Inhomogeneities of charge distribution in porous graphitic carbon nitride g-CxNy nanosheets

Porous graphitic carbon nitrides g-CxNy (g-CN, g-C2N and g-C3N4) were studied computationally using semi-empirical molecular orbital method to obtain insights into charge distribution in them. It is found that the charge distribution is inhomogeneous but has good symmetry in the symmetrical structure. And sheet boundary has significant effect on the charge distribution. All N atoms have negative charge due to electrons enrichment. The absolute charge value of the edge atoms is significantly larger than that of the internal atoms in g-CN and g-C2N, which is opposite in g-C3N4. For the C atom, all C atoms show positive charge in g-CN. However, in g-C2N, the double-bond and triple-bond C atoms at the boundary have different gain and loss electrons. The internal triple-bond C atoms show the same positive charge value.