Selective generation of hydroxyl and sulfate radicals under electric field regulation for micropollutants degradation: Mechanism and structure-activity relationship

Abstract

Peroxymonosulfate (PMS) activation generates potent reactive oxygen species (ROS) such as sulfate radical (SO₄^·–) and hydroxyl radical (·OH), which play a key role in organic pollutant degradation. However, controlling the generation of these free radicals remains challenging. In this study, various metal (Co, Ni, and Cu)-doped nitrogen carbon compounds (NCs) were synthesized, and their performance in PMS activation under electric field regulation was explored to modulate ROS production for selective pollutant degradation. Bisphenol A (BPA), a readily degradable compound, and ibuprofen (IBU), a recalcitrant pollutant, were chosen as model pollutants to assess degradation efficiency. All catalysts achieved over 95 % BPA removal without the electric field, but the application of an electric field significantly accelerated BPA degradation, achieving complete removal within 3 min. In contrast, IBU degradation showed significant variation depending on the catalyst used and the electric field intensity, with Cu-NC demonstrating the highest performance, enhancing the degradation rate by 3.78-fold. Mechanistic studies revealed that the electric field altered the electron density on the catalyst surface, shifting ROS production from SO₄^·– to·OH in Co-NC systems. The findings could provide valuable insights into PMS activation under electric field regulation, offering a novel strategy for enhancing micropollutant removal through controlled ROS generation.