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1.
Water oxidation is a key reaction for water splitting. The decomposition of Fe-based-molecular structures toward Fe-based oxides is a promising method for oxygen-evolution reaction (OER) through water oxidation. The decomposition of Fe-based-molecular structures method results in a slow decomposition of precatalysts and forms Fe oxide-based catalysts. In this study, the Fe species formed through the decomposition of a dinuclear Fe(III) complex under OER is investigated by X-ray photoelectron spectroscopy, scanning electron microscopy, energy dispersive spectrometry, X-ray diffraction, and the electrochemical method. In addition, using Ni(OH)2, a new approach is reported for detecting trace Fe species on the electrode surface. The resulting Fe oxide-based catalyst shows a catalytic current with an onset of 621 mV overpotential and the Tafel slope of 113.7 mV/decade at pH 11 in a buffer phosphate.  相似文献   
2.
Dark fermentation (DF) is a promising technology for biohydrogen production. Low efficiency of biohydrogen production is a bottleneck of the scale-up prospects for DF. Additives have been extensively studied to improve the biohydrogen production efficiency. Among of them, iron-based additives present a promising application potential due to their demonstrated significant enhancement of DF efficiency and among the low-cost bioactive agents. However, current reviews mainly examined the effects of nano-materials on DF and an in-depth analysis of enhancing mechanisms with addition of iron-based additives in DF is still lacking. To this end, this article comprehensively reviewed and evaluated the effects of iron-based additives on DF. Further, the potential mechanisms, including altering metabolic pathways, improving activities of microbes and enzymes, promoting electron delivery, and enriching hydrogen-producing bacteria, were discussed. Lastly, prospects and challenges of iron-based additives for subsequent research and large-scale application for DF were summarized.  相似文献   
3.
The widespread use of fuel cell technology is hampered by the use of expensive and scarce platinum metal in electrodes which is required to facilitate the sluggish oxygen reduction reaction (ORR). In this work, a viable synthetic approach was developed to prepare iron-based sulfur and nitrogen dual doped porous carbon (Fe@SNDC) for use in ORR. Benzimidazole, a commercially available monomer, was used as a precursor for N doped carbon and calcined with potassium thiocyanate at different temperatures to tune the pore size, nitrogen content and different types of nitrogen functionality such as pyridinic, pyrrolic and graphitic. The Fe@SNDC–950 with high surface area, optimum N content of about 5 at% and high amount of pyridinic and graphitic N displayed an onset potential and half-wave potential of 0.98 and 0.83 V vs RHE, respectively, in 0.1 M KOH solution. The catalyst also exhibits similar oxygen reduction reaction performance compared to Pt/C (20 wt%) in acidic media. Furthermore, when compared to commercially available Pt/C (20 wt%), Fe@SNDC–950 showed enhanced durability over 6 h and poison tolerance in case of methanol crossover with the concentration up to 3.0 M in oxygen saturated alkaline electrolyte. Our study demonstrates that the presence of N and S along with Fe-N moieties synergistically served as ORR active sites while the high surface area with accessible pores allowed for efficient mass transfer and interaction of oxygen molecules to the active sites contributing to the ORR activity of the catalyst.  相似文献   
4.
In this study, the iron-based chemical looping process driven by various biomasses for hydrogen production purposes is studied and evaluated thermodynamically through energy and exergy approaches. The overall system consists of some key units (combustor, reducers and oxidizer) a torrefier, a drying chamber, an air separation unit, a heat exchanger, and auxiliary units as well. The biomasses considered are first dried and torrified in the drying chamber and sent to reactors to produce hydrogen. The exergy and energy efficiencies of the iron based chemical looping facility are investigated comparatively for performance evaluation. The maximum exergy destruction and entropy production rates are calculated for the torrefaction process as 123.15 MW and 4926 kW/K respectively. Under the steady–state conditions, a total of 8 kg/s hydrogen is produced via chemical looping process. The highest energy efficiency is obtained in the looping of rice husk with 86% while the highest exergy efficiency is obtained in the looping using sugarcane bagasse with 91%, respectively.  相似文献   
5.
