Unveiling the Origins of Selective Oxidation in Single-Atom Catalysis via Co–N₄–C Intensified Radical and Nonradical Pathways

Abstract

Single-atom catalysts (SACs)-based peroxymonosulfate (PMS) systems are highly selective to the type of organic pollutants while the mechanisms remain ambiguous. In this work, we carried out experimental and theoretical investigations to reveal the origins of selectivity of radical and nonradical pathways in a designated Co−N 4 −C/PMS system. Two typical pollutants [bisphenol A (BPA) and metronidazole (MNZ)] with different molecular structures were employed for comparison. We found that radical oxidation (SO 4•− and HO • ) and nonradical electrontransfer pathway (ETP) co-existed in the Co−N 4 −C/PMS system. Pollutants (e.g., MNZ) with a high redox potential were degraded primarily by free radicals rather than ETP, while the oxidization of low-redox pollutants (e.g., BPA) was dominated by ETP at the surface region of Co−N 4 −C which overwhelmed the contributions of radicals in the homogeneous phase. Intriguingly, the contributions of radical and nonradical pathways could be manipulated by the PMS loading, which simultaneously increased the radical population and elevated the oxidation potential of Co−N 4 −C-PMS* complexes in ETP. Findings from this work will unravel the mysterious selective behavior of the SACs/PMS systems in the oxidation of different micropollutants.

Boosting Fenton-like Catalysis via Electron Tunneling-Based C–Co Charge-Transfer Bridge in Nitrogen-Doped Cobalt@Carbon Nanotube-Grafted Carbon Polyhedron

“…Before BPA disappears completely, the utilization rate of H 2 O 2 reaches more than 66% in the Co@NCNT/NC/H 2 O 2 system, whereas the H 2 O 2 utilization rate in the Co@NC/H 2 O 2 system is only 35%. However, the utilization rate of H 2 O 2 in the Co@CNTA/H 2 O 2 system is much higher than that of the traditional Fe 3 O 4 (∼5%) and Cu 2 O (∼20%) Fenton-like systems. − The mineralization ratio of BPA was 58.17% after 30 min through TOC analysis (Figure d). Also, the Co@NCNT/NC’s reusability was evaluated, and the removal efficiency of BPA decreased to 60.73% within 180 min (Figure d, inset).…”

Efficient Single-Atom Fe-Catalyzed Fenton-like Reaction Involving Peroxymonosulfate for BPA Degradation by High-Valent Fe(IV)=O

“…Methanol and tert -butyl alcohol (TBA) are sensitive probes for radicals due to high reaction rates, e.g., k ( · OH/CH 3 OH) = (1.2–2.8) × 10 9 M –1 s –1 , k (SO 4 · – /CH 3 OH) = (1.6–7.8) × 10 7 M –1 s –1 , and k ( · OH/TBA) = (3.8–7.6) × 10 8 M –1 s –1 . , The reaction rate constants for BPA with the hydroxyl radical and sulfate radical are 5.8 × 10 9 and 1.4 × 10 9 M –1 s –1 , respectively. , Methanol and tert -butyl alcohol (TBA) were thus employed to examine the possible contribution of the free radicals to the pollutant degradation process in the Fe 0.4 -NC-catalyzed reaction system (Figure a). BPA with a concentration of 100 μM could be eliminated rapidly within 60 s in the presence of 400 mM methanol or TBA (4 × 10 6 time of the concentration of BPA).…”

“…51,52 The reaction rate constants for BPA with the hydroxyl radical and sulfate radical are 5.8 × 10 9 and 1.4 × 10 9 M −1 s −1 , respectively. 15,53 Methanol and tert-butyl alcohol (TBA) were thus employed to examine the possible contribution of the free radicals to the pollutant degradation process in the Fe 0.4 -NCcatalyzed reaction system (Figure 4a). BPA with a concentration of 100 μM could be eliminated rapidly within 60 s in the presence of 400 mM methanol or TBA (4 × 10 6 time of the concentration of BPA).…”

Integrating energy-environmental functions into multifaceted lignocellulose valorization: high-performance supercapacitors and antibiotic decomposition

“…In contrast, pollutants with high redox potentials are less easily degraded through surface-electron-shuttling induced oxidation. 52 Hence we carried out electrochemical tests and theoretical calculations to investigate the direct electron-transfer mechanism of the overall catalytic process. As depicted in Fig.…”