Pd–Ag/Graphene Electrochemical Sensor for Chlorophenol Contaminant Determination

Abstract

A graphene-supported Pd–Ag bimetallic alloy catalyst for rapid detection of low concentrations of chlorophenols (CPs) in environmental monitoring was prepared by wet chemical reduction. The catalyst was used to construct an electrochemical CP sensor. Catalyst-modified glassy carbon electrodes were evaluated for the determination of aqueous CP contaminants, i.e., 4-chlorophenol (4-CP), 3-chlorophenol (3-CP), 2-chlorophenol (2-CP), and 2,4-dichlorophenol (2,4-DCP), at low concentrations. Synergies between the Pd–Ag bimetallic alloy component and the graphene component of the electrochemical catalyst significantly affected the electrochemical reactions of the CPs, by enhancing the electron transfer rate and the electrochemical oxidation–reduction reaction efficiency. The optimal experimental conditions for a Pd0.5Ag0.5/reduced graphene oxide-modified electrode sensor were 0.1 mol/L phosphate-buffered saline, a scan rate of 100 mV/s, and pH 7. The detection ranges for the monochlorophenols (4-CP, 3-CP, and 2-CP) were wide, namely 0.1–80, 0.1–100, and 0.1–80 μmol/L, respectively. The dichlorophenol (2,4-DCP) detection range was broader, i.e., 0.002–100 μmol/L. The detection limits were low, namely 0.0075, 0.0077, 0.0047, and 0.00036 μmol/L (S/N = 3), respectively. These electrode sensors give good accuracy and reproducibility, and high recovery rates (almost 100%). They have anti-interference properties and long-term stability. The results indicate that such sensors could be used for detection of low concentrations of CPs in wastewater, and have good potential for use in practical applications.