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α-Fe 2 O 3 nanomaterials with an elongated nanorod morphology exhibiting superior electrochemical performance were obtained through hydrothermal synthesis assisted by diamine derivatives as shape-controlling agents (SCAs) for application as anodes in lithium-ion batteries (LIBs). The physicochemical characteristics were investigated via XRD and FESEM, revealing well-crystallized α-Fe 2 O 3 with adjustable nanorod lengths between 240 and 400 nm and aspect ratios in the range from 2.6 to 5.7. The electrochemical performance was evaluated by cyclic voltammetry and charge-discharge measurements. A SCA test series, including ethylenediamine, 1,2-diaminopropane, 2,3-diaminobutane, and N -methylethylenediamine, was implemented in terms of the impact on the nanorod aspect ratio. Varied substituents on the vicinal diamine structure were examined towards an optimized reaction center in terms of electron density and steric hindrance. Possible interaction mechanisms of the diamine derivatives with ferric species and the correlation between the aspect ratio and electrochemical performance are discussed. Intermediate-sized α-Fe 2 O 3 nanorods with length/aspect ratios of ≈240 nm/≈2.6 and ≈280 nm/≈3.0 were found to have excellent electrochemical characteristics with reversible discharge capacities of 1086 and 1072 mAh g -1 at 0.1 C after 50 cycles.

Laser pyrolyzed SnO 2 nanoparticles with an option of nitrogen (N) doping are prepared using a cost-effective method. The electrochemical performance of N-doped samples is tested for the first time in Li-ion batteries where the sample with 3% of N-dopant exhibits optimum performance with a capacity of 522 mAh g active material -1 that can be obtained at 10 A g -1 (6.7C)., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Polyoxometalates (POMs) have been reported as promising electrode materials for energy storage applications due to their ability to undergo fast redox reactions with multiple transferred electrons per polyanion. Here we employ a polyoxovanadate salt, Na 6 [V 10 O 28 ], as an electrode material in a lithium-ion containing electrolyte and investigate the electron transfer properties of Na 6 [V 10 O 28 ] on long and short timescales. Looking at equilibrated systems, in situ V K-edge X-ray absorption near edge structure (XANES) studies show that all 10 V 5+ ions in Na 6 [V 10 O 28 ] can be reversibly reduced to V 4+ in a potential range of 4-1.75 V vs. Li/Li + . Focusing on the dynamic response of the electrode to potential pulses, the kinetics of Na 6 [V 10 O 28 ] electrodes and the dependence of the fundamental electron transfer rate k 0 on temperature are investigated. From these measurements we calculate the reorganization energy and compare it with theoretical predictions. The experimentally determined reorganization energy of λ = 184 meV is in line with the theoretical estimate and confirms the hypothesis of small values of λ for POMs due to electrostatic shielding of the redox center from the solvent.

Electrochemical in operando X-ray diffraction (XRD) is a powerful method to analyze structural changes of energy storage materials while inserting/de-inserting charge carriers, such as Li- or Na-ions, into/from a host structure. The design of an XRD in operando cell is presented, which enables the use of thin (6 μm) aluminum foil as X-ray window as a non-toxic alternative to conventional beryllium windows. Owing to the reduced thickness, diffraction patterns and their changes during cycling can be observed with excellent quality, which was demonstrated for two cathode materials for sodium-ion batteries in a half-cell set-up, P2-Na(0.7)MnO2 and Na(2.55)V6O16 ⋅ 0.6H2O.

A novel nanohybrid material that combines single-walled carbon nanotubes (SWCNTs) with a polyoxometalate (TBA)5[PVMoO40] (TBA-PV2Mo10, TBA: [(CH3(CH2)3)4N](+), tetra-n-butyl ammonium) is investigated for the first time as an electrode material for supercapacitors (SCs) in this study. The SWCNT-TBA-PV2Mo10 material has been prepared by a simple solution method which electrostatically attaches anionic [PV2Mo10O40](5-) anions with organic TBA cations on the SWCNTs. The electrochemical performance of SWCNT-TBA-PV2Mo10 electrodes is studied in an acidic aqueous electrolyte (1 M H2SO4) by galvanostatic charge/discharge and cyclic voltammetry. In this SWCNT-TBA-PV2Mo10 nanohybrid material, TBA-PV2Mo10 provides redox activity while benefiting from the high electrical conductivity and high double-layer capacitance of the SWCNTs that improve both energy and power density. An assembled SWCNT-TBA-PV2Mo10 symmetric SC exhibits a 39% higher specific capacitance as compared to a symmetric SC employing only SWCNTs as electrode materials. Furthermore, the SWCNT-TBA-PV2Mo10 SC exhibits excellent cycling stability, retaining 95% of its specific capacitance after 6500 cycles.

