Hematite Nanorod Electrodes Modified with Molybdenum: Photoelectrochemical Studies

The preparation of hematite nanorod electrodes modified with molybdenum and their photoelectrochemical behavior for water photooxidation have been addressed in the quest for improved electrodes for water splitting. The hematite nanorods were synthesized through chemical bath deposition, and Mo was added by following two variants of a drop-casting method based on ammonium heptamolybdate solutions. FE-SEM, TEM, XRD, and XPS were employed for electrode structural and morphological characterization. The reported results reveal that the impregnation method does not cause significant changes in the hematite structure and nanorod morphology. Importantly, the modification with Mo triggers a significant improvement in the photoactivity of the electrodes, obtaining a photocurrent increase of up to 43×. A specific Mott−Schottky analysis applicable to nanostructured electrodes was performed, revealing that the modification with Mo leads to an increase in electron concentration and to a shift of the flat band potential toward more positive values. A second role of Mo as a passivating agent needs to be invoked to explain the experimental observations. It is worth noting that this modification method allows precise control of the amount of Mo contained in the samples while maintaining the morphology of the electrode.We are grateful to the Spanish MINECO for financial support through projects MAT2012-37676 and MAT2015-71727-R both supported with FEDER funds. A.C. thanks the Vicepresidency of Research, Development and Innovation of University of Alicante for financial support through an initiation research grant. D.C. is also grateful to MINECO for the award of an FPI grant