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Sustainable development of renewable energy sources is one of the most important themes that humanity faces in this century. Wide use of renewable energy sources will require a drastically increased ability to store electrical energy. Electrochemical energy storage devices are expected to play a key role. With the increased demand in flexible energy resource for wearable electronic devices, great efforts have been devoted to developing high-quality flexible electrodes for advanced energy storage and conversion systems. Because of its high specific surface area, good chemical stability, high mechanical flexibility, and outstanding electrical properties, graphene, a special allotrope of carbon with two-dimensional mono-layered network of sp2 hybridized carbon, have been showing great potential in next-generation energy conversion and storage devices. This review presents the latest advances on the flexible graphene-based materials for the most vigorous electrochemical energy storage devices, that is, supercapacitors and lithium-ion batteries. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Freestanding multiwalled carbon nanotube and titanium (IV) oxide anode paper was prepared by vacuum filtration of multiwall carbon nanotubes/TiO2 hybrid material, which was synthesized by the radio frequency magnetron sputtering techniques. Field emission scanning electron microscopy images revealed that the carbon nanotubes (CNTs) form a three-dimensional nanoporous network, in which ultrafine TiO2 crystals that had crystallite sizes ranging between 7.14 nm and 12.21 nm were distributed homogenously over the surfaces of multiwalled CNT bundles. Electrochemical measurements demonstrated that the prepared powder by using 200 W radio frequency power had excellent cyclic retention, with the high specific capacity of 230 rnAh g−l up to 50 cycles at a current density. Freestanding papers composed of multiwall carbon nanotubes could act as a flexible mechanical support for strain release offering an efficient electrically conducting channel ,whereas the TiO2 provides the high capacity. The electrochemical response is maintained in the initial and further cycling process. Such capabilities demonstrate that this model hold great promise for applications requiring flexible and bendable Li-ion batteries. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Summary: This paper reports a feasible approach to offer LiNi0.8Co0.1Mn0.1O2 (NCM811) layered cathode materials with enhanced lattice ordering and improved electrochemical performance through a nano grinding assisted solid‐state reaction. Different from the commercial precursor method, oxide raw materials, NiO, CoO and MnO2, rather than the hydroxides, was employed as the starting raw material which was milled into submicron size, pressed into pellets and crushed into granular powder. After calcination under oxygen atmosphere under different temperature, such a simple approach provides layered cathode materials with controllable Li/Ni disordering. Powder XRD results show that when sintered at 800°C, a largest I(003)/I (104) ratio is observed, indicating that the cationic disordering is the lowest, as been confirmed by the XRD refinement data, showing that only 1.08% Ni is misplaced at 3b site. For the electrochemical test, the pNCM800 sample presented an initial specific discharge capacity of 203 mAh/g at 0.1C, together with a capacity retention of 91.77% after 100 cycles at 0.5C. Compared to the value of the sample obtained at normal routine (163.8 mAh/g and 74.85%), the improvement in electrochemical behavior is obvious. Furthermore, the rate performance is also improved, with a specific capacity of 144.1 mAh/g even at 5C rate. The reason for such enhancement could be ascribed to the better kinetic process with low interfacial resistance and fast Li diffusion contributed from the promoted lattice ordering. The results obtained in the experiments greatly indicate the significance of the approach in controlling the Li/Ni disordering, and thus offer an alternative routine for the mass production of layered cathode materials besides the so‐called precursor method. [ABSTRACT FROM AUTHOR]