Herein, the controlled synthesis of 3D hierarchical films on carbon cloth (CC) in a high yield through a hydrothermal process and their high photocatalytic properties are reported. As representative examples, the obtained ZnIn2 S4 /CdIn2 S4 composites are composed of porous nanosheets. During the hydrothermal process, l-cysteine plays an important dual role as a coordinating agent and sulfur source, which is in favor of adjusting stoichiometry of the final product and forming the nanoporous structure. This facile method can be extended to synthesize other sulfides and oxides on CC substrates, such as CoIn2 S4 , MnIn2 S4 , FeIn2 S4 , SnS2 , and Bi2 WO6 . When evaluated the photocatalytic activity, the optimized ZnIn2 S4 /CdIn2 S4 (20%)-CC with an easily recycling feature shows higher photocatalytic degradation activity for methylene blue (MB) than ZnIn2 S4 -CC, CdIn2 S4 -CC, and ZnIn2 S4 /CdIn2 S4 (20%) powder. More importantly, ZnIn2 S4 /CdIn2 S4 (20%)-CC also exhibits superior H2 production activity. The enhanced photocatalytic activity is attributed to the unique porous sheet-like structure and the formation of heterojunction. Our results could provide a promising way to develop high-performance photocatalytic films, which makes it possible to be used in real devices., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A facile and general method is developed to fabricate one-dimensional (1D) spinel composite oxides with complex architectures by using a facile single-spinneret electrospinning technique. It is found that precursor polymers and heating rates could control the structures of the products, such as 1D solid, nanotube and tube-in-tubes structures. Especially, the tube-in-tube structures have been successfully fabricated for various mixed metal oxide, including CoMn2O4, NiCo2O4, CoFe2O4, NiMn2O4 and ZnMn2O4. Benefiting from the unique structure features, the tube-in-tube hollow nanostructures possess superior electrochemical performances in asymmetric supercapacitors and Li-O2 batteries.

