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

Highlights: • A novel PbO₂ electrode with a GNS interlayer (GSN-PbO₂) was prepared. • The GNS interlayer reduced grain size of β-PbO₂ crystals. • The GNS interlayer enhanced electrochemical activity of PbO₂ electrode. • The lifetime of GSN-PbO₂ electrode was 1.93 times that of PbO₂ electrode. • An electrochemical mineralization mechanism of 2-chlorophenol was proposed. - 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 (107.9 h) was 1.93 times longer than that of traditional PbO₂ electrode (55.9 h). The electrochemical degradation rate constant of 2-CP on GNS-PbO₂ electrode (k_app = 2.75 × 10⁻² min⁻¹) is much higher than for PbO₂ electrode (k_app = 1.76 × 10⁻² min⁻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.