Peanut oil cake biomass is a major by‐product of oil industry and can be a suitable precursor for the production of biomass‐based porous carbon. Herein, dual‐stage activation, physical activation at 400°C, and chemical activation using KOH between 600 and 900°C are adopted to prepare hierarchical porous carbons (HPCs) from peanut oil cake biomass for use as electrode material in electrochemical supercapacitors. The textural and structural properties of the HPC were evaluated by N2‐adsorption/desorption, X‐ray diffraction, Raman, FT‐IR spectroscopy, and scanning electron microscopy. The prepared HPC inherited sufficient micropores and mesopores distribution with a maximum BET surface area of 640 m2/g. The electrochemical properties of the HPC electrodes were evaluated by cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopic analysis. Among different HPC electrodes prepared, the carbon prepared at 800°C (HPC‐P8) electrode material exhibited a high specific capacitance of 187 F/g at 0.5 A/g in 1M Na2SO4 electrolyte in three‐electrode systems. Symmetric supercapacitors were also fabricated using HPC‐P8//HPC‐P8 as positive and negative electrodes using 1M Na2SO4 electrolyte, in a two‐electrode cell configuration via split cell method. Maximum specific capacitance of 30 F/g was achieved with superior cycle stability of 93.8% capacitance retention over 5,000 cycles for the symmetric device. The device operated at a wide potential window (0–2.0 V) resulted in appreciable specific energy and power density of 15.89 Wh/kg and 493 W/kg, respectively. HPC‐P8 had an ion diffusion coefficient of 7.79 × 10−8 cm2/s which is higher than the other prepared carbon samples. The symmetric device showed relatively high charge storage capacity and cyclic stability without any material degradation. The fabricated prototype portable supercapacitor module was tested for red LED glow with maximum intensity brightness up to 4 min. Thus, the present study reveals that HPC derived from peanut oil cake biomass can behave as a promising electrode material for supercapacitor applications. [ABSTRACT FROM AUTHOR]

The aim of this paper is to investigate the effects of variable parameters on the performance of a unitized regenerative solid oxide fuel cell (URSOFC) using a two-dimensional axisymmetric simulation model. This model was validated using the performance curves of an in-house button-type URSOFC. The parameters studied include the operating temperature and the porosity, tortuosity, and grain diameter of the electrodes while the URSOFC is operated in the solid oxide fuel cell mode and the solid oxide electrolyzer cell (SOEC) mode. The predicted results show that the temperature and the electrode porosity have a beneficial effect on the performance of the URSOFC because of an enhancement of the electrochemical reactions and the species mass transfer, respectively. However, when the URSOFC is operated in the SOEC mode, the cell performance decreases as the electrode porosity increases. This indicates that the decreasing reaction active sites as a result of the higher porosity have a dominant effect on the performance in the SOEC mode. The cell performance also decreases as the tortuosity and grain diameter of the electrodes increase. In addition, the effect of the electrode grain diameter on the cell performance is predicted to be insignificant for the URSOFC operated in the SOEC mode. The results of investigations presented in this paper can assist in the optimal design and management of a URSOFC. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Summary: In this paper, a systematic method has been developed to produce highly flexible and robust graphene/LiMn2O4 (G/LMO) and graphene/LiCr0.05Mn1.95O4 (G/LCMO) free‐standing composite cathode electrodes with increased specific capacity and improved electrochemical capability. Spinel LMO nanorods are synthesized by calcination method followed by a hydrothermal reaction technique. As‐synthesized nanorods were then embedded in a graphene layer which will in turn serve as a self‐standing binder‐free cathode electrode. Spinel LMO and LCMO nanorods with a length of 600 nm and width of 50 nm were then homogenously entrapped and distributed within the layers of conductive graphene structure. This hybrid structure will help to eliminate the use of heavy metal current collectors and electrically resistant binders or even conductive additives. A discharge capacity of 114.5 mAh g−1 is obtained after first cycle and %72 capacity retention is obtained after 250 cycles from G/LCMO freestanding samples. The enhancement in the electrochemical properties is due to the unique freestanding structure of the cathode electrodes. [ABSTRACT FROM AUTHOR]

The integration of micro/nanostructured metal/metal oxides with carbon-based materials has emerged as a promising approach for developing electrochemical electrodes. However, the fabrication of such hybrids entails complex and multistep procedures involving the grain boundaries and interfaces between the constituent materials, thus, degrading the overall performance. Herein, we report a facile electrothermal process (ETP) for the scalable fabrication of hybrid carbon fiber (CF) sheets integrated with tunable morphology of silver micro/nanoparticles. The application of an electric field across the layered film, consisting of AgNO3 and CF, enabled the rapid dissipation of thermochemical energy in an open-air environment via ETP. The ETP facilitated ultrafast heat dissipation within a few milliseconds, leading to the rapid decomposition of AgNO3, which resulted in the formation of liquefied Ag on the CF surface affording a reduced Ag-CF composite with adjustable structures through input power. The capability of ETP driven by controlling duration and number of electrical pulses was demonstrated by examining the corresponding physiochemical and electrochemical characteristics of the resulting composite. The Ag-CF composite fabricated using three cycles of a screened ETP pulse (1500 W and 75 ms for power and duration) acted as a supercapacitor electrode demonstrating excellent area capacitance (13 F/cm2) and exceptional capacitance retention (98% after 10,000 cycles). Thus, the utilization of ETP can provide manufacturing strategies enabling scalable synthesis of functional hybrids in vacuum-free ambient environments within milliseconds. These hybrids possess unique interfaces and particle boundaries, exhibiting considerable potential for diverse electrochemical applications. [ABSTRACT FROM AUTHOR]

