α-Fe2O3 Nanosheets Research Articles

Facile preparation of network-like porous hematite (α-Fe2O3) nanosheets via a novel combustion-based route

Network-like porous hematite (ɑ-Fe2O3) nanosheets have been successfully prepared by a facile and novel combustion-based route with three simple steps. First, a sheet-like precursor with uniformly mixed amorphous iron oxide and carbon was fabricated via combustion synthesis derived from a homogeneous solution containing ferric nitrate, glycine and glucose. Subsequently, ultrasmall intermediate Fe3C nanoparticles were formed and evenly embedded into the sheet-like carbon support through calcination of the precursor in argon. Finally, the decarbonization and pore formation were carried out by heat-treating the calcined product in air. The as-prepared ɑ-Fe2O3 nanosheets exhibit a network-like porous structure, perforated by a large quantity of well-formed round single-pores with ~40nm in diameter as well as a small quantity of through-pores. A possible formation mechanism for the network-like porous nanosheets has been proposed. Such unique network-like porous structure makes this low-cost material a highly promising candidate for potential applications in energy conversion and storage, water treatment, gas sensors, etc.

Interconnected α-Fe2O3 nanosheet arrays as high-performance anode materials for lithium-ion batteries

The electrode materials with structure stability and binder-free are urgently required for improving the electrochemical performance of lithium-ion batteries. In this work, interconnected α-Fe2O3 nanosheet arrays directly grown on Ti foil were fabricated via a facile galvanostatic electrodeposition method followed by thermal treatment. The as-prepared α-Fe2O3 has an open network structure constituted of interconnected nanosheets and can be directly used as integrated electrodes for lithium-ion batteries. The α-Fe2O3 nanosheet arrays exhibit a high reversible capacity of 986.3mAhg−1 at a current density of 100mAg−1. Moreover, a reversible capacity of ca. 425.9mAhg−1 is achieved even at a superhigh current density of 10Ag−1, which is higher than the theoretical capacity of commercially used graphite. The excellent performance could be attributed to the efficient electron transport, the large electrode/electrolyte interfaces and the good accommodations for volume expansion from the interconnected nanosheet arrays structure.

Controlled Growth of Ferrihydrite Branched Nanosheet Arrays and Their Transformation to Hematite Nanosheet Arrays for Photoelectrochemical Water Splitting.

The morphology engineering represents an alternative route toward efficient hematite photoanodes for photoelectrochemical (PEC) water splitting without changing the chemical composition. In this work, a facile and mild solvothermal synthesis of unique ferrihydrite branched nanosheet arrays vertically aligned on FTO substrate was achieved at around 100 °C. The hierarchical branched ferrihydrite nanosheet arrays consisted of tiny branches up to 40 nm in length grown almost vertically on stem nanosheets ∼10 nm in thickness. Moreover, the variation of the morphology of the ferrihydrite nanostructures from bare nanosheet arrays through branched nanosheet arrays to dense branched structures can be readily achieved through the regulation of the reaction time and temperature. The obtained ferrihydrite branched nanosheet arrays can be in situ transformed into α-Fe2O3 nanosheet arrays with small surface protrusions upon annealing at 550 °C. After a simple postgrowth Ti-doping process, the resulting Ti-doped α-Fe2O3 nanosheet arrays showed a good PEC performance for water splitting with a photocurrent density of 1.79 mA/cm(2) at 1.6 V vs RHE under AM 1.5G illumination (100 mW/cm(2)). In contrast, the Ti-doped irregular aggregates of the α-Fe2O3 nanograins transformed from dense ferrihydrite branched structures exhibited a much lower photocurrent density (0.41 mA/cm(2) at 1.6 V vs RHE), demonstrating the important influence of the morphology of α-Fe2O3 photoanodes on the PEC performance.

Hierarchical Assembly of α-Fe₂O₃ Nanosheets on SnO2₂Hollow Nanospheres with Enhanced Ethanol Sensing Properties.

We present the preparation of a hierarchical nanoheterostructure consisting of inner SnO2 hollow spheres (SHS) surrounded by an outer α-Fe2O3 nanosheet (FNS). Deposition of the FNS on the SHS outer surface was achieved by a facile microwave hydrothermal reaction to generate a double-shell SHS@FNS nanostructure. Such a composite with novel heterostructure acted as a sensing material for gas sensors. Significantly, the hierarchical composites exhibit excellent sensing performance toward ethanol, which is superior to the single component (SHS), mainly because of the synergistic effect and heterojunction.

Rapid and up-scalable fabrication of free-standing metal oxide nanosheets for high-performance lithium storage.

Free-standing α-Fe2 O3 nanosheets, SnO2 mesoporous nanosheets and sandwich-like polyaniline (PAN)/SnO2 /PAN nanosheets are fabricated at very mild conditions (room temperature or 60 °C) via a galvanic replacement method for the first time. These nanosheets show excellent high-rate capability and long-term durability as anodes for lithium-ion batteries.

