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Highlights • Morphology engineering on iron oxides is carried out via an electrochemical method. • Morphology transition from zero-dimension to one-dimension is realized. • Iron oxide electrode delivers a high capacity of 184 mAh g−1 at 2 A g−1 (∼6C rate). • The Ni/Fe full cell exhibits a good energy density of 82.3 Wh kg−1. Abstract Aqueous rechargeable Ni/Fe batteries possess potential advantages for large-scale energy storage applications due to their low cost, high safety and fast ion diffusions in electrolyte. However, the electrochemical performance of the iron-based anode is still far from ideal due to particle aggregations. Herein, we carry out the morphology engineering on the iron oxide active materials via a facile electrochemical method to improve its charge storage capability. The morphology transition from zero-dimensional particles to one-dimensional nanorods is realized by tuning the electrolyte composition, while subsequent annealing treatment results in further morphology modification into 3D interconnected nanoparticles (10–20 nm). The hierarchical structure allows facile ion and electron transfers, and the large surface provides various active sites for the charge storage conversion reaction. As a result, even at the high current density of 2 A g−1 (∼6C rate), the iron oxide electrode can still deliver a high specific capacity of 184 mAh g−1. At the same time, the morphology integrity and stability of the electrode leads to a good cycle life, with 87.5% capacity retained upon 5000 cycles. The Ni/Fe full cell assembled with the iron oxide anode and a Ni-Co double hydroxide cathode exhibits a good energy density of 82.3 Wh kg−1 at the power density of 3.3 kW kg−1. Our fundamental study would provide new insights for the electro-deposition of iron-based materials and endow new opportunities for the fabrication of high-performance iron-based electrodes for energy storage systems. [ABSTRACT FROM AUTHOR]

Today, one of the most important global tasks is the treatment of waste water from various pollutants, including heavy metal. Adsorption is a promising method of wastewater treatment in terms of efficiency and cost. In this paper, the Al/Fe oxide-oxyhydroxide composite powders, prepared by hydrothermal method using metal sulfate solutions and urea as precursors, are investigated as adsorbents for chromium. The influence of the [Al 3+ ]:[Fe 3+ ] ratio on the phase composition, textural properties, morphology, and thermal effects of composites was also investigated. It is shown that the maximum specific surface area (190 m 2 /g) is reached for samples synthesized from solutions with [Al 3+ ]:[Fe 3+ ] = 1:0 and 1:1. Cr(VI) adsorption from solutions was performed under static (batch adsorption) and dynamic (column adsorption) conditions. It is shown that the presence of sulfate ions on the surface of Al-containing samples suppresses the Cr(VI) adsorption. The maximum adsorption capacity in batch adsorption (3.66 mg/g) has a sample synthesized from solutions with [Al 3+ ]:[Fe 3+ ] = 1:6, which is characterized by a high (but not maximal) surface area (102 m 2 /g), a low content of sulfates and maximum zeta potential. Sorption experiments showed that the mean free adsorption energy is below 8 kJ/mol for all samples, indicating the adsorption process as the physical in nature and suggesting the possibility of Cr(VI) desorption and adsorbent regeneration. Based on the results of fixed-bed adsorption experiments, an atypical form of breakthrough curves is noted, as well as an increase in sorption capacity of about 4–5 times as compared with batch adsorption. [ABSTRACT FROM AUTHOR]

