O4 Nanorods Research Articles

LiNi0.5Mn0.5O2 hierarchical nanorods as high-capacity cathode materials for Li-ion batteries

LiNi0.5Mn0.5O2 nanorods (LNMO-NRs) stacked with nanoparticles have been prepared and investigated as cathode materials for rechargeable lithium-ion batteries. The LNMO NRs were obtained through solid-state Li and Ni implantation of α-MnO2 nanotubes. Without surface modification, the as synthesized LNMO NRs exhibited superior high-capacity compared to the bulk samples. An initial discharge capacity of 172 mAh g−1 could be delivered at 0.2 C and about 88% capacity retention could be achieved after 100 cycles. The remarkable performance was attributed to the one-dimensional structure assembled with nanoparticles that shows fast Li-intercalation kinetics and high structural stability.

Evidence of ferroelectricity in ferrimagnetic κ-Al2O3-type In0.25Fe1.75O3 films

We report direct evidence of the multiferroic nature of the κ-Al2O3-type InxFe2-xO3 films (x = 0–0.25) grown on the SrTiO3(111) substrates at room temperature. The κ-Al2O3-type InxFe2-xO3 films show a clear saturated and opened P-E hysteresis loop at room temperature with a remnant polarization of 1.8 μC cm−2. Also, the ferrimagnetic-incommensurate magnetic phase transition is observed at 205 K, which is compatible with the recent report on the In0.24Fe1.76O3 nanorods. The results indicate that the substitution of Me3+ ion, which has a larger ionic radius than Fe3+, is effective to grow good insulating ferroelectric κ-Al2O3-type Fe2O3 films, leading to the genuine multiferroic nature.

Facile Synthesis of Fe3 C@Graphene Hybrid Nanorods as an Efficient and Robust Catalyst for Oxygen Reduction Reaction.

Robust and efficient catalysts for the oxygen reduction reaction (ORR) are required for the development of various energy storage and conversion devices. In this study, a durable and high-performance Fe3 C@graphene ORR catalyst has been developed by the carbonization of urea- and agar-modified Fe2 O3 nanorods. The influence of the carbonization temperature and annealing time on the activity and stability of the resulting Fe/C catalyst was studied in detail. The Fe/C catalyst synthesized at a temperature of 700 °C (holding time: 60 min) showed better ORR activity and improved stability compared to a commercial Pt/C catalyst. The improved ORR catalytic activity of the catalyst is due to its high Fe3 C content and its good durability results from the unique microstructure of the Fe3 C@graphene hybrid.

Synergistic effects in biphasic nanostructured electrocatalyst: Crystalline core versus amorphous shell

The recent study on active amorphous catalytic materials provokes rethinking of the previous research on atomic and electronic structures in the crystalline catalyst. Is there any active catalyst with biphasic structure, in particular the integration of crystalline and amorphous components? Inspired by this question, a crystalline-amorphous biphasic quaternary oxide catalyst is novelly fabricated via one-step solvothermal method in this work. The as-prepared catalyst displays a well-designed core–shell architecture composed of crystalline Co(ZnxNi2−x)O4 nanorod (core) and amorphous NiO nanosheet (shell). This heterogeneous core–shell catalyst exhibits high activity in the oxygen evolution reaction by demonstrating a low over-potential of 1.57V vs RHE, a high half-wave potential (0.89V vs RHE), and long-term electrochemical stability for 25h. It is found that the synergistic effects from the amorphization of the shell on the one hand, and the atomic/electronic structure of the crystalline core on the other hand, could significantly facilitate the catalytic activity both at the surface and in the bulk volume of the solid oxides. Therefore, this new developed crystalline-amorphous biphasic catalyst could provide instructive roles in the future design of new catalysts for O2 evolution and other catalytic reactions.

