Photoelectrochemical Properties of Nitrogen Doped Graphene Quantum Dots Sensitized Copper Oxide Nanotaper Photoanode

The photoelectrochemical (PEC) and stability performance of CuO nanotapers (CuO NT) sensitized with nitrogen-doped graphene quantum dots (NGQD) has been investigated. NGQDs and CuO NTs were synthesized using facile, low-cost, and scalable solvothermal and hydrothermal methods, respectively. Morphological characterization of the CuO NTs and NGQDs was achieved through the analysis of scanning electron microscopy (SEM) and transmission electron microscope (TEM) images. The CuO NTs are about 500 nm in length, and the NGQDs have diameters ranging from 2.5 nm to 6 nm. The X-ray photoelectron spectroscopy (XPS) analysis confirmed nitrogen doping in GQDs and the attachment of NGQDs to CuO NTs. Photoluminescence (PL) and UV-visible (UV-vis) spectroscopy were used to study the optical properties of NGQDs. Linear sweep voltammetry, amperometric i-t measurements, and electrochemical impedance spectroscopy were used to investigate the photoelectrochemical properties of the photoanodes. Sensitization with NGQDs significantly enhanced the performance of the CuO NT photoanode, yielding a two-fold increase in short-circuit photocurrent density and a 13.35-fold enhancement in the photocurrent-to-dark current ratio. A photostability study using extended amperometric i-t measurements demonstrated that NGQD sensitization significantly enhanced the CuO NT photoanode’s ability to retain photocurrent.

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