Vanadium redox flow batteries (VRFB), originally proposed by Skyllas-Kazacos et al., have been considered as one of the most promising energy storage systems for intermittently renewable energy. However, the poor electrochemical activity and hydrophobicity of graphite felt electrode greatly limit energy storage efficiency of VRFB system. In this paper, two nitrogen-doped (N-doped) graphite felts, obtained by heat-treating in an NH3 atmosphere at 600 °C and 900 °C, have been investigated as electrodes with high electrochemical performance for vanadium redox flow batteries. In particular, the one obtained at 900 °C exhibits an excellent electrochemical activity for both V2+/V3+ and VO2+/VO2+ redox couples. The cells with different graphite felt electrodes were assembled, and the charge-discharge performance was evaluated. The cell with the N-doped graphite felts has larger discharge capacity, discharge capacity retention, and energy efficiency, especially with the sample treated at 900 °C. The average energy efficiency of the cell with the 900 °C treated N-doped graphite felts is 86.47%, 5.44% higher than that of the cell with the pristine graphite felt electrodes. These enhanced electrochemical properties of the N-doped graphite felt electrodes are attributed to the increased electrical conductivity, more active sites, and better wettability provided by the introduction of the nitrogenous groups on the surface of graphite felts. It indicates that N-doped graphite felts have promising application prospect in VRFB. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The rapid development of current wearable electronics motivates the promotion of energy storage devices. Supercapacitor with flexible, lightweight, highly efficient, and long cycling life is one of the potential and glittering candidates. Here, the composite film of carboxylated graphene (CG) and commercially available poly (3, 4-ethylene dioxythiophene): poly (styrene sulfonate) (PEDOT:PSS) are prepared as electrodes for flexible electrochemical capacitors by ultrasonication and vacuum filtration. The CG/PEDOT:PSS films were roundly characterized by SEM, XPS, FTIR, XRD and Raman spectrometer. The as-prepared free-standing films exhibited high specific capacitance (192.7 F g-1 at 0.5 A g-1), excellent rate capability (up to 80.4% from 0.5 to 20 A g-1), and good electrochemical stability (95.5% of specific capacitance retention after 50000 cycles). Surprisingly, the post treated free-standing films by Dimethyl Formamide (DMF) shows better capacitive properties than those of the pristine electrode, such as higher specific capacitance (204.3 F g-1 at 0.5 A g-1), and ultralong-cycling stability (104.6% retention at a high current density of 20 A g-1 after 50000 cycles). It is expected that the free-standing CG/PEDOT:PSS films can be used as flexible electrodes for various wearable energy storage devices. [ABSTRACT FROM AUTHOR]

Summary: A highly dispersed single‐wall carbon nanotube (HD‐SWCNT) thin film is introduced on a WO3 film (HD‐SWCNT/WO3) by ultrasonic spray coating method to accelerate electron and Li‐ion transport for realizing ultrafast multi‐functional electrochromic (EC) energy‐storage electrodes. Uniform grafting of polyvinylpyrrolidone onto the SWCNTs induces their amicable debundling without any surface defects. The highly debundled and continuous morphology of the HD‐SWCNT thin film enables accelerated electron transport along the sp2 carbons, which leads to excellent electrical properties (electrical conductivity of ~1361 S/cm and sheet resistance of ~7.3 Ω/□). Functional groups such as amides and carbonyls on the HD‐SWCNTs enhance Li‐ion wettability, which accelerates Li‐ion diffusion kinetics. In addition, the uniform structure of the HD‐SWCNT thin film with its porosity effectively shortens the Li‐ion diffusion pathways and increases the contact area between the functional groups and the electrolyte, improving the electrochemical activity of the electrode. Such behaviors to promote electron and Li‐ion transport at the interface between the electrolyte and the WO3 film enhance the EC energy‐storage performances compared to those of aggregated SWCNT film on WO3 and a bare WO3 electrode. The corresponding performances of HD‐SWCNT/WO3 include the transmittance modulation (58.7% at 633 nm), switching speeds (3.1 s for coloration and 4.5 s for bleaching), coloration efficiency (51.9 cm2/C), and specific capacitance (87.9 F/g at 2 A/g). In particular, owing to the synergistic effect of the accelerated electrical conductivity and the Li‐ion diffusivity of the HD‐SWCNT thin film for ultrafast electrochemical kinetics, HD‐SWCNT/WO3 exhibits a remarkable high‐rate capability (82.9%, specific capacitance retention at 20 A/g compared to 2 A/g), which demonstrates ultrafast charge/discharge characteristics. In this regard, the introduction of an HD‐SWCNT thin film as a functional layer to improve the ultrafast charge transport at the interface between a WO3 and an electrolyte could be a promising strategy for ultrafast multi‐functional electrochemical devices. [ABSTRACT FROM AUTHOR]