Bimetal–Organic Framework: One‐Step Homogenous Formation and its Derived Mesoporous Ternary Metal Oxide Nanorod for High‐Capacity, High‐Rate, and Long‐Cycle‐Life Lithium Storage

Metal–organic frameworks (MOFs) and relative structures with uniform micro/mesoporous structures have shown important applications in various fields. This paper reports the synthesis of unprecedented mesoporous NixCo3−xO4 nanorods with tuned composition from the Co/Ni bimetallic MOF precursor. The Co/Ni‐MOFs are prepared by a one‐step facile microwave‐assisted solvothermal method rather than surface metallic cation exchange on the preformed one‐metal MOF template, therefore displaying very uniform distribution of two species and high structural integrity. The obtained mesoporous Ni0.3Co2.7O4 nanorod delivers a larger‐than‐theoretical reversible capacity of 1410 mAh g−1 after 200 repetitive cycles at a small current of 100 mA g−1 with an excellent high‐rate capability for lithium‐ion batteries. Large reversible capacities of 812 and 656 mAh g−1 can also be retained after 500 cycles at large currents of 2 and 5 A g−1, respectively. These outstanding electrochemical performances of the ternary metal oxide have been mainly attributed to its interconnected nanoparticle‐integrated mesoporous nanorod structure and the synergistic effect of two active metal oxide components.

Self-template synthesis of Li1.13Ni0.30Mn0.57O2 anothorn spheres and nanorods as high-performance cathode materials for lithium-ion batteries

Commercial cathode materials for lithium-ion batteries require both excellent electrochemical and processing performance. Nanoscaled cathode materials with high surface area usually have low compacted density and low loading of active materials on the electrode because of high-content usage of conductive agent and binder, which is expected to be solved by incorporating one-dimensional (1D) particles into dense three-dimensional (3D) structure. In this work, a topochemical method is used to synthesize high-capacity Li-rich cathode material Li1.13Ni0.30Mn0.57O2 with controllable 3D and 1D hybrid structure containing nanothorn spheres and nanorods by using γ-MnO2 and β-MnO2 as templates. Structural and electrochemical lithium insertion/desertion properties are investigated. Experimental results show that Li1.13Ni0.30Mn0.57O2 with well-designed 3D structure exhibits superior electrochemical performance especially higher volumetric capacity than 1D material.

Domain structure of tetragonal Pb(Zr,Ti)O3 nanorods and its size dependence

We fabricated {100} Pb(Zr0.35Ti0.65)O3 (PZT) nanorods by partly etching a film grown on a Nb-doped SrTiO3 substrate using a focused ion beam, followed by annealing to recover the etching damage and promote the formation of a stable domain structure in the form of nanorods. The application of synchrotron micro-X-ray diffraction enabled the detection of the diffraction intensity from a single nanorod, which allowed us to clarify the size dependence of the domain structure of the fabricated nanorods. We found that the a-domain fraction in the tetragonal PZT nanorods decreased with decreasing rod width and that an exclusively c-domain structure was formed in nanorods of ≤1 µm width. The preferred formation of the c-domain in these nanorods can be rationalized in terms of the large depolarizing field in the a-domain and/or the in-plane compressive strain near the PZT/substrate interface.

Graphene wrapped ordered LiNi0.5Mn1.5O4 nanorods as promising cathode material for lithium-ion batteries

LiNi0.5Mn1.5O4 nanorods wrapped with graphene nanosheets have been prepared and investigated as high energy and high power cathode material for lithium-ion batteries. The structural characterization by X-ray diffraction, Raman spectroscopy, and Fourier transform infrared spectroscopy indicates the LiNi0.5Mn1.5O4 nanorods prepared from β-MnO2 nanowires have ordered spinel structure with P4332 space group. The morphological characterization by scanning electron microscopy and transmission electron microscopy reveals that the LiNi0.5Mn1.5O4 nanorods of 100–200 nm in diameter are well dispersed and wrapped in the graphene nanosheets for the composite. Benefiting from the highly conductive matrix provided by graphene nanosheets and one-dimensional nanostructure of the ordered spinel, the composite electrode exhibits superior rate capability and cycling stability. As a result, the LiNi0.5Mn1.5O4-graphene composite electrode delivers reversible capacities of 127.6 and 80.8 mAh g−1 at 0.1 and 10 C, respectively, and shows 94% capacity retention after 200 cycles at 1 C, greatly outperforming the bare LiNi0.5Mn1.5O4 nanorod cathode. The outstanding performance of the LiNi0.5Mn1.5O4-graphene composite makes it promising as cathode material for developing high energy and high power lithium-ion batteries.

