Fe Salts Research Articles

Oxygen-Evolution Reaction by a Palladium Foil in the Presence of Iron.

Herein, we investigate the oxygen-evolution reaction (OER) and electrochemistry of a Pd foil in the presence of iron under alkaline conditions (pH ≈ 13). As a source of iron, K2FeO4 is employed, which is soluble under alkaline conditions in contrast to many other Fe salts. Immediately after reacting with the Pd foil, [FeO4]2- causes a significant increase in OER and changes in the electrochemistry of Pd. In the absence of this Fe source and under OER, Pd(IV) is stable, and hole accumulation occurs, while in the presence of Fe this accumulation of stored charges can be used for OER. A Density Functional Theory (DFT) based thermodynamic model suggests an oxygen bridge vacancy as an active site on the surface of PdO2 and an OER overpotential of 0.42 V. A substitution of Pd with Fe at this active site reduces the calculated OER overpotential to 0.35 V. The 70 mV decrease in overpotential is in good agreement with the experimentally measured decrease of 60 mV in the onset potential. In the presence of small amounts of Fe salt, our results point toward the Fe doping of PdO2 rather than extra framework FeOx (Fe(OH)3, FeO(OH), and KFeO2) species on top of PdO2 as the active OER sites.

Treatability of five micro-pollutants using modified Fenton reaction catalysed by zero-valent iron powder (Fe(0))

Diuron, gabapentin, sulfamethoxazole, terbutryn and terbuthylazine are emerging micro-pollutants with concentrations in water and wastewater ranging from tens of ng/L to >10 μg/L levels. The Fenton oxidation catalysed either by zero-valent iron (Fe(0)) or by Fe(II) salts was studied to treat the targeted micro-pollutants and their mixtures at compound concentrations between 1 and 1000 µg/L. The Fe(0)-catalytic Fenton oxidation exhibited complete degradation of all micro-pollutants at initial solution pH 3 but at pH 5, the degradation was 90% for diuron, 80% for gabapentin, 95% for sulfamethoxazole, 100% for terbutryn and 70% for terbuthylazine, respectively. Moreover, dissolved organic carbon in multiple micro-pollutant solutions can be reduced by 70% at pH 3 and 46% at pH 5, which were much better than Fe(II)-catalytic Fenton reaction for the same pH conditions. SEM/EDX analysis showed the corrosion of iron surface and FTIR analysis evidenced the adsorption of oxidation by-products onto solid iron surface. Additionally, the toxicity of effluent after the treatment was reduced to minimal and the Behnajady-Modirshahla-Ghanbery (BMG) model fitted well to the kinetics of the mineralisation of the studied micropollutants. Finally, Fe(0) catalyst can be reused up to three times and the process produced no or less sludge at pH 3 and pH 5, respectively. The impact of this study is that the Fe(0)-catalytic Fenton oxidation would be an alternative to the traditional Fenton reaction to combat the environmental issues caused by the emerging micro-pollutants.

Adsorptive and Photocatalytic Properties of Green Synthesized ZnO and ZnO/NiFe2O4 Nanocomposites for Tannery Wastewater Treatment