Summary: Lithium‐ion batteries (LIBs) are the main driving force behind the proliferation of mobile devices and electric vehicles. The production technologies of LIBs have been developed with the aim of lowering the energy cost (US$ kWh−1) and environmental impact while increasing the production efficiency. Here, we report dry‐processed Ni‐rich oxide cathodes coated with carbon nanotubes (CNTs) for LIBs. Specifically, LiNi0.8Co0.15Al0.05O2 (NCA) particles coated with multi‐walled CNTs (MWCNTs) were used to fabricate the cathodes by employing dry‐type electrode processing. In addition, the amount of polytetrafluoroethylene binder in the electrode was minimized and the inclusion of conventional carbon black (CB) conductive additives was eliminated. This approach enabled the fabrication of CB‐free, dense cathodes with an extremely high NCA content (99.6 wt%) and high electrode density of ~4.0 g cm−3. The NCA cathode had a high volumetric capacity of ~821 mAh cm−3 at a current rate of 0.5 C (~4.6 mA cm−2) and delivered good full‐cell cycling performance over 300 cycles (~60% capacity retention). Our results offer a viable way to lower the energy cost and the environmental damage toward next‐generation LIBs. Highlights: Ni‐rich particles with a CNT‐coating were used for dry‐processed cathode preparation.The CNTs replace conventional carbon black conductive additives.The CNT‐coated Ni cathodes were fabricated with minimal binder content (0.4 wt%).The cathode has good rate and cycling performance with high volumetric capacities. [ABSTRACT FROM AUTHOR]

Summary: Dye‐sensitized solar cells have received immense interest in the research society since its finding in 1991 mainly because of the ease of fabrication and the resources employed are low‐cost and also be environmentally friendly. In conventional dye‐sensitized solar cells, platinum is used as a counter electrode since it offers good electrocatalytic activity toward the triiodide ion reduction and also possesses high electrical conductivity. However, the corrosive nature and scarcity of platinum are considered the limitations of platinum counter electrodes in the dye‐sensitized solar cell. To overcome this, significant research is going on to explore alternative counter electrode materials. This review focuses on MoS2 and its composites. We also discuss reports where, interestingly, MoS2 can also be applied as the photoanode in dye‐sensitized solar cells (DSSCs). Importantly, the influence of morphology on the performance of the devices is summarized. Further, in the context of counter electrodes, the importance of electrochemical investigation and electrochemical stability of the electrodes have also been discussed. [ABSTRACT FROM AUTHOR]

Summary: Metal co‐doping of metal oxide nanostructures is a promising approach for enhancing the electrochemical performance of supercapacitors. Herein, calcium (Ca) and cobalt (Co) co‐doped ZnO capsules (Ca‐Co@ZnO) were fabricated using a facile and single‐step hydrothermal process. The physical, chemical, and morphological properties of the Ca‐Co@ZnO were analyzed using a range of characterization techniques such as X‐ray diffraction, X‐ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. Ca‐Co@ZnO showed a remarkable supercapacitor performance in a 3 M KOH aqueous electrolyte. The specific capacitance was 1020 F/g at a current density of 0.75 A/g, which was 3.2, 1.7, and 1.6 times higher than the pristine ZnO, Ca‐ZnO, and Co‐ZnO capsules, respectively. Ca‐Co@ZnO showed more than 50% capacity retention at a higher current density and strong cycling stability up to 5000 cycles with only 8% capacity loss. The Ca‐Co@ZnO//Ca‐Co@ZnO symmetric performance was also investigated. This device showed a specific capacitance of 187 F/g at a current density of 1 A/g and an energy density of 25.9 Wh/kg at a power density of 556.6 W/kg. The superior performance was attributed to the fast electron accessibility, strong ion diffusion, and higher active sites. Overall, the superior electrochemical performance and novel structures could be beneficial for developing metal co‐doped metal oxide electrodes for supercapacitor applications. [ABSTRACT FROM AUTHOR]