Design of composite maghemite/hematite/carbon aerogel nanostructures with high performance for organic dye removal

Composite Fe3O4/α-Fe2O3 nanorods (180N) with a specific surface area of 16.2m2/g were successfully synthesized via a facile hydrothermal reaction at 180°C. To increase the specific surface area, a mesoporous carbon aerogel (CA) with a large specific surface area was added to the hydrothermal reaction to form mesoporous Fe3O4/α-Fe2O3/CA structures (CA-180) with a specific surface area of 267.7m2/g instead of nanorods. The as-prepared 180N and CA-180 samples were further annealed at 400°C to oxidize the Fe3O4 phase, resulting in the formation of composite γ-Fe2O3/α-Fe2O3 nanorods (400N) with a specific surface area of 27.7m2/g and mesoporous γ-Fe2O3/α-Fe2O3/CA structures (CA-400) with a specific surface area of 551m2/g. The CA-400 samples were further used to remove the dye Rhodamine B (RhB) from aqueous solution, and 98.2% of the RhB dye was removed using the CA-400 sample when the initial RhB concentration was 8ppm. The as-prepared CA-400 sample exhibits strong potential for use in wastewater treatment applications, such as organic dye removal.

Surface spins enhanced magnetoelectric coefficient and impedance spectroscopy of BaFe0.01Ti0.99O3 and BaFe0.015Ti0.985O3 nanorods

Multiferroic BaFe0.01Ti0.99O3 (BFT1) and BaFe0.015Ti0.985O3 (BFT15) nanorods were prepared by a sol–gel synthesis and annealed at 700°C/2h. The tetragonal phase and nano dimensions of BFT samples are identified by X-ray diffraction and transmission electron microscopy. The enhancement in ferroelectricity depends upon low porosity, tetragonal phase, space charge field, larger surface area and oriented growth. The ferromagnetism depends upon partially filled inner shells, surface spins and oxygen vacancies. The magnetoelectric coefficient is explained on the basis of surface spins, short-range interactions near surface boundary, compressive stress and twin structure contributed by nano grains which can reside stress near grain boundaries. The frequency dependent real (Z′) and imaginary (Z″) parts of impedance spectra are confirmed by the variations that observed in dielectric properties. The values of resistance of grain boundaries, Rgb is higher than grains, Rg indicating that the effect of grain boundaries is dominant in BFT nanorods.

ChemInform Abstract: Nanostructured Mn‐Based Oxides for Electrochemical Energy Storage and Conversion

AbstractReview: 249 refs.

(001)-orientation single crystalline Pb(Zr0.3Ti0.7)O3 pyroelectric nanorod array synthesized by hydrothermal reaction

The fabrication and pyroelectric coefficient of Pb(Zr0.3Ti0.7)O3 (PZT) nanorod array on Nb:SrTiO3 (NSTO) substrates were reported. XRD and TEM revealed that PZT nanorods were (001) orientation single crystalline. Dense PZT nanorod array were synthesized on NSTO using optimal 0.8 g/L poly(vinyl alcohol) (PVA) and 3.2 g/L poly(acrylate acid) (PAA). Maximum pyroelectric coefficient, 5.8 × 10−9 C/(cm2·K), was measured for samples synthesized at 230 °C and poled under 5 V. The single crystalline PZT nanorod array material has potential application in small spatial (1–10 µm) infrared detectors, benefiting to achieve distinguished detector performances.

Nanostructured Mn-based oxides for electrochemical energy storage and conversion.

Batteries and supercapacitors as electrochemical energy storage and conversion devices are continuously serving for human life. The electrochemical performance of batteries and supercapacitors depends in large part on the active materials in electrodes. As an important family, Mn-based oxides have shown versatile applications in primary batteries, secondary batteries, metal-air batteries, and pseudocapacitors due to their high activity, high abundance, low price, and environmental friendliness. In order to meet future market demand, it is essential and urgent to make further improvements in energy and power densities of Mn-based electrode materials with the consideration of multiple electron reaction and low molecular weight of the active materials. Meanwhile, nanomaterials are favourable to achieve high performance by means of shortening the ionic diffusion length and providing large surface areas for electrode reactions. This article reviews the recent efforts made to apply nanostructured Mn-based oxides for batteries and pseudocapacitors. The influence of structure, morphology, and composition on electrochemical performance has been systematically summarized. Compared to bulk materials and notable metal catalysts, nanostructured Mn-based oxides can promote the thermodynamics and kinetics of the electrochemical reactions occurring at the solid-liquid or the solid-liquid-gas interface. In particular, nanostructured Mn-based oxides such as one-dimensional MnO2 nanostructures, MnO2-conductive matrix nanocomposites, concentration-gradient structured layered Li-rich Mn-based oxides, porous LiNi0.5Mn1.5O4 nanorods, core-shell structured LiMnSiO4@C nanocomposites, spinel-type Co-Mn-O nanoparticles, and perovskite-type CaMnO3 with micro-nano structures all display superior electrochemical performance. This review should shed light on the sustainable development of advanced batteries and pseudocapacitors with nanostructured Mn-based oxides.

