In-Situ solid-state synthesis of 2D/2D interface between Ni/NiO hexagonal nanosheets supported on g-C3N4 for enhanced photo-electrochemical water splitting

Abstract Herein, we report a synthesis of 2D/2D interfaces between nickel/nickel oxide (Ni/NiO) hexagonal nanosheets with graphitic-carbon nitride (g-C3N4) using an in-situ solid-state heat treatment that shows enhanced activity for electrochemical as well as photo-electrochemical (PEC) water splitting. The transmission electron microscopy characterization confirms the homogenous dispersion of 2D hexagonal nanosheets of Ni/NiO on the surface of g-C3N4. The higher electrochemical and PEC water splitting activity of 2D/2D interface may be due to the more intimate contact between 2D sheets of NiO with g-C3N4. Moreover, the effect of NiO loading in nanoheterostructures have been studied towards overall water splitting by varying the ratio of precursors for NiO to that of g-C3N4 viz. 1:1, 1:8, and 1:16. A compositional ratio of 1:8 have been found to show the best PEC activity towards OER depicting a maximum photocurrent density of 20 mA cm−2 at an over potential of 190 mV. Whereas, the highest ratio of NiO to g-C3N4 nanosheets (i.e. 1:1) was noted to demonstrate the best performance towards electrochemical hydrogen evolution reaction showing dramatically reduced over potential of 26 mV to drive a current density of 10 mA cm−2.