A series of modified γ-Al2O3 supported iron-based catalysts (M-Fe/γ-Al2O3) was developed to reduce SO2 in actual smelter off-gases using CO–H2 gas mixture as reducing agent for sulfur production. Used as modifiers, three metal additives — Ni, Co, and Ce were added to Fe/γ-Al2O3 catalysts. Changes in catalyst structure and active phase were characterized with X-ray diffraction, XPS, SEM, and EDS. The reduction ability of catalysts was exhibited via CO-TPR. The prepared catalysts only need to be pre-reacted for a period of time, eliminating the need for presulfidation treatment. Reaction conditions were optimized in a fixed bed reactor to achieve high SO2 conversion and sulfur selectivity. XRD characterization was carried out to verify the resulting sulfur products. Combining in situ infrared characterization and catalyst evaluation of support and active component, the reaction mechanism was investigated and proposed.  相似文献   
6.
《Ceramics International》2016,42(15):16941-16947
Tungsten carbide-reinforced iron-based surface composites were prepared via in situ solid-phase diffusion method; the variables included three temperatures (1085, 1100, and 1125 °C) and four heat treatment times (15, 45, 75, and 105 min). The samples were examined by X-ray diffraction, scanning electron microscopy, and Vickers hardness test. Results show that the tungsten carbide-reinforced iron-based surface composites consist of WC, α-Fe, W, and iron carbide phases, and the thickness of the WC-Fe layer ranges from 20.57±1.24 µm to 63.27±2.02 µm at 1085 °C. Furthermore, the maximum microhardness value of the WC-Fe layer at 1085 °C for 15 min is 2169 HV0.1, whereas that of the iron matrix is 239 HV0.1; such values demonstrate that the hardness of the composites are markedly enhanced. The kinetic of WC-Fe layer was analyzed by measuring the depth of pure WC layer as a function of heat treatment time and temperature. The results show a parabolic relationship between the thickness of pure WC layer and heat treatment time, and the activation energy for the pure WC layer was estimated to be 184.06 kJ mol−1.  相似文献   
7.
Hydrogen is the simplest bipolar element and its valence state can be controlled from +1 to −1. We synthesized the 1111-type iron arsenides CaFeAsH and LnFeAsO1−xHx (Ln = lanthanide; 0  x  0.5) with the ZrCuSiAs type structure by a high-pressure synthesis method. The position and valence state of the substituted H were determined by neutron diffraction and density functional theory calculations. The close similarity in the structural and electrical properties of CaFeAsH and CaFeAsF indicated the formation of the hydride ion (H), which is isovalent with the fluoride ion (F), in the 1111-type iron arsenides. When some of the O2− ions in LnFeAsO are replaced by H, superconductivity is induced by electron doping to the FeAs-layer to maintain charge neutrality. Since the substitution limit of hydrogen in LnFeAsO (x  0.5) is much higher than that of fluorine (x  0.2), the hydrogen substitution technique provides an effective pathway for high-density electron-doping, making it possible to draw the complete electronic phase diagram of LnFeAsO. The x–T diagrams of LnFeAsO1−xHx (Ln = La, Ce, Sm, Gd) have a wide superconducting (SC) region spanning the range x = 0.04–0.4, which is far from the parent antiferromagnetic region near x = 0.0. For LaFeAsO1−xHx, another SC dome region was found in the range x = ∼0.2 to ∼0.5 with a maximum Tc = 36 K, in addition to a conventional SC dome located at x  0.08 with maximum Tc = 29 K. Density functional theory calculations performed for LaFeAsO1−xHx indicated that the newly observed Tc is correlated with the appearance of degeneration of the Fe 3d bands (dxy, dyz and dzx), which is caused not only by regularization of the tetrahedral shape of FeAs4 due to chemical pressure effects but also by selective band occupation with doped electrons. In this article, we review the recent progress of superconductivity in 1111-type iron (oxy)arsenides and related compounds induced by hydrogen anion substitution.  相似文献   
8.
