Electrochemical Sensors for Heavy Metals: Progress, Hurdles, and Future Directions

Heavy metal contamination remains a critical global challenge with serious implications for environmental safety and public health. Electrochemical sensing techniques have emerged as powerful tools for heavy metal detection owing to their high sensitivity, portability, rapid response, and cost-effectiveness. Despite significant progress, translating laboratory-scale electrochemical sensors into reliable, field-deployable systems remains constrained by challenges such as poor selectivity in complex matrices, electrode fouling, reproducibility issues, and the need for extensive sample pretreatment. This review critically examines recent advances (post-2020) in electrochemical techniques for heavy metal detection, encompassing voltammetry, potentiometry, and electrochemical impedance spectroscopy. Particular emphasis is placed on the role of advanced electrode materials, including nanomaterials, nanocomposites, and biofunctional interfaces, in enhancing sensitivity, selectivity, and operational stability. Beyond material innovation, this review highlights emerging trends in microfluidics and sustainable electrode design, as well as the integration of Internet of Things (IoT) platforms and artificial intelligence-assisted data analysis for smart sensing. Practical limitations and performance trade-offs under real environmental conditions are systematically analysed. Finally, future directions are outlined, focusing on standardisation, sustainability, and the development of robust, user-friendly, and interconnected electrochemical sensors capable of real-time environmental monitoring and large-scale deployment.