H2O molecule adsorption on s-triazine-based g-C3N4

Abstract

The interaction between a gas molecule and photocatalyst is vital to trigger photocatalytic reaction. The surface state of photocatalyst affects much in this interaction. Herein, adsorption of H2O molecules on s-triazine-based g-C3N4 was thoroughly studied by first-principle calculation. Although various initial adsorption models with multifarious locations of H2O molecules were built, the optimized models with strong adsorption energy pointed to the same adsorption configuration, in which the H2O molecule hold an upright orientation above the corrugated g-C3N4 monolayer. An intermolecular O–H…N hydrogen bond formed via the binding of a polar O–H bond in H2O molecule and a two-coordinated electron-rich nitrogen atom in g-C3N4. Under the bridging effect of this intermolecular hydrogen bond, electrons would transfer from g-C3N4 to the H2O molecule, thereby lowering the Fermi level and enlarging work function of g-C3N4. Interestingly, regardless of the substitute, i.e. g-C3N4 multilayer, large supercell and nanotube, this adsorption system was highly reproducible, as its geometry structure and electronic property remained unchanged. In addition, the effect of nonmetal element doping on adsorption energy was explored. This work not only disclosed a highly preferential H2O adsorbed g-C3N4 architecture established by intermolecular hydrogen bond, but also contributed to the deep understanding and optimized design in water-splitting process on g-C3N4-based photocatalysts.