Active electronic structure derived by Fe-Cl-C coordination of single-atom cathode applied in antibiotics degradation by electro-Fenton: Enhanced transformation of oxygen to hydroxyl radicals via 3-electron pathway

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Vol. 474; p. 145545
• Main Authors: Ren, Ruijun, Shang, Xiaomeng, Song, Zilong, Li, Chen, Wang, Zhenbei, Qi, Fei, Ikhlaq, Amir, Kumirska, Jolanta, Maria Siedlecka, Ewa, Ismailova, Oksana
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.10.2023
• Subjects: Atomically dispersed Fe site; Chlorine-coordination configurations; electro-Fenton; Electronic structure; Hydroxyl radicals; Hydroxyl radicals; Chlorine-coordination configurations; Atomically dispersed Fe site; Electronic structure; electro-Fenton
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2023.145545

[Display omitted] •Electronic structure of Fe-Cl-C catalytic sites was tuned to enhance EF reaction.•Fe-Cl2C2 and Fe-Cl2C3 configurations were constructed with Fe2+ and Fe3+ states.•Reactions from O2 to •OH were verified via 3-electron pathway by two configurations.•FeCl2Cx/PC showed efficient antibiotics removal from water and structure stability.••OH as a major ROS contributed on AMX decaying by opening β-lactam ring. Designing heterogeneous catalysts with atomically dispersed active sites is vital to promote electro-Fenton (EF) activity, but how to regulate the electronic structure of metal centers to overcome the rate-limiting step over electron transfer triggered by reduction-/oxidation-state cycle in Fenton still remains a great challenge. Herein, we report a systematic investigation into heteroatom-doped engineering for tuning the electronic structure of iron single-atom sites by integrating electron-acceptor chlorine atoms into MOF-derived carbon substrate, in which the conversion of O2 toward •OH in EF were enhanced over the electronic structures of Fe-Cl2C2 and Fe-Cl2C3 formed by iron unsaturated coordination with chlorine and carbon atoms via a 3-electron pathway, and overcame the restriction of the rate-limiting step for reducing oxidized metal ions. The resulting accumulative concentration of •OH by FeCl2Cx/PC surpassed that of iron oxide nanoparticles by almost 2 times. Iron site shielding experiments and density functional theory calculations further demonstrated that the vital effect of Fe-Cl2C3 configuration corresponds to Fe(III) on Fe center contributes to H2O2 production and the dominant role of Fe-Cl2C2 configuration corresponds to Fe(II) in H2O2 activation to form •OH. Meanwhile, FeCl2Cx/PC exhibited less pH dependence, high stability, and efficient applicability for various antibiotics and wastewater remediation. The above results provide a new perspective into the reaction mechanism of multi-electron oxygen reduction pathway on single-atom catalysts by modulating the electronic structure of chlorine coordination.