A theoretical study on the photocatalytic activity of g-C3N4/CoN4 for water splitting reaction

Density functional theory was employed to calculate the photocatalytic activity of the gC3N4/CoN4 heterojunction. g-C3N4 is a semiconductor and CoN4 is a half metal, eventually the resultant heterojunction is half metallic in nature. The metallicity originates from the spin down channel of the g-C3N4/CoN4 heterojunction while the spin up channel behaves as a semiconductor. The stability of the heterojunction was confirmed by calculating the formation energy from its isolated analogs. Charge density analysis and work function calculation suggests a substantial amount of charge transfer in g-C3N4/CoN4 heterojunction and the direction of charge transfer was found to be from g-C3N4 to CoN4 unit. The optical absorption of the nanocomposite was found to be significantly enhanced in the UV-visible region in comparison to g-C3N4 and CoN4. In g-C3N4/CoN4, the valence band maximum (VBM)(+1.42V) exhibits a more positive potential compared to O2/H2O(+1.23V) on the NHE scale, while the conduction band minimum (CBM)(-0.38V) displays a more negative potential than that of H+ /H2(0V) on the NHE scale. Consequently, this heterojunction can be effectively utilized for water splitting. Finally, details of band structure, density of states and band edge position determining calculations confirm that g-C3N4/CoN4 composite forms type 1 heterojunction, making it a suitable photocatalyst for water splitting reaction. The state-of-theart theoretical modeling of g-C3N4/CoN4 heterojunction is the first theoretical study incorporating CoN4 crystal.