Modulating oxygen evolution reaction intensity for organic pollutant degradation and anode catalyst self-cleaning in...

Conventional constant-current electrolysis shows limited effectiveness for wastewater distillate treatment, as the fixed intensity of the oxygen evolution reaction (OER) fails to dynamically address the combined challenges of sluggish organic mass transfer and severe anode catalyst fouling. To overcome this limitation, the role of OER intensity in regulating mass transfer behavior and catalyst organic fouling was systematically investigated. At low current densities of 2-6 mA/cm², oxygen bubble generation enhanced interfacial mass transfer, enabling energy-efficient organic degradation while simultaneously inducing pronounced catalyst fouling. Under these conditions, organic removal predominantly proceeded through direct electron transfer (DET) pathways and redox reactions mediated by high-valence iridium species. In contrast, high OER intensities ranging from 200 to 1000 mA/cm² markedly improved catalyst self-cleaning performance. This effect was primarily attributed to vigorous oxygen bubble scouring. However, operation under high OER intensity shifted the system into an electrooxidation-limited regime, leading to compromised energy efficiency. Based on these mechanistic insights, an alternating electrolysis strategy was developed by alternately applying low and high OER intensities to reconcile the intrinsic trade-off between energy-efficient organic oxidation at low current density and OER-driven anode self-cleaning at high current density in proton exchange membrane (PEM) wastewater electrolysis. When applied to real wastewater distillate, the proposed strategy achieved 91.3% removal of phenolic compounds with an energy consumption of 7.46 kWh/m³. In addition, stable operation was maintained for 48 h without a noticeable increase in cell voltage. These findings provide mechanistic insights into OER-mediated interfacial regulation in electrochemical systems.