Iron Sites Research Articles

Diatomic iron nanozyme with lipoxidase-like activity for efficient inactivation of enveloped virus

Enveloped viruses encased within a lipid bilayer membrane are highly contagious and can cause many infectious diseases like influenza and COVID-19, thus calling for effective prevention and inactivation strategies. Here, we develop a diatomic iron nanozyme with lipoxidase-like (LOX-like) activity for the inactivation of enveloped virus. The diatomic iron sites can destruct the viral envelope via lipid peroxidation, thus displaying non-specific virucidal property. In contrast, natural LOX exhibits low antiviral performance, manifesting the advantage of nanozyme over the natural enzyme. Theoretical studies suggest that the Fe-O-Fe motif can match well the energy levels of Fe2 minority β-spin d orbitals and pentadiene moiety π* orbitals, and thus significantly lower the activation barrier of cis,cis-1,4-pentadiene moiety in the vesicle membrane. We showcase that the diatomic iron nanozyme can be incorporated into air purifier to disinfect airborne flu virus. The present strategy promises a future application in comprehensive biosecurity control.

Reactive high-spin iron(IV)-oxo sites through dioxygen activation in a metal-organic framework.

In nature, nonheme iron enzymes use dioxygen to generate high-spin iron(IV)=O species for a variety of oxygenation reactions. Although synthetic chemists have long sought to mimic this reactivity, the enzyme-like activation of O2 to form high-spin iron(IV) = O species remains an unrealized goal. Here, we report a metal-organic framework featuring iron(II) sites with a local structure similar to that in α-ketoglutarate-dependent dioxygenases. The framework reacts with O2 at low temperatures to form high-spin iron(IV) = O species that are characterized using in situ diffuse reflectance infrared Fourier transform, in situ and variable-field Mössbauer, Fe Kβ x-ray emission, and nuclear resonance vibrational spectroscopies. In the presence of O2, the framework is competent for catalytic oxygenation of cyclohexane and the stoichiometric conversion of ethane to ethanol.

Contamination and source-specific health risk assessment of polycyclic aromatic hydrocarbons in soil from a mega iron and steel site in China

The iron and steel industry has always been a key and difficult point of environmental pollution control. In the present study, 493, 175, 153, 72, and 42 soil samples were collected from the soil depths of 0–0.5, 0.5–2, 2–3, 3–4, and 4–5 m (herein called the layers) of the Shougang Steel site, respectively. Compared with the evaluation criteria, the Shougang Steel surface soil was severely polluted by polycyclic aromatic hydrocarbons (PAHs). Inverse distance-weighted interpolation and the Kruskal-Wallis H test revealed that the soil PAH pollution in the iron-making area, especially the coking area, was severer than those in other areas. The PAH concentrations first decreased, and then, increased with the increase of depth. With the increase in depth, the contributions of 2- and 3-ring PAHs increased, while those of 4-, 5-, and 6-ring PAHs decreased. The bivariate local indicators of spatial association (LISA) analysis was used to identify the areas prone to soil PAH pollution due to atmospheric deposition of industrial waste gas and traffic emissions. The method could be used to analyze the impact of anthropogenic activities on soil's PAH pollution for other contaminated sites. Three main pollution sources of soil PAHs, the backfill source, the combustion of coal, and the traffic emissions, were identified based upon three diagnostic ratios, positive matrix factorization and the bivariate LISA analysis, and accounted for 53.8%, 23.5%, and 22.7%, respectively. The combination of bivariate LISA analysis and other source analysis methods could improve the accuracy of source analysis. Benzo[a]pyrene contributed the most to the total health risk among sixteen PAHs. The health risks related to the three pollution sources decreased in the order of backfill sources > coal combustion > traffic emissions. The incremental life-time carcinogenic risks were all below 10−4, indicating negligible or acceptable risks.

