Combination of microporous hollow carbon spheres and Nafion for the individual metal-free stripping detection of Pb ²⁺ and Cd ²⁺

Here, the combination of Nafion with microporous hollow carbon spheres (MHCS) is first proposed to fabricate a disposable metal-free electrode for heavy metal stripping sensing. The MHCS-Nafion composite film electrode is prepared by drop-casting a mixture of MHCS and Nafion onto the lab-made screen-printed carbon electrode (SPCE*). Results demonstrate that the interfusion of MHCS into Nafion offers enhanced performance for the electro-enrichment and stripping of lead and cadmium over the only Nafion film: 1) abundant MHCS immobilized on the electrode surface serve as effective nucleation sites for metal ion reduction; 2) the mixing of MHCS into Nafion enlarges the active surface of negative-charged Nafion for the electrostatic adsorption of metal cations. The proposed MHCS-Nafion/SPCE* provides linear responses for Pb ²⁺ and Cd ²⁺ in the range of 2-200 μg/L, with a detection limit of 1.37 and 1.63 μg/L, respectively. Practical applications of the sensor in water sample detection with good accuracy have also been confirmed.