Insight into bay-/end-substituted perylene diimide and its S-scheme heterojunction for enhanced photocatalytic H2O2 production under visible-light irradiation

Here, 1D bis(N-carboxymethyl) peryleneimide (H 2 PDI), 0D 1,6,7,12-tetrachloro-bis(N-carboxymethyl) peryleneimide (4Cl-H 2 PDI), and 2D 4Cl-H 2 PDI/graphene quantum dot (4Cl-H 2 PDI/GQD) nanostructures are synthesized and carefully analyzed. The effect of bay-/end-substitution and S-scheme heterojunction of PDI-based materials as main catalysts on the photocatalytic H 2 O 2 evolution is first studied through the oxygen reduction reaction (ORR). Under the visible-light irradiation (> 420 nm), 4Cl-H 2 PDI and 4Cl-H 2 PDI/GQD as photocatalysts exhibit the ∼7 and ∼16 times H 2 O 2 evolution rate than H 2 PDI (1059.6 vs. 2484.0 vs. 160.0 µM g −1 h −1 ), respectively. The systematical experiments reveal that 4Cl-H 2 PDI and 4Cl-H 2 PDI/GQD should prefer a two-step single-electron ORR process, while H 2 PDI may involve a 4e ‒ water oxidation and one-step 2e ‒ ORR process. Further experiments confirm that the bay-substitution and GQD doping of H 2 PDI can promote the generation, transportation, and separation of photogenerated electrons and holes, and prolong the carrier lifetime. This work provides insight into PDI-based photocatalytic H 2 O 2 production.