Accelerating Fe(III)/Fe(II) redox cycling in heterogeneous electro-Fenton process via S/Cu-mediated electron donor-shuttle regime

In this study, we developed a Cu0.5Fe2.5S4 nanocatalyst through facile sulfidation of the Cu-MIL-88B(Fe) precursor to expedite surface Fe(III) reduction and enhance H2O2 activation in the heterogeneous electro-Fenton (HEF). The as-prepared catalyst possesses relatively large specific surface area and uniformly dispersed metal active sites. The Cu0.5Fe2.5S4-catalyzed HEF system allowed complete removal of naproxen with minimal metal leaching, surpassing that of Cu-MIL-88B(Fe) or Fe3S4. Quantitative XPS analysis, electrochemical characterization and density functional theory calculations reveal an electron donor-shuttle regime in which S2- and Cu species serve as the electron donor and shuttle, respectively. The Cu species significantly accelerate the internal electron transfer between S and Fe and mitigate the dissolution of the adjacent iron sites, securing the sustainable reducing capacity. Moreover, Cu0.5Fe2.5S4-based HEF exhibits great practicability for treatment of various organics in urban wastewater. This study opens new avenue for addressing the challenge of sluggish Fe(III)/Fe(II) cycling in HEF.

Tracking the binding site of anticancer drug fluxoridin with Fe-related proteins to achieve intelligent drug delivery

In cancer cells that need a lot of iron for growth and metastasis, halo-transferrin (TF-containing iron) enters the cell with the help of the transferrin receptor 1 (TFR1) protein. If the anticancer drug can bind to the iron site by interacting with apo-transferrin (iron-free FT), it can enter the cancer cell by the same mechanism. Two iron-related proteins, Bovine liver catalase (BLC) and apo-Transferrin (TF), that are important in cancer patients were selected and their interaction with the anti-cancer drug Floxuridine (FUDR) was investigated. Here, the protective role of FUDR was evaluated by several variables such as drug concentration, interaction time, and temperature-induced degradation of enzyme function. The results showed that the protective effect of the FUDR is greater in high concentrations (in 5 × 10-5 M:1.78 % and 2.59 % after 24 and 48 h). The interaction of the FUDR with both proteins can reduce the intensity of the fluorescence emission by a static mechanism. The binding strength of the FUDR with both proteins was almost similar and with the order of 104 M−1 (Kb = 3.90 ± 0.41 × 104 M−1 for BLC-FUDR and 5.01 ± 0.36 × 104 M−1 for TF-FUDR at 310 K). The thermodynamic calculations (in agreement with the docking results) indicated that FUDR-protein complex formation was exothermic and the main binding forces in the binding process were van der Waals interactions and hydrogen bonds. Both fluorophores tryptophan (Trp) and tyrosine (Tyr) of both proteins had significant roles in fluorescence quenching and the interaction process, the polarity of their microenvironment changed. CD results showed that the secondary structure changes of TF are slightly more than BLC. Molecular docking showed that the binding of the FUDR to TF is very close to the Fe-specific site and is placed in the cavity among the wrapping domain, N-Terminal arm, and β-barrel in BLC.

Porous Fe-doped graphitized biochar: An innovative approach for co-removing per-/polyfluoroalkyl substances with different chain lengths from natural waters and wastewater

Legacy long-chain per-/polyfluoroalkyl substances (PFAS) are being replaced by short-chain homologs, which have been widely detected in the environment. To achieve the co-removal of different chain length PFAS, this study systematically explored the single and synergistic effects of FeCl3-impregnation, wet ball-milling and different carbonization temperatures on the surface chemistry and pore structures of different biochars as well as sorption performances and mechanisms towards long-chain perfluorooctanoic acid (PFOA) and short-chain perfluorobutyric acid (PFBA). As a consequence, we presented a new method to synthesize magnetic sorbents by wet ball-milling with FeCl3 solution and high-temperature carbonization. Through this process, we tailored a magnetic porous Fe-doped graphitized biochar (named Fe-M−BC900) that contains abundant dispersed positive iron sites with stable Fe0/Fe3C, multi-stage pore structure, highly hydrophobic graphite-like carbon, and O-containing functional groups. Fe-M−BC900 exhibited a high sorption capacity of 10.1 mg PFBA/g and 39.1 mg PFOA/g. PFAS sorption on Fe-M−BC900 was mainly governed by pore-filling, electrostatic interaction, and hydrophobic partitioning. The sorption of PFBA on Fe-doped biochars depends more on electrostatic interaction and is less affected by hydrophobic partitioning compared to PFOA. Finally, we demonstrated that Fe-M−BC900 performed high co-removal rates (>96 %) for a wide range of legacy and emerging PFAS with different chain lengths and functional groups in natural waters (∑PFAS: 142 ∼ 265 μg/L) and simulated wastewater (∑PFAS: 600 μg/L), with a high relative sorption capacity of > 91 %, even after four consecutive recycling processes. This new adsorbent could help water facilities comply with upcoming PFAS regulations if tested on a larger scale.

