Characterizing surface states in hematite nanorod photoanodes, both beneficial and detrimental to solar water splitting efficiency

The performance of hematite and Ti-substituted hematite nanorods as photoanodes for solar water splitting was quantitatively evaluated from the photoelectrochemical point of view. The nanostructure, morphology and chemical/electronic structure were characterized using various complementary methods, including X-ray diffraction, electron microscopy, X-ray photoelectron spectroscopy and scanning transmission X-ray microscopy. The presence of both reductive and oxidative surface states was evidenced and their impact on the photoelectrochemical efficiency was characterized. We show that both electronic conduction enhancement provided by the Ti substitution and charge transfer promoted by oxidative surface states improve the solar water splitting performance.