[Display omitted] • Carbon nanotube (CNT)-Fe x O y composites (CFs) are developed for lithium-ion batteries. • CNT-guided combustion waves offer scalable synthesis-optimization strategy for CFs. • CNTs provide path of thermochemical reaction and help disperse iron oxide particles. • CNTs form conductive network and prevent loose Fe x O y particles during pulverization. • Optimized CFs exhibit notably high cycle capacity, rate capability and cycle life. The design and synthesis of suitable transition metal oxide (TMO) with carbonaceous material are crucial to produce high-performance anodes for Lithium-ion batteries (LIBs). Here, we show a facile synthesis method for iron oxide and carbon nanotube (CNT) composite via CNT-guided combustion waves. The combustion waves propagate through a freestanding film composed of multi-walled CNTs (MWCNTs), iron nitrate, and combustible nitrocellulose, synthesizing the composite in one-pot within a few seconds. The resulting composite consists of MWCNT networks encapsulating iron oxide submicron particles (CFs). The composite electrode employing optimized CFs provides exceptional initial specific capacity and rate capability (792 mAh/g at 0.1C and 588 mAh/g at 5C) and an increased capacity of 1215 mAh/g after 500 charge–discharge cycles at 1C. The morphological and electrochemical characterization reveal pulverized nanoparticles encapsulated within MWCNT networks, entailing hybrid capacities of redox conversion and pseudocapacitance. This facile synthesis method for TMO–MWCNT composites provides a feasible family of low-cost composite electrodes for high-performance LIBs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel catalytic system consisted of iron oxide magnetic nanoparticle and catechol. • Catechol-generated ROS further converted to hydroxyl radical by iron. • Initiates polymerization of wide ranges of monomers in an oxygenated solution. • Magnetic, bilayer hydrogels were formed with improved mechanical property. Phenol and its derivatives are the most used polymerization inhibitors for vinyl-based monomers. Here, we reported a novel catalytic system composed of mussel inspired adhesive moiety, catechol, in combination with iron oxide nanoparticles (IONPs) to generate hydroxyl radical (OH) at pH 7.4. Catechol-containing microgel (DHM) was prepared by copolymerizing dopamine methacrylamide (DMA) and N -hydroxyethyl acrylamide (HEAA), which generated superoxide (O 2 −) and hydrogen peroxide (H 2 O 2) as a result of catechol oxidation. In the presence of IONPs, the generated reactive oxygen species were further converted to OH, which initiated free radical polymerization of various water-soluble acrylate-based monomers including neutral (acrylamide, methyl acrylamide, etc.), anionic (2-acrylamido-2-methyl-1-propanesulfonic acid sodium salt), cationic ([2-(methacryloyloxy)ethyl]trimethylammonium chloride), and zwitterionic (2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide) monomers. Compared with the typical free radical initiating systems, the reported system does not require the addition of extra initiators for polymerization. During the process of polymerization, a bilayer hydrogel was formed in situ and exhibited the ability to bend during the process of swelling. The incorporation of IONPs significantly enhanced magnetic property of the hydrogel and the combination of DHM and IONPs also improved the mechanical properties of these hydrogels. [ABSTRACT FROM AUTHOR]

Organoarsenicals are widely used as antibiotics in the livestock industry and largely discharged into water environment directly, their safe, efficient and cost-effective treatment are actively perused. Herein, a heterogeneous iron-based Fenton-like technology was designed and validated with much reduced secondary pollution, mainly attributed to the bi-functional properties of both Fenton-active and arsenic-affinitive iron oxides. This simple one-step strategy not only exhaustively degraded organoarsenicals, but also selectively adsorbed the released high-toxicity arsenic from treated water. With Roxarsone as target, the FeOOH-based Fenton-like system exhibited a much superior capacitie for both Roxarsone degradation and arsenic adsorption in various water matrices, compared to typical homogeneous systems under similar conditions. More than 80% of Roxarsone was degraded after 3.0 h, and most of the released AsO 4 3− was removed simultaneously, without any additional post-treatment. The superior capacity of FeOOH might be mainly attributed to its strong redox-cycling capacity of surface central Fe atoms from their thermodynamically favorable electronic structure. Taking the important advantages of iron oxides and Fenton technology into account, our findings might provide a new chance to develop simple and efficient technologies for organoarsenicals removal from water with much reduced secondary pollution at a low cost. [ABSTRACT FROM AUTHOR]

Porous Clays Heterostructures (PCH) from natural pillared clays (bentonite with a high proportion of montmorillonite) have been used as supports of iron oxide for two reactions of environmental interest: i) the elimination of toluene (a representative compound of one of the most toxic subsets of volatile organic compounds, aromatics) by total oxidation and ii) the selective oxidation of H 2 S to elemental sulfur. For both reactions these catalysts have resulted to be remarkably more efficient than similar catalysts prepared using conventional silica as a support. Thus, in the total oxidation of toluene it has been observed that the catalytic activity obtained using siliceous PCH is two orders of magnitude higher than that with conventional silica. The catalytic activity has shown to be dependant of the capacity of the support for dispersing iron oxide in a way that the higher the dispersion of iron oxide on the surface of the support, the higher is the activity. In the case of the selective oxidation of H 2 S to S both higher catalytic activity and higher selectivity to S have been observed using siliceous porous clays heterostructures than using conventional silica. Highly dispersed FeOx species have been shown as highly selective towards elemental sulfur whereas more aggregated FeOx species favour the formation of sulphur oxides decreasing the selectivity to S. Analyses of the surface by XPS have shown the predominance of sulfate species in the catalysts presenting low selectivity to elemental sulfur. [ABSTRACT FROM AUTHOR]

