Influence of Cu–Zn co-doping on the degradation performance of a Ti/SnO2–Sb anode

Abstract

A Ti/SnO₂–Sb–Cu–Zn electrode was prepared for the electrocatalytic oxidation of Acid Red 18 (AR18). The addition of Zn to the coating results in smaller surface cracks and greater roughness. When Cu and Zn coexist, high-index crystal planes are generated on smaller-sized grains formed on the coating surface, which allows the coating surface to adsorb oxygen. Sb⁵⁺ and the adjacent Cu²⁺–Zn²⁺ on the surface of the Cu–Zn co-doped coating are the advantageous active sites for adsorbed oxygen. The electrode exhibits a larger electrochemically active surface area and smaller electrochemical reaction resistance. The appearance of high-index crystal planes is beneficial to improve the electrocatalytic activity of the electrode, although the oxygen evolution potential of the electrode is not greatly improved. Cu–Zn co-doping produces synergistic mineralisation and enhances the ability to degrade AR18, and ˙OH is the main active species. During the thermal decomposition of the coating, Zn induces Cu to form more active sites on the high-index crystal planes of SnO₂, a phenomenon that may be responsible for the synergistic production of more reactive oxygen species on the electrode surface.