Fabrication of a novel PbO2 electrode with a graphene nanosheet interlayer for electrochemical oxidation of 2-chlorophenol

Abstract

A novel PbO2 electrode with a graphene nanosheet interlayer (marked as GNS-PbO2) was prepared combining electrophoretic deposition and electro-deposition technologies. The micro morphology, crystal structure and surface chemical states of GNS-PbO2 electrodes were characterized using scanning electronic microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Their electrochemical properties and stability were determined using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), ·OH radicals test and accelerated life test, and compared with traditional PbO2 electrodes. Besides, their potential application in the electrochemical degradation of 2-chlorophenol (2-CP) was investigated. The GNS-PbO2 electrode possessed perfect octahedral β-PbO2 microcrystals, and its grain size was much smaller than that of traditional PbO2 electrode. It exhibited higher electrochemical activity than traditional PbO2 electrode due to its larger electrochemical active surface area and stronger ·OH radicals generation ability. The service lifetime of GNS-PbO2 electrode (107.9h) was 1.93 times longer than that of traditional PbO2 electrode (55.9h). The electrochemical degradation rate constant of 2-CP on GNS-PbO2 electrode (kapp=2.75×10−2min−1) is much higher than for PbO2 electrode (kapp=1.76×10−2min−1). 2-CP oxidation yielded intermediates including aromatic compounds (catechol, phenol and ortho-benzoquinone) and organic acids (oxalic acid, maleic acid and glutaconic acid), and a possible degradation pathway for 2-CP was proposed accordingly.