A carbonate-based mesoporous magnetic adsorbent IO@CaCO 3 was synthesized via a hydrothermal method. The IO@CaCO 3 adsorbent removed both anionic (As(V) and Cr(VI)) and cationic (Pb(II)) heavy metal ions at a rate orders of magnitude faster than any conventional adsorbents reported to date; due to synergistic effect of needle-like IO and CaCO 3 , it completely removed (99.99%) the toxic heavy metal ions from wastewater in only 9 min. In addition, it exhibited excellent As(V), Cr(VI), and Pb(II) removal capacities of 184.1, 251.6, and 1041.9 mg g −1 , respectively, over a wide pH range. The heavy metal ion adsorption mechanism involves ion-exchange reactions between the cationic/anionic heavy metal ions and the positively/negatively charged groups on the adsorbent. Along with the batch adsorption tests, heavy metal ion removal by IO@CaCO 3 was also performed by column filtration, demonstrating the potential of IO@CaCO 3 for use in practical applications. Moreover, the excellent removal efficiencies of the adsorbent for the heavy metal ions up to drinking water level and its easy separation by an external magnetic field enabled it to be effectively reused. [ABSTRACT FROM AUTHOR]

• Layered metal thiophosphates-based magnetic 2D microrobots are presented. • 1D/2D hetero-dimensional hybrids are fabricated by versatile electrostatic assembly. • Anisotropic Fe 3 O 4 nanochains enable an effective tumbling motion of MnPS 3 sheets. • Moving 2D-photocatalysts exhibited enhanced photodegradation of organic pollutant and nerve agent. • On-the-fly 2D-microrobotic photocatalyst paves the way toward a new concept of on-the-move catalysis. Micro/nanorobots, deployed to programmable missions, are at the forefront of next-generation machinery and robotics. Here, we present magnetically actuated 2D-microrobot photocatalysts with enhanced photocatalysis due to enhanced mass transfer by photocatalytic on-the-fly microrobot action. The magnetic 2D-microrobots, consisting of layered manganese thiophosphates (MnPS 3) and Fe 3 O 4 nanochains, are fabricated by electrostatic assembly, which provides versatile and efficient 1D/2D hetero-dimensional nanoarchitectonic hybridization. The resulting MnPS 3 -Fe 3 O 4 microrobots are actively propelled by vertical tumbling under a transversal rotating external magnetic field. Particularly, a programmed swarming mode enables local fluid convection and self-stirring, which enhances the photochemical reaction. The promise of swarming 2D-microrobots was shown for enhanced photodegradation of an organic pollutant (Rhodamine B, Rh-B) and the nerve agent chlorpyrifos (CPS); here, MnPS 3 -Fe 3 O 4 microrobots act like moving 2D photocatalysts, with enhanced degradation efficiency of 10.3% (Rh-B) and 8.8% (CPS) compared to that of static hybrids. The moving 2D photocatalyst and hetero-dimensional nanoarchitectonic methodology demonstrated here can potentially inspire a variety of high-performance magnetic 2D-micro/nanorobots for catalytic applications. [ABSTRACT FROM AUTHOR]

Rectorite-TiO2-Fe3O4 (RTF) composites were assembled by orderly depositing anatase TiO2 and magnetic Fe3O4 nanoparticles on rectorite (REC) surfaces. Rectorite-TiO2 (RT) and RTF composites were characterized by transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). TiO2 particles partially exfoliated the REC layers, while Fe3O4 particles completely exfoliated the REC sheets. Fe3O4 particles was absorbed by REC and consequently appeared on its surface instead of being on the TiO2 particles. RTF can be easily separated from aqueous solution by magnet. The adsorption and photodegradation of methylene blue (MB) by RT and RTF were also investigated. The kinetic adsorption fit the pseudo-second-order model and the isotherm data followed the Langmuir model. The maximum adsorption capacities for MB were 187.61 and 169.20 mg/g for RT and RTF, respectively. RTF exhibited a good capability for removal of MB from aqueous solution, and about 95% MB was removed after 12 h UV-light irradiation, and about 75% MB removal for RT. And RTF exhibited the similar photocatalytic activity with RT for the persistent organic pollutant 4-nitrophenol (4-NP) under UV irradiation. [ABSTRACT FROM AUTHOR]

