The overlooked role of different Fe-N4Cx configuration in single atom catalyst for efficient peroxymonosulfate activation

Transition metal single-atom embedded on N-doped carbon as a catalyst for peroxymonosulfate activation: A DFT study

Theoretical study of local S coordination environment on Fe single atoms for peroxymonosulfate-based advanced oxidation processes

Bioinspired axial S-coordinated single-atom cobalt catalyst to efficient activate peroxymonosulfate for selective high-valent Co-Oxo species generation

Identifying Key Descriptors for the Single-Atom Catalyzed CO Oxidation

Facile synthesis of high loading and highly electron-delocalized Co single-atom catalyst for PMS activation: An in-depth study of molecular orbital and catalytic mechanisms.

Transforming plastics into single-atom catalysts is a promising strategy for upcycling waste plastics into value-added functional materials. Herein, a graphene-based single-atom catalyst with atomically dispersed FeN4Cl sites (Fe─N/Cl─C) is produced from high-density polyethylene wastes via one-pot catalytic pyrolysis. The Fe─N/Cl─C catalyst exhibited much higher turnover frequency and surface area normalized activity (Kac) compared with the Fe─N─C catalyst without axial Cl modulation. Both experiments and density functional theory (DFT) computations demonstrated that the axial incorporation of chloride fine-tuned the coordination environment of FeN4 sites and enhanced peroxymonosulfate (PMS) activation because of improved conductivity and modulated spin state. In situ, Raman, and infrared spectroscopic techniques revealed that PMS is activated by the Fe─N/Cl─C catalyst through an electron transfer process. The formation of a key PMS* intermediate at the Fe site effectively elevated the redox capacity of the catalyst surface to realize a fast degradation of diverse pollutants. The non-radical oxidation manner secures high selectivity toward target pollutants and high chemical utilization efficiency. A continuous operation in a column reactor also demonstrated the high efficiency and stability of the (Fe─N/Cl─C + PMS) system for practical water treatment.

Bio-porphyrin supported single-atom iron catalyst boosting peroxymonosulfate activation for pollutants degradation: A Singlet Oxygen-dominated nonradical pathway

N-doped carbon nanosheets supported-single Fe atom for p-nitrophenol degradation via peroxymonosulfate activation

Efficacy and mechanism of peroxymonosulfate activation by single-atom transition metal catalysts for the oxidation of organic pollutants: Experimental validation and theoretical calculation

Enhanced degradation of sulfamethoxazole by non-radical-dominated peroxymonosulfate activation with Co/Zn co-doped carbonaceous catalyst: Synergy between Co and Zn

