Singlet oxygen mediated iron-based Fenton-like catalysis under nanoconfinement

Abstract

For several decades, the iron-based Fenton-like catalysis has been believed to be mediated by hydroxyl radicals or high-valent iron-oxo species, while only sporadic evidence supported the generation of singlet oxygen (1O2) in the Haber–Weiss cycle. Herein, we report an unprecedented singlet oxygen mediated Fenton-like process catalyzed by ∼2-nm Fe2O3nanoparticles distributed inside multiwalled carbon nanotubes with inner diameter of ∼7 nm. Unlike the traditional Fenton-like processes, this delicately designed system was shown to selectively oxidize the organic dyes that could be adsorbed with oxidation rates linearly proportional to the adsorption affinity. It also exhibited remarkably higher degradation activity (22.5 times faster) toward a model pollutant methylene blue than its nonconfined analog. Strikingly, the unforeseen stability at pH value up to 9.0 greatly expands the use of Fenton-like catalysts in alkaline conditions. This work represents a fundamental breakthrough toward the design and understanding of the Fenton-like system under nanoconfinement, might cause implications in other fields, especially in biological systems.

Janus electrocatalytic flow-through membrane enables highly selective singlet oxygen production

“…2c , Region C, blue triangles), suggesting a constant production of 1 O 2 within the membrane. The detected products of FFA agree well with the oxidation products of FFA by 1 O 2 oxidation 32 , 52 (Supplementary Fig. 11 ; detailed detection methods provided in the Supplementary methods).…”

“…2b ), suggesting oxygen to be the precursor for the electro-generated 1 O 2 . Other ROS potentially produced in situ via the sequential electro-redox reaction during filtration, including hydrogen peroxide (H 2 O 2 ), superoxide (O 2 •− ), and hydroxyl radicals ( • OH), could be involved as critical intermediates for 1 O 2 production 32 , 53 (detailed ROS measurement provided in the Supplementary methods). Hydrogen peroxide (H 2 O 2 ) was generated at the vicinity of the Pd–CM surface (Fig.…”

“…These porous substrates spatially confine reactants and electrified active sites at the micrometer- and nanometer-scale. Spatial confinement by membrane pores and channels allows for optimal utilization of electrons by reactants due to minimal diffusion distance and mass transfer enhancement 30 , 32 , thereby overcoming intensive chemical usage in conventional EC systems. In addition, studies also highlighted the importance of flow-through configuration of membrane electrodes, which renders electrons to flow parallel to the fluid flow direction, further enhancing the charge transfer rates compared to the conventional flow-by mode (i.e., when the flow direction and electric field direction are perpendiculars) 33 , 34 .…”

Naphthalimide Assemblies for Simultaneous Detection of Ferrous Ion and H2O2 to Prevent Fenton Reaction

“…Further, to examine the possibility of interactions between in situ generated singlet oxygen ( via interactions between Fe 2+ ions with H 2 O 2 ) and supramolecular assemblies of Naph‐MDHP , we utilized ROS indicator, 9,10‐anthracenediyl‐bis (methyelene) dimalonic acid (ABDA) (1 M) which is known to exhibit sharp decline in absorption intensity in the presence of in‐situ generated singlet oxygen [35] . The UV‐vis spectrum of ABDA shows characteristic absorption bands in the range of 350–400 nm.…”

Regeneration of a deactivated surface functionalised polyacrylonitrile supported Fenton catalyst for use in wastewater treatment

“…28 Another study by Yang et al used only ethanol washing to remove poisoning from Fe 2 O 3 nanoparticles working with hydrogen peroxide in the oxidation of methylene blue. 29 These studies provide insight into Fenton catalyst regeneration in terms of deactivation by poisoning.…”