Radical Attack Research Articles

Oxidative degradation of Piperazine (PZ) in aqueous KOH/K2CO3 solutions

KOH and K2CO3 aqueous solutions have demonstrated potential for CO2 absorption processes due to their low toxicity, non-volatility of the capture agent and resistance to degradation. However, their absorption kinetics are typically slower than those of primary and secondary amines, and therefore promotors may be needed to allow competitive absorption rates and thus absorber heights. Here, we selected piperazine (PZ) as a promoter and investigated its oxidative degradation when blended with KOH or K2CO3. The changes in PZ concentration were analyzed by gas chromatography–mass spectrometry (GC–MS), while the degradation products were analyzed by GC–MS and anion chromatography. The results showed that PZ oxidative degradation followed the order KOH/PZ > PZ > K2CO3/PZ indicating that KOH enhanced PZ oxidation while K2CO3 inhibited PZ oxidation. Therefore, KOH/PZ may still be a promising solvent with appropriate CO2 loading as the CO2 protects the PZ from hydroxyl and oxygen radical attacks. The degradation products are similar across the blends and identified as Ethylenediamine (EDA), 2-oxopiperazine (OPZ), Formylpiperazine (FPZ), formate, acetate and oxalate, with formate being the most abundant product for all blends. Furthermore, the PZ first-order rate constants for all solutions were provided, and the oxidation degradation pathway of PZ-based solutions was proposed.

Radical Attack and Damage Mitigation in Hydrocarbon-Based Ionomers

An antioxidant strategy for aromatic hydrocarbon based proton exchange membranes for fuel cells and electrolyzers requires an understanding of the mechanisms of radical attack and follow-up reactions. We provide experimental evidence that radical scavenging is ineffective. Instead, focus has to be placed on repairing intermediates. Recent studies of exposure of model compounds to radicals formed in a γ-irradiation cell are reported. Fuel cell tests of membranes containing polymer-bound antioxidants with cerium and copper metal complexes show improved chemical stability in an accelerated stress test. Requirements for a successful implementation of a damage-repair mechanism in hydrocarbon membranes are discussed.

Sulfite activation by Jahn-Teller-driven oxygen vacancies Cu-Mn composite oxide for chlortetracycline degradation

Copper-manganese composite metal oxides (CuMnOy) were prepared by hydrolysis-driven oxidation-reduction method and used to activate sulfite to degrade chlortetracycline hydrochloride (CTC) for the first time. The Jahn-Teller ions Mn3+ and Cu2+ exist in CuMnOy, which form a solid electric charge transport redox system and ensure the continuous generation of reactive oxygen species (ROS). Through the systematic study of the experimental parameters such as sulfite concentration, catalyst metal molar ratio, catalyst amounts and initial pH, the optimal degradation rate of CTC could reach 91.74% within 10 min and 94.46% after 30 min. The major reactive radicals were determined by radical quenching experiments and electron paramagnetic resonance (EPR) trapping techniques, and it was confirmed that SO4•- and •O2- played a nonnegligible role in the process of degrading CTC. Density functional theory (DFT) calculations show that higher Fukui indices (f- and f0) of CTC sites are more vulnerable to free radical attack. CuMnOy has low CTC degradation intermediate toxicity, high catalytic performance, good anti-interference ability, reusability and stability, and possesses decent application potential in the actual water treatment field.

A novel DBD/VUV/PMS process for efficient sulfadiazine degradation in wastewater: Singlet oxygen-dominated nonradical oxidation