Water contamination by refractory organics is one of the most critical and challenging problems in industrialization. Advanced oxidation processes based on peroxymonosulfate (PMS) activation is increasingly becoming popular due to its high ability to completely decompose toxic and refractory organic pollutants. Heteroatom-doped nanocarbons have attracted considerable attention over the conventional metal-based catalysts (e.g., Fe- or Co-based catalyst, etc.) to activate PMS, because carbocatalysts with the environmentally benign nature, corrosion resistance and biocompatibility can overcome the sintering and metal leaching problems caused by metal-based catalysts. The main objective of this study is to fabricate carbocatalysts to activate PMS for the degradation of recalcitrant organic contaminants, especially sulfonamide antibiotics in the aqueous environment. In the first part of this study, nitrogen-doped graphenes (NG) was fabricated to activate PMS for sulfacetamide (SAM) degradation. The contents of reactive functional groups and catalytic performance of NG were delicately controlled by adjusting thermal annealing temperature. NG600 (NG thermally annealed at 600°C) with the optimized amount of N species and C=O group exhibited a better PMS-activating activity than NGs prepared under other thermal annealing temperatures or via other optimized synthesis methods. Quenching experiment, electron paramagnetic resonance (EPR) study and Density Functional Theory (DFT) calculations revealed that non-radical pathway with surface activated PMS as the key reactive oxygen species (ROS) contributed more to SAM degradation than radical pathway in the NG/PMS/SAM system. The effect of catalyst loading, PMS dosage and common matrix species on PMS activation by NG600 for SAM degradation, the SAM degradation pathway, and the reusability of NG600 were investigated. In the second part of this study, nitrogen and boron-co-doped graphene was synthesized through two-step thermal annealing (2sNBG) and one-step thermal annealing (1sNBG). Boron-doped graphene was also synthesized via thermal annealing (BG). The carbocatalysts were employed as PMS activators to degrade SAM. The concentration of the main reactive functionalities and catalytic activity of 2sNBGs were delicately maneuvered through tuning the thermal annealing temperatures. 2sNBG800 (prepared at 800°C) with the highest N and B doping levels, the highest contents of pyridinic N and BC3 (substitutional B) that serve as the main active sites, and absence of hexagonal boron nitride (h-BN), performed best to activate PMS for SAM degradation. By contrast, the 1sNBG contained h-BN which could hamper its catalytic activity. The catalytic performances of the various doped graphenes prepared in this study followed the order of 2sNBG800 > 2sNBG900 > 2sNBG700 > 2sNBG600 > NG600 > 1sNBGs > BG800. Both radical quenching experiment and DFT calculation revealed that the introduction of B into NG can facilitate the shift of reaction pathway from a non-radical oxidation dominating in the NG/PMS system to the coexistence of non-radical and radical oxidations in the 2sNBG/PMS system. The synergistic coupling effect from bonding configuration of B-C-C-C-pyridinic N was the main reason for the enhanced catalytic activity of 2sNBG800 to activate PMS for SAM degradation. The SAM degradation was negligibly influenced by NO3- in the 2sNBG800/PMS/SAM system, while Cl- and humic acid led to 33% and 64% decrease in kapp, respectively. The transformation of the aromatic amino group and subsequent mineralization of SAM can effectively minimize the hazardous potentials of sulfonamides to the environment. Nevertheless, the adsorbed intermediates could deactivate 2sNBG to some extent. In the third part of this study, nitrogen-doped chitosan-derived carbon nanosheets (CNUs) were synthesized as a renewable, cheap and easily accessible alternative to the graphene-based carbocatalyst. The contents of reactive functionalities, graphitization degree and porous structure of CNU can be effectively tailored by pyrolysis temperature (Tp). The outstanding PMS-activating activity of CNU800 (prepared at Tp = 800°C) for SAM degradation can be attributed to its high level of C=O/C and graphitic N/C, relatively high graphitization degree, and its large specific surface area and hierarchically porous structure. The introduction of urea with the presence of NaHCO3 during chitosan pyrolysis facilitated formation of the graphene-like carbocatalyst with hierarchically porous structure and an enhanced PMS-activating activity. Quenching experiment and EPR collectively revealed that non-radical oxidation with singlet oxygen (1O2) as the main ROS was the dominant catalytic pathway in the CNU800/PMS/SAM system. The effect of catalyst loading, PMS dosage and common matrix species on PMS activation by CNU800 for SAM degradation, SAM degradation pathway, and reusability of CNU800 were probed.

Design of active dual atom Ni-Co-2H-MoS2 catalyst: Synergistic effect of Ni-adsorption and co-catalysis for activating peroxymonosulfate

The microenvironment regulation of Fe-N4 single atom catalysts (SACs) critically governs peroxymonosulfate (PMS) activation. Although conventional heteroatom substitution in primary coordination enhances activity, it disrupts Fe-N4 symmetry and compromises stability. Herein, we propose oxygen doping in the secondary coordination shell to construct Fe-N4-C6O2 SAC, which amplifies the localized electric field while preserving the pristine coordination symmetry, thus trading off its activity and stability. This approach suppresses Fe-N bond structural deformation (bond amplitude reduced from 0.875–3.175 Å to 0.925–2.975 Å) during PMS activation by lowering Fe center electron density to strengthen Fe-N bond, achieving extended catalytic durability (>240 h). Simultaneously, the weakened coordination field lowers the Fe=O σ* orbital energy, promoting electrophilic σ-attack of high-valent iron-oxo towards bisphenol A, and increasing its degradation rate by 41.6-fold. This work demonstrates secondary coordination engineering as a viable strategy to resolve the activity-stability trade-off in SAC design, offering promising perspectives for developing environmental catalysts.

Versatile pathways for oxidating organics via peroxymonosulfate activation by different single atom catalysts confining with Fe–N4 or Cu–N4 sites

A metal-organic framework (MOF) and graphene oxide (GO) based peroxymonosulfate (PMS) activator applied in pollutant removal