Session: Applications & Implications of Nanomaterials in the Environment:

Contaminants of emerging concern (CECs) detected at trace concentrations in water and wastewater have been threatening the public health and ecological systems. Advanced oxidation processes (AOPs) hold promising for degrading CECs, and they are continuously improved for energy efficiency and environmental sustainability. Heterogeneous single-atom catalysts with fine-tuned coordination environment show superior activity, selectivity, and stability in AOPs for water purification. We rationally designed a single-atom Fe catalyst under the guidance of molecular simulations, and the catalyst degraded a wide range of CECs by high-valent Fe species at neutral pH through activating peroxides such as peroxymonosulfate (PMS). Tailoring the electronic structure of the catalyst, molecular simulations first highlighted that high-valent Fe species were readily produced in oxygen substituted Fe complexes (O_x-Fe-N_x) upon oxidation, compared to native Fe-nitrogen complexes (Fe-N_x). Then a single-atom Fe catalyst with oxygen doping (SAFe-OCN) was synthesized, showing enhanced reactivity in phenol degradation compared to the Fe catalyst without oxygen (Fe-CN) by activating PMS, which supported the prediction of molecular simulations. The susceptibilities of CECs to catalytic degradation in SAFe-OCN/PMS system were likely dependent on their structures and properties. By activating PMS, SAFe-OCN produced high-valent Fe species exclusively for contaminant oxidation, instead of using radicals (hydroxyl radicals, sulfate radicals, and superoxide radicals), singlet oxygen, or catalyst-mediated electron transfer. Moreover, the reactivity of SAFe-OCN was maintained in complex water matrices and for long-term oxidation. In summary, the molecular simulation properly instructs the design of effective catalysts, and the single-atom catalyst facilitates the development of sustainable water treatment technologies.

Sebastian Stoian

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