In this study, a novel process of dielectric barrier discharge plasma/vacuum ultraviolet/peroxymonosulfate (DBD/VUV/PMS) for the nonradical-dominated degradation of sulfadiazine (SDZ) was investigated. The hybrid system has significant synergistic effects, with 95.5% SDZ and 68.3% TOC removal within 10 min. The activation efficiency of DBD/VUV (69.0%) on PMS via multipath was 2.07 times higher than that of single DBD (33.3%) under alkaline conditions. Electron paramagnetic resonance analyses and trapping experiments showed 1O2 was the primary active substance in the DBD/VUV/PMS process. The predominant role of 1O2 revealed that SDZ removal mainly followed the nonradical reaction pathway, contrary to the previously reported non-thermal plasma (NTP)-based radical-dominated process. Multiple spectroscopy analysis showed the efficient degradation process of SDZ. Unlike the radical attack sites, the SDZ transformation pathway by nonradical 1O2 was probably initiated by an aniline ring site attack based on density functional theory (DFT) calculations and product analyses. The DBD/VUV/PMS process reduced energy consumption by 69% compared to DBD. Finally, the evaluation of ecotoxicity and PMS utilization demonstrated the advantages and application prospects of the DBD/VUV/PMS process. This research developed a new nonradical-dominated pathway for antibiotic degradation by the photo/plasma/persulfate process.

Degradation of xanthene-based dyes by photoactivated persulfate: experimental and computational studies.

Dyes are naked-eye detectable even at low concentration levels and can cause environmental damage when released into aquatic effluents; therefore, methods for removing the residual color from the aquatic media are always a current issue. In this paper, degradation of three xanthene dyes, Rhodamine B, Eosin Y, and Sodium Fluorescein, using photoactivated persulfate was evaluated at pH 3.0 and 11.0. The dyes' degradation followed a pseudo-first-order reaction. Although the solution is completely decolorized in 40min at pH 3.0, achieving 75% mineralization requires a longer reaction time of 180min. Furthermore, GC-MS analyses indicate that degradation products are mainly low-molecular weight acids, CO2 and H2O. Experiments carried out in dark and under UV irradiation showed substantial contribution of radical (SO4•- and HO•) and non-radical pathways to dye degradation in both pH. Additionally, to get more insights into the degradation pathways, HOMO-LUMO energy gaps of the dyes were calculated by DFT using MPW1PW91/MidiXo level of theory and, in general, the lower the bandgap, the faster the degradation. Fukui functions revealed that the preferential sites to radical attack were the xanthene or the benzoate portion depending on the pH, wherein attack to the xanthene ring provided better kinetic and mineralization results.

Photocatalytic degradation of alkyl imidazole ionic liquids by TiO2 nanospheres under simulated solar irradiation: Transformation behavior, DFT calculations and promoting effects of alkali and alkaline earth metal ions

In this study, TiO2 nanospheres prepared by the sol-gel method were found to efficiently catalyze the photodegradation of 1-butyl-2,3-dimethylimidazolium bromide salt ([BMMIm]Br) under simulated solar irradiation through the main attack of hydroxyl radicals (•OH). The promoting effect of alkali metal (Li+→Cs+) and alkaline earth metal ions (Mg2+→Ba2+) was particularly emphasized. In-situ EPR tests showed that the introduction of alkali and alkaline earth metal ions could enhance the formation of •OH thus leading to a 7%−30.3% increase in the degradation efficiency of. [BMMIm]+. Moreover, the removal efficiency of [BMMIm]+ still reached > 96.19% in four real waters. A total of 23 products of [BMMIm]Br were detected, and hydroxyl substitution, bond breaking, direct oxidation and ring opening were considered as the main reactions during the photocatalytic degradation process. The results of toxicity evaluation showed that hydroxylation was a reaction process of increasing toxicity, while the bond breaking reaction had great detoxification capacity for [BMMIm]+. These findings may enhance our understanding on the effects of alkali or alkaline earth metal ions on the photocatalytic activity of TiO2, which could also provide reference for the efficient and green removal of alkylimidazolium ionic liquids in waters.

Radical Substitution of Polyfluoroarenes and Heteroarenes Promoted by Photoredox Activation of Organozinc Iodides

AbstractAromatic compounds interact with organozinc reagents under photoredox conditions, leading to the substitution products. The reaction is performed under blue light irradiation via in situ generated organozinc reagents (Barbier conditions), which are oxidized by the photocatalyst, followed by radical attack at the aromatic substrate. The method works with polyfluorinated arenes, 2‐chlorobenzoxazoles, and 2‐sulfonyl‐substituted benzothiazole.

