Activation of persulfate on fluorinated carbon: Role of semi-ionic C-F in inducing mechanism transition from radical to electron-transfer nonradical pathway

Carbon-driven nonradical persulfate activation exhibits compelling advantages due to its good reactivity in complex aquatic surroundings. However, uncertainties still exist in the construction of nonradical-oriented activation systems and the role of positively charged carbon is ambiguous because of intricate carbon structure. In this regard, this study found that F-doping strategy not only improved the catalytic activity of carbon material, but also switched free radical persulfate (PS)-activated process into the electron-transfer-based nonradical process. The CF-1.0 achieved the promising performance in degrading bisphenol A (BPA) with a removal rate of 99.5% within 60 min, where the percentage of electron transfer contribution was up to 73.27%. Based on the Bader charge analysis in density functional theory (DFT) calculation, the “electron-loss” induced catalytic mechanism was proposed. Stimulated by the incorporation of F atom that can create the electron-deficient carbon layer, the electron-rich BPA tended to transfer electrons to carbon-activated persulfate complex (C-S2O82-*), in an effort to balance the electron loss in the carbonaceous matrix, thereby realizing the oxidative degradation of pollutant. Quantitative structure-activity relationships (QSARs) indicated that semi-ionic C-F, C-OH, and structural defects could function as electron transfer channel, SO4•−/• OH, and 1O2 formation sites, respectively. In addition, the catalytic behaviors towards periodate (PI) were also investigated in detail. Overall, this research develops nonradical reaction-targeted fluorinated carbocatalyst for persulfate activation and deepens the understanding of positively charged carbon in electron-transfer regime.