α-FeOOH Precursor Research Articles

X-shaped hollow α-FeOOH penetration twins and their conversion to α-Fe2O3 nanocrystals bound by high-index facets with enhanced photocatalytic activity

Nonspherical hollow nanoparticles (NHNPs) have attracted a great deal of attention in recent years due to their unique properties and many promising applications. However, compared to hollow spheres, the fabrication of NHNPs is generally much more difficult and there are only a few successful examples to date. In this work, X-shaped hollow α-FeOOH penetration twins were first synthesized by a facile hydrothermal reaction. X-shaped α-Fe2O3 hollow nanostructures with high-index {112¯3} facets exposed were further obtained via the topotactic transformation of α-FeOOH precursor. To the best of our knowledge, this is the first report on the nanostructures with high-index facets as well as a hollow interior. Owing to the special hollow structure and the high-energy surface, the as-obtained α-Fe2O3 nanocrystals show excellent visible-light photocatalytic activity toward the degradation of RhB.

Facile synthesis of single crystalline mesoporous hematite nanorods with enhanced supercapacitive performance

α-Fe2O3 nanorods with a length of 400–700nm and a diameter of 20–80nm, which have single-crystalline and mesoporous structure, could be obtained from these α-FeOOH precursors after calcining at 300°C in air. The as-prepared single-crystalline mesoporous α-Fe2O3 nanorodes exhibited a large specific surface area and porosity, effectively increasing the contact area between the electrode materials and electrolyte, minimizing both the ionic and electronic transportation in the Fe2O3 during the charge-discharge process. The porous nanostructure facilitates the faster faradic reaction toward electrolytes and delivers highest specific capacitance (534Fg−1) and an excellent long cycle life (upto 1500 cycles) in 1M KOH electrolyte at current density of 4Ag−1, demonstrating that the porous α-Fe2O3 nanorods can serve as an excellent electrode material for supercapacitors. It is believed that the single-crystalline mesoporous α-Fe2O3 nanorods are beneficial to the charge transfer in the electrode and to the ion transport in the solution during redox reaction.

ChemInform Abstract: A Microbial‐Mineralization Approach for Syntheses of Iron Oxides with a High Specific Surface Area.

Abstractγ‐Fe2O3 and α‐Fe2O3 with BET surface areas of 253 and 148 m2/g, resp., are synthesized by thermal treatment of γ‐FeOOH or α‐FeOOH precursors at 400 °C for 2—3 min.

Porous α-Fe2O3 hollow microspheres: Hydrothermal synthesis and their application in ethanol sensors

The hydrothermal method was employed to synthesize α-FeOOH hollow microspheres by using Fe(NO3)3·9H2O, oxalic acid and urea without templates. The porous α-Fe2O3 hollow microspheres were obtained by calcining the α-FeOOH precursors at 300°C for 2h. The structure and morphology of the as-synthesized products were characterized by techniques of powder X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM) and N2-sorption analysis. XRD studies indicated that the as-prepared product was well-crystallized hematite phase of α-Fe2O3. The SEM and TEM images showed that the obtained α-Fe2O3 sample consisted of porous hollow microspheres. N2-sorption analysis indicated that the as-prepared sample possesses mesoporous structure and specific surface area of 75.5m2g−1. The gas-sensing measurement results demonstrated that the porous α-Fe2O3 hollow microspheres presented a much higher response than that of α-Fe2O3 nanoparticles to ethanol vapor. Due to the fact that it has exciting gas-sensing properties and can be obtained easily, the as-prepared porous α-Fe2O3 hollow microspheres would be an ideal candidate for application in ethanol sensors.

Facile synthesis of single-crystalline mesoporous α-Fe2O3 and Fe3O4 nanorods as anode materials for lithium-ion batteries

In this work, single-crystalline α-FeOOH nanorods with a length of 400–700 nm and a diameter of 20–80 nm were successfully synthesized via a facile template-free hydrothermal method. Single-crystalline mesoporous α-Fe2O3 and Fe3O4 nanorods could be obtained from these α-FeOOH precursors after calcining at 350 °C in air and 500 °C in nitrogen, respectively. The as-prepared single-crystalline mesoporous α-Fe2O3 and Fe3O4 nanorods exhibited a large specific surface area and porosity, effectively enhancing the electrochemical reaction area and accommodate the strain during the charge–discharge cycling process.

The comparative lithium storage properties of urchin-like hematite spheres: hollow vs. solid

Urchin-like α-Fe2O3 spheres, hollow or solid, are obtained by thermally annealing their α-FeOOH precursor structures, which are synthesized via a facile hydrothermal method. The “hollowness” of these α-FeOOH spheres can be readily controlled by varying the glycerol concentration. The structure-dependent lithium storage properties of these α-Fe2O3 samples might shed light on the future development of advanced electrode materials for lithium-ion batteries.

Low temperature solution-based synthesis of porous flower-like α-Fe 2O 3 superstructures and their excellent gas-sensing properties

A facile solution approach was employed to synthesize flower-like α-FeOOH precursors by using FeSO 4·7H 2O and CO(NH 2) 2 as raw materials at 80 °C for 6 h without any template and surfactant. After annealing in air at 500 °C for 2 h, the porous flower-like α-Fe 2O 3 superstructures were successfully obtained, whose morphological feature is characterized as self-assembled by porous nanorods with an average length of 0.1–1.0 μm and diameter of 50–150 nm. Transmission electron microscopy (TEM) images show that there are many porous walls with a pore size of about 10 nm on the surface. As a demonstration of potential application for gas-sensing materials, the porous flower-like superstructures exhibited short response/recovery time within 6/3 s, and presented a much higher gas response than α-Fe 2O 3 nanoparticles aggregations towards different concentrations of ethanol, methanol and acetone.