Exploring the CO2 photocatalytic evolution onto the CuO (1 1 0) surface: A combined theoretical and experimental study

A combined theoretical and experimental study was performed to elucidate the photocatalytic potential of tenorite, CuO (1 1 0) and to assess the evolution pathway of carbon dioxide (CO2) evolution pathway. The calculations were performed with density functional theory (DFT) at a DFT + U + J0 and spin polarized level. The CuO was experimentally synthesized and characterized with structural and optical methodologies. The band structure and density of states revealed the rise of band gaps at 1.24 and 1.03 eV with direct and indirect band gap nature, respectively. These values are in accordance with the experimental evidence at 1.28 and 0.96 eV; respectively, which were obtained by UV-Vis DRS. Such a behavior could be related to enhanced photocatalytic activity among copper oxide materials. Experimental evidence such as SEM images and work function measurements were also performed to evaluate the oxide. The redox potential suggests a catalytic character of tenorite (1 1 0) for the CO2 transformation through aldehydes (methanal) intermediate formation. Furthermore, a route through methylene glycol CH2(OH)2 was also explored with the theoretical methodology. The reaction path exhibits an immediate reduction of ▪ into a •OH radical and an [OH]− anion, in the first step. This •OH radical attacks a double bond (C = O) of ▪ to form bicarbonate ([▪]−) and subsequently, carbonic acid (▪). The carbonic acid reacts with other •OH radical to finally form orthocarbonic acid (▪).

Primary and Secondary Coordination Sphere Effects on the Structure and Function of S-Nitrosylating Azurin.

Much progress has been made in understanding the roles of the secondary coordination sphere (SCS) in tuning redox potentials of metalloproteins. In contrast, the impact of SCS on reactivity is much less understood. A primary example is how copper proteins can promote S-nitrosylation (SNO), which is one of the most important dynamic post-translational modifications, and is crucial in regulating nitric oxide storage and transportation. Specifically, the factors that instill CuII with S-nitrosylating capabilities and modulate activity are not well understood. To address this issue, we investigated the influence of the primary and secondary coordination sphere on CuII-catalyzed S-nitrosylation by developing a series of azurin variants with varying catalytic capabilities. We have employed a multidimensional approach involving electronic absorption, S and Cu K-edge XAS, EPR, and resonance Raman spectroscopies together with QM/MM computational analysis to examine the relationships between structure and molecular mechanism in this reaction. Our findings have revealed that kinetic competency is correlated with three balancing factors, namely Cu-S bond strength, Cu spin localization, and relative S(ps) vs S(pp) contributions to the ground state. Together, these results support a reaction pathway that proceeds through the attack of the Cu-S bond rather than electrophilic addition to CuII or radical attack of SCys. The insights gained from this work provide not only a deeper understanding of SNO in biology but also a basis for designing artificial and tunable SNO enzymes to regulate NO and prevent diseases due to SNO dysregulation.

Substitution effect on the adiabatic ionization potential, vertical ionization potential, electrophilicity, and nucleophilicity of some hydantoin drug derivatives: Computational study

