DFT calculations for single-atom confinement effects of noble metals on monolayer g-C 3 N 4 for photocatalytic applications.

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-C 3 N 4 confining noble metal single atoms (NM 1 @g-C 3 N 4 ) will be performed by using DFT calculations. The geometric structure calculations indicate that the most favorable anchored sites for the NM 1 is located in the six-fold cavity, and the deformed wrinkle space of g-C 3 N 4 helps the NM 1 to be stabilized in the six-fold cavity. The electronic structure calculations show that the conduction band of NM 1 @g-C 3 N 4 moved down and crossed through the Fermi level, resulting in narrowing the band gap of the NM 1 @g-C 3 N 4 . Moreover, the confined NM 1 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 NM 1 in NM 1 @g-C 3 N 4 show that Rh 1 @, Pd 1 @, Ir 1 @ and Pt 1 @g-C 3 N 4 SACs may have better photocatalytic performance than other NM 1 @g-C 3 N 4 SACs. Finally, Pt 1 @g-C 3 N 4 SACs are considered to have higher photocatalytic activity than other NM 1 @g-C 3 N 4 SACs. These results demonstrate that the confinement effects of noble metals on monolayer g-C 3 N 4 not only makes the single atom more stable to be anchored on g-C 3 N 4 , but also enhances the photocatalytic activity of the system through the synergistic effect between the confined NM 1 and the monolayer g-C 3 N 4 . These detailed research may provide theoretical support for engineers to prepare photocatalysts with higher activity.