Flexible morphology-controlled synthesis of mesoporous hierarchical α-Fe2O3 architectures and their gas-sensing properties

Mesoporous flower-like and urchin-like α-Fe2O3 nanostructures have been successfully synthesized by a simple solution-based reaction and sequential calcination. Detailed experiments demonstrated that the morphology of the hierarchical α-FeOOH precursors could be easily controlled by adjusting the experimental conditions including reactant concentration, solvent composition, reaction time, and reaction temperature. On the basis of time-dependent experiments, a multistage growth mechanism for the formation of the α-FeOOH super-architectures was proposed. In addition, by virtue of the unique hierarchical mesoporous structure and comparative high specific surface area, these obtained α-Fe2O3 nanostructures exhibited enhanced sensing performances to ethanol. This method is expected to be a useful technique for controlling the diverse morphologies of iron oxide superstructures that could meet the demands of a variety of applications, such as gas sensors, lithium-ion batteries, catalysis, waste-water treatment, and pigments.

Highly sensitive and selective LPG sensor based on α-Fe2O3 nanorods

The α-Fe2O3 nanorods were successfully synthesized without any templates by calcining the α-FeOOH precursor in air at 300°C for 2h and their LPG sensing characteristics were investigated. The α-FeOOH precursor was prepared through a simple and low cost wet chemical route at low temperature (40°C) using FeSO4·7H2O and CH3COONa as starting materials. The formation of α-FeOOH precursor and its topotactic transformation to α-Fe2O3 upon calcination was confirmed by X-ray diffraction measurement (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) analysis. The α-Fe2O3 nanorods exhibited outstanding gas sensing characteristics such as, higher gas response (∼1746–50ppm LPG at 300°C), extremely rapid response (∼3–4s), relatively slow recovery (∼8–9min), excellent repeatability, good selectivity and lower operating temperature (∼300°C). Furthermore, the α-Fe2O3 nanorods are able to detect up to 5ppm for LPG with reasonable response (∼15) at the operating temperature of 300°C and they can be reliably used to monitor the concentration of LPG over the range (5–60ppm). The experimental results clearly demonstrate the potential of using the α-Fe2O3 nanorods as sensing material in the fabrication of LPG sensors. Plausible LP G sensing mechanism of the α-Fe2O3 nanorods is also discussed.

Visible Light Induced Photocatalytic Degradation of Rhodamine B on One-Dimensional Iron Oxide Particles

Visible light (λ > 420 nm) induced photocatalytic degradation of rhodamine B (RhB) in the presence of H2O2 by one-dimensional (1D) nanorods of goethite (α-FeOOH) and hematite (α-Fe2O3) has been investigated, and results were compared to those of micrometer-sized rods. α-FeOOH nanorods were self-assembled by oriented attachment of α-FeOOH primary nanoparticles, while porous α-Fe2O3 rods were prepared by thermal dehydration of respective α-FeOOH precursors via a topotactic transformation. The as-prepared samples were characterized by powder X-ray diffraction, micro-Raman spectroscopy, diffuse reflectance UV−visible spectroscopy, X-ray photoelectron spectroscopy, nitrogen adsorption−desorption, high-angle annular dark-field scanning transmission electron microscopy, transmission electron microscopy, and high-resolution transmission electron microscopy. Nanosized α-FeOOH and α-Fe2O3 particles appeared to be more active than microsized ones in terms of surface area normalized reaction rate, suggesting intrinsi...

Facile Synthesis of Porous α-Fe2O3 Nanorods and Their Application in Ethanol Sensors

A facile solution approach was employed to synthesize α-FeOOH nanorods by using FeSO4·7H2O and CH3COONa without templates at low temperature (40 °C). The porous α-Fe2O3 nanorods were successfully obtained by calcining the α-FeOOH precursors at 300 °C for 2 h. The as-prepared products were characterized by thermogravimetry-differential thermal analysis, X-ray powder diffraction, transmission electron microscopy (TEM), high-resolution TEM, and N2 adsorption−desorption analysis techniques. The as-prepared porous α-Fe2O3 nanorods have a tiny crystal size (5 nm) and a pore size distribution of 1−10 nm, resulting in a high specific surface area of 221.9 m2·g−1. A possible growth mechanism of the porous α-Fe2O3 nanorods was proposed. The gas-sensing measurement results demonstrated that the porous α-Fe2O3 nanorods presented a much higher response than the α-Fe2O3 nanoparticles and showed excellent selectivity and stability to ethanol vapor. Due to the fact that it has exciting gas-sensing properties and can be o...

γ-Fe<inf>2</inf>O<inf>3</inf>with condensed phosphates as antisintering agents

Magnetic and rheological properties for pure and phosphates surface modified γ-Fe 2 O 3 were determined in order to evaluate different kinds of phosphate ions, as antisintering agents, during the transformation of α-FeOOH into γ-Fe 2 O 3 via Fe 3 O 4 . The magnetic data show that hexametaphosphate (HMP) and tripolyphosphate (TPP) ions, which adsorb onto the α-FeOOH precursor surface, behave like effective antisintering additives in the same way as silica Coating. On the contrary, no antisintering properties are shown by pyrophosphate (PP) ions. The wettability and the specific surface area of the HMP and TPP modified γ-Fe 2 O 3 , are higher than those of the pure and PP treated γ-Fe 2 O 3 , since the increase of surface roughness produces a much higher real surface area.