AbstractIn the current paper, the adiabatic ionization potentials (AIP) for 29 hydantoin derivatives and hydantoin‐based drugs such as allantoin, phenytoin, mephenytoin, nilutamide, iprodione, nitrofurantoin, and ethotoin were calculated using the double hybrid ωB97XD density functional theory (DFT) in coupling with 6‐311+G(2df,2p) basis set at the B3LYP/6‐31+G(d,p) optimized geometry. The neutral and cationic radicals of the examined species were firstly optimized using the B3LYP/6‐31+G(d,p) level. Final energies were improved by single point calculation using 16 different DFT methods such as B3LYP, ωB97, B97D, TPSSTPSS, M06‐2X, …, and so forth, with 6‐311+G(2df,2p) basis. Statistical tools such as root mean square error (RMSE) was used to examine the accuracy of the DFT method with respect to the standard reference AIP values. These standard references were calculated, for 12 hydantoin derivatives with less than nine non‐hydrogen atoms, by taking the average values of the AIP computed using the G4, G3B3, and CBS‐QBS methods. The vertical ionization potentials (VIPs), the vertical electron affinity (VEA), and global quantum parameters such as electrophilicity and nucleophilicity of the 29 molecules were also calculated. Substitution effect on the AIP, VIP, VEA, fundamental gap, electrophilicity, and nucleophilicity of the species under probe was studied and discussed. The results reveal that substitution of electron withdrawing group (EWG) raises the AIP and VIP, electrophilicity, and the fundamental gap, while substitution of electron donating group (EDG) raises the VEA and the nucleophilicity. Furthermore, the condensed Fukui functions were used to identify the active centers for nucleophilic, electrophilic, and free radical attacks.

Kinetics and mechanism of sulfate radical-and hydroxyl radical-induced disinfection of bacteria and fungal spores by transition metal ions-activated peroxymonosulfate.

Peroxymonosulfate(PMS)-based advanced oxidation process have been recognized as efficient disinfection processes. This study comprehensively investigated the role of sulfate radical (SO4•-) and hydroxyl radical (•OH)-driven disinfection of bacteria and fungal spores by the PMS/metals ions (Me(II)) systems and modeled the CT value based on the relationship between survival and ∫[Radical]dt, with the aim to provide an accurate and quantitative kinetic data of inactivation processes. The results indicated that •OH played a more central role than SO4•- in the inactivation process, and bacteria were more vulnerable to radical attack than fungal spores due to the differences in antioxidant mechanisms and external structures. The k value of •OH -induced inactivation of E. coli was approximately 3-fold higher than that of A. niger, and the shoulder length of •OH -induced inactivation of E. coli was closely 52-fold shorter than that of A. niger after treated with the PMS/Co(II) system. The morphological and biochemical changes revealed that PMS/Me(II) treatment caused membrane damage, intracellular ROS accumulation and esterase activity loss in microorganisms. This study significantly improved the understanding of the contribution of radicals in the process of microbial inactivation by PMS/Me(II) and would provide important implications for the further development of technologies to cope with the highly resistant fungal spores in drinking water.

Synthesis of Isatin-based Chalcone Derivatives and Their Activity as Antioxidants

The body needs antioxidants to combat free radicals and guard against their damaging effects on healthy cells that might result in degenerative disorders. Several degenerative diseases include hypertension, heart disease, diabetes, stroke, and cancer. The human body can deal with free radical attacks caused by radiation, stress, cigarette smoke, and environmental pollution, so it requires additional external antioxidants to protect against free radical attacks. Chalcone is a compound that has an α,β-unsaturated carbonyl system, which makes chalcone compounds have biological activity. Chalcone compounds may be used in pharmacology as antioxidants, antifungals, antibacterial agents, anticancer agents, and for other biological activities. This study aims to synthesize a chalcone derivative, namely 3-(2-oxo-2-phenylethylidene)indolin-2-one and 5-chloro-3-(2-oxo-2-phenylethylidene)indolin-2-one containing a chloro substituent, as well as test the potential of these compounds as antioxidants. The reflux method of claisen-schmidt condensation of isatin and acetophenone was used to create chalcone derivatives. Spectroscopy was used to characterize the produced chemicals (UV-VIS, IR, and LCMS) and their antioxidant activity using the DPPH method. This study showed that the antioxidant activity of 3-(2-oxo-2-phenylethylidene)indolin-2-one and 5-chloro-3-(2-oxo-2-phenylethylidene)indolin-2-one compounds is very weak at low concentrations.

