Iron Single-Atom Based Double-Reaction-Center Catalysis Triggers Internal-Driven and External-Driven Pathways for Green Fenton-like Chemistry.

Double-reaction-centers (DRCs) Fenton-like chemistry with low or zero oxidant addition has garnered increasing attentions due to their alignment with the principles of green and sustainable development. However, the regulation of such processes remains a significant challenge, primarily due to deficiencies in the microscopic interpretation of their electron migration mechanisms operating with low or zero oxidant addition. In this work, iron single-atom DRCs catalyst (Fe/N-SAC) was prepared for internal-driven system (zero oxidant addition) and external-driven system (low peroxymonosulfate (PMS) addition). Results indicated the absence of dissolved oxygen activation in the PMS-zreo Fe/N-SAC system, and the iron single atoms in the Fe/N-SAC acted as the predominate electron acceptors to extract the electrons from the electron-donating pollutants with iron valence decreasing from +2.37 to +2.07 and they could also be recovered under O2 atmosphere. In contrast, the electrons from the pollutants could be transferred to both PMS and iron atoms in the external-driven Fe/N-SAC/PMS system involving both predominant electron transfer process (ETP) and iron internal-driven. Furthermore, two experimental devices based on core mechanisms of internal-driven and external-driven systems were designed to achieve long-term operation. These studies will complement the core catalytic mechanisms and module applications of internal-driven and external-driven DRCs systems.