ELECTROCHEMICAL SENSOR BASED ON CdS/CeO2/Ag2CO3 MODIFIED CARBON PASTE ELECTRODE FOR DETECTION OF PHENOL

Abstract

In this Thesis work, ternary systems with different molar ratios (1:1, 2:1 and 3:1) of CdS/ CeO2/Ag2CO3 nanocomposites were synthesized by precipitation method. The crystal structure, morphology and electronic structure of the as-synthesized nanomaterials (CdS, CeO2, Ag2CO3, CdS/CeO2, CeO2/Ag2CO3 and CdS/CeO2/Ag2CO3) were characterized by using XRD, SEM-EDX and UV/V spectroscopy, respectively. Electrochemical behaviors of nanomaterials modified carbon paste electrode were characterized using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) in the presence of 2 mM K3Fe(CN)6 in aqueous solution of 0.1 M KCl. The acquired voltammograms revealed that CdS/CeO2/Ag2CO3 nanocomposite showed the highest electrochemical signals compared to the carbon paste electrode (CPE) and the other modified electrodes. The EIS were spectra results also consistent to that of the CV and CPE modified by the ternary system have low charge transfer resistance. These behaviors can improve the sensitivity and response of the proposed sensor for detection of phenol. Electrochemical property of phenol in all nanomaterials modified carbon paste electrode was irreversible. Oxidation potential of phenol in CdS/CeO2/Ag2CO3 MCPE was less compared to the other modified electrodes and increased peak current. This could be as a result of synergetic effect the high absorption capacity of CeO2 and electro-catalytic properties CdS. To improve the performance of CdS/CeO2/Ag2CO3/CPE sensor for the detection of phenol pH and scan rate experimental parameters were optimized. Under the optimized condition (pH 7 and υ= 100 mVs1) the electrode was applied to determine the concentration of phenol in standard solution (2 – 10 mM) using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The sensor exhibited a linear range (2 – 10 mM), detection limits 0.539 µmol L−1 and sensitivity 127.54 µA/mMcm2 using CV and a linear range (2 – 10 mM), detection limits 0.243 µmol L−1and sensitivity 27.0289 µA/mMcm2 using DPV methods, besides, the sensor has good stability (99.2%) and repeatability (3.7%). The electrode was also applied to determine phenol in waste water. The findings demonstrated that the developed sensor can be a potential candidate for routine analysis of phenol in various sources.