Insight into Nitrogen Doped Waste-Tire Carbon for Radical and Nonradical Oxidation via a Probe-Based Kinetic Model

Nitrogen doping can enhance the catalytic activity of carbon materials for activating peroxymonosulfate (PMS). The structure of nitrogen may strongly influence the generation of reactive oxygen species (ROS). However, few studies have focused on the methods for measuring ROS concentrations, making it difficult to assess the role of nitrogen species in PMS activation. Herein, we synthesized a series of nitrogen-doped waste-tire carbon and established a kinetic model with probes to estimate the ROS concentrations. Waste-tire carbon was doped with nitrogen via vibration milling and calcination, which generated the structures of graphitic N and pyridinic N. Both radical (^•OH, SO₄^•-) and nonradical (¹O₂) species were discovered by electron paramagnetic resonance. The calculations with the kinetic model revealed that ¹O₂ was the main ROS. Besides, combined with the density functional theory, graphitic N was suggested to be responsible for the generation of ¹O₂. This work provides a green catalyst developed from solid waste and an effective protocol to monitor the ratios of ROS in the degradation of pollutants with PMS.