Fabrication and enhanced electrocatalytic activity of 3D highly ordered macroporous PbO2 electrode for recalcitrant pollutant incineration

By virtue of the self-assembled colloidal crystal template with face-centered cubic structure, a novel three-dimensional highly ordered macroporous PbO2 (3DOM-PbO2) electrode was fabricated by electrochemical deposition method. In the 3DOM-PbO2 film, every spherical cavity was interconnected to three adjacent spherical cavities on the upper and lower layer, respectively, and the pore size was about 500 nm. Compared to the traditional flat microcrystalline PbO2 (Flat-PbO2), the nanocrystalline 3DOM-PbO2 with beta-PbO2 crystal phase possessed larger specific surface area (46 m(2) g(-1)), higher oxygen evolution potential (1.92 V), smaller electron transfer resistance (35.5 Omega), and more abundant crystal defect sites, resulting in better electrocatalytic performance. The electrochemical mineralization of refractory metalaxyl with 3DOM-PbO2 anode demonstrated that, the electrocatalytic reaction followed pseudo-first-order kinetics and the value of apparent rate constant (k(app)) is 0.017 min(-1), about 2.4 times that with Flat-PbO2, and total organic carbon (TOC) and chemical oxygen demand (COD) removals are all approximately 95% after 300 min. The mineralization current efficiency with the 3DOM-PbO2 was much higher than that with the Flat-PbO2, and corresponding electrical energy consumption was lower. Moreover, the intermediates were identified by high-performance liquid chromatography (HPLC) and Gas chromatography-Mass spectrometer (GC-MS), and possible electrocatalytic oxidation mechanism of metalaxyl on the 3DOM-PbO2 electrode was also discussed in detail. (C) 2013 Elsevier B.V. All rights reserved.