Influence of the Substrate Nature on the Structural and Electrochemical Characteristics of PbO₂ Electrodes in Sulfide-Containing Aqueous Systems

Electrochemical treatment of sulfide‑containing industrial effluents and gas emissions remains a pressing challenge for the development of clean technologies, whose solution requires anodes with low operating potential, stable performance, and facile, cost‑effective fabrication. The paper studies the influence of the substrate nature on the structural and electrochemical characteristics of lead dioxide anodes in sulfide-containing aqueous systems using the electrolysis of an aqueous solution of sodium sulfide Na₂S as an example. The substrates used were composite materials based on polylactic acid with the addition of 7 and 10 wt.% multiwalled carbon nanotubes, designated as PLA (7% mCNT)/PbO₂ and PLA (10% mCNT)/PbO₂, as well as a PLA (Graphite)/PbO₂ composite containing dispersed graphite as a conducting phase; PbO₂ coatings were applied to all of the above polymer substrates by electrochemical deposition. For comparison, a traditional Ti/PbO₂ anode and a graphite electrode without a lead dioxide coating, used as a standalone anode, were also considered. Cyclic voltammetry in a Na₂S solution was used to evaluate the anodic reaction overpotential, specific current densities, and current-voltage curve shapes on various substrates, as well as to analyze the influence of the conductive composite composition on the electrochemical behavior of the PbO₂ layer. It was shown that the PLA (7% mCNT)/ PbO₂, PLA (10% mCNT)/PbO₂, and especially PLA (Graphite)/PbO₂ anodes provide operating potentials, ohmic resistance, and cyclic stability comparable to or superior to those of the traditional Ti/PbO₂ anode in a sulfide-containing electrolyte, whereas the uncoated graphite electrode is inferior to the composite PbO₂ electrodes in terms of a combination of parameters. The obtained results allow us to conclude that the nature and composition of the substrate play a key role in the formation of the morphology, conductivity and electrochemical properties of PbO₂ anodes and confirm their high potential for use in electrochemical systems for treating sulfide-containing aqueous media and gas emissions.