Dual-atoms iron sites boost the kinetics of reversible conversion of polysulfide for high-performance lithium-sulfur batteries

Atomically dispersed metal catalysts have offered significant potential for accelerating sluggish kinetics of lithium polysulfides conversion and inhibiting the shuttle effect, so as to achieve the long-life cycle and high-rate performance of lithium sulfur batteries. However, the end-on adsorption structure between single metal site and polysulfide limits the adsorption capacity and catalytic activity of single atom catalysts. Here, we construct dual-atoms iron sites on nitrogen doped graphene to serve as highly efficient catalyst for lithium sulfur batteries. As expected, the dual-atoms sites can firmly bind polysulfides by forming double Fe-S bonds between polysulfides and the two adjacent iron atoms. Such double-bond adsorption structure is also favorable for electron transfer and polysulfides activation, resulting in reducing the energy barrier and accelerating the reaction kinetics. As a result, the as-obtained dual-atoms iron catalyst can effectively alleviate the shuttle effect and improve the utilization of active sulfur, thus the batteries present high initial capacity of 1615 mAh g−1 at 0.05 C and long-cycle life with a decay rate per cycle as low as 0.015% at 2C over 1000 cycles.

Insight into Defect Engineering of Atomically Dispersed Iron Electrocatalysts for High-Performance Proton Exchange Membrane Fuel Cell.

Atomically dispersed and nitrogen coordinated iron catalysts (Fe-NCs) demonstrate potential as alternatives to platinum-group metal (PGM) catalysts in oxygen reduction reaction (ORR). However, in the context of practical proton exchange membrane fuel cell (PEMFC) applications, the membrane electrode assembly (MEA) performances of Fe-NCs remain unsatisfactory. Herein, improved MEA performance is achieved by tuning the local environment of the Fe-NC catalysts through defect engineering. Zeolitic imidazolate framework (ZIF)-derived nitrogen-doped carbon with additional CO2 activation is employed to construct atomically dispersed iron sites with a controlled defect number. The Fe-NC species with the optimal number of defect sites exhibit excellent ORR performance with a high half-wave potential of 0.83V in 0.5M H2 SO4 . Variation in the number of defects allows for fine-tuning of the reaction intermediate binding energies by changing the contribution of the Fe d-orbitals, thereby optimizing the ORR activity. The MEA based on a defect-engineered Fe-NC catalyst is found to exhibit a remarkable peak power density of 1.1W cm-2 in an H2 /O2 fuel cell, and 0.67W cm-2 in an H2 /air fuel cell, rendering it one of the most active atomically dispersed catalyst materials at the MEA level. This article is protected by copyright. All rights reserved.

Exploring the Methane to Methanol Oxidation over Iron and Copper Sites in Metal–Organic Frameworks

The direct oxidation of methane to methanol (MTM) is a significant challenge in catalysis and holds profound economic implications for the modern chemical industry. Bioinspired metal–organic frameworks (MOFs) with active iron and copper sites have emerged as innovative catalytic platforms capable of facilitating MTM conversion under mild conditions. This review discusses the current state of the art in applying MOFs with iron and copper catalytic centers to effectuate the MTM reaction, with a focus on the diverse spectroscopic techniques employed to uncover the electronic and structural properties of MOF catalysts at a microscopic level. We explore the synthetic strategies employed to incorporate iron and copper sites into various MOF topologies and explore the efficiency and selectivity of the MOFs embedded with iron and copper in acting as catalysts, as well as the ensuing MTM reaction mechanisms based on spectroscopic characterizations supported by theory. In particular, we show how integrating complementary spectroscopic tools that probe varying regions of the electromagnetic spectrum can be exceptionally conducive to achieving a comprehensive understanding of the crucial reaction pathways and intermediates. Finally, we provide a critical perspective on future directions to advance the use of MOFs to accomplish the MTM reaction.

