Construction of metal-free oxygen-doped graphitic carbon nitride as an electrochemical sensing platform for determination of antimicrobial drug metronidazole

Highlights: • Metal-free oxygen doped g-C₃N₄ (O-gCN) was prepared via thermal polymerization of urea and oxalic acid. • The prepared O-gCN was fabricated on a glassy carbon electrode for simple, inexpensive, and sensitive determination of MTZ. • The enhanced electrocatalytic effect was due to the change in the electronic structure and high surface area. • The proposed electrode displayed low detection and a wide linear range. • The viability of the O-gCN electrode was applied in water samples with acceptable results. A metal-free, cost-effective electrode modifier for the electrochemical sensor was reported in this work. Heteroatom doping is an interesting strategy to modify the electronic structure and enhance electrochemical performance. Herein, we developed oxygen-doped graphitic carbon nitride (O-gCN) via one-step thermal polymerization of urea and oxalic acid. The structural and morphology of the prepared samples were characterized using various analytical techniques. The electrochemical activity of O-gCN was analyzed using EIS, CV, and DPV studies revealed lower impedance, improved surface area, and excellent reduction current response than pristine graphitic carbon nitride due to the successful doping. Besides, the O-gCN/GCE showed a higher sensitivity of 7.784 µA µM⁻¹ cm⁻², a low detection limit of 0.005 µM with a wide linear range of 0.01–2060 µM. Additionally, the viability of the proposed sensor has been applied to determine the MTZ in water samples with desirable results.