Penambahan ekstrak kunyit (Curcuma domestica Val) cair terhadap karakteristik organoleptik dan kandungan antioksidan krispi bayam (crispy spinach)

The human immune system can protect the body from bacteria, viruses, and parasites that cause disease. The immune system becomes more active when enough amounts of macro and micro nutrients are consumed. Antioxidants can also guard against the attack of free radicals and radical chemicals found in the body, limiting the damage caused by the oxidation process. One of them is using turmeric and spinach extract as a supplement. Turmeric extract can be used in the production of crispy spinach cookies. The research was purposed to find out the effect of turmeric extract addition on organoleptic characteristics and antioxidant content crispy spinach. This research used a Experimental research design (Pre-Experimental Design) with three treatments consisting of the addition of 50 ml, 60 ml, and 70 ml of turmeric extract. All three formulations were conducted hedonic tests for know the best formulation, followed by antioxidant content (DPPH method), carbohydrate content (method by different), protein content (Kjedahl), and fat content (Soxhlet). Furthermore, economic analysis and product ranking are carried out. Formulation 3 was chosen because of the highest nutritional content.
 
 Keywords: crispy spinach, immunity, turmeric extract

Therapeutic Hypothermia for Hypoxic-Ischemic Brain Injury Is More Effective in Newborn Infants than in Older Patients: Review and Hypotheses.

Posthypoxic therapeutic hypothermia has been tested in newborn infants, with seven randomized trials showing consistent evidence of reduction in death, cerebral palsy, and cognitive impairment at school age. In contrast, randomized trials of hypothermia after cardiac arrest in adults have not shown consistent evidence of lasting neurological protection. The apparently greater effectiveness of therapeutic hypothermia in newborns may be due to important biological and clinical differences. One such difference is that adults are heavily colonized with microbes, and many have active inflammatory processes at the time of arrest, but few newborns are heavily colonized or infected at the time of birth. Inflammation can interfere with hypothermia's neuroprotection. A second difference is that apoptosis is more commonly the pathway of neuronal death in newborns than in adults. Hypothermia inhibits apoptosis but not necrosis. Newborns have a larger endogenous supply of stem cells (which reduce apoptosis) than adults and this may favor regeneration and protection from hypothermia and regeneration. A third difference is that immature oligodendroglia are more sensitive to free radical attack then mature oligodendroglia. Hypothermia reduces free radical release. In addition, immature brain has increased N-methyl-D-aspartate receptor subunits compared with adults and hypothermia reduces excitotoxic amino acids. Adults suffering cardiac arrest often have comorbidities such as diabetes, hypertension, and atherosclerosis, which complicate recovery, but newborn infants rarely have comorbidities before asphyxia. Adult hypothermia treatment may have been too short as no trial has cooled for longer than 48 hours, some only 24 or 12 hours, but neonatal therapeutic hypothermia has routinely lasted 72 hours. We hypothesize that this combination of differences favors the effectiveness of therapeutic hypothermia in newborn infants compared with adults.

Coupling of N2 and O2 in the Gas Phase to Synthesize Nitric Oxide at Room Temperature: A Zeldovich-Like Strategy.

Dinitrogen (N2) activation and its chemical transformations are some of the most challenging topics in chemistry. Herein, we report that heteronuclear metal anions AuNbBO- can mediate the direct coupling of N2 and O2 to generate NO molecules. N2 first forms the nondissociative adsorption product AuNbBON2- on AuNbBO-. In the following reactions with two O2 molecules, two NO molecules are gradually released, with the formation of AuNbBO2N- and AuNbBO3-. In the reaction with the first O2, the generated nitrene radical (N••-) originating from the dissociated N2, induces the activation of O2. Subsequently, the second O2 is anchored and forms a superoxide radical (O2•-); this radical attacks the other N atom to form an N-O bond, releasing the second NO. The N••- and O2•- radicals play key roles in the reactions. The mechanism adopted in this direct oxidation of N2 by O2 to NO can be labeled as a Zeldovich-like mechanism.