Biomimetic anode with atomically dispersed iron sites to enhance biotic-abiotic interfacial interaction towards efficient wastewater energy recovery in bioelectrochemical systems

Bioelectrochemical systems (BESs) are promising for future wastewater treatment towards carbon neutrality. Hemes, as the active centers of outer-membrane c-type cytochromes, play an important role in anodic electron transfer. In this work, a biomimetic Fe–Nx incorporated carbon membrane (Fe-NCM) mimicking the heme active center was proposed based on a nanocage confinement-electrospinning strategy and applied as the anode in BESs. The aligned carbon fibers with high electrical conductivity could serve as the electron “expressway” for swift electron transfer while the Fe–Nx nexus served as the “gas station” and endowed the membrane anode with boosted redox activity. The Fe-NCM anode featuring great biocompatibility and electrochemical activity was conducive to microbe adhesion and biotic-abiotic interfacial interaction. The power output and chemical oxygen demand (COD) removal rate constant in the BES with this Fe-NCM anode reached 1406 ± 44 mW m−2 and 0.42 ± 0.01 h−1 under filtration operation mode, which were 156% and 191% as high as those of the pristine carbon membrane. The introduction of Fe–Nx species exerted a significant influence on the anodic biofilm property, composition and function, which were of importance to bolstering wastewater energy conversion. Metagenomics unveiled that simultaneous intensification of intracellular electron production and extracellular electron transfer processes was achieved in the Fe-NCM BES. The Fe-NCM anode with electroactive Fe–Nx sites facilitated the biotic-abiotic interfacial interaction in BESs and highlighted the rational design of anodes for efficient wastewater treatment and energy conversion.

Construction of highly dispersed iron active sites for efficient catalytic ozonation of bisphenol A

The essential factor of catalytic ozonation technology relies on an efficient and stable catalyst. The construction of highly dispersed active sites on heterogeneous catalysts is an ideal strategy to combine the merits of homogeneous and heterogeneous catalysis with high activity and stability. Herein, an iron-containing mesoporous silica material (Fe-SBA15) with sufficient iron site exposure and enhanced intrinsic activity of active sites was employed to activate ozone for bisphenol A (BPA) degradation. Approximately 100% of BPA and 36.6% of total organic carbon (TOC) removal were realized by the Fe-SBA15 catalytic ozonation strategy with a reaction constant of 0.076 min−1, well beyond the performance of FeOx/SBA15 mixture and Fe2O3. Radical quenching experiments and electron paramagnetic resonance (EPR) analysis demonstrated that the hydroxyl radicals (HO•) and superoxide radicals (O2•−) played an important role in the degradation process. The iron sites with recyclable Fe(III)/Fe(II) pairs act as both the electron donors and active sites for catalytic ozonation. The mesoporous framework of SBA15 in Fe-SBA15 stabilizes the iron sites that enhance its stability. With high catalytic performance and high reusability for catalytic ozonation of BPA, the Fe-SBA15 is expected to be a promising catalyst in catalytic ozonation for wastewater treatment.

Band–gap reduction of aluminum substituted M−type hexagonal ferrite to study its characteristics

The sol-gel auto-combustion approach was used to create a binary combination of Strontium aluminum chromium M−type hexaferrites at the iron site. The hexagonal phase and normal composition of prepared substances were confirmed through X-ray diffraction technique(XRD) and FT-IR spectroscopy. The structural investigation was evaluated using XRD, which determined crystalline size, lattice constants, miller indices, and cell volume. The production of hexaferrite is confirmed by FTIR measurement in all samples. The existence of metal-oxygen bonds on tetrahedral sites and also on octahedral confirms that all prepared samples exhibit M−type hexagonal ferrites. SEM study reveals the morphology of all prepared samples which gives the defined shape and boundary. The UV and Energy gap of all prepared samples were measured to analyze their absorption.

Modulating the electronic spin state of atomically dispersed iron sites by adjacent zinc atoms for enhanced spin-dependent oxygen electrocatalysis

Modulating the electronic spin state of atomically dispersed iron sites by adjacent zinc atoms for enhanced spin-dependent oxygen electrocatalysis

Well-Defined Iron Sites in Crystalline Carbon Nitride.

Carbon nitride materials can be hosts for transition metal sites, but Mössbauer studies on iron complexes in carbon nitrides have always shown a mixture of environments and oxidation states. Here we describe the synthesis and characterization of a crystalline carbon nitride with stoichiometric iron sites that all have the same environment. The material (formula C6N9H2Fe0.4Li1.2Cl, abbreviated PTI/FeCl2) is derived from reacting poly(triazine imide)·LiCl (PTI/LiCl) with a low-melting FeCl2/KCl flux, followed by anaerobic rinsing with methanol. X-ray diffraction, X-ray absorption and Mössbauer spectroscopies, and SQUID magnetometry indicate that there are tetrahedral high-spin iron(II) sites throughout the material, all having the same geometry. The material is active for electrocatalytic nitrate reduction to ammonia, with a production rate of ca. 0.1 mmol cm-2 h-1 and Faradaic efficiency of ca. 80% at -0.80 V vs RHE.

