Limited by the retarded charge carrier migration and the sluggish four-electron reaction kinetics, it is still a great challenge for polymeric semiconductors to achieve efficient photocatalytic water oxidation. Herein, single Co atoms and ultra-small CoOx clusters are simultaneously introduced into polymeric perylene diimide (PDI) through a facile impregnation-calcination two-step method. The obtained Co-PDI exhibits excellent photocatalytic water oxidation activity under visible-light irradiation, with an oxygen evolution rate reaching as high as 5.53 mmol h–1 g–1 (λ > 420 nm). The apparent quantum yield for oxygen evolution is determined to be 8.17% at 450 nm, and remains 0.77% at even longer visible light wavelength of 700 nm without redundant co-catalysts, indicating that Co-PDI may serve as an excellent oxygen evolution photocatalyst for water splitting. Theoretical calculations and experimental results demonstrate that single Co atoms act as the electron mediators connecting adjacent PDI layers to build directional channels for rapid charge transfer, while ultra-small CoOx clusters as hole collectors and reaction sites to accelerate oxygen evolution reaction kinetics. The study presents a facile and reliable strategy to effectively activate polymeric semiconductors for efficient photocatalysis by rationally modulating atomic structures and active sites for promoted charge carrier transfer and surface reaction kinetics.
