Resolving the activity-stability trade-off in electrocatalytic oxidation via asymmetric dual-atom modification of packed electrodes.

Electrocatalytic oxidation is a promising technology for the removal of emerging organic pollutants from wastewater. However, improvements in catalytic activity are often achieved at the expense of stability. Herein, we report a freestanding SnO2-Sb packed electrode (PE) integrated with an asymmetric dual-atom modification strategy using Ni and Ru to resolve the activity-stability trade-off in anodic electrooxidation. Structural characterization revealed strong electron metal-support interactions and the formation of stabilized NiORu motifs within the SnO2-Sb matrix. As a result, the Ni5Ru1-SnO2-Sb PE exhibited markedly enhanced electrocatalytic performance, achieving nearly complete degradation of moxifloxacin within 60 min, with a rate constant 6.4 times higher than that of the conventional 2D anode system without PE and 3.5 times higher than that of the pristine SnO2-Sb PE. Meanwhile, Ni leaching was markedly suppressed, with the released Ni concentration reduced to only one-tenth of that observed for Ni-SnO2-Sb, demonstrating excellent stability that meets drinking water quality standard. Mechanistic investigations combining quenching experiments and electron paramagnetic resonance revealed that the degradation process is dominated by direct electron transfer oxidation at the anode surface, accompanied by the generation of both radical and non-radical reactive oxygen species. Furthermore, a continuous flow-through electrochemical system was constructed and demonstrated efficient pollutant removal in real pharmaceutical wastewater. This work provides a promising strategy for designing durable and highly active electrocatalysts for practical electrochemical water treatment.