Enhanced photoelectrochemical performance of NaNbO ₃ nanofiber photoanodes coupled with visible light active g-C ₃ N ₄ nanosheets for water splitting

Sodium niobate nanofibers (NaNbO 3 -NF) have been synthesized using a hydrothermal technique and further coupled with visible light responsive graphitic carbon nitride (g-C 3 N 4 ) 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-C 3 N 4 /NaNbO 3 -NF (4-CN) nanostructured photoanode compared to the bare NaNbO 3 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-C 3 N 4 /NaNbO 3 -NF (4-CN) photoanode, which is ∼3 times higher than the NaNbO 3 -NF photoanode. Also, compared to NaNbO 3 -NF, the g-C 3 N 4 /NaNbO 3 -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-C 3 N 4 /NaNbO 3 -NF (4-CN) nanocomposite is attributed to the improved photoresponse of NaNbO 3 -NF due to the coupling of g-C 3 N 4 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-C 3 N 4 /NaNbO 3 -NF (4-CN) photoanode.