Ce(0.6)Zr(0.3)Y(0.1)O(2) nanorod supported gold and palladium alloy nanoparticles: high-performance catalysts for toluene oxidation.

The Ce0.6Zr0.3Y0.1O2 (CZY) nanorods and their supported gold and palladium alloy (zAuxPdy/CZY; z = 0.80-0.93 wt%; x or y = 0, 1, 2) nanoparticles (NPs) were prepared using the cetyltrimethyl ammonium bromide-assisted hydrothermal and polyvinyl alcohol-protected reduction methods, respectively. Physicochemical properties of the samples were characterized by means of numerous analytical techniques, and their catalytic activities were evaluated for the oxidation of toluene. It is shown that the CZY in zAuxPdy/CZY was cubic in crystal structure, surface areas of CZY and zAuxPdy/CZY were in the range 68-77 m(2) g(-1), and the Au-Pd NPs with a size of 4.6-5.6 nm were highly dispersed on the surface of CZY nanorods. Among all the samples, 0.90Au1Pd2/CZY possessed the highest adsorbed oxygen concentration and the best low-temperature reducibility, and performed the best: T50% and T90% (temperatures required for achieving toluene conversions of 50 and 90%) were 190 and 218 °C at a space velocity of 20 000 mL (g h)(-1), respectively. The partial deactivation due to water vapor introduction was reversible. The active sites might be the surface oxygen vacancies on CZY, oxidized noble metal NPs, and/or interfaces between noble metal NPs and CZY. The apparent activation energies (37-43 kJ mol(-1)) obtained over 0.90-0.93AuxPdy/CZY were much lower than that (88 kJ mol(-1)) obtained over CZY for toluene oxidation. It is concluded that the excellent catalytic performance of 0.90Au1Pd2/CZY was associated with its high adsorbed oxygen species concentration, good low-temperature reducibility, and strong interaction between Au-Pd NPs and CZY nanorods as well as good dispersion of Au-Pd NPs.

Hierarchical Cu0.27Co2.73O4/MnO2 nanorod arrays grown on 3D nickel foam as promising electrode materials for electrochemical capacitors

Cu0.27Co2.73O4/MnO2 hybrid hierarchical nanostructure arrays directly on pressed nickel foam, with thin MnO2 nanoflakes homogeneously wrapped on Cu0.27Co2.73O4 nanorod arrays, are successfully synthesized by a simple hydrothermal and post heat-treatment method.

Au/Ce0.6Zr0.3Y0.1O2 Nanorods: Highly Active Catalysts for the Oxidation of Carbon Monoxide and Toluene

The Ce0.6Zr0.3Y0.1O2 (CZY) nanorods and its supported nanosized gold (xAu/CZY, Au loading (x) = 0.4–4.7 wt %) were prepared using the cetyltrimethylammonium bromide-assisted hydrothermal and polyvinylpyrrolidone-protected reduction methods, respectively. Physicochemical properties of the samples were characterized by means of numerous analytical techniques, and their catalytic activities were evaluated for the oxidation of CO and toluene. It is shown that the CZY in xAu/CZY was cubic in crystal structure, surface areas of CZY and xAu/CZY were in the range of 68–79 m2/g, and the Au nanoparticles (NPs) with a size of 3.1–3.9 nm were well dispersed on the surface of CZY nanorods. Among the xAu/CZY samples, the 4.7Au/CZY sample possessed the highest adsorbed oxygen concentration and the best low-temperature reducibility, and showed the highest catalytic activity at a space velocity of 20 000 mL/(g h): the T50% and T90% (temperatures required for achieving reactant conversions of 50 and 90%) were 32 and 60 °C for CO oxidation and 218 and 265 °C for toluene oxidation, respectively. Deactivation of water vapor addition was reversible, a result due to the competitive adsorption of H2O and toluene as well as oxygen on the sample surface. The apparent activation energies (27–37 and 39–53 kJ/mol) obtained over xAu/CZY were lower than those (42 and 88 kJ/mol) obtained over CZY for CO and toluene oxidation, respectively. On the basis of the characterization results and activity data, we conclude that the excellent catalytic performance of 4.7Au/CZY was associated with its higher oxygen adspecies concentration, better low-temperature reducibility, and stronger interaction between Au NPs and CZY nanorods as well as better Au NPs dispersion.