Highlights: [•] MnO2/Fe3O4/o-MWCNTs were prepared and well characterized. [•] Chromium removal using MnO2/Fe3O4/o-MWCNTs was studied for the first time. [•] The adsorption process for chromium removal was studied in detail. [•] The maximum adsorption capacity was 186.9mgg−1. [•] The reusability of MnO2/Fe3O4/o-MWCNTs was high. [ABSTRACT FROM AUTHOR]

[Display omitted] • Design of CTAB-OA bilayer coating structured IONCs for enhanced light adsorption properties. • Highly effective and reusable bilayer IONCs for Cr(VI) photoreduction under UVA. • Mechanistic description of Cr(VI) photoreduction process. Photoactive cetyltrimethylammonium bromide-oleic acid (CTAB-OA) bilayer coated iron oxide nanocrystals (IONCs) were precisely synthesized and demonstrated for photo-enhanced hexavalent chromium (Cr(VI)) treatment. For these materials, an outward facing, CTAB layer offers specific affinity for Cr(VI), while the core IONC (8–25 nm, as Fe 3 O 4 single domain) surface participates in Fe(II)/Fe(III) redox cycling. Further, at the coating-particle interface, the OA layer alters material photoactive dynamics (near UV and visible light) via a ligand-to-metal charge transfer (LMCT) mechanism, significantly enhancing Cr(VI) reduction. To delineate process variables, we first quantified photo-catalytic Cr(VI) reduction rates under UVA irradiation (sunlight mimic intensities) as a function of IONC core size, which correlates with the amount of surface available ferrous ion (Fe(II)). It was observed that 25 nm CTAB functionalized IONC showed outstanding Cr(VI) sorption and photoreduction performance compared with other IONC explored and controls (e.g. TiO 2 nanocrystals). We systematically explored the photoreduction mechanism(s) through a matrix of control experiments, considering solution pH, dissolved gas (air, O 2 , and CO 2), along with hydroxyl and superoxide radicals. Results indicate that Fe(II) (at the IONC interface) acts as the primary Cr(VI) reductant and that Fe(III) (oxidized from Fe(II)) (re)cycles via a photocatalyzed pathway. Taken together, this work presents a clear physical and mechanistic description of CTAB-OA bilayer IONCs which, when optimized, are highly effective for Cr(VI) treatment under UVA irradiation. In addition to potential broad application for other contaminant targets that are reactive with Fe(II), which are many, this work also highlights the need for precise interfacial understanding of nano composite materials towards process optimization. [ABSTRACT FROM AUTHOR]

Abstract: Shape- and size-controlled single-phase α-Fe2O3 (hematite) nanoparticles have been successfully synthesized via a simple and facile thermal treatment route using modified precursors. At first, various ferric-surfactant systems such as: ferric-sugars, ferric-hydrazine, ferric-oleic acid, and ferric-sugar-hydrazine were prepared via a wet-chemical precipitation method and then, these intermediate adducts as precursor were decomposed in at ordinary atmosphere to iron oxide. The morphology and particle size of products were investigated by SEM and TEM images and XRD patterns. These results revealed that the best quality α-Fe2O3 nanoparticles are synthesized through thermal decomposition of ferric-glucose precursor with molar ratio of 1:8 heated at 500°C in a step-wise manner. [Copyright &y& Elsevier]

Abstract: A chemical looping process using the redox reactions of iron oxide has been used to produce separate streams of pure H2 and CO2 from a solid fuel. An iron oxide carrier prepared using a mechanical mixing technique and comprised of 100wt.% Fe2O3 was used. It was demonstrated that hydrogen can be produced from three representative coals – a Russian bituminous, a German lignite and a UK sub-bituminous coal. Depending on the fuel, pure H2 with [CO] ≲50vol.ppm can be obtained from the proposed process. The cyclic stability of the iron oxide carrier was not adversely affected by contaminants found in syngas which are gaseous above 273K. Stable quantities of H2 were produced over five cycles for all three coals investigated. Independent of the fuel, SO2 was not formed during the oxidation with steam, i.e. the produced H2 was not contaminated with SO2. Since oxidation with air removes contaminants and generates useful heat and pure N2 for purging, it should be included in the operating cycle. Overall, it was demonstrated that the proposed process may be an attractive approach to upgrade crude syngas produced by the gasification of low-rank coals to pure H2, representing a substantial increase in calorific value, whilst simultaneous capturing CO2, a greenhouse gas. [Copyright &y& Elsevier]

