Molten salt assistant synthesis of three-dimensional cobalt doped graphitic carbon nitride for photocatalytic N2 fixation: Experiment and DFT simulation analysis

Abstract In this work, three-dimensional cobalt doped graphitic carbon nitride was synthesized by molten salt assistant method. XRD, N 2 adsorption, SEM, XPS, UV–Vis spectroscopy, N 2 -TPD and Photoluminescence were used to characterize the prepared catalysts. The result shows that the addition of molten salt remarkably changes the morphology of as-prepared catalyst. Cobalt exists as coordinative Co-N bond, which can chemisorb and activate N 2 molecules, and promote the electron transfer from catalyst to the nitrogen molecules. The as-prepared cobalt doped g-C 3 N 4 displays the NH 4 + production rate of 5.8 mg·L −1 ·h −1 ·g cat −1 , which is 24 times of bulk g-C 3 N 4 . Density functional theory (DFT) simulations show that cobalt doping can not only prolong N N bond which activate N 2 molecules, but promote the electrons-holes separation efficiency of g-C 3 N 4 . The d orbit of cobalt easily acts as a channel for transferring electrons from the transition metal to the N 2 molecule, which enhances the N 2 photofixation ability.