The production of hydrogen and filamentous carbon by means of methane decomposition was investigated in a fixed-bed reactor using iron-based catalysts. The effect of the textural promoter and the addition of Mo as a dopant affects the catalysts performance substantially: iron catalyst prepared with Al2O3 showed slightly higher catalytic performance as compared to those prepared with MgO; Mo addition was found to improve the catalytic performance of the catalyst prepared with MgO, whereas in the catalyst prepared with Al2O3 displayed similar or slightly poorer results. Additionally, the influence of the catalyst reduction temperature, the reaction temperature and the space velocity on the hydrogen yield was thoroughly investigated. The study reveals that iron catalysts allow achieving high methane conversions at operating temperatures higher than 800 °C, yielding simultaneously carbon nanofilaments with interesting properties. Thus, at 900 °C reaction temperature and 1 l g−1cat h−1 space velocity, ca. 93 vol% hydrogen concentration was obtained, which corresponds to a methane conversion of 87%. Additionally, it was found that at temperatures higher than 700 °C, carbon co-product is deposited mainly as multi walled carbon nanotubes. The textural and structural properties of the carbonaceous structures obtained are also presented.  相似文献   
9.
The effects of La, Mg and Ca promoters on carbonaceous surface and bulk iron carbide species formed in the alkali promoted iron catalysts are studied under realistic Fischer–Tropsch synthesis (FTS) conditions. Compositions of bulk iron phase and phase transformations of carbonaceous species during pretreatment and FTS reaction were characterized using the temperature-programmed surface reaction with hydrogen (TPSR-H2) and XRD techniques. Many carbonaceous species on surface and bulk were qualitatively and quantitatively identified by combined TPSR-H2 and XRD spectra of the alkali promoted iron catalyst. These species, sorted by the their reactivity with H2 from high to low, were recognized as (a) adsorbed, atomic carbon; (b) amorphous, lightly polymerized hydrocarbon or carbon surface species; (c) bulk carbides and (d) disordered and moderately ordered graphitic surface carbons. The results revealed that while the surface basicity of the iron catalyst increased the CO dissociation proceeds faster than carbon hydrogenation. This phenomenon leads to excessive carbon deposition and formation of inactive iron carbide phases and graphitic type carbonaceous surface species, and consequently leads to catalyst deactivation.  相似文献   
10.
A systematic study was undertaken to investigate the effects of the initial oxidation degree of iron on the bulk phase composition and reduction/carburization behaviors of a Fe–Mn–K/SiO2 catalyst prepared from ferrous sulfate. The catalyst samples were characterized by powder X-ray diffraction (XRD), Mössbauer spectroscopy, X-ray photoelectron spectroscopy (XPS) and H2 (or CO) temperature-programmed reduction (TPR). The Fischer–Tropsch synthesis (FTS) performance of the catalysts was studied in a slurry-phase continuously stirred tank reactor (CSTR). The characterization results indicated that the fresh catalysts are mainly composed of α-Fe2O3 and Fe3O4, and the crystallite size of iron oxides is decreased with the increase of the initial oxidation degree of iron. The catalyst with high content of α-Fe2O3 in its as-prepared state has high content of iron carbides after being reduced in syngas. However, the catalyst with high content of Fe3O4 in its as-prepared state cannot be easily carburized in CO and syngas. FTS reaction study indicates that Fe-05 (Fe3+/Fetotal = 1.0) has the highest CO conversion, whereas Fe-03 (Fe3+/Fetotal = 0.55) has the lowest activity. The catalyst with high CO conversion has a high selectivity to gaseous hydrocarbons (C1–C4) and low selectivity to heavy hydrocarbons (C5+).  相似文献   
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