Summary: The significant influences of the external stress in the electrochemical performances of the supercapacitors require the optimization of the electrode materials with reasonable morphology. In this work, activated carbon spheres (ACSs) of different sizes are prepared from hydrothermal processing of glucose aqueous solution, pre‐carbonization, and KOH activation. The energy storage performance of ACS‐based supercapacitors (SCs) under compression is analyzed. Increasing the compressive stress from 1 MPa to 8 MPa promotes the specific capacitance of the ACS‐based SCs, which achieves 374 F/g at 0.5 A/g for the ACSs with the smallest diameter of 1.48 μm. Applying higher compressive stress also reduces IR drop and the self‐discharge rate. The compression is found to have more significant positive effects on the electrochemical properties of the ACSs with larger sizes. The understanding of the morphological effect of the electrode materials on the electrochemical properties under compressive stress can help design and select appropriate electrode materials for supercapacitors applied under certain stresses. [ABSTRACT FROM AUTHOR]

Summary: The hydrogen oxidation reaction on Sr2Fe1.5Mo0.5O6−δ + Ce0.8Sm0.2O2−δ (SFM‐SDC), Sr2Fe1.5Mo0.5O6−δ + BaCe0.89Gd0.1Cu0.01O3−δ (SFM‐BCGC) and Sr1.95Fe1.4Ni0.1Mo0.5O6−δ + BaCe0.89Gd0.1Cu0.01O3−δ (SFNM‐BCGC) composite electrodes in contact with BaCeO3‐based proton‐conducting electrolytes was studied for the first time. Despite the high electronic and oxygen‐ionic conductivity in the SFM‐SDC, its electrochemical performance was not satisfactory, while the presence of the proton‐conducting phase and exsolved nickel particles on the SFNM‐BCGC electrode increased the electrochemical activity about 3 to 5 times. In series SFM‐SDC, SFM‐BCGC, SFNM‐BCGC the polarization resistance was about 1.06, 0.54, 0.37 Ohm cm2 at 800°C and 10.02, 3.55, 2.12 Ohm cm2 at 600°C in wet hydrogen. The presence of sufficient proton conductivity in the electrode is supposed to be crucial for the efficient performance of the anodes in contact with proton‐conducting oxides. [ABSTRACT FROM AUTHOR]

Summary: Manganese‐based oxides are being actively studied as cathode materials for rechargeable aqueous zinc ion batteries (AZIBs) because of their high capacity, cost‐effectiveness, safety, and eco‐friendliness. Herein, we propose a binder‐free electrode of bivalent manganese oxide with the chemical composition of Mn5O8 deposited on stainless steel as a cathode of AZIBs. Mn5O8 nanoparticles with a layered structure, which provide a facile pathway for Zn2+ ion transport and diffusion, were directly deposited on a three‐dimensional stainless steel mesh via a hydrothermal method using different temperatures. The structures of the active materials in the cathode were characterized by X‐ray diffraction, high‐resolution transmission electron microscopy, X‐ray photoelectron spectroscopy, and field‐emission scanning electron microscopy. The Mn5O8 cathode materials exhibited a high specific capacity of 254.98 mAh g−1, and simultaneously demonstrated satisfactory reversible charge/discharge and high rate performance. The Zn2+ insertion/extraction behaviors were studied in detail by cyclic voltammetry. In addition, factors that influence the electrochemical performance of the cathode, such as the phase structure and particle size of manganese dioxide, are discussed. Smaller and homogeneous Mn5O8 particles provide a large interface area and facilitate more zinc ions for diffusion, leading to improved ionic current and specific capacity. [ABSTRACT FROM AUTHOR]