Improvement of leakage, magnetic and magnetodielectric properties in cobalt doped gallium ferrite

Gallium ferrite (GFO) is a magnetoelectric (ME) material, capturing growing attention due to its strong ME coupling at room temperature. However, the application of the material in practical use is hindered due to its high leakage. In this work, the effects of cobalt (Co) substitution at the iron (Fe) sites of GaFe1−x Co x O3 (0.0 ⩽ x ⩽ 0.1) polycrystals on the structure, electric and magnetic properties are investigated in detail. 5 at. wt.% substitution (x = 0.05) with cobalt ions achieves a reduction in leakage current density by four orders of magnitude due to reduced hopping between Fe3+ and Fe2+ ions and suppression of the oxygen vacancy formation. This is supported by higher dielectric constant and lower dielectric loss, as well as a significant difference between grain and grain boundary resistances. Two-phase-like magnetic behavior in magnetic hysteresis loop with enhanced magnetization and two magnetic transition temperatures are observed in the doped samples. All samples exhibited an increase in the magnetodielectric factor, indicating enhanced coupling between magnetic and electrical parameters. By concurrently increasing dielectric, magnetic, and coupling between them, this study describes a viable technique for lowering the most significant impediment to GFO’s usage as a ME device.

Structures of the holoenzyme TglHI required for 3-thiaglutamate biosynthesis

Structural diverse natural products like ribosomally synthesized and posttranslationally modified peptides (RiPPs) display a wide range of biological activities. Currently, the mechanism of an uncommon reaction step during the biosynthesis of 3-thiaglutamate (3-thiaGlu) is poorly understood. The removal of the β-carbon from the Cys in the TglA-Cys peptide catalyzed by the TglHI holoenzyme remains elusive. Here, we present three crystal structures of TglHI complexes with and without bound iron, which reveal that the catalytic pocket is formed by the interaction of TglH-TglI and that its activation is conformation dependent. Biochemical assays suggest a minimum of two iron ions in the active cluster, and we identify the position of a third iron site. Collectively, our study offers insights into the activation and catalysis mechanisms of the non-heme dioxygen-dependent holoenzyme TglHI. Additionally, it highlights the evolutionary and structural conservation in the DUF692 family of biosynthetic enzymes that produce diverse RiPPs.

(Invited, Digital Presentation) The Low T Water Electrolyzer Current-Voltage Relationship: Electrocatalysis and More

