Enhanced photoelectrochemical performance of NaNbO3 nanofiber photoanodes coupled with visible light active g-C3N4 nanosheets for water splitting.

Sodium niobate nanofibers (NaNbO3-NF) have been synthesized using a hydrothermal technique and further coupled with visible light responsive graphitic carbon nitride (g-C3N4) nanosheets in different concentration ratios of 2:1 (2-CN), 4:1 (4-CN) and 8:1 (8-CN). A significant improvement in the photoelectrochemical (PEC) performance of the g-C3N4/NaNbO3-NF (4-CN) nanostructured photoanode compared to the bare NaNbO3 photoanode is observed. A current density of 12.55 mA cm-2 at 1 V with respect to the Ag/AgCl reference electrode is achieved for the g-C3N4/NaNbO3-NF (4-CN) photoanode, which is ∼3 times higher than the NaNbO3-NF photoanode. Also, compared to NaNbO3-NF, the g-C3N4/NaNbO3-NF (4-CN) nanocomposite photoanode showed ∼3 times improvement in the incident photon-to-current conversion efficiency. The improvement in the PEC performance of visible light active g-C3N4/NaNbO3-NF (4-CN) nanocomposite is attributed to the improved photoresponse of NaNbO3-NF due to the coupling of g-C3N4 and the formation of a type-II heterojunction between them leading to the enhanced separation of the photogenerated charge carriers. A possible reaction mechanism for the improved PEC water splitting performance has been proposed for the g-C3N4/NaNbO3-NF (4-CN) photoanode.