DFT calculations for single-atom confinement effects of noble metals on monolayer g-C3N4 for photocatalytic applications

Abstract

Graphitic carbon nitride, as a very promising two-dimensional structure host for single atom catalysts (SACs), has been studied extensively due to its significant confinement effects of single atoms for photocatalytic applications. In this work, a systematic investigation of g-C₃N₄ confining noble metal single atoms (NM₁@g-C₃N₄) will be performed by using DFT calculations. The geometric structure calculations indicate that the most favorable anchored sites for the NM₁ is located in the six-fold cavity, and the deformed wrinkle space of g-C₃N₄ helps the NM₁ to be stabilized in the six-fold cavity. The electronic structure calculations show that the conduction band of NM₁@g-C₃N₄ moved down and crossed through the Fermi level, resulting in narrowing the band gap of the NM₁@g-C₃N₄. Moreover, the confined NM₁ provide a new channel of charge transport between adjacent heptazine units, resulting in a longer lifetime of photo-generated carriers except Ru, Rh, Os and Ir atoms. Furthermore, the d-band centres of NM₁ in NM₁@g-C₃N₄ show that Rh₁@, Pd₁@, Ir₁@ and Pt₁@g-C₃N₄ SACs may have better photocatalytic performance than other NM₁@g-C₃N₄ SACs. Finally, Pt₁@g-C₃N₄ SACs are considered to have higher photocatalytic activity than other NM₁@g-C₃N₄ SACs. These results demonstrate that the confinement effects of noble metals on monolayer g-C₃N₄ not only makes the single atom more stable to be anchored on g-C₃N₄, but also enhances the photocatalytic activity of the system through the synergistic effect between the confined NM₁ and the monolayer g-C₃N₄. These detailed research may provide theoretical support for engineers to prepare photocatalysts with higher activity.