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Developing advanced heterogeneous catalysts with atomically dispersed active sites is an efficient strategy to boost the kinetics of peroxymonosulfate (PMS) activation for micropollutant removal. Here, we report a binary Mo2TiC2Tx MXene-based electroactive filter system with abundant surface Mo vacancies for effective activation of PMS. The Mo vacancies assumed two essential roles: (i) as anchoring sites for Fe single atoms (Fe-SA) and (ii) as cocatalytic sites for the Fenton-like reaction. Fe-SA formed strong metal–oxygen bonds with the Mo2TiC2Tx support, stabilizing at the sites previously occupied by Mo. The resulting Fe-SA/Mo2TiC2Tx nanohybrid filter achieved 100% degradation of sulfamethoxazole (SMX) in the single-pass mode (hydraulic retention time <2 s) when assisted by an electric field (2.0 V). The rate constant (k = 2.89 min–1) for SMX removal was 24 and 67 times greater than that of Fe nanoparticles immobilized on Mo2TiC2Tx and the pristine Mo2TiC2Tx filter, respectively. Operation in the flow-through configuration outperformed the conventional batch reactor model (k = 0.17 min–1) due to convection-enhanced mass transport. The results obtained from experimental investigations and theoretical calculations suggested that atomically dispersed Fe-SA, anchored on Mo vacancies, was responsible for the adsorption and activation of PMS to produce sulfate radicals (SO4•–) in the presence of an electric field. This study provides a proof-of-concept demonstration of an electroactive Fe-SA/Mo2TiC2Tx filter for broader application in the treatment of water contaminated by emerging micropollutants.
Jin et al. (Fri,) studied this question.