Summary: In this study, lab‐made modified graphite cathodes were used to design and implement floating PV assisted alkaline electrolysis cell. The influence of temperature on PV performance was studied both experimentally and theoretically, and the PV module performance was investigated in floating as well as non‐floating modes. Power generation of floating PV panel and non‐floating PV panel at four different air temperatures was examined. Although there was no substantial improvement in power generation at 6°C or 16°C, values improved by 6.25% and 10.75% at 24°C and 37°C, respectively. For alkaline electrolysis cell part of this system, the graphite (G) cathode was galvanostatically coated with nickel (G/Ni) and decorated with cobalt nano‐particles (G/Ni/Co). The characterization of the electrode was achieved using X‐Ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The Co(111)‐decorated Ni was determined by XRD, the electrode surface was very rough in FE‐SEM micrographs, the detected features provided a larger contact area that supported the formation of simultaneous electrochemical reactions. The electrochemical behavior of electrodes were determined in 1 M KOH by cyclic voltammetry (CV). The modified cathode (G/Ni/Co) enhanced the hydrogen production performance owing to lower hydrogen onset potential. Electronic structure calculations were carried out in order to investigate water as well as proton adsorption on a Co‐decorated Ni(111) surface. Density Functional Theory (DFT) calculations identified the role of Co cluster and Ni surface on water and proton adsorptions. According to our knowledge of the literature to date, the practical and theoretical analysis of a floating PV assisted‐an alkaline electrolysis system that worked with the laboratory‐made electrodes has not been performed before. Results showed that floating PV panels were beneficial than land mounted panels and the G/Ni/Co enhanced the hydrogen generation performance of the system. [ABSTRACT FROM AUTHOR]

Summary: Core‐shell nanostructured three‐dimensional binderless electrode porosity makes them ideal candidates for electrochemical energy storage applications. This article proposes NiCo2S4@MnOx electrodes fabricated using a facile hydrothermal approach and subsequently annealed at 120°C for 12 hours. The resultant nanoarrays@nanosheets structure allows rapid ion and electron transport. Coating with pseudocapacitive MnOx on NiCo2S4 nanoarrays improves overall capacitance, and the amorphous MnOx nanosheets promote electrode cycling stability. The proposed NiCo2S4@MnOx electrode achieved excellent specific capacitance of 1640 F·g−1 at 5 mA·cm−2 and cyclic stability ≈ 90%; and the subsequently fabricated asymmetric electrochemical supercapacitor achieved specific capacitance ~96.91 F·g−1, and specific energy (SE) 26.38 Wh·kg−1 at specific power (SP) 466.66 W·kg−1, with impressive electrochemical stability ≈ 80% over 5000 charge/discharge cycles. [ABSTRACT FROM AUTHOR]

Summary: Epitaxial growth of three‐dimensional (3D) architectures has led to new opportunities in the optoelectronic devices and nanoscale thermal engineering. The feature that makes these materials distinct is to form a complex geometry while preserving crystal epitaxy. This enables to exploit functionalities given by 3D interconnected pores and suppress charge trapping at defects. One technology that finds it useful is electrochemical energy storage in response to ultrafast alternate current (AC) switch. Here, we extend the concept of 3D mesostructured single crystals to electrochemical capacitors (ECs) for AC line filtering. We present bottom‐up epitaxial infilling of Fe3O4 into the self‐assembled 300 nm diameter colloid templates using electrodeposition. The resulting 3D mesostructured single crystalline Fe3‐δO4 (111) film (δ ≈ −0.06) is highly oriented along both out‐of‐plane and in‐plane crystallographic orientations. The mesostructured epitaxial electrode responds as an EC capacitor to ultrafast voltage scans at a rate of 50 V s−1 and exhibits excellent AC line filtering properties at 120 Hz including the small resistor–capacitor time constant (0.86 ms), large areal capacitance (601 μF cm−2), and modest phase angle (−60°). We attribute this to combined effects of efficient charge transport in epitaxial matrix with low defect density and rapid ion diffusion through 3D interconnected periodic pores. The present study demonstrates the power of the 3D structured epitaxy as a tool of advancing the broader area of technology where fast delivery of both charge and mass is important. [ABSTRACT FROM AUTHOR]

