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.