As described in a recent publication [1], mechanisms of electrocatalytic processes have a common pattern which provides the basis for a universal rate expression for electrode processes in fuel cells. The same universal rate expression is applicable for low T water electrolyzers, serving as an effective predictor of the form of the non-linear dependence of the overpotential h on log J. The general form of this equation is exemplified by equation (1): (1) J (E) = Cr g Fk0A* x f(E - E0 surf. redox) 10^(- D H#/2.3RT) 10^ (E- E0 cell)/b. It can be seen that this expression considers two effects of the electrode potential on the current: one is the effect on the activation energy through the term 10^(E- E0 cell)/b, and the other is the effect of the electrode potential on the fractional population of active surface sites (or the fractional surface coverage by adsorbed intermediates), described in Eq 1 as: f(E - E0 surf.redox) where E0 surf.redox is the standard potential of a surface redox couple which “mediates” the faradaic electrode process . Consequently, E0 surf.redox determines the value of the onset potentialfor that faradaic process.Overpotential-driven activation of catalyst surface sites is a key component of processes taking place in electrodes of water electrolyzers, much the same as in the case of the fuel cell. The reason is that, as a rule, catalyst surface sites are inactive under open circuit conditions. In the case of the anode of the water electrolyzer , the origin of the main component of the electrode kinetic losses, the reason is the relatively low oxidation state of the metal ions in the oxyhydroxide catalyst surface sites. Iron sites are typically Fe(III) and iridium sites are Ir(IV) under open circuit conditions in contact with the aqueous electrolyte and O2 , whereas a higher oxidation state is required to withdraw electrons from water to form an *OH adsorbed intermediate. Such higher oxidation states are first generated at an anode overpotential of the order 0.15-0.20V, i.e., at ~1.40V vs. RHE.Highly active OER catalyst are all characterized by an oxide redox couple M+nox/ M+(n+1)ox of E0 ~1.40V , as can be verified from relevant Pourbaix diagrams. This means that the loss associated with catalyst site activation is significantly lower than in the case of the ORR, where it is near 0.30V. It is interesting to examine the reasons for this apparent advantage of the oxide catalyst in the OER vs. the PGM catalyst in the ORR. As explained in detail in reference [1], each electrocatalytic process is characterized by a two-step sequence: a pre-RDS step (“pre-step”) which involves surface site activation, followed by the rate determining step. The pre-step determines the onset potential and the RDS determines the rate of the electrocatalytic process at a given potential beyond the onset [1]. To large degree, the electrocatalysts of highest activity are determined by the value of the onset potential, as is best set to achieve the optimized bond strength required by the “Sabatier Principle” for the catalytic processes, which all involve bond formation followed by bond scission. In the case of the ORR process, Pt and it’s alloys which exhibit highest activity are characterized by a M/Mox surface potential of ~085V vs. RHE This means that forming a surface population of 1% of active M sites for the ORR, requires a minimum overpotential of ~0.30V whereas metal catalysts of lower oxygen affinity than Pt , which exhibit “bare” metal sites at much lower overpotentials, fail to reactively bond the diatomic oxygen molecule in the RDS. In the case of the OER, the relatively high activity of oxide catalyst sites in forming *OH ,as reflected by the low onset overpotential, does not seem to result in an excessive scission energy for the *OOH intermediate which most likely forms last in the sequence of the OER.Finally and importantly, the typical form of the polarization curves observed for low T aqueous electrolyzers, is fully accounted for by Eq. 1 which predicts very well the form of the non-linear h vs. log J polarization characteristics.Reference:[1] Shimshon Gottesfeld , A Perspective of Polymer Electrolyte Fuel cell Science and Technology, highlighting a general mechanistic pattern and a general rate expression for electrocatalytic processes , JES, in press

Microwave-Assisted Sol-Gel Synthesis of High-Voltage Ruthenium-Doped LiFePO4 Cathodes for Solid-State Lithium-Ion Batteries

The demand for high voltage and high-capacity energy systems has grown due to increased use of portable electronics, electric vehicles, and grid energy storage systems. LiFePO4 (LFP) shows great promise as a cathode material due to its low cost, structural stability, safety characteristics, and low environmental impact. However, LFP cathodes possess a low Li-ion diffusion coefficient and poor electrical conductivity compared to oxide-based cathodes that are used currently. To make LFP competitive with oxide-based cathodes, LFP was modified to improve its characteristics. Doping of materials is a highly effective method for improving electrochemical characteristics in LFP cathodes. Ruthenium-doping of iron sites within LFP has shown positive effects in the promotion of Li-ion diffusion, reduction in band gap energies, and improved electrical conductivity. Previous studies have shown that ruthenium-doping at 0.01 moles has an increased specific capacity of 162 mAh g-1, better cycling characteristics, and reduced resistance compared to pristine LFP.1 Ruthenium doping levels above 0.02 moles have shown a decrease in specific capacity, cycling characteristics, and an increased resistance due to the formation of ruthenium oxide that disrupts the crystal lattice of LFP. In this study, LiFe1-xRuxPO4 (x= 0.01, 0.0075, and 0.005) and pristine LFP were prepared via microwave-assisted sol-gel synthesis to explore the effects of lower levels of ruthenium-doping on LFP electrochemical characteristics. Microwave synthesis was employed for reduced sintering time, beneficial effects on microstructure, and decreased cost. Samples were characterized via scanning electron microscopy, in-situ/ex-situ X-ray diffraction, energy dispersive X-ray spectroscopy, electrochemical impedance spectroscopy, and cyclic voltammetry.The authors acknowledge financial support from the NSF IUCRC program for the “Center for solid-state electric power storage” (#2052631) and support from the South Dakota Board of Regents for the “Governor’s Research Center (GRC) for electrochemical energy storage”.1.) Gao, Y.; Xiong, K.; Zhang, H.; Zhu, B. Effect of RU Doping on the Properties of Lifepo4/c Cathode Materials for Lithium-Ion Batteries. ACS Omega 2021, 6 (22), 14122–14129.

