Thermodynamic regulation of interfacial proton donor and oxidant molecular states for enhancing alkaline reaction kinetics over Fe-NC/peroxymonosulfate systems

• Published in: Applied catalysis. B, Environmental Vol. 375; p. 125450
• Main Authors: Zuo, Shiyu, Wang, Yan, Wan, Jinquan, Ma, Yongwen, Yan, Zhicheng, Yi, Jianxin, Alemán, José
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.10.2025
• Subjects: Fenton-like reaction; Oxidants; PH dependence; Proton donors; Thermodynamic; Proton donors; Fenton-like reaction; PH dependence; Oxidants; Thermodynamic
• ISSN: 0926-3373
• DOI: 10.1016/j.apcatb.2025.125450

The origin of the substantial kinetic pH dependence in the Fenton-like reaction, specifically the approximately two orders of magnitude reduction in reaction kinetics as the pH shifts from acidic to alkaline, remains a subject of considerable debate. However, the role of thermodynamic pathways and energy barriers of the reaction has been overlooked due to the changes in molecular states, which lead to pH dependence. In this study, it was found that the molecular state of the proton donor and oxidant in the Fenton-like reaction of Fe-NC/peroxymonosulfate (PMS) changed with the increase of pH, which changed the thermodynamic pathway and energy barrier of the reaction, resulting in pH dependence of the reaction. Empirical data and theoretical computations jointly substantiate that under high pH alkaline conditions, proton donors and oxidants (H2O/SO52-) display increased voltage amplitudes and thermodynamic energy barriers, in contrast to their counterparts at low pH acidic conditions (H3O+/HSO5-), thereby exhibiting weakened kinetic reaction rate constants. A groundbreaking method for quantifying voltage amplitudes was devised, unveiling a robust correlation between pH-dependent oxidation potential and reaction kinetics (R2>0.97). Based on this perspective, the enhancement of proton adsorption on the catalyst surface by the interfacial electric field increases the surface proton concentration, which can transform proton donors and oxidants in alkaline solutions into H3O+ and HSO5-. This significantly reduces the thermodynamic energy barrier and strengthens the alkaline reactions kinetics, with the pH dependence decreasing from 13.016 to 4.296. This finding elucidates the thermodynamic effects of reactant molecular states on the pH dependence in Fenton-like reactions. It provides new theories and methods for achieving efficient alkaline Fenton-like reactions. [Display omitted] •pH-induced changes in molecular state lead to an increase in thermodynamic pathways and reaction barriers.•Thermodynamic pathway and energy barrier changes lead to pH dependence.•The interfacial electric field regulates the molecular state of the interfacial proton donor and oxidant.•Fenton-like high kinetic rates were achieved at alkaline pH.•A voltage amplitude method was developed to quantitatively analyze the correlation between oxidation potential and reaction kinetics.