This study investigated adsorptive and catalytic behaviour of ZnO and ZnO/NiFe2O4 nanocomposites for the removal and degradation of organic pollutants in tannery wastewater. ZnO and ZnO/NiFe2O4 nanomaterials were synthesized via a green method using Zn, Fe and Ni salts precursor and leaves extract of Anacardium occidentale (linn.). Subsequently, the synthesized samples were characterized by different analytical tools. The adsorptive and catalytic performance of the prepared nanomaterial were assessed using reduction in Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD) and Total Organic Carbon (TOC) in tannery wastewater as indicator parameters. High Resolution Scanning Electron Microscope (HRSEM), High Resolution Transmission Electron Microscope (HRTEM), and X-Ray Diffraction (XRD) analysis of ZnO and ZnO/NiFe2O4 confirmed the formation of hexagonal wurtzite nanoparticle and cubic spinel phase with an average crystallite sizes in the range of 13- 28 nm and 30.44 – 42.53 nm respectively. XRD analysis confirmed no change in the polymorph of ZnO upon the addition NiFe2O4. XPS spectrum showed the existence of the elements in the following oxidation state (+2) for Zn, (+1, +2) for Ni and (+2 and +3) for Fe. BET analysis revealed order of the specific surface area of ZnO/NiFe2O4 (44.61 m2/g) > NiFe2O4 (40.39 m2/g) > ZnO (8.91 m2 /g). The adsorptive and photocatalytic results revealed that 3% ZnO/NiFe2O4 exhibits higher efficiency compared to ZnO and NiFe2O4 nanoparticles alone and in the order of 3% ZnO/NiFe2O4 > NiFe2O4 > ZnO. The study revealed that the prepared nanomaterial behaved better as photocatalyst than as nanoadsorbent.
 Keywords: Adsorption, photocatalytic technology; ZnO; ZnO/NiFe2O4, tannery wastewater

Identification of atomically dispersed Fe-oxo species as new active sites in HZSM-5 for efficient non-oxidative methane dehydroaromatization

Non-oxidative methane dehydroaromatization (MDA) provides a promising and efficient technology for the valorization of huge amount of CH4 resources. Fe-based HZSM-5 zeolite as the second most researched catalyst system for MDA, however, commonly showed a much lower activity or/and selectivity for aromatics’ formation, probably due to an unsuitable Fe phase in the zeolite. Different from the reported Fe/HZSM-5 catalysts by the traditional impregnation method with Fe(NO3)3, a Fe/HZSM-5 catalyst was specially designed for the title reaction which was prepared by ion-exchange method with a stable, soluble and divalent Fe salt, i.e., FeSO4. Interestingly, the Fe2+-exchanged HZSM-5 catalyst can show an extremely higher aromatics formation activity with a maximum selectivity of 75–80% at a CH4 conversion of about 15% than any other Fe3+-exchanged and Fe-impregnated HZSM-5 zeolite catalysts at 1073 K. With various characterizations (UV-vis, UV-Raman, CO-DRFIT, HADDF-STEM and, especially, 57Fe Mössbauer spectroscopy), atomically dispersed Fe-oxo species anchored at framework Al sites are recognized to be responsible for selectively activating CH4 into CHx species available for aromatics’ formation. By comparison, the common Fe/HZSM-5 catalysts prepared by impregnation method with Fe(NO3)3 had a large amount of reducible Fe3O4 clusters on zeolite surface, and as they were reduced and carburized, the resulted metallic Fe and Fe carbide were both favorable for CH4 decomposition only, probably due to their poor dispersion. Fortunately, the limited S residuals (about 0.05 wt%) in the Fe2+-exchanged HZSM-5 catalyst from FeSO4 did not show its negative side on strongly promoting C–H cleavage. By comparison, the two impregnated Fe/HZSM-5 catalysts from FeSO4 and Fe2(SO4)3 both showed a complete CH4 decomposition due to considerable SO42- remained. Thanks to the application of the ion-exchange method and FeSO4 as Fe precursor, a highly active and selective Fe-based HZSM-5 catalyst has been successfully modeled and Fe-oxo species are recognized as new active sites for MDA, which may give us a new insight into constructing a catalyst with better catalytic performance for MDA and other reactions.

Maghemite nanoparticles coated by methacrylamide-based polymer for magnetic particle imaging

