Nanostructured Iron Vanadate Photoanodes with Enhanced Visible Absorption and Charge Separation

Nanostructuring has been an effective method to improve the charge separation of semiconductors with poor charge transport properties. FeVO4 is a promising photoanode with a band gap of ∼2.1 eV, theoretical photocurrent of 13 mA cm–1, and solar-to-hydrogen efficiency of up to 16%. However, its photoelectrochemical (PEC) activity is limited by the low charge transport properties. In this report, a two-step synthesis method is found to control the growth of FeVO4 photoanodes to become a nanorod or film. Nanostructured FeVO4 is demonstrated to achieve higher photocurrent density due to the higher charge separation efficiency and enlarged absorption range. In addition, the band gap of FeVO4 nanorods has decreased by 0.16 eV, which is attributed to the formation of vanadium vacancy, as supported by calculation results. This work demonstrates that nanostructuring and vacancy incorporation synergistically improve the PEC performance of FeVO4-based photoanodes.