Photo-assisted simultaneous electrochemical detection of multiple heavy metal ions with a metal-free carbon black anchored graphitic carbon nitride sensor

The simultaneous detection of multiple heavy metal ions in solution is an important yet highly challenging problem. In this work, a metal-free g-C3N4/carbon black (CB) composite electrode was synthesized by a one-step thermal polycondensation method and characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and ultraviolet visible light spectroscopy. In addition, the photoelectrochemical response of the g-C3N4/CB nanocomposite to Cd2+, Pb2+ and Hg2+ both separately and as a mixture of the three analytes was investigated by differential pulse anodic stripping voltammetry. The g-C3N4/CB electrode demonstrated an excellent sensing performance to Cd2+, Pb2+ and Hg2+ in the range of 0–700 nM, 0–300 nM and 0–500 nM, respectively, with limits of detection (LOD) of Cd2+, Pb2+, and Hg2+ of 2.1, 0.26 and 0.22 nM, respectively. The LOD of the combined solution of the three analytes was slightly higher at 3.3 nM. Additionally, the metal-free g-C3N4/CB photoelectrochemical sensor exhibited excellent electrochemical stability and electrode reproducibility. Finally, g-C3N4/CB sensor also showed satisfactory results in the detection of trace analyte ions in real environmental systems. This work provides a novel and promising approach in the simultaneous detection of multiple heavy metal ions in solution for practical applications.