A wise selection of tracers is critical for magnetic particle imaging (MPI). Most of the current tracers are based on superparamagnetic iron oxide nanoparticles (SPIONs) with a suitable coating. We prepared maghemite cores (γ-Fe2O3) by coprecipitation of Fe(II) and Fe(III) salts with ammonium hydroxide followed by oxidation with hydrogen peroxide and stabilization as an anionic (γ-Fe2O3⊖) or cationic colloid (γ-Fe2O3⨁). The cores were coated by poly(N-(2-hydroxypropyl)methacrylamide)-co-N-[2-(hydroxyamino)-2-oxo-ethyl]-2-methyl-prop-2-enamide. The particles were characterized by dynamic light scattering, transmission electron microscopy, X-ray diffraction, Mössbauer spectroscopy, tested in vitro in a field-free point MPI scanner, and compared to nanoparticles prepared by oxidation with sodium hypochlorite and to the commercially available Resovist®. The cores had an average diameter of 8.0 nm (γ-Fe2O3⨁) and 8.7 nm (γ-Fe2O3⊖); the hydrodynamic diameter was 88 nm. Zeta potential values for both positively charged (+52 mV) and negatively charged particles (–60 mV) provided for good colloidal stabilization. Spinel structure of maghemite was confirmed by Mössbauer spectroscopy. The uncoated γ-Fe2O3⨁ particles yielded an MPI signal lower (by 16 %) than Resovist; the coated ones reached 88 % of the Resovist signal. Anionic γ-Fe2O3⊖ particles reached a higher (uncoated particles, by 15 %) or comparable (coated ones) signal relative to Resovist with a substantially lower signal dispersion. Control particles prepared by oxidation with sodium hypochlorite scored the weakest results. To conclude, a suitable size, narrow size distribution, and colloidal stability predispose the synthetized particles for use as a tracer for MPI. The anionic particles provided a higher signal with a lower dispersion than commercial tracers.

Bifunctional multi-metallic nitrogen-doped nanocarbon catalysts derived from 5-methylresorcinol

High-performance bi- and trimetallic nitrogen-doped nanocarbon catalysts for the electrochemical oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) were prepared by high-temperature pyrolysis from 5-methylresorcinol, dicyandiamide and transition metal (Ni, Fe and/or Co) salts. The electrocatalytic activity of the catalysts was studied using the rotating disc electrode (RDE) method in alkaline solution. The trimetallic NiFeCoNC electrocatalyst showed the best bifunctional ORR/OER performance with the ΔE value of 0.75 V. This is attributed to the synergistic effects between transition metals in the active sites of the material and a hierarchically porous microstructure, achieved through the reactive carbonitride template formed from dicyandiamide during the pyrolysis.

Novel space-confinement synthesis of two-dimensional Fe, N-codoped graphene bifunctional oxygen electrocatalyst for rechargeable air-cathode

The 2D Fe, N-codoped graphene (2D Fe-NG) with high oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) performances for Zn-air batteries (ZABs) is prepared by a facile synthesis method, which used nitrogen-containing polymer (2,5-benzimidazole) (ABPBI), Fe salts and the cationic surface-active agent treated montmorillonite (CMMT) layer template. The vacuum assist and heat treatment of ABPBI/CMMT at 350 °C are the keys of Fe3+ addition. The characterization analysis demonstrates that added Fe3+ exists in the form of Fe-Nx bonds formed by coordination with N species of ABPBI in MMT. Owing to the existed Fe-Nx sites in 2D Fe-NG, it possesses excellent ORR performance better than 2D NG and 20 wt% Pt/C in O2-saturated 0.1 M KOH electrolyte. For OER, the performance of 2D Fe-NG is close to that of RuO2. The self-made ZAB based on 2D Fe-NG exhibits high peak power density, excellent rechargeable performance, and higher D-C cycling stability.

Iron-catalyzed benzylic addition of 2-methyl azaarenes to substituted trifluoromethyl ketones

This paper demonstrated a new and economical methodology using Fe(ClO4)2·H2O as a catalyst for the direct C(sp3)–H functionalization of 2-methyl azaarenes via addition to trifluoromethyl ketones. The use of Fe salts as a Lewis acid catalyst has shown great potential as an accessible, affordable, and effective catalyst for the reaction. Under mild, optimized conditions, an extensive range of 2-alkenylated azaarenes was produced with yields of up to 95%.

One-step synthesis, characterization and properties of novel hybrid electromagnetic nanomaterials based on polydiphenylamine and Co-Fe particles in the absence and presence of single-walled carbon nanotubes.

