The effect of water on the structural, electronic and photocatalytic properties of graphitic carbon nitride

Abstract

g-C3N4, as a typical metal-free catalyst for water splitting, has attracted special attention. The structural and electronic properties of water adsorption on g-C3N4 play a key role in understanding the water splitting mechanism at the atomic level. The properties of a single g-C3N4 sheet and the water adsorption on a single g-C3N4 sheet were thoroughly explored based on density functional theory (DFT) calculations. The results show that water adsorption on one side of the single g-C3N4 sheet will lead the initial flat structure to change to a buckle one, while water molecule adsorption on both sides of g-C3N4 will not disturb the flat structure. The flat g-C3N4 is an indirect semiconductor, and interestingly the band structure of g-C3N4 changes from an indirect to a direct one during the flat structure transformation from flat to buckle because of the water adsorption. Water molecules prefer to adsorb around the intrinsic vacancy of the single g-C3N4 sheet at low coverage, and further adsorbed water molecules stay around the intrinsic vacancy. Water adsorption also affects the band edge position of g-C3N4 for water splitting. These results provide a deep insight into the structure and adsorption properties of g-C3N4 in the water environment, which will greatly help to design a new type of metal-free catalyst for water-splitting.

The g‐C3N4/C2N Nanocomposite: A g‐C3N4‐Based Water‐Splitting Photocatalyst with Enhanced Energy Efficiency

“…From Figure b, we find that the g‐C 3 N 4 /C 2 N nanocomposite possesses a broad absorption from the visible‐ to UV‐light regions, with an intensity of 10 4 cm −1 . Compared with the isolated g‐C 3 N 4 monolayer, which only shows a clear absorption above 3.6 eV, as also observed in previous studies, the optical absorption of the g‐C 3 N 4 /C 2 N nanocomposite is enhanced notably, with the absorption edge significantly shifted down by about 0.85 eV. The enhancement of the optical absorption is expected to result from C 2 N, and also the interlayer coupling between the two components …”

Charge Modulation in Graphitic Carbon Nitride as a Switchable Approach to High‐Capacity Hydrogen Storage

“…Here, we used g-C 4 N 3 [28,29] and g-C 3 N 4 [30] as examples, whichw ere synthesized by cross-linking nitride-containing anionsi na n ionic liquid. Consistent with previouss tudies, [29,31] g-C 4 N 3 adopts a(22) reconstructed structure whereas g-C 3 N 4 prefers ab uckle structure. Consistent with previouss tudies, [29,31] g-C 4 N 3 adopts a(22) reconstructed structure whereas g-C 3 N 4 prefers ab uckle structure.…”

Mechanistic insight into the water photooxidation on pure and sulfur-doped g-C3N4 photocatalysts from DFT calculations with dispersion corrections

“…The calculated H N distances in the hydrogen bonds are between 2.10 and 2.40 Å. The adsorption energy is computed to be −0.62 eV, lower than that by a periodic first-principles (PBE) study and in good agreement with the other two previous theoretical reports with correction for dispersion interaction [39,40]. Due to its physisorption characteristic, the H 2 O* molecule almost keeps intact with its H O bond lengths of 0.98 Å and the angle H O H of 101.46 • .…”