Highly oriented Ge-doped hematite nanosheet arrays for photoelectrochemical water oxidation

We report a simultaneous strategy of impurity doping and crystal growth for building highly oriented Ge-doped α-Fe2O3 nanosheet arrays vertically aligned on fluorine-doped tin oxide (FTO) glass substrates in hydrothermal environments, by using β-FeOOH nanorod arrays as sacrificial templates and highly reactive Ge colloidal solutions as dopant source. Microstructure characterization and elemental analysis reveal the preferential growth orientation, distribution of dopants, and doping level of Ge-doped α-Fe2O3 nanosheet arrays. Based on the doping of Ge atoms, proper feature size of nanosheets (with thickness <10nm) and preferential growth orientation within (001) basal plane of perpendicular nanosheet arrays, Ge-doped α-Fe2O3 nanosheet arrays show a photocurrent density of 1.4mAcm−2 at 1.23V vs. RHE, which is more than 50 times of the undoped α-Fe2O3 nanorod arrays. Moreover, we find that the annealing temperature remarkably affects the majority carrier density and optical absorption efficiency, which enabled the determination of photocurrent density of hematite nanostructure arrays.

A General Method to Grow Porous α‐Fe2O3 Nanosheets on Substrates as Integrated Electrodes for Lithium‐Ion Batteries

Porous α-Fe2O3 nanosheets grown on various metallic substrates are successfully fabricated through a facile solvothermal method combined with a thermal treatment. As an advanced integrated electrode for lithium-ion batteries, the architecture exhibits enhanced cycling stability and excellent rate capability.

Solid-state chemical synthesis of mesoporous α-Fe2O3 nanostructures with enhanced xylene-sensing properties

Uniform mesoporous α-Fe2O3 nanostructures have been handily prepared by a solid-state chemical reaction with the features of simple process, mild condition, and high yield. The as-prepared samples with 3-dimensional (3D) honeycomb structures consist of a number of small nanosheets. These mesoporous α-Fe2O3 nanostructures have been investigated for application as a sensor to detect various vapors. The experiment results have shown that the mesoporous α-Fe2O3 nanostructures exhibited improved performances for xylene-sensing in comparison with the α-Fe2O3 nanosheets. The response of mesoporous nanostructures to 1000ppm xylene was up to 6 times higher than that of nanosheets. The mesoporous α-Fe2O3 nanostructures-based sensor had also wide detection range of 1–1000ppm, good selectivity, and short response time to xylene. The enhancement of properties may be attributed to the large specific surface area and porous nanostructure.

Layer Structured α-Fe2O3 Nanodisk/Reduced Graphene Oxide Composites as High-Performance Anode Materials for Lithium-Ion Batteries

A composited anode material with combined layered α-Fe2O3 nanodisks and reduced graphene oxide was produced by an in situ hydrothermal method for lithium-ion batteries. As thin as about 5-nm-thickness α-Fe2O3 nanosheets, open channels, and face-to-face tight contact with reduced graphene oxide via oxygen bridges made the composite have a good cyclability and rate performance, especially at high charge/discharge rates.

Unusual formation of α-Fe2O3 hexagonal nanoplatelets in N-doped sandwiched graphene chamber for high-performance lithium-ions batteries

Nowadays, 2D nanosheets or nanoplatelets have attracted great attention due to their wide applications. However, the synthesis of 2D α-Fe2O3 nanosheets with well-defined hexagonal shape is extremely challenging, because the selective growth along one specific facet is very hard to be realized. In our work, we studied the non-capping ligand mediated reaction within graphene layer chamber, and successfully synthesized α-Fe2O3 hexagonal nanoplatelets sandwiched between graphene layers (HP-Fe–G). These materials exhibit an improved electrochemical performance compared with the pre-existing α-Fe2O3 nanoparticles loaded graphene (G-Fe2O3) composites because of the uniqueness of such architectures: thin nanoplatelets, large enough sandwiched spaces to buffer the volume expansion and N-doped graphene. HP-Fe–G delivered an ultrahigh reversible capacity of 1100mAh/g after 50 cycles, thus higher than their theoretical value (926mAh/g); while G-Fe2O3 composites showed relatively low capacity retention even after only 20 cycles (582mAh/g). In addition, HP-Fe–G also reveal superior rate capability, 887mAh/g at 1C; in comparison, this value was only 135mAh/g at 1C for G-Fe2O3.

SnO2/α-Fe2O3 hierarchical nanostructure: Hydrothermal preparation and formation mechanism

Abstract In this paper, we reported a simple solution method to assemble SnO2 nanorods hierarchically on the surface of α-Fe2O3 nanosheets using Fe3O4 nanosheets as precursor. The product was characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM). Our experimental results show that the lattice mismatch at the interface of SnO2 nanorods with α-Fe2O3 nanosheets played an important role in determining the growth direction of SnO2 nanorods. The interface prefers to take the least lattice mismatch and thus the preferential growth direction of SnO2 nanorods was along [1 0 1] direction. The result may have important impact on the understanding of the nucleation growth process in a heterogeneous system.