Effects of PbO2/Pb3O4 ratio alteration for enhanced electrochemical advanced oxidation performance

Highlights: • Ratio of PbO₂ and Pb₃O₄ can be adjusted by hydrothermal reaction durations. • PbO₂/Pb₃O₄ composite displayed enhanced electro-catalytic performance. • Role of different operating conditions was investigated. • Degradation byproducts of MO were identified and the possible pathways were proposed. PbO₂, PbO₂/Pb₃O₄ composite, and Pb₃O₄ were synthesized respectively via the simple hydrothermal method under different reaction durations (3–48h). All the prepared samples were used as anode materials to decontaminate methyl orange (MO) to explore the corresponding electrochemical advanced oxidation performance. The detailed experimental designs suggested that the combination of PbO₂ and Pb₃O₄ offered enhanced electrochemical advanced oxidation performance, which was due to possible synergistic effects. XPS results suggest that the content of adsorbed oxygen species (O_ads) is obviously higher in PbO₂/Pb₃O₄ composite. It is very likely due to more oxygen vacancies in the crystal structure of PbO₂/Pb₃O₄ composite, which will adsorb more oxygen species, promote charge transfer and provide more electrochemical active surface area to generate oxidizing agents. Besides, the presence of Pb₃O₄ can suppress the oxygen evolution and improve the accelerated life. Meanwhile, the effects of current density, catalyst loading amount and initial MO concentration on electro-catalysis degradation of MO were explored. Experimental results suggested that MO removal efficiency was 94.3%, the reaction kinetic constant could reach 2.08 ⅹ 10^-2 min^-1, and COD removal efficiency was 34.2% after 150min of reaction under optimized conditions: current density was 5mAcm^-2, catalyst loading amount was 1mgcm^-2 and initial MO concentration was 50mgL^-1. Furthermore, possible degradation mechanisms of MO was proposed according to the analyzed results obtained from UV–Vis and HPLC-MS.