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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.

ZnO nanorods have been grown on indium-tin-oxide coated glass substrates by a low cost chemical process. Current-voltage characteristics have been studied using ZnO nanorods as photoanode in an electrochemical cell. The flat band voltage shift and depletion width of ZnO nanorods/electrolyte interface have been estimated from Mott-Schottky (MS) characteristics. The electrochemical impedance measurements have been carried out to study the charge transport mechanism at the semiconductor-electrolyte interface under dark and white light (100 mW/cm2) illumination. The doping concentration of nanorods has been extracted from MS plot. Photoresponse behavior of ZnO nanorods is found to be enhanced than seed layers with the incident of white light. Spectral dependent photovoltage of ZnO nanorods has been carried out using monochromatic light of wavelength 250–600 nm. The photopotential recovery time has been estimated for nanorods and seed layers. The stability of ZnO nanorods as a photoanode has been investigated.

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