A one-step preparation method for hybrid electromagnetic nanomaterials based on polydiphenylamine (PDPA) and bimetallic Co–Fe particles in the absence and presence of single-walled carbon nanotubes (SWCNT) was proposed. During IR heating of PDPA in the presence of Co(ii) and Fe(iii) salts in an inert atmosphere at T = 450–600 °C, the polycondensation of diphenylamine (DPA) oligomers and dehydrogenation of phenyleneamine units of the polymer with the formation of C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> N bonds and reduction of metals by evolved hydrogen with the formation of bimetallic Co–Fe particles dispersed in a polymer matrix occur simultaneously. When carbon nanotubes are introduced into the reaction system, a nanocomposite material is formed, in which bimetallic Co–Fe particles immobilized on SWCNT are distributed in the matrix of the polymer. According to XRD data, reflection peaks of bimetallic Co–Fe particles at diffraction scattering angles 2θ = 69.04° and 106.5° correspond to a solid solution based on the fcc-Co crystal lattice. According to SEM and TEM data, a mixture of particles with sizes of 8–30 nm and 400–800 nm (Co–Fe/PDPA) and 23–50 nm and 400–1100 nm (Co–Fe/SWCNT/PDPA) is formed in the nanocomposites. The obtained multifunctional Co–Fe/PDPA and Co–Fe/SWCNT/PDPA nanomaterials demonstrate good thermal, electrical and magnetic properties. The saturation magnetization of the nanomaterials is MS = 14.99–31.32 emu g−1 (Co–Fe/PDPA) and MS = 29.48–48.84 emu g−1 (Co–Fe/SWCNT/PDPA). The electrical conductivity of the nanomaterials reaches 3.5 × 10−3 S cm−1 (Co–Fe/PDPA) and 1.3 S cm−1 (Co–Fe/SWCNT/PDPA). In an inert medium, at 1000 °C the residue is 71–77%.

The role of legume peptides released during different digestion stages in modulating the bioaccessibility of exogenous iron and zinc: An in-vitro study

The effects of legume protein fractions on Fe and Zn bioaccessibility remain equivocal to date, largely due to the protein’s structure and the presence of anti-nutritional compounds. We administered Fe and Zn salts with legume concentrates consisting mainly of albumin or globulin from lupin, pea and faba to in vitro gastrointestinal digestion. Under the fasted intestinal state, faba globulins were found to enhance Fe2+ and Zn solubility compared to control salts without legume proteins. Meanwhile, other fractions had no effect or significantly lowered Fe and Zn solubility. Under the fed intestinal state, the presence globulins enhanced Fe solubility versus the control, where protein solubilization due to high bile concentration likely played a role in circumventing precipitation. The lupin albumin fraction significantly enhanced Fe2+ and Zn solubility, whilst other fractions generally reduced Zn solubility under fed state. Our results highlight the complex role of legume proteins towards Fe and Zn solubility.

Synthesis, spectroscopic characterization, DFT, oxygen binding, antioxidant activity on Fe(III), Co(II) and Ni(II) complexes with a tetradentate ONNO donor Schiff base ligand

The Schiff base ligand, namely (7E)-N-benzylidene-2-styrylbenzenamine- 1,2-diamine-2,4-dihydroxy-phenol (L), was synthesized by condensation of 2,4-dihydroxybenzaldehyde with o-phenylenediamine. The reaction of the ligand with Fe(III), Co(II) and Ni(II) salts in an 1:1 ratio yielded three complexes (1?3). Different analytical tools, like elemental analysis, ESI-MS, UV?Vis, FT-IR, NMR and EPR spectroscopy, then molar conductivity and magnetic susceptibility spectra, were used to elucidate the structure of the ligand and complexes. Density functional theory calculation at the B3LYP/3- -211G++/LANL2DZ level of the theory has been carried out to optimize the geometry of the ligand and complexes. The tetradentate ligand has coordinated to metals through ONNO donors affording octahedral geometry. Complexes were studied for their oxygen-binding activity and free radical scavenging activities. Complexes 1 and 2, which contain Fe(IIl) and Co(II), displayed reversible oxygen binding activity. On the other hand, complex 3 fails to show oxygen binding. The order of antioxidant activity is: 3 > 1 > 2 > L.

