Fe3+ doping promoted N2 photofixation ability of honeycombed graphitic carbon nitride: The experimental and density functional theory simulation analysis

Honeycombed iron doped graphitic carbon nitride with outstanding N-2 photofixation ability is synthesized in this work. Characterization results indicate that Fe3+ inserts at the interstitial position and is stabilized in the electron-rich g-C3N4 through the coordinative Fe-N bonds. Fe3+ sites can chemisorb and activate N-2 molecules, then transfer the photogenerated electrons from the g-C3N4 to adsorbed N-2 molecules. Fe0.05-CN displays the highest NH4+ generation rate, which is approximately 13.5-fold higher than that of neat g-C3N4. Density functional theory simulations prove the N-2 activation effect of Fe3+ sites due to the high adsorption energy and prolonged N equivalent to N bond. Charge density difference result confirms the electrons transfer process from the Fe3+ doping sites to N-2 molecule. DOS results indicate that the electrons of sigma(g)2p orbital (HOMO) in nitrogen atom is delocalized significantly when N-2 adsorbed on Fe3+ doping sites, leading to its orbital energy almost connects to that of pi g*2p orbital (LUMO), which confirming that Fe3+ doping sites can activate the N-2 molecule effectively. The Mulliken charge of nitrogen is -3.1 when the N-2 adsorbed on Fe3+ doping sites, indicating that N-2 molecule is enriched by large number of electrons, which is beneficial to the le attack to form NH4. (C) 2016 Elsevier B.V. All rights reserved.