Magnetically assembled electrodes based on Pt, RuO2-IrO2-TiO2 and Sb-SnO2 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/RuO2-IrO2-TiO2 and Ti/Sb-SnO2 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 Fe3O4/Sb-SnO2 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/RuO2-IrO2-TiO2 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(-2) 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/RuO2-IrO2-TiO2 based MAE, and no chlorinated compound was identified. Finally, the structure-activity relationships of these MAEs were proposed.

Automated summary

The study found that auxiliary electrodes play a vital role in the activity and selectivity of electrodes, while the main electrodes also have an impact on the performance of the magnetically assembled electrodes. Under chlorine-free conditions, Ti/RuO2-IrO2-TiO2 exhibited the best organic degradation efficiency but also showed noticeable accumulation of intermediate products. The presence of chloride ions enhanced the performance of all electrodes.