Environmental friendly application of ultrasonic rays for extraction of natural colorant from Harmal (P. harmala) for dyeing of bio-mordanted silk

Global heat, carcinogenic, and viral diseases created due to industrial pollutants has led people to shift toward natural products particularly natural dyes in all walks of life. In this study, U.S. rays up-to 60 min, were used to extract the color in aqueous medium and employed onto silk fabric at selected conditions. It has been observed that good color strength has been found when 30 mL of acidic extract ( pH = 4.0) obtained from 6.0 g of Harmal powder containing 3.0 g/100 mL of salt as an exhausting agent was employed onto the US treated silk at 65ºC for 55 min. The utilization of the extract obtained from 7% of pomegranate as post-bio-mordant, 3% of acacia extract as meta-bio-mordant, and 7% of henna extract as meta-bio-mordants has given excellent color strength. In comparison, 5% of Al salt as meta mordant, 5% of Fe salt as pre mordant, and 7% of tannic acid as meta-mordant has given better results. ISO standard methods for fastness employed onto optimum mordanted dyed fabrics have given well to excellent fastness ratings. Hence, natural colorant extracted from Harmal seeds has excellent coloring efficacy to dye silk fabric under sustainable conditions, whereas the addition of eco-friendly mordants for shade development process has made the coloration of silk more sustainable with improved colorfastness properties.

Preparation of iron and nitrogen co-doped carbon material Fe/N-CCM-T for oxygen reduction reaction

In this paper, iron and nitrogen co-doped carbon material with nanotube structure (Fe/N-CCM-T) was synthesized by pyrolyzing a mixture of Fe salt, chitosan and melamine and displayed high electrocatalytic performance for oxygen reduction reaction (ORR). The structure of the Fe/N-CCM-T was characterized and their ORR performance in alkaline media was investigated by linear sweep voltammetry, cyclic voltammetry and chronoamperometry. Fe/N-CCM-T displayed better ORR performance than other carbon materials like Fe/N-CC-800. The Fe/N-CCM-800 with a large surface area (302.5 m2/g) especially exhibited the best ORR electrocatalytic performance among the prepared carbon materials, which was also proved by its similar Tafel slope (76 mV decade−1) to Pt/C catalyst (74 mV decade−1). Fe/N-CCM-800 showed similar ORR activity as commercial Pt/C catalyst, but superior tolerance to methanol and stability. Such high ORR performance of the Fe/N-CCM-T can be attributed to its nanotube structure, high specific surface area (SSA), high graphitic-N and pyridinic-N contents.

Stabilization methods for the treatment of weathered arsenopyrite mine wastes: Arsenic immobilization under selective leaching conditions

The release of arsenic from weathered arsenopyrite mine wastes represents a grave environmental issue, especially when dealing with former mining areas. The evaluation and development of measures to manage this type of wastes in a sustainable and economic way are required. In this study different methods based on the application of chemical amendments were assessed as stabilization systems. For this purpose, weathered arsenopyrite mine wastes with the occurrence of amorphous ferric arsenates (AFA)/scorodite as main secondary products, as determined by X-ray diffraction (XRD) and polarizing microscopy, were used. Stabilization studies were performed employing two different amendments applied at diverse doses, namely a combination of calcite and ferric sulfate (CC + Fe(III) salt) and a by-product generated from the processing of aluminum salt slags (BP-AlOx). The efficacy of such treatments was assessed using both batch and column leaching essays. Under the equilibrium conditions imposed by the applied standard batch leaching tests, both of the treatments at their optimal conditions attained important reductions in the leachable As concentrations (95–98% and 52–79%, respectively), making mine wastes acceptable at controlled landfills as established by international legislation. Nevertheless, under flow leaching conditions the treatment employing CC + Fe(III) salt was shown not to be an appropriate long-term stabilization method. Conversely, the treatment with BP-AlOx proved to be more perdurable, decreasing considerably the As release (>50%) under prolonged leaching conditions. This stabilization system allowed simultaneously an important transformation of AFA to scorodite. Additionally, it partially neutralized the acidity generated from mine wastes without exceeding the pH values above which the solubilization of scorodite could be enhanced importantly.

