Step-scheme perylenediimide supramolecular nanosheet and TiO2 nanoparticle composites for boosted water splitting performance

Adjusting the band gap of organic-inorganic composites by chemical bonding can effectively construct Step-scheme (S-scheme) heterojunctions, featuring properties of fast photogenerated charge migration and excellent photocatalytic performance. In this work, a novel perylene-3, 4, 9, 10-tetracarboxylicdiimide (PDI)-titanium dioxide (TiO₂) heterojunction is elaborately synthesized through simple solvent compounding method. The monodispersed spherical TiO₂ nanoparticles was prepared with the capping agents of oleylamine and oleic acid, and suffered by a ligand exchange process with nitrosonium tetrafluoroborate (NOBF₄) to remove oleylamine and oleic acid. The NOBF₄ ligands were further replaced by PDI super molecular nanosheets to obtain two dimensional (2D)-zero dimensional (0D) PDI-TiO₂ composites. TiO₂ nanoparticles are evenly anchored on the surface of PDI nanosheets with intimate contact. The PDI-TiO₂ composites has emerged considerably superior activity in hydrogen evolution. The highest hydrogen evolution rate for PDI-TiO₂composites with the PDI weight percentage of 2.4% was 9766 μmol h^?1 g^?1 under solar light irradiation, which is 2.56 times of TiO₂-NOBF₄ catalyst. Moreover, PDI-TiO₂ composites possess stoichiometric overall water splitting performance with H₂ and O₂ release rates of 238.20 and 114.18 μmol h^?1 g^?1. The superior photocatalytic performance of PDI-TiO₂ composites can be attributed to the dramatic increase in visible and NIR light absorption caused by π-π stacking structure of PDI, the prevented charge recombination by the S-scheme heterojunction, and the enhanced oxygen evolution by the stronger oxidation capability of PDI. PDI supramolecular nanosheets may work as a novel functional support for many types of semiconductor nanomaterials as graphene, which will display a wide range of application prospects in the energy and environmental fields.