<i>Citrullus lanatus</i> Peel Extract Templated Synthesis of ZnO/MnO ₂ Nanocomposites as Porous Catalytic Working Electrode for Electrochemical Lead Detection and Quantification

Abstract

ABSTRACT Contamination of water by heavy toxic metal ions poses a significant health risk around the globe. Particularly, lead has a severe impact on human health and the ecosystem. This study explores green synthesis of ZnO/MnO 2 NCs and their single NPs using Citrullus lanatus peel extract. Characterization of synthesized NPs and NCs was performed using TGA/DTA, XRD, FTIR, SEM‐EDX, TEM, HRTEM, SAED, UV‐Vis DRS, BET, CV, and EIS. The synthesized NCs and NPs were thermally stable above 45 °C. XRD analysis confirmed formation of crystallite sizes of 17.05, 22.6, and15.6 nm for ZnO, α‐MnO 2 , and ZnO/α‐MnO 2 NCs, respectively. SEM‐EDX and TEM analyses attest spherical structural arrangement while UV‐Vis DRS confirms band gaps of 3.00, 1.36, and 2.35 eV for ZnO NPs, α‐MnO 2 NPs, and ZnO/α‐MnO 2 NCs, respectively. The specific surface area was calculated to be 509.00, 521.00, and 525.48 m 2 /g for ZnO NPs, α‐MnO 2 NPs, and ZnO/α‐MnO 2 NCs, respectively. Lead detection was performed in an acidic environment (0.1 M HCl) using chronoamperometry at −1.0 V for 150s, with further quantification and optimization via square wave anodic stripping voltammetry (SWASV). The study proved that ZnO, α‐MnO 2 , and ZnO/α‐MnO 2 based MWE are able to detect low concentrations of Pb 2+ ions in aqueous medium. Under optimized conditions, Pb 2+ detection and quantification were conducted for the ZnO/α‐MnO 2 based MWE under various parameters with a correlation coefficient (R 2 ) of 0.93577 and a limit of detection (LOD) of 0.008 ppm. ZnO/α‐MnO 2 based MWE exhibits excellent sensitivity toward Pb 2+ ion due to improved electrocatalytic property.