Macroporous Carbon Films Support Vs. Conventional Carbon Particles with FeN4 Sites for Oxygen Reduction in Gas-Diffusion-Electrodes

Novel synthetic approaches have been developed to maximize the active site density of atomically dispersed Fe sites coordinated to nitrogen in carbon matrix. (Fe-N-C) (1,2) Nevertheless, the realistic maximum for single iron sites in these catalysts is deduced to be limited to 1021 sites per gram. (3) Therefore, for the application these Fe-N-C catalysts at the cathode for the oxygen reduction reaction in fuel cells, the catalyst material loading has to be increased to be able compete with the performance of Pt/C catalysts. Due to the resulting increased thickness of Fe-N-C catalyst layers, the oxygen available for the ORR at high current densities is dependent on the insufficient transport of oxygen across the catalyst layer. Freestanding catalyst nanostructured films, whose porosity is controlled across the entire thickness of the catalyst layer are expected to improve the mass transport at high current densities. Carbon nanostructures could provide the support substrate for such freestanding catalyst films. For instance, mesophase pitch-based films have been templated by silica (SiO2) nanoparticles have favourable morphologies for supporting Pt. (4) However, harsh conditions and long reaction times are required to etch away the SiO2. In our work, SiO2 nanoparticles are substituted by polystyrene nanoparticles, which decompose and tracelessly evaporate during the carbonization process. We have fabricated carbonized films of multiple thicknesses. We found 100 µm to be optimal, substantially thicker than Pt based electrodes to accommodate the lower density of sites and cheaper catalyst material. which is a usual thickness for Fe-N-C-based cathodes. Iron phthalocyanine (FePc) as a model active site is adsorbed on the freestanding carbon film. Gas-Diffusion-Electrodes (GDE) enable us to investigate the performance of such freestanding thin film catalysts at high current densities relevant for fuel cells. (5) A comparison of the ORR performance of catalyst layers, based on carbon films support (A) and conventional carbon particle support (B) are presented. We discuss the effect of adjusting the thickness of the two types of catalyst layers on the performance.1 Barrio J, Pedersen A, Feng J, Sarma S. C., Wang M, Li A. Y. , Luo, H. Ryan M. P., Titirici M.-M., Stephens I. E. L. J. Mater. Chem. A, 2022;10: 6023-302 Mehmood A, Pampel J, Ali G, Ha H Y, Ruiz-Zepeda F, Fellinger T P Adv. Energy Mater., 2018; 8: 11649-553 Mehmood A, Gong M, Jaouen F, Roy A, Zitolo A, Khan A, Sougrati M.-T., Primbs M., Martinez Bonastre A, Fongalland D, Drazic G, Strasser P, Kucernak A Nat. Cat., 2022;5, 311-234 Atwa M, Li X, Wang Z, Dull S, Xu S, Tong X, Tang R, Nishihara H, Prinz F, Birss V 2021;8: 2451-625 Inaba M, Jesen A W, Sievers G W, Escudero-Escribano M, Zana A, Arenz M Energy Environ. Sci,2018;11: 988-94

Fractal-like kinetics for enhanced boron adsorption on heterogeneous magnetic composite surfaces

Co-precipitated 14 nm γ-Fe2O3 and 35 nm MgO nanoparticles (NPs) decorated on zeolite 5 A (Z5A) templates were systematically studied. 57Fe Mössbauer and transmission electron microscopy data indicated a broad particle size distribution. The spinel structure of γ-Fe2O3 is strongly affected by size effects (particles smaller than 10 nm in size have an octahedral/tetrahedral iron site ratio of 7/3 instead of 5/3 found in bulk). 27Al nuclear magnetic resonance (NMR) showed the formation of octahedral Al species after boric acid reaction with MgO NPs. 11B NMR spectra indicated adsorption of B on the MgO/Z5A surface, whereas B adsorption in the pure Z5A framework is absent. Adsorption isotherms and kinetic studies of the nanohybrids showed that the B-rich species adsorption is described by Freundlich and fractal-like models, respectively. B adsorption occurs dominantly by the MgO fraction. The nanohybrids presented a good B removal efficiency when compared with other materials reported in literature.