First-principles calculation the electronic structure and the optical properties of Mn-decorated g-C3N4 for photocatalytic applications

Abstract

The electronic structure and the optical properties of Mn-decorated graphitic carbon nitride (g-C3N4) were investigated using the density functional method. The large absorption energy of the Mn atoms on the g-C3N4 surface was found to suppress the clustering of the Mn atoms, which led to a conservation of the photocatalytic activity. The electronic structures of the Mn-decorated g-C3N4 showed that impurity energy levels emerged in the forbidden band of g-C3N4 and that the band edge of g-C3N4 shifted upward to 0.40 eV. In addition, the calculated optical constants showed that the novel photon absorption in the range of visible light originated from electronic transitions from the N 2p states in the upper valence band to impurity Mn 3d states. Moreover, the photon absorption reached a maximum when all sites of triangular N holes were decorated with Mn atoms. Our results provide evidence that the Mn-decorated C3N4 system could be a highly-efficient photocatalyst for solar light due to the extension of the range of photon absorption to include almost all visible light.