Peroxymonosulfate-Based Electrochemical Advanced Oxidation: Complication by Oxygen Reduction Reaction

Area of Science:

• Environmental Chemistry
• Electrochemistry
• Advanced Oxidation Processes

Background:

• Peroxymonosulfate (PMS)-based electrochemical advanced oxidation processes (EAOPs) are promising for pollutant remediation.
• The mechanisms of PMS activation and their influence on EAOP performance are not fully understood.
• Understanding PMS activation is crucial for optimizing pollutant degradation strategies.

Purpose of the Study:

• To demonstrate the critical role of the oxygen reduction reaction (ORR) in PMS activation.
• To elucidate the interplay between ORR, PMS activation, and pollutant degradation.
• To explore a novel pathway for enhancing PMS-based EAOPs.

Main Methods:

• Utilized a nitrogen-doped carbon nanotube catalyst for cathodic PMS activation.
• Investigated the concurrent generation of hydrogen peroxide (H2O2) via ORR.
• Analyzed the influence of local pH changes and reactive oxygen species (ROS) on pollutant degradation.

Main Results:

• Observed concurrent generation of H2O2 during cathodic PMS activation by the catalyst.
• Identified a complex interplay between H2O2 generation, PMS activation, and localized pH increase.
• Demonstrated the formation of a mixed sulfate radical (SO4•−) and hydroxyl radical (•OH) oxidation environment.

Conclusions:

• The oxygen reduction reaction plays a critical role in effective PMS utilization and pollutant remediation in EAOPs.
• A synergistic effect between H2O2 generation and PMS activation, coupled with pH modulation, enhances pollutant degradation.
• This study reveals a previously unexplored route for improving PMS-based treatment processes.