Electrochemical Sensor Using Glassy Carbon Electrode Modified By Pd-Ag/Graphene And Its Chlorophenols Contaminants Determination

Chlorophenol contaminants which often exist in water exhibit great harm and security risk to human and environment,because of its high toxicity,fat-soluble,carcinogenic mutagenicity and strong biological stability.The requirement of rapid detection of low chlorophenol concentration makes electrochemical detection become a hotspot.In this paper,the palladium-silver bimetallic supported graphene catalyst was prepared and applied for the electrochemical sensor construction.The modified glass carbon electrode was used for the determination of aqueous chlorophenol contaminants such as 4-chlorophenol,3-chlorophenol,2-chlorophenol and 2,4-dichlorophenol in low concentration.Pd-PVP/RGO,Ag-PVP/RGO and Pd-Ag-PVP/RGO were prepared by wet chemical reduction method successfully using polyvinylpyrrolidone(PVP)as the dispersant.The catalysts were characterized by X-ray diffraction(XRD),field emission scanning electron microscopy(FESEM)and EDS-Mapping,transmission electron microscopy(TEM),atomic force microscopy(AFM)and fourier transform infrared spectroscopy(FTIR),electrochemical impedance spectroscopy(EIS)and cyclic voltammetry(CV).The results showed that the diameters of metal particles on graphene sheets were 6.41±0.60 nm,8.90±0.05 nm and 4.47±0.02 nm when the weight of loaded metal was 1%,1%and 0.5%:0.5%,respectively.And the loaded metal was evenly dispersed without agglomeration.And Pd(?80%)and Ag(100%)existed in the form of zero valence.And the presence of a small amount of oxygen-containing functional groups in the reduced graphene oxide and its large monolayer sheet struction provided loading sites for the metal nanoparticles,and meantime PVP makes the metal dispersed evenly.EIS and CV results showed that the electrochemical impedance of Pdo.5Ag0.5-PVP/RGO catalyst was the smallest,the electron transfer rate was the fastest and it had the strongest enhancement of the voltammetric signal(63.04 times)and the best electrochemical catalytic effect.And the results indicated that Pd0.5Ag0.5-PVP/RGO catalyst has excellent electrocatalytic ability for the contaminants determination.The Pd0.sAg0.5-PVP/RGO catalyst modified electrode was prepared and acted as a working electrode in electrochemical sensor.The optimal experimental conditions were as follows:0.1 mol/L PBS,100 mV/s scan rate and pH=7.The relatively wide detection range for 4-CP,3-CP,2-CP and 2,4-DCP were 0.1-80 ?mol/L,0.1-100?mol/L,0.1-80 ?mol/L and 0.002-100 ?mol/L,respectively.And their low detection limits were 0.0075 ?mol/L,0.0077 ?mol/L,0.0047?mol/L and 0.00036?mol/L(S/N=3),respectively.The electrochemical sensor with Pd0.5Ag0.5-PVP/RGO catalyst modified electrode has good accuracy,repeatability,stability and anti-interference,and the high recovery rate(almost 100%)illustrated that this sensor can be used for low concentration chlorophenol detection in the actual wastewater because of its strong practicality and good application prospects.