Spontaneous FeIII/FeII redox cycling in single-atom catalysts: Conjugation effect and electron delocalization
Zheng Qian,
Lingzhen Wang,
Mawuli Dzakpasu,
Yujia Tian,
Dahu Ding,
Rongzhi Chen,
Gen Wang,
Shengjiong Yang
Affiliations
Zheng Qian
School of Environmental and Municipal Engineering, Xi’an University of Architecture and Technology, No. 13, Yanta Road, Xi’an, Shaanxi 710055, China
Lingzhen Wang
School of Environmental and Municipal Engineering, Xi’an University of Architecture and Technology, No. 13, Yanta Road, Xi’an, Shaanxi 710055, China
Mawuli Dzakpasu
School of Environmental and Municipal Engineering, Xi’an University of Architecture and Technology, No. 13, Yanta Road, Xi’an, Shaanxi 710055, China
Yujia Tian
School of Environmental and Municipal Engineering, Xi’an University of Architecture and Technology, No. 13, Yanta Road, Xi’an, Shaanxi 710055, China
Dahu Ding
College of Resources and Environmental Sciences, Nanjing Agricultural University, No. 1, Weigang, Nanjing, Jiangsu 210095, China
Rongzhi Chen
College of Resources and Environment, University of Chinese Academic of Science, 19A Yuquan Road, Beijing, 100049, China; Corresponding author
Gen Wang
School of Environmental and Municipal Engineering, Xi’an University of Architecture and Technology, No. 13, Yanta Road, Xi’an, Shaanxi 710055, China
Shengjiong Yang
School of Environmental and Municipal Engineering, Xi’an University of Architecture and Technology, No. 13, Yanta Road, Xi’an, Shaanxi 710055, China; Corresponding author
Summary: The mechanism of spontaneous FeIII/FeII redox cycling in iron-centered single-atom catalysts (I-SACs) is often overlooked. Consequently, pathways for continuous SO4·-/HO⋅ generation during peroxymonosulfate (PMS) activation by I-SACs remain unclear. Herein, the evolution of the iron center and ligand in I-SACs was comprehensively investigated. I-SACs could be considered as a coordination complex created by iron and a heteroatom N-doped carbonaceous ligand. The ligand-field theory could well explain the electronic behavior of the complex, whereby electrons delocalized by the conjugation effect of the ligand were confirmed to be responsible for the FeIII/FeII redox cycle. The possible pyridinic ligand in I-SACs was demonstrably weaker than the pyrrolic ligand in FeIII reduction due to its shielding effect on delocalized π orbitals by local lone-pair electrons. The results of this study significantly advance our understanding of the mechanism of spontaneous FeIII/FeII redox cycling and radical generation pathways in the I-SACs/PMS process.