Transition Metal-Containing Nitrogen-Doped Nanocarbons Derived from 5-Methylresorcinol for Anion Exchange Membrane Fuel Cell Application

Development of novel energy conversion and storage technologies is highly relevant for the future renewable energy-based economy. Low-temperature polymer electrolyte fuel cells are clean and efficient devices, but their commercialization is hindered by high cost and scarcity of Pt-based cathode catalysts for the electrochemical oxygen reduction reaction (ORR). Among the various non-precious metal catalysts that have been intensively explored through the last decades, transition metal-containing nitrogen-doped carbon nanomaterials have shown the most promising results. One of the most common and simple strategies to prepare these catalysts is high-temperature pyrolysis of organic carbon precursors in the presence of nitrogen and metal sources, where carbonization and N-doping occur simultaneously.1 This work describes preparation of highly active ORR electrocatalysts from 5-methylresorcinol, Co and/or Fe salts and dicyandiamide (DCDA) via a simple one-step pyrolysis procedure at 800 °C. It has been proposed that DCDA forms graphitic carbon nitride below 600 °C, which acts as a reactive template during carbonization of organic precursors, decomposing at above 750 °C and yielding N-doped graphene-like carbon structures.2 The SEM and TEM analysis showed that the materials consist of wrinkled carbon structures doped with nitrogen and metals, and also contain metal nanoparticles encapsulated in N-doped carbon layers. According to XRD analysis, these nanoparticles are mainly composed of Co, Fe/Fe3O4 and FeCo alloy for the CoNC, FeNC and FeCoNC catalysts, respectively. The specific surface area of the materials was between 290 and 410 m2 g−1. The XPS analysis revealed that the pyridinic- N is the most abundant N species in all materials and the catalysts also contain metal-coordinated N centers.The electrocatalytic activity of the catalysts for ORR was evaluated in alkaline solution using the rotating disc electrode (RDE) method and the optimal ratio of the precursors was determined. The bimetallic catalysts were more active toward ORR than their monometallic counterparts. Treatment of the materials in acid solutions followed by a second pyrolysis slightly increased their ORR activity. The acid-treated bimetallic catalyst (FeCoNC-at) showed a remarkable ORR performance, comparable to that of commercial Pt/C (20 wt%), which can be attributed to the high surface metal and nitrogen contents (Figure 1a). This material also demonstrated a rather high stability in short-time tests (15000 potential cycles) and good tolerance to methanol. The FeCoNC-at catalyst was further tested in anion exchange membrane fuel cell (AEMFC) with hexamethyl-p-terphenyl poly(benzimidazolium) (HMP-PMBI)3 membrane, where a high value of peak power density (P max= 415 mW cm–2) was achieved (Figure 1b). References A. Sarapuu, E. Kibena-Põldsepp, M. Borghei, and K. Tammeveski, J. Mater. Chem. A, 6, 776-804 (2018).X.H. Li, S. Kurasch, U. Kaiser, and M. Antonietti, Angew. Chem. Int. Ed., 51, 9689-9692 (2012).A.G. Wright, J. T. Fan, B. Britton, T. Weissbach, H. F. Lee, E. A. Kitching, T. J. Peckham, and S. Holdcroft, Energy Environ. Sci., 9, 2130-2142 (2016). Figure 1

The Use of the Adaptation Potential Reduction Model for Reproductive Toxicity Research In Vivo.