Immobilized hindered amine radical scavenger for durability enhancement of perfluorosulfonic acid membrane in PEMFCs

Membrane durability is one of the crucial considerations that restrict the development of proton exchange membrane fuel cells (PEMFCs). The widely used and inexpensive stabilizer hindered amine 4-amino-2,2,6,6-tetramethylpiperidine (TEMP) was selected as the free radical scavenger and tethered onto the skeleton of carboxyl-functionalized metal-organic frameworks for addressing its migration problem. The resulted inorganic-organic hybrid dopant (UIO-66-TEMP) was then incorporated into the Nafion matrix to alleviate the attacks of free radicals on the membrane in the fuel cell working circumstances. Besides the improved mechanical strength and oxidative stability, and restricted water swelling and hydrogen crossover, the resulted hybrid membranes also possess excellent proton conductivity up to 176 mS cm−1, endowing them with high power density up to 612.78 mW cm−2, 1.5 times higher than recast Nafion. After accelerated durability testing for 120 h, the OCV decay rate of the hybrid membranes decreased to 0.74 mV h−1, only 40% of recast Nafion (1.89 mV h−1). Meanwhile, the optimized hybrid membrane still maintained a high peak power density of 463.62 mW cm−2 and a low hydrogen crossover density of 4.44 mA cm−2, which were superior to recast Nafion after OCV durability tests. Hindered amines can be “regenerated” by the “Denisov cycle” to ensure that they can be used sustainably in the fuel cell. The results demonstrate that the novel UIO-66-TEMP decorated with hindered amine radical scavengers are promising nanofillers for mitigating the membrane degradation and improving the proton conductivity, thereby significantly enhancing the performance and durability of PEMFCs.

Enhanced photocatalytic activity of methylene blue using heterojunction Ag@TiO2 nanocomposite: Mechanistic and optimization study

The objective in this study is to investigate the adsorption-degradation of the methylene blue (MB) dye using a fabricated heterojunction Ag@TiO2 nanocomposite. The batch factors used in photo catalytic reactions were pH, UV-irradiation time, temperature, catalytic dosage, and concentration of MB. The results showed that 0.2 × 103 g·ml−1) of the catalytic dose caused the Ag@TiO2 adsorption to degrade by 96.67% with darks and UV exposure. Using the Langmuir-Hinshelwood model to determine the kinetic, the Ag@TiO2 displays a greater kinetic rate than TiO2 and silver nanoparticle (AgNPs). The photocatalytic degradation of MB, which is an endothermic reaction involving all catalysts, is shown by the thermodynamic parameter to have the positive value of enthalpy (ΔH°). The enthalpies observed were Ag@TiO2 (126.80 kJ·mol−1) < AgNPs (354.47 kJ·mol−1) < TiO2 (430.04 kJ·mol−1). Ascorbic acid (OH scavenger), 2-propanol (O2 scavenger), and ammonium oxalate (AO) (hole h+ scavenger) were employed to conduct the scavenger effects. The Ag@TiO2 demonstrated a reduction in MB degradation when combined with 2-propanol, and this clearly demonstrated that, in contrast to hydroxyl radicals (OH) and hole (h+) scavengers, superoxide radical anion (O2 scavenger) plays a significant role in MB degradation. Utilizing density functional theory (DFT) to elucidate the mechanism and B3LYP/6-311+G(d,p) level optimization, the degradation-adsorption process was explained. When the NN, CN or CC bonds were severed, the Fukui faction was demonstrated for nucleophilic, electrophilic, and radical attack.

6-Endo-dig vs 5-exo-dig: Exploring Radical Cyclization Preference with First-, Second-, and Third-row Linkers using High-level Quantum Chemical Methods.

