Drastic enhancement of H₂O₂ electro-generation by pulsed current for ibuprofen degradation: Strategy based on decoupling study on H₂O₂ decomposition pathways

Efficient H₂O₂ electrogeneration from 2-electron oxygen reduction reaction (ORR) represents an important challenge for environmental remediation application. H₂O₂ production is determined by 2-electron ORR as well as H₂O₂ decomposition. In this work, a novel strategy based on the systematical investigation on H₂O₂ decomposition pathways was reported, presenting a drastically improved bulk H₂O₂ concentration. Results showed that bulk phase disproportion, cathodic reduction, and anodic oxidation all contributed to H₂O₂ depletion. To decrease the extent of H₂O₂ cathodic reduction, the pulsed current was applied and proved to be highly effective to lower the extent of H₂O₂ electroreduction. A systematic study of various pulsed current parameters showed that H₂O₂ concentration was significantly enhanced by 61.6% under pulsed current of “2 s ON + 2 s OFF” than constant current. A mechanism was proposed that under pulsed current, less H₂O₂ molecules were electroreduced when they diffused from the porous cathode to the bulk electrolyte. Further results demonstrated that a proper pulse frequency was necessary to achieve a higher H₂O₂ production. Finally, this strategy was applied to Electro-Fenton (EF) process with ibuprofen as model pollutant. 75.0% and 34.1% ibuprofen were removed under pulsed and constant current at 10 min, respectively. The result was in consistent with the higher H₂O₂ and ·OH production in EF under pulsed current. This work poses a potential approach to drastically enhance H₂O₂ production for improved EF performance on organic pollutants degradation without making any changes to the system except for power mode.