The modeling of adaptation potential decrease in rats due to modification of the diet's vitamin–mineral composition allows to increase animals' sensitivity to toxic load in reprotoxicological experiments. The threshold values of vitamins B1, B2, B3, and B6 and mineral substances Fe3+ and Mg2+ in the diet, which lead to a considerable reduction of laboratory animals' adaptation potential, have been determined as 19% (from the basic level in the diet) for males and 18% for females. The efficiency of this model has been confirmed in a reprotoxicological experiment with glyphosate as a toxic factor: the action of the toxic factor against the background of reduced availability of B vitamins and salts Fe3+ and Mg2+ led to significant changes in such indicators of reproductive function as mating efficiency, postimplantation loss, and the total number of alive pups, while the toxic effect of glyphosate was not so pronounced against the normal level of essential substances. The obtained results prove that this adaptation potential reduction model can be recommended for the research of the low-toxicity objects reproductive toxicity in rats and for the safety assessment of novel food, in particular.

Microscopic Observation of π Spin Polarization by d Localized Spin in λ Type BETS Based Organic Superconductors

In this study, 77Se NMR measurements were carried out to detect the π spin polarization of the organic BETS (BETS = Bis(ethylenedithio)tetraselenafulvalene) molecule of the field induced superconductor, λ-(BETS)2Fe1−xGaxCl4, which shows a superconducting transition at relatively low magnetic field compared to the non-doped λ-(BETS)2FeCl4. From the analysis of the NMR spectrum at low temperature, it was clarified that the exchange interaction between π and 3d spins in the Ga doping system is smaller than that in the Fe salt. It is also clarified that the conduction π spins feel the “averaged” exchange field from the localized 3d spins at the dilute Fe sites.

Facile synthesis of flower-like α-Fe2O3/ZnFe2O4 architectures with self-assembled core-shell nanorods for superior TEA detection

Uniform flower-like α-Fe2O3 architectures with self-assembled core-shell nanorods are constructed and successfully prepared via the facile process. The concentration of Fe salt plays a great significance for morphological evolution from nanorods to self-assembled microflowers. Flower-like α-Fe2O3/ZnFe2O4 consisting of α-Fe2O3 core and ZnFe2O4 shell nanorods are derived from FeOOH/ZIF-8 precursors. The detailed studies reveal that the tunable growth of ZIF-8 nanoparticles on three-dimensional FeOOH microflowers at room temperature and the availble calcination regulation are responsible for the formation of core-shell Fe2O3/ZnFe2O4 composites. The highest response value of flower-like α-Fe2O3/ZnFe2O4 architectures to 100 ppm triethylamine (TEA) has been improved to 141 at 280 °C, which is calculated to be 6.2 times compared with flower-like α-Fe2O3 architectures (22.7). The enhanced gas-sensing mechanism of α-Fe2O3/ZnFe2O4 composites can be attributed to the typical microflowers structures, the large specific surface area, the effective heterojunctions between α-Fe2O3 core and ZnFe2O4 shell, and the improved electron transfer process.

Transition metal-containing nitrogen-doped nanocarbon catalysts derived from 5-methylresorcinol for anion exchange membrane fuel cell application

Highly active electrocatalysts for electrochemical oxygen reduction reaction (ORR) were prepared by high-temperature pyrolysis from 5-methylresorcinol, Co and/or Fe salts and dicyandiamide, which acts simultaneously as a precursor for reactive carbonitride template and a nitrogen source. The electrocatalytic activity of the catalysts for ORR in alkaline solution was studied using the rotating disc electrode (RDE) method. The bimetallic catalyst containing iron and cobalt (FeCoNC-at) showed excellent stability and remarkable ORR performance, comparable to that of commercial Pt/C (20 wt%). The superior activity was attributed to high surface metal and nitrogen contents. The FeCoNC-at catalyst was further tested in anion exchange membrane fuel cell (AEMFC) with poly-(hexamethyl-p-terphenylbenzimidazolium) (HMT-PMBI) membrane, where a high value of peak power density (Pmax = 415 mW cm−2) was achieved.

Inhibitory protection of steels in hydrochloric and phosphoric acid mixtures containing Fe(III) salts

Inhibitory protection of steels in hydrochloric and phosphoric acid mixtures containing Fe(III) salts