Amperometric detection of nitrate using sn-cuxo nanocomposite

Abstract

This thesis presents a comprehensive investigation into the structural, physical, and electrochemical characteristics of CuxO and Sn-doped CuxO nanocomposite thin films as catalysts for the amperometric detection of nitrate. Excessive Nitrate is harmful to human thus the motivation of this work. The unique electrochemical and electronic properties of CuxO (Cu2O/CuO) gives it merit to be used in the development of electronic devices. The nanocomposite thin films were constructed by a simple chemical route, a two-step spin-coating method and calcination technologies. The study involves X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) for physical characterization. The XRD analysis reveals the presence of cubic Cu2O and monoclinic CuO phases in pristine CuxO, while Sn doping induces crystallographic changes. Doping with Sn led to an increase in the quantity of electron transfers, increasing from 1 to 2 when compared to undoped CuxO. The electrochemical characterization, performed through cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) in alkaline electrolyte, evaluates the catalytic performance for nitrate detection. Sn-doped CuxO exhibits enhanced electro catalytic activity compared to pristine CuxO, attributed to the incorporation of Sn into the lattice. The developed Sn-doped CuxO/FTO sensor demonstrates a high sensitivity of 100.27 μA.mM-1.cm-2 with a low limit of detection (LOD) of 0.04 μM (S/N) = 3), a linear concentration range of up to 15 mM and a fast response time of less than 5s was observed at a potential of -1 V (vs. Ag/AgCl). The sensor shows selectivity for nitrate ions in the presence of common interfering anions. Reproducibility, stability, and shelf life assessments affirm the practical viability of the Sn-doped CuxO/FTO electrode. The sensing device was applied to the determination of nitrate in spiked tap water, the Mowbray River and Bore Hole water samples. The study contributes valuable insights into the design and optimization of catalysts for electrochemical sensing applications.