Magnetically assembled electrodes based on Pt, RuO-IrO-TiO and Sb-SnO for electrochemical oxidation of wastewater featured by fluctuant Cl concentration.

Magnetically assembled electrode (MAE) flexibly attracts magnetic particles (auxiliary electrodes, AEs) on a main electrode (ME) by the magnetic force, where the role of ME is always ignored. In this study, Ti/Pt, Ti/RuO-IrO-TiO and Ti/Sb-SnO were selected as the ME for comparison in treating synthetic wastewater (acid red G or phenol) with variable Cl content. The effects of ME type, loading amount of FeO/Sb-SnO AEs, and Cl concentration were investigated, followed by varied electrochemical characterizations. Results show that AEs played a vital role in electrode activity and selectivity, and MEs also exerted an unignorable influence on the performance of the MAEs. Among the three MEs, Ti/RuO-IrO-TiO has the best OER/CER ability, activating more extra active sites with same AEs loading amount, leading to higher organics degradation efficiency under chlorine-free condition. However, this MAE is featured by the noticeable accumulation of intermediate products under chlorine-free condition even if 0.3 g·cm of AEs are loaded. All electrodes' performances were enhanced in the presence of Cl. With high concentration chloride (0.5 M NaCl), the accumulation of intermediate products was reduced significantly, especially on Ti/RuO-IrO-TiO based MAE, and no chlorinated compound was identified. Finally, the structure-activity relationships of these MAEs were proposed.