## 3 Results
### Identification of Reactive Species and Mechanism  
Quenching experiments and EPR tests were conducted to confirm the influence of reactive oxygen species (ROS) in the reaction system of CoN@C + PMS system for RhB degradation. MeOH and TBA were utilized as quenchers for SO\({}_{4}\).- and HO- radicals, respectively, PMSO as a quencher for radicals adsorbed on the catalyst surface, and FFA as an quenchers for \({}^{1}\)O\({}_{2}\)[44]. Figure 8a,b exhibit the variations in the reaction rates of RhB degradation by CoSN@C and CoN@C activated PMS following the addition of various quenchers. RhB's degradation efficiency in the CoN@C + PMS system was not significantly altered by adding MeOH, TBA, or PMSO, as compared to the control group's efficiency of 83.77%. However, the degradation rate plummeted dramatically to 48.8% when FFA was added. It indicates that the free and adsorbed SO\({}_{4}\).- and HO-radicals on the catalyst surface do not exist in the CoN@C + PMS reaction system, while \({}^{1}\)O\({}_{2}\) plays a major role in the degradation of RhB in the CoN@C + PMS system. The PMS is oxidized into -O\({}_{2}\)-, while -O\({}_{2}\)- is reorganized as an intermediate to produce a large amount of \({}^{1}\)O\({}_{2}\), which oxidatively degrades RhB, which is consistent with the results of previous studies [21, 45, 46]. The addition of TBA decreased the RhB degradation rate from 100% in the control group to 97.6%, whereas adding MeOH decreased the RhB degradation rate to 84.0% (Figure 8a). The results demonstrated that both MeOH and TBA inhibited the degradation of RhB, but not to a significant degree, indicating that the reactive oxygen species in the reaction system that played a significant role in the degradation of RhB were not free SO\({}_{4}\).- and  
Figure 8: Influence of quenching agents on RhB degradation in the different catalyst/PMS system: (a) CoSN@C + PMS; (b) CoN@C + PMS. Figure 7: XRD spectra of CoSN@C and CoSN@C after the reaction. free HO., and that the slight decrease in the reaction rate was likely caused by the addition of alcohols that interfered with the contact between PMS and the active sites on the catalyst surface. SO4.- and HO- adsorbed on the catalyst surface played the primary role in the RhB degradation by CoSN@C + PMS system; the RhB degradation was also severely inhibited by the addition of FFA, and the rate decreased to 23.8%. According to literature, FFA can quench 1O2 and has an influence on SO4.- and HO-radicals; when combined with the PMSO quenching results, in addition to the SO4.- and HO- adsorbed on the catalyst surface, 1O2 may be generated and contribute to the reaction. Consequently, the results of the quenching experiments must be validated using EPR tests on CoSN@C [47]. For electron paramagnetic resonance (EPR) tests, DMPO is commonly used. As shown in Figure 9, compared to the DMPO/PMS system, the addition of CoSN@C resulted in a quadruple peak with a intensity ratio of 1:2:2:1 and a sextuple peak with a intensity ratio of 1:1:1:1:1, corresponding to DMPO-HO- and DMPO-SO4.-, respectively, indicating that CoSN@C has strongly oxidized the SO4.- and HO-radicals upon contact with the quadruple peak signal of HO- that was observed in both the DMPO/PMS system and the system with the addition of the catalyst; however, the intensity of the signal in the PMS/DMPO/CoSN@C system was significantly higher than that in the PMS-only system, indicating that the content of HO- was substantially increased in the system with the addition of the catalyst and that the weak quadruple peak signal in the PMS solution alone was due to the autodecomposition of PMS [36]. Figure 10 displays the outcomes of using TEMP as the spin-trapping agent to confirm the presence of the non-radical species 1O2. Since there was no TEMP-1O2 signal for the PMS/TEMP system, the presence of reaction-generated 1O2 in the system was confirmed. A triple peak signal with the ratio of 1:1:1 was seen for the PMS/TEMP/CoSN@C system, corresponding to the capture of 1O2 by TEMP to form TEMP-1O2 [48].