Zerovalent Fe Atom-Enriched Fe3C@C Electrocatalysts for Selective Heavy Metals Sensing

This study addresses emerging concerns regarding the toxicity of heavy metals in daily consumption and their severe health implications. Hence, there is a critical need to develop an accurate monitoring tool for heavy metals in environmental sources. Herein, we report zerovalent iron-enriched Fe₃C@C (Fe⁽⁰⁾/Fe₃C@C) obtained from carbonization of matériaux l’institut lavoisier-88A (MIL-88A), a member of the metal–organic framework (MOF) as a superior electrocatalyst for the simultaneous detection of various heavy metals. The morphology and properties of Fe⁽⁰⁾/Fe₃C@C are controllable at different temperature conditions so that the maximum carbon-confined zerovalent iron (ZVI) atoms are achieved at higher temperature pyrolysis (900 °C) of MIL-88A. As a result, it shows the best performance in the electrochemical detection of heavy metals owing to its reduction capability, higher affinity, strong adsorption capacity, abundant active sites, and ionic conductivity. The X-ray absorption spectroscopy (XAS) performed under different conditions indicates that the additional charges from modified Fe clusters significantly enhance the electrochemical performance. The simultaneous and individual electrochemical sensing performance based on Fe⁽⁰⁾/Fe₃C@C-900 demonstrated an excellent sensitivity with a lower limit of detection (LOD) of 0.29 nM, 0.54 nM, 0.68 nM, and 0.92 nM for simultaneous sensing and 3.20 nM, 1.69 nM, 7.96 nM, and 2.04 nM for individual sensing of cadmium ion (Cd²⁺), lead ion (Pb²⁺), copper ion (Cu²⁺), and mercury ion (Hg²⁺), respectively, over concentrations ranges from 15 μM to 75 μM using the differential pulse voltammetry (DPV) technique. Furthermore, real-time analysis in water samples for the electrochemical detection of proposed heavy metals is demonstrated. Overall, this study aims to highlight the importance of controlling pyrolysis and electrode characterization and enabling simultaneous electrochemical detection of heavy metal for further commercial applications.