Influence of a MnO2-WC interlayer on the stability and electrocatalytic activity of titanium-based PbO2 anodes

Abstract

In order to overcome the unsatisfactory stability drawback of titanium-based PbO2-coated anodes used in electrochemical oxidation treatments of refractory organic wastewater, a novel PbO2-coated anode obtained by introducing a tungsten carbide (WC) modified manganese dioxide composite coating (MnO2-WC) via anodic co-deposition in a MnSO4 solution mixed with WC particles as an intermediate is fabricated (Ti/MnO2-WC/β-PbO2). Characterization measurements including scanning electronic microscopy accompanied by energy dispersive X-rays, X-ray diffraction, and X-ray photoelectron spectroscopy are used to analyze the microstructure and chemical composition of the coated anode, including the interlayer coating and superficial coating. The electrochemical and electrocatalytic properties of the interlayer and anode surfaces are analyzed using linear sweep voltammetry, cyclic voltammetry, and electrochemical impedance spectroscopy. Meanwhile, the failure mechanism of the anode coated with the MnO2-WC composite interlayer, and the life-extension mechanism due to introducing the composited interlayer, are determined via accelerated-life tests and a comprehensive failure analysis of the tested samples. The results show that, compared with MnO2, the conductivity of the MnO2-WC interlayer is greatly improved and exhibits higher oxygen evolution potential as well as better electrocatalytic activity. The anodic β-PbO2 grains deposited on the MnO2-WC interlayer surface become finer, more compact and homogeneous. The MnO2-WC composite interlayer increases the number of surface active sites and promotes the electro-crystallization process of the PbO2 surface coatings, which results in thicker PbO2 coatings. As a result, the Ti/MnO2-WC/β-PbO2-coated anode shows better electrocatalytic activity and superior stability in this work, and its accelerated life is more than twice that of Ti/β-PbO2 anodes.