states, and thus reducing surface electron–hole recombination. Shields up! A thin Fe2TiO5 layer was decorated on nanostructured hematite photoanodes by a facile water‐based solution method. The Fe2O3/Fe2TiO5 heterostructure exhibits an obvious enhancement in solar water splitting. The enhancement in photocurrent can be attributed to the effect of Fe2TiO5 overlayers passivating surface states and thus reducing surface electron–hole recombination.