As an expansion upon Baldwin rules, the cyclization reactions of hex-5-yn-1-yl radical systems with different first-, second-, and third-row linkers are explored at the CCSD(T) level via means of the SMD(benzene)-G4(MP2) thermochemical protocol. Unlike C, O, and N linkers, systems with B, Si, P, S, Ge, As, and Se linkers are shown to favor 6-endo-dig cyclization. This offers fundamental insights into the rational synthetic design of cyclic compounds. A thorough analysis of stereoelectronic effects, cyclization barriers, and intrinsic barriers illustrates that structural changes alter the cyclization preference by mainly impacting 5-exo-dig reaction barriers. Based on the high-level computational modeling, we proceed to develop a new tool for cyclization preference prediction from the correlation between cyclization barriers and radical structural parameters (e.g., linker bond length and bond angle). A strong correlation is found between the radical attack trajectory angle and the reaction barrier heights, i.e., cyclization preference. Finally, the influence of stereoelectronic effects on the two radical cyclization pathways is further investigated in stereoisomers of hypervalent silicon system, which provides novel insight into cyclization control.

Polyphenol synergistic cerium oxide surface engineering constructed core-shell nanostructures as antioxidants for durable and high-performance proton exchange membrane fuel cells

The chemical degradation of proton exchange membranes (PEMs) suffering from radical attack is a crucial issue in the development of proton exchange membrane fuel cells (PEMFCs), while incorporating cerium oxide (CeO2) nanoparticles (NPs) with regenerative redox properties to eliminate radicals could effectively alleviate degradation. However, the low stability and restricted activity of CeO2 in the PEMFC operating condition and the poor compatibility with PEM due to CeO2 agglomeration stimulate the urgency for structural modulation of CeO2. Achieving a balance of membrane performance and oxidation resistance through a rational surface modification strategy of CeO2 is important for expanding PEMFC applications. Herein, polyphenols surface functionalized CeO2 core-shell structure (CeO2@TP) were constructed via assembling oxidation-induced coupling tea polyphenols (TP) on CeO2 NPs. The TP oligomeric shell as a protective layer enhances the stability of CeO2, mitigating radical scavenging activity degradation and improving compatibility with PEMs. Physicochemical characterisation shows that the overall performance of the nanocomposite membrane is improved due to the interaction of CeO2@TP nanoparticles with the polymer matrix. Gratifyingly, the phenolic hydroxyl-rich reductive TP oligomeric shell accelerates the regeneration of Ce(IV) to Ce(III), increasing the proportion of Ce(III) and oxygen vacancies on the CeO2 surface, thus boosting antioxidation efficiency. As a result, the CeO2@TP-based PEMs exhibited an OCV decay rate of 0.22 mV h−1, a maximum power density of 1.06 W cm−2, an H2 crossover value of 2.18 mA cm−2, thickness retention (91.1%), and negligible Ce migration after 404 h of accelerated degradation testing. It is proven that the desired consequences of doping antioxidants in PFSA matrix can be intensified by surface modulation of the physicochemical properties of CeO2.

Instantaneous Free Radical Scavenging by CeO2 Nanoparticles Adjacent to the Fe-N4 Active Sites for Durable Fuel Cells.

To achieve the Fe-N-C materials with both high activity and durability in proton exchange membrane fuel cells, the attack of free radicals on Fe-N4 sites must be overcome. Herein, we report a strategy to effectively eliminate radicals at the source to mitigate the degradation by anchoring CeO2 nanoparticles as radicals scavengers adjacent (Scaad-CeO2 ) to the Fe-N4 sites. Radicals such as ⋅OH and HO2 ⋅ that form at Fe-N4 sites can be instantaneously eliminated by adjacent CeO2 , which shortens the survival time of radicals and the regional space of their damage. As a result, the CeO2 scavengers in Fe-NC/Scaad-CeO2 achieved ∼80 % elimination of the radicals generated at the Fe-N4 sites. A fuel cell prepared with the Fe-NC/Scaad-CeO2 showed a smaller peak power density decay after 30,000 cycles determined with US DOE PGM-relevant AST, increasing the decay of Fe-NCPhen from 69 % to 28 % decay.