Abstract: This paper reports the synthesis of iron oxide nanostructures with well-defined shapes, including rod, cube, and sphere, in 1-butyl-3-methylimidazolium bis(triflylmethyl-sulfonyl) imide ([BMIM][Tf2N]) ionic liquid (IL). Surfactants including oleic acid and oleylamine, which are commonly used as surface capping agents for size and shape control in molecular solvents, can be employed for making morphologically well-defined nanostructures in this IL. Iron pentacarbonyl thermally decomposes at elevated temperatures in [BMIM][Tf2N] ionic liquid and subsequently form nanoparticles. Nanorods, nanocubes, and spherical particles were synthesized depending mainly on the reaction temperatures and surfactants. X-ray diffraction and transmission electron microscopy data indicated these nanostructures were largely cubic iron oxide, maghemite. Our results show that imidazolium-based ionic liquids can be used as solvent for achieving very high level control over the size and shape of nanostructures. The approach developed in this work can potentially be used as a viable method for making various other uniform nanostructures in ionic liquids. [Copyright &y& Elsevier]

[Display omitted] • Sludge-based Biochar/Iron oxide effectively removed metals from OSPW. • High removal efficiency was attributed to the improved specific surface area and pore volume. • Langmuir isotherm showed the best performance for modeling the adsorption equilibrium. • The adsorption process could be described using the pseudo second order model. • The functional groups in the composite played an important role in the removal process. In this work, anaerobic sludge from a wastewater treatment plant was used to prepare a sludge-based biochar/iron oxide (B-FeO x) adsorbent. The B-FeO x adsorbent was successfully used to remove metals, including Cr, Cu, Se and Pb from oil sands process water (OSPW) for the first time. Compared with biochar or FeO x alone, a higher removal efficiency of Cr (80.79%±3.44%), Cu (98.21%±0.25%), Se (88.82%±0.31%) and Pb (90.96%±1.86%) was obtained using the B-FeO x composite. The high removal efficiency was attributed to the improved specific surface area and pore volume of the B-FeO x composite, which increased by about 5.9 and 5.7 times, respectively, when compared to biochar. In addition, functional groups in the composite, such as C-O, C = O, O–H, and some iron-bound functional groups, played an important role in the improvement of the removal efficiency of metals. Moreover, the adsorption process was best modelled by the pseudo-second order kinetic model and Langmuir model. Intraparticle diffusion modelling for adsorption of the four metals using B-FeO x composite resulted in two distinct regions: film and pore diffusion. This study provides the details of a low cost, effective, and environmentally friendly adsorbent for the removal of metals from real OSPW. [ABSTRACT FROM AUTHOR]

• CO oxidation activity at 30 °C enhanced by loading of Fe-oxide on Pt/Al 2 O 3. • This enhancement was observed in various atmospheric conditions. • Various analyses attributed enhancement to the increased boundary sites of Pt-Fe. • Fe-oxide-loaded Pt/Al 2 O 3 showed high thermal stability. • Potential of our simple Fe-loading method for practical applications is stated. Fe-oxide particles were deposited on commercial Pt/Al 2 O 3 in a highly dispersed manner via simple temperature regulated-chemical vapor deposition. We found that the catalytic activity of Pt/Al 2 O 3 toward CO oxidation at room temperature can be enhanced by deposition of Fe-oxide on Pt/Al 2 O 3. Particularly, as Fe-loading decreased from ∼10 to 0.34 wt%, catalytic activity toward CO oxidation gradually increased. Results of various analyses of catalysts attributed this Fe-oxide-induced enhancement effect to the boundary sites of Pt-Fe on Fe-Pt/Al 2 O 3. It is worth noting that the enhanced catalytic activity of Pt/Al 2 O 3 upon Fe-oxide loading was observed even in the presence of water vapor (40% of the relative humidity). In addition, Fe-oxide-loaded Pt/Al 2 O 3 showed high thermal stability, and the catalytic activity at room temperature was retained after repeated exposure to high temperatures. Our results show the potential of Fe-oxide-loaded Pt/Al 2 O 3 prepared by tr-CVD as a catalyst for low-temperature CO oxidation in practical applications. [ABSTRACT FROM AUTHOR]