Applications of Ti/TiO<sub>2</sub> nanotube arrays/CeO<sub>2</sub>@PbO<sub>2</sub> and Ti/β-PbO<sub>2</sub>-CuO <sub><i>x</i></sub> electrodes for efficient electrocatalytic degradation of paraquat: cell design and comprehensive mechanistic studies.

Abstract

Ti/TiO₂ nanotube arrays (NTA)/CeO₂@PbO₂ and Ti/β-PbO₂-CuO _<i>x</i> electrodes were used for the electrocatalytic degradation of paraquat (PQ²⁺), a highly toxic and widely used herbicide. The fabricated electrodes were characterized by XPS, SEM, EDS, mapping, XRD and EIS methods. The results show that the performance of the Ti/TiO₂ nanotube in the electrocatalytic degradation of PQ²⁺ is better than that of the Ti/β-PbO₂-CuO _<i>x</i> electrode. This electrode increases the production of hydroxyl radicals and degradation efficiency. The results show that the highest degradation efficiency of 75% was achieved at pH = 7, a current density of 7.8 mA cm^-2 and an initial concentration of 50 ppm. The intermediate species formed during the electrolysis of PQ²⁺ were analyzed based on cyclic voltammetry, UV-vis spectroscopy and LC-MS techniques, and a possible mechanism for the degradation of PQ²⁺ was proposed. In the second part of this study, the electrochemical behavior of PQ²⁺ was studied, gaining a deeper insight and understanding of the redox properties and adsorption activity of this molecule.