Photoactive PDI–Cobalt Complex Immobilized on Reduced Graphene Oxide for Photoelectrochemical Water Splitting

We report the synthesis of a perylene derivative (perylene tetracarboxylic di­(propyl imidazole), abbreviated as PDI) that is coordinated with Co­(II) ions to form a coordination polymer [PDI–Co­(Cl)<sub>2</sub>(H<sub>2</sub>O)<sub>2</sub>]<sub><i>n</i></sub> (abbreviated as PDI-Co). The PDI-Co complex combines the photoactivity of the perylene dye with the electrocatalytic activity of the “Co­(II)” center for photoelectrochemical hydrogen evolution reaction (HER). To improve charge transfer interactions, the PDI-Co complex is immobilized on reduced graphene oxide (rGO) via noncovalent interactions to form the rGO–PDI-Co complex. The composite shows good performance in multiple cycle testing and the turnover number (TON vs Co<sup>II</sup>) of this hybrid material for hydrogen evolution reaction (754 after 5 h) is considerably higher than previously reported dye-sensitized cobalt-based catalysts.