Synthesis of single-crystalline spinel LiMn2 O4 Nanorods for lithium-ion batteries with high rate capability and long cycle life.

The long-standing challenge associated with capacity fading of spinel LiMn2 O4 cathode material for lithium-ion batteries is investigated. Single-crystalline spinel LiMn2 O4 nanorods were successfully synthesized by a template-engaged method. Porous Mn3 O4 nanorods were used as self-sacrificial templates, into which LiOH was infiltrated by a vacuum-assisted impregnation route. When used as cathode materials for lithium-ion batteries, the spinel LiMn2 O4 nanorods exhibited superior long cycle life owing to the one-dimensional nanorod structure, single-crystallinity, and Li-rich effect. LiMn2 O4 nanorods retained 95.6 % of the initial capacity after 1000 cycles at 3C rate. In particular, the nanorod morphology of the spinel LiMn2 O4 was well-preserved after a long-term cycling, suggesting the ultrahigh structural stability of the single crystalline spinel LiMn2 O4 nanorods. This result shows the promising applications of single-crystalline spinel LiMn2 O4 nanorods as cathode materials for lithium-ion batteries with high rate capability and long cycle life.

LiNi0.5Mn1.5O4 nanorod clusters as cathode material for high energy and high power lithium-ion batteries.

High tap density LiNi0.5Mn1.5O4 nanorod clusters composed of well-crystallined LiNi0.5Mn1.5O4 nanorods with diameter of about 150 nm and length of about 1 μm were synthesized by a template method. β-MnO2 nanorods synthesized by a hydrothermal method were used as the template. LiNi0.5.Mn1.5O4 nanorod clusters were then synthesized by solid-state reaction of a mixture containing β-MnO2 nanorods, nickel acetate, and lithium hydroxide. It is found that a preheat treatment and grinding of the precursor for the solid state reaction is critical to form pure phase ordered LiNi0.5Mn1.5O4 and the nanorod cluster structure. LiNi0.5Mn1.5O4 nanorod clusters can deliver charge and discharge capacities as high as 140.61 mA h g(-1) and 128.42 mA h g(-1), respectively, at a 0.1 C rate between 3.0 and 4.9 V versus Li/Li+. Moreover, the nanorod clusters exhibit high power capability, maintaining capacities of 105.90 and 98.05 mA h g(-1) at 2 C and 5 C rates, respectively.

Growth of Fe(3)O(4) nanorod arrays on graphene sheets for application in electromagnetic absorption fields.

A facial strategy is developed to fabricate a three-dimensional (3D) Fe3 O4 nanorod array/graphene architecture, in which Fe3 O4 nanorods with a length and diameter of about 600 and 100 nm, respectively, are grown on both surfaces of the graphene sheets. The measured electromagnetic parameters show that the 3D architecture exhibits excellent electromagnetic wave-absorption properties, that is, more than 99 % of electromagnetic wave energy can be attenuated by the 3D architecture if it is added in only 20 wt % of the paraffin matrix, as the thickness of the absorber is in the range from 2.38 to 5.00 mm. The analysis of the electromagnetic (EM) absorption mechanism reveals that the excellent EM absorption properties are related to the special 3D architecture, and therefore, the construction of graphene-based 3D heteronanostructures is effective in obtaining lightweight EM absorbers with strong absorption properties.

White-light-controlled resistance switching in TiO2/α-Fe2O3 composite nanorods array

White-light-controlled resistance switching in TiO2/α-Fe2O3 composite nanorods array grown on fluorine-doped tin oxide substrate by hydrothermal process is investigated. The average length of TiO2/α-Fe2O3 nanorods is about 3.5 μm, and the average diameter is about 250 nm. The sizes of the α-Fe2O3 particles are in the range of 30 ~ 70 nm. The current–voltage characteristics of the composite nanorods array show a good rectifying property and bipolar resistive-switching behavior, and the resistive-switching behavior can be regulated by white-light illumination at room temperature. This study is helpful for exploring the multifunctional materials and their applications in nonvolatile multistate memory devices.