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 Pd 0.5 Ag 0.5 /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.

α-Fe2O3/graphene oxide powder and thin film nanocomposites as peculiar photocatalysts for dye removal from wastewater

“…In fact, graphene is considered an important material in wastewater treatment technologies because of its outstanding features 3 , 21 , 22 . Up to now, graphene and its derivatives are used as a matrix of metal/metal oxide materials to enhance the catalytic performance of materials, including Ni 19 –NiO 23 for dye-synthesized solar cell, CuO 24 for catalysts, Pd–Ag 25 and AuNPs/MoS 2 26 for the electrochemical sensor, TiO 2 27 and MoS 2 28 for electrode, AgBr 29 and Fe 3 O 4 30 for water purification, or water splitting 19 . Yuan et al suggested a new mechanism for the improvement of photocatalytic activities with graphene.…”

Tunable construction of electrochemical sensors for chlorophenol detection

“…The key premise for electrochemical CP detection is the construction of an electrochemical cell that usually employs a three-electrode configuration. [39][40][41][42][43][44][45] No matter what signal read-out technique is used, to obtain a high intensity, undistorted, well-defined, and reproducible electric signal that is essential for a stable, reliable sensor performance, it is usually imperative to design synergistically the electrochemical cell in a configuration as shown in Fig. 3, which includes electrolytes, a reference electrode, a counter electrode, and a working electrode.…”

“…Metals can be doped into mesoporous materials to synthesize composites with a large specific area, providing a high density of active sites that are accessible to CPs for electrocatalytic reactions. 40 Ya et al 90 reported on a CPE modified with Al-doped mesoporous cellular foam, which demonstrated an enhanced electrochemical oxidation peak towards PCP with a linear detection range of 0.376-18.8 mM and a LOD of 0.3 mM. 90 Besides, Pd can be doped into Ag to form heterostructured Pd/Ag bimetallic alloys, enhancing the intrinsic electrochemical activity.…”

A High-Response Electrochemical As(III) Sensor Using Fe3O4–rGO Nanocomposite Materials

“…By using graphene and its compounds to modify the electrode, considerable sensitivity and detection limits have been obtained. When graphene and its derivatives are matched with other different materials, different substances can be detected, such as copper, lead, chromium, nickel, and other pollutants [10,11], chlorophenols that are toxic to aquatic organisms [12], melatonin and pyridoxine in plants [13], ascorbic acid, dopamine, and uric acid [14].…”