Roles of Cobalt‐Coordinated Polymeric Perylene Diimide in Hematite Photoanodes for Improved Water Oxidation

Abstract Interfacial charge recombination is a permanent issue that impedes the photon energy utilization in photoelectrochemical (PEC) water splitting. Herein, a conjugated polymer, urea linked perylene diimide polymer (PDI), is introduced to the designation of hematite‐based composite photoanodes. On account of its unique molecule structure with abundant electronegative atoms, the O and N atoms with lone electron pairs can bond with Fe atoms at the surface of Zr 4+ doped α ‐Fe 2 O 3 (Zr:Fe 2 O 3 ) and thus establish charge transfer channels for expediting hole separation and migration. Meanwhile, PDI molecules can passivate the surface states in Zr:Fe 2 O 3 , which is in favor of suppressing carrier recombination. Particularly, Co 2+ is used to coordinate with PDI (Co‐PDI) to accelerate hole extraction as well as utilization, and the as‐obtained Co‐PDI form type‐II heterojunction with Zr:Fe 2 O 3 . Such a photoanode configuration takes advantage of the unique molecule structure of PDI, and the target Co‐PDI/Zr:Fe 2 O 3 photoanodes eventually attain a photocurrent density of 2.17 mA cm −2 , which is inspirational for unearthing the potential use of conjugative molecules in PEC fields.