Conversion of waste eggshell into difunctional Au/CaCO₃ nanocomposite for 4-Nitrophenol electrochemical detection and catalytic reduction

Eggshell is renewable, abundantly available and economic. It holds great business potentials if eggshell as waste can be converted into valuable functional materials for various applications. Herein, we describe an economic and environmental-friendly transforming strategy for the synthesis of Au nanoparticles coated chicken eggshell composites (defined as Au/CaCO₃ nanocomposite), which can be further used as a sensor and catalyst for the efficient detection and treatment of 4-Nitrophenol (4-NP). The prepared Au/CaCO₃ nanocomposite achieved a significant electrochemical enhancement behavior compared with naked electrode. A wide linear response range of 0.1–100 μM and a relatively low detection limit of 0. 54 nM were obtained. Meanwhile, the nanocomposite can also be used as catalyst for the efficient reduction of 4-NP with outstanding activity and stability. The catalytic system followed the pseudo first-order kinetic model with the K value of 1.0750 min⁻¹. Our “waste into treasure” turning strategy not only provides a practical and low-cost method for the comprehensive utilization of eggshell into value functional materials, but also provides a new direction for the sensitive detection and rapid deletion of organic pollutants.