Wearable supercapacitors have broad application prospects in emerging portable devices. To realize the large-scale application, it is necessary to develop a low-cost and large-scale method to fabricate wearable electrode with high electrochemical performance. Here, polyaniline supported by graphene coated polyester textile (PANI/GPT) electrode is prepared through a simple and lowcost method. First, graphene ink with high concentration is prepared, and then the polyester textile is coated by graphene through a repeatedly soaking-drying process. Subsequently, PANI/GPT electrode is prepared by electrochemical deposition of polyaniline (PANI) on graphene coated polyester textile. The ratio of PANI in the textile electrode has been systematically modified and the obtained textile electrode possesses good energy storage performance with specific capacitance reaching 896.50 F g-1 and good rate capability. The assembled flexible supercapacitor also owns excellent flexibility with capacitance retention of 95.10% after bending for up to 5000 cycles. Such high-performance textile electrodes and the low-cost method can be widely applied to develop other wearable energy storage devices. [ABSTRACT FROM AUTHOR]

Summary: In this work, Li2Mn1–xCrxSiO4 cathode material was synthesized by the solid‐phase doping method and two‐step calcination. The appropriate calcination temperature can be obtained by TG‐DTA curve. XRD, SEM and TEM tests show that the prepared Li2Mn1–xCrxSiO4 has a Pmn21 space group structure, and the particle size decreases from 570 to 140 nm with the increase of the doped Cr content. Cr doping enhances the structural stability of Li2Mn1–x CrxSiO4 and improves the electrochemical activity of the cathode. The results of XRD, EDS and XPS show that Cr3+ is successfully doped into the Li2MnSiO4 lattice, and the element distribution is uniform. The electrochemical results show that Li2Mn0.8Cr0.2SiO4 exhibits significantly enhanced cycle stability and discharge capability. [ABSTRACT FROM AUTHOR]

Summary: Li2 + xMn1‐xSiO4 compounds with a deficiency and an excess of lithium as a cathode material for Li‐ion batteries were synthesized by the solid‐state synthesis method, and a two‐step calcination process was applied to improve the electrochemical properties. The calcination temperature was determined by the thermogravimetric analysis and differential scanning calorimetry (TG‐DSC) curves. The synthesized compounds were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X‐ray photoelectron spectroscopy (XPS), X‐ray diffraction (XRD), and other material testing methods. A MnO and Mn2SiO4 impurity was detected in the Li2 + xMn1‐xSiO4 compounds. The cycle performance of Li1.96Mn1.04SiO4, Li1.98Mn1.02SiO4, and Li2.02Mn0.98SiO4 cathode materials for lithium‐ion batteries was tested to compare with that of pure Li2MnSiO4. The Li2.02Mn0.98SiO4 sample doped with an excess of Li both has a high first discharge specific capacity and excellent electrochemical cycle stability. The introduction of an appropriate strategy to produce a lithium excess is an effective way to improve the electrochemical performance of cathode materials. [ABSTRACT FROM AUTHOR]

Summary: The lithium transition metal orthosilicates (Li2MnSiO4) compounds are considered key materials for the next‐generation lithium‐ion batteries (LIBs). However, they exhibit poor electronic conductivity and structural stability. Herein, the dual‐phase (Pmn21, and Pn) coexisting Li2Mn1−xNixSiO4@C is prepared successfully via a two‐step calcination process to address the aforementioned problems. The orthorhombic Pmn21 and Pn phase are expected to bring well solid‐state Li diffusion properties (DLi+) and structural stability for electrode material, respectively. Also, the Ni doping and carbon coating are expected to raise electronic conductivity. Then, the electrochemical performance of LIBs utilizing LiMn0.995Ni0.005SiO4@C, LiMn0.985Ni0.015SiO4@C, and LiMn0.92Ni0.08SiO4@C (ZNi‐02 to ZNi‐04) as cathode materials are investigated and compared with that of the LiB using Li2MnSiO4@C (ZNi‐01). The ZNi‐04 sample‐based LiB shows well DLi+ and a peak discharge capacity as high as 188.4 mAh g−1. In addition, the ZNi‐04 sample can still maintain a capacity of about 80 mAh g−1 at rate of 8 C. Such excellent electrochemical performance is ascribed to the synergistic effect of the dual‐phase coexistence, the proper amount of Ni doping, and surface coating of carbon, which enhances the electrical conductivity and structural stability. Thus, Li2Mn1−xNixSiO4@C has broad application chances as a high‐performance LIBs electrode material. [ABSTRACT FROM AUTHOR]

