Melamine-derived graphene-like C3N4 materials for electrochemical detection of Cr(VI) in wastewater

This study presents a comprehensive investigation into the synthesis, structural evolution, and electrochemical performance of fewer layers of graphitic carbon nitride (g-C 3 N 4 ) materials derived from melamine via a single-step solid-state thermal polycondensation process. Varying synthesis temperatures, the research elucidates the transformation from granular to rod-like morphologies finally the nanosheets, confirmed through SEM, TEM, XRD, Raman, and FTIR analyses. The physicochemical properties, including surface area and bandgap, were found to be highly temperature-dependent, with optimal exfoliation of g-C 3 N 4 resulting in fewer layers, exhibited enhanced surface characteristics observed at 650 °C. Furthermore, the electrochemical characterization using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) revealed quasi-reversible redox behaviour and diffusion-controlled kinetics, with the 650 °C sample exhibiting superior electron transfer capabilities (k° = 4.77 × 10 -9 cm s -1 , R ct = 1905.5 Ω). The optimized fewer layered g-C 3 N 4 modified carbon screen-printed electrode (CSPE), with a linear range from 2.5 to 7.5 μg L -1 , demonstrated high sensitivity (109.021 kΩ/μg L -1 ) and a low detection limit (0.13 μg L -1 ) for Cr (VI) in acid mine drainage. These findings highlight the potential of thermally exfoliated g-C 3 N 4 nanosheets for developing cost-effective, disposable electrochemical sensors for environmental monitoring of toxic heavy metals. • The synthesis of g-C 3 N 4 was successful using solid-state thermal synthesis method in a nitrogen environments. • The residence time affects the g-C 3 N 4 the number of layers • The as residence time increases the band gab decreased and the g-C 3 N 4 showed excellent electrochemical properties. • The fabricated sensor exhibited low detection limit for Cr (VI) in simulated and mine-impacted wastewater.