Nitrogen‐Doped Graphene Quantum Dot‐Decorated ZnO Nanorods for Improved Electrochemical Solar Energy Conversion

Nitrogen‐doped graphene quantum dots (N‐GQDs) have been synthesized using a hydrothermal process. The N‐GQDs are highly crystalline with a size of 3–7 nm and made up of 1–3 layers of graphene. UV/Vis absorption studies reveal two major absorption peaks at 237 and 334 nm, which are attributed to the π→π* transition of C=C and n→π* transition of C=O bonds, respectively. The additional broad peak observed at 460–500 nm is attributed to the n→π* transition of C=N bonds. The N‐GQDs are highly luminescent and exhibit excitation‐dependent emission. The photoelectrochemical properties of pristine ZnO and N‐GQD‐sensitized ZnO nanorods have been investigated. N‐GQD‐sensitized nanorod photoanodes demonstrate superior photoconversion efficiency, incident photon‐to‐current conversion efficiency, and power conversion efficiency compared with pristine ZnO nanorods.