Cathodic polarization sustaining MXene-mediated fenton-like reactions: Performance, reaction mechanisms, and life cycle assessment

A variety of electron-rich heterogeneous catalysts have been used to promote successive Fenton-like reactions for water purification. However, as the inherent electrons of the catalyst are used up, its catalytic efficiency drops dramatically. Herein, we introduced cathodic polarization to sustain Ti3C2TX MXene, a typical electron-rich heterogeneous catalyst, in Fention-like reactions. Results showed that the electrified MXene with peroxymonosulfate exhibited great performance in removing various contaminants, including anticonvulsant pharmaceuticals, nonsteroidal anti-inflammatory drugs, antibiotics, and chlorinated herbicides. The great cyclic stability of the electrified MXene indicated that external electrons replaced the low-valence titanium to activate peroxymonosulfate. Thus, low-valence titanium and structural integrity of MXene can be largely sustained at cathodic polarization, with the efficiency maintained at > 60 % following the 7-cycle operation compared to that decreased to 35 % in the control group. Moreover, cathodic polarization could promote the formation of adsorbed Fe-species, resulting in the preferable formation of free radicals (e.g., HO center dot and SO4 center dot-). Life cycle assessment results showed that the cycling of MXene under cathodic polarization was also critical for alleviating the environmental impact of Fenton-like reactions. Our study provides insights into the catalytic mechanism of electrified Fenton-like processes and demonstrates the significance of developing sustainable catalytic systems for water purification.