Theoretical Insights into the Atomic and Electronic Structures of Polyperyleneimide: On the Origin of Photocatalytic Oxygen Evolution Activity

Polymeric perylene diimide (PDI) has been evidenced as a good candidate for photocatalytic water oxidation, yet the origin of the photocatalytic oxygen evolution activity remains unclear and needs further exploration. Herein, with crystal and atomic structures of the self-assembled PDI revealed from the X-ray diffraction pattern, the electronic structure is theoretically illustrated by the first-principles density functional theory calculations, suggesting the suitable band structure and the direct electronic transition for efficient photocatalytic oxygen evolution over PDI. It is confirmed that the carbonyl O atoms on the conjugation structure serve as the active sites for oxygen evolution reaction by the crystal orbital Hamiltonian group analysis. The calculations of reaction free energy changes indicate that the oxygen evolution reaction should follow the reaction pathway of H₂O → *OH → *O → *OOH → *O₂ with an overpotential of 0.81 V. Through an in-depth theoretical computational analysis in the atomic and electronic structures, the origin of photocatalytic oxygen evolution activity for PDI is well illustrated, which would help the rational design and modification of polymeric photocatalysts for efficient oxygen evolution.