Summary: Strontium (Sr) incorporated LaMnO3 (La0.7Sr0.3MnO3) nanoparticles have been synthesized by ball‐milling‐assisted solid‐state reaction to study their performance as electrode material for energy storage applications. The La0.7Sr0.3MnO3 nanoparticles exhibit superior electrochemical performance in neutral aqueous electrolyte (1 M Na2SO4) in comparison to LaMnO3 and SrMnO3 nanoparticles. This neutral electrolyte provides relatively higher ionic conductivity and viscosity compared to the ionic liquids and a wider potential window compared to the alkaline electrolytes. Electrochemical study of the electrodes prepared using La0.7Sr0.3MnO3 nanoparticles reveals pseudocapacitive behaviors with fast reversible Faradaic charge storage, which plays a key role in charge storage. The composite materials exhibit highest specific capacitance of 393.5 F g−1 at a scan rate of 2 mV s−1. Asymmetric supercapacitors fabricated using La0.7Sr0.3MnO3 nanoparticle and activated carbon operates over a wide potential window of 1.8 V, and it reveals high specific capacitance (197 F g−1) as well as high capacitive retention (87%) even after 4000 charge–discharge cycles. [ABSTRACT FROM AUTHOR]

Summary: Nanorods‐like structured ternary metal sulfides of Ni1‐xCuxS with various compositions (x = 0.1, 0.2 and 0.3), and binary sulfides of NiS and Cu9S5 were synthesised via a single‐step hydrothermal process. The structural properties and the functional groups of the synthesized materials were characterized by X‐ray diffraction (XRD) and Fourier transform infrared (FTIR) studies. Surface structure and chemical composition of the samples were inspected using field emission scanning electron microscopy (FE‐SEM) and energy dispersive X‐ray spectroscopy (EDAX). The electrochemical properties of the as‐synthesised metal sulfide based electrodes were investigated by cyclic voltammetry (CV) and galvanostatic charge‐discharge (GCD) analyses and the maximum specific capacitance (SC) of ~1092 F/g was achieved for the Ni0.8Cu0.2S at a current density of 15 mA/g, while pure NiS and Cu9S5 electrodes showed the minimum SC of ~575 and ~70 F/g, respectively. Further, the electrochemical impedance studies (EIS) revealed low Rct value (3.4 Ω) for the Ni0.8Cu0.2S electrode and improved electrochemical supercapacitor properties of Ni0.8Cu0.2S electrode because of to the synergistic effect and its well crystalline nanorods structure which offers more electrochemical active sites for faradaic reactions and fast electrolyte ions diffusion in to electrode. Additionally, the stability performance of the Ni0.8Cu0.2S electrode was performed at a fixed current density of 20 mA/g, and the Ni0.8Cu0.2S sample possesses the good cycling stability with the retention of 80% capacitance after 3000 GCD cycles. These results demonstrate that the as‐synthesised binary and ternary metal sulfides are suitable cost effective and pollution free electrode materials for supercapacitors. [ABSTRACT FROM AUTHOR]

Summary: To recover Pr from molten chlorides, the electrode reactions of Pr3+ on Sn‐coated W and liquid Sn electrodes were studied by a group of electrochemical techniques. CV and SWV results exhibited that the electrochemical signals pertaining to the formation of Pr‐Sn alloy compounds and solid solution appeared at less negative potentials than that of Pr3+ on W electrode. The thermodynamic data of Pr‐Sn alloy compounds and the kinetic parameters for PrSn3/Pr3+ pair were determined employing OCP, LP, and Tafel methods, separately. The measured diffusion coefficient (D) of Pr in liquid Sn metal was 9.40 × 10−6 cm2 s−1. Furthermore, the electrochemical recovering Pr from molten salt was performed using liquid Sn as a working electrode, and the formed Pr‐Sn samples characterized by XRD and SEM‐EDS were composed of Sn and PrSn3 phases. [ABSTRACT FROM AUTHOR]

Summary: Rechargeable sodium‐ion batteries are facing the challenge of highly electrochemical active anode for their realization. In this study, we report a dual coating strategy of CoS2 with metallic Co particles and carbon to boost the charge transfer and stability. The phase of CoS2 and the existence of Co metallic particles were confirmed using x‐