Flexible three-dimensional (3D) nanoarchitectures have received tremendous interest recently because of their potential applications in wearable electronics, roll-up displays, and other devices. The design and fabrication of a flexible and robust electrode based on cobalt sulfide/reduced graphene oxide/carbon nanotube (CoS2 /RGO-CNT) nanocomposites are reported. An efficient hydrothermal process combined with vacuum filtration was used to synthesize such composite architecture, which was then embedded in a porous CNT network. This conductive and robust film is evaluated as electrocatalyst for the hydrogen evolution reaction. The synergistic effect of CoS2 , graphene, and CNTs leads to unique CoS2 /RGO-CNT nanoarchitectures, the HER activity of which is among the highest for non-noble metal electrocatalysts, showing 10 mA cm(-2) current density at about 142 mV overpotentials and a high electrochemical stability., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Hierarchical CoS2 hollow nanospheres (HSs) with a nitrogen-doped-carbon coating (NC@CoS2 ) are fabricated by a simple solution method. The uniform 300 nm-sized NC@CoS2 HSs are composed of ultrathin nanosheet subunits with a thickness of around 2 nm. It was found that polyvinylpyrrolidone and ethylenediamine not only controlled the morphology of the products, but also provided the sources of nitrogen-doped carbon. Benefiting from their unique structural characteristics, hierarchical NC@CoS2 HSs can be applied in lithium-ion batteries, supercapacitors, and photocatalysis. When evaluated as an electrode material, NC@CoS2 with a coating of optimal thickness showed a high lithium-storage capability with a good cycling stability. Moreover, NC@CoS2 had a remarkable supercapacitive performance and photocatalytic activity. The attractive electrochemical and photocatalytic performances were attributed to the overall structural features of the NC@CoS2 hollow spheres: the N-doped-carbon (NC) coating, hollow interior, and ultrathin nanosheets., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Room-temperature sodium-ion batteries have the potential to become the technology of choice for large-scale electrochemical energy storage because of the high sodium abundance and low costs. However, not many materials meet the performance requirements for practical applications. Here, we report a novel sodium-ion battery electrode material, Na(2.55)V(6)O(16)⋅0.6 H(2)O, that shows significant capacities and stabilities at high current rates up to 800 mA g(-1). X-ray photoelectron spectroscopy measurements are carried out to better understand the underlying reactions. Moreover, due to the different oxidation states of vanadium, this material can also be employed in a symmetric full cell, which would decrease production costs even further. For these full cells, capacity and stability tests are conducted using various cathode:anode mass ratios., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Hierarchical CaCo2O4 nanofibers (denoted as CCO-NFs) with a unique hierarchical structure have been prepared by a facile electrospinning method and subsequent calcination in air. The as-prepared CCO-NFs are composed of well-defined ultrathin nanoplates that arrange themselves in an oriented manner to form one-dimensional (1D) hierarchical structures. The controllable formation process and possible formation mechanism are also discussed. Moreover, as a demonstration of the functional properties of such hierarchical architecture, the 1D hierarchical CCO-NFs were investigated as materials for lithium-ion batteries (LIBs) anode; they not only delivers a high reversible capacity of 650 mAh g(-1) at a current of 100 mA g(-1) and with 99.6% capacity retention over 60 cycles, but they also show excellent rate capability with respect to counterpart nanoplates-in-nanofibers and nanoplates. The high specific surface areas as well as the unique feature of hierarchical structures are probably responsible for the enhanced electrochemical performance. Considering their facile preparation and good lithium storage properties, 1D hierarchical CCO-NFs will hold promise in practical LIBs., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Novel, porous NiCo2O4 nanotubes (NCO-NTs) are prepared by a single-spinneret electrospinning technique followed by calcination in air. The obtained NCO-NTs display a one-dimensional architecture with a porous structure and hollow interiors. The effect of precursor concentration on the morphologies of the products is investigated. Due to their unique structure, the prepared NCO-NT electrode exhibits a high specific capacitance (1647 F g(-1) at 1 A g(-1)), excellent rate capability (77.3 % capacity retention at 25 A g(-1)), and outstanding cycling stability (6.4 % loss after 3000 cycles), which indicates it has great potential for high-performance electrochemical capacitors. The desirable enhanced capacitive performance of NCO-NTs can be attributed to the relatively large specific surface area of these porous and hollow one-dimensional nanostructures., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Novel eggroll-like CaSnO(3) nanotubes have been prepared by a single spinneret electrospinning method followed by calcination in air for the first time. The electrospun sample as a lithium-ion battery electrode material exhibited improved cycling stability and rate capability by virtue of the high surface area and unique hollow interior structure, compared to nanorod-structured CaSnO(3).

Apatite-like materials are of considerable interest as potential solid oxide fuel cell electrolytes, although their structural vagaries continue to attract significant discussion. Understanding these features is crucial both to explain the oxide ion conduction process and to optimise it. As the composition of putative P6(3)/m apatites with ideal formula [A(I)(4)][A(II)(6)][(BO(4))(6)][X](2) is varied the [A(I)(4)(BO(4))(6)] framework will flex to better accommodate the [A(II)(6)X(2)] tunnel component through adjustment of the A(I)O(6) metaprism twist angle (varphi). The space group theory prescribes that framework adaptation during phase changes must lead to one of the maximal non-isomorphic subgroups of P6(3)/m (P2(1), P2(1)/m, P1[combining macron]). These adaptations correlate with oxygen ion conduction, and become crucial especially when the tunnels are filled by relatively small ions and/or partially occupied, and if interstitial oxygens are located in the framework. Detecting and completely describing these lower symmetry structures can be challenging, as it is difficult to precisely control apatite stoichiometry and small departures from the hexagonal metric may be near the limits of detection. Using a combination of diffraction and spectroscopic techniques it is shown that lanthanum strontium germanate oxide electrolytes crystallise as triclinic (A), monoclinic (M) and hexagonal (H) bi-layer pseudomorphs with the composition ranges: [La(10-x)Sr(x)][(GeO(4))(5+x/2)(GeO(5))(1-x/2)][O(2)] (0