Single Fe atoms confined in two-dimensional MoS2 for sulfite activation: A biomimetic approach towards efficient radical generation

Sulfite has been recently recognized as a source of radicals for oxysulfur radical-based advanced oxidation process due to its low cost and low toxicity. Inspired by sulfite oxidase enzyme, we demonstrate single Fe atoms confined in two-dimensional MoS2 nanosheets (FexMo1-xS2) as highly reactive catalysts for heterogeneous activation of sulfite, thereby promoting efficient oxidative degradation of propranolol in water. Highest propranolol degradation efficiency of similar to 90 % was observed at pH 4.0. The Fe or Mo sites of FexMo1-xS2 activate sulfite via the Fe2+/Fe3+ or Mo4+/Mo5+/Mo6+ redox cycle. More importantly, the synergistic catalysis involving the Fe and Mo sites play an essential role. SO5.- is the major radical responsible for propranolol degradation with the 2nd-order rate constant of (1.1 +/- 0.6) x 10(7) M-1 s(-1). Furthermore, the FexMo1-xS2/sulfite system is capable of degrading a wide range of recalcitrant organic pollutants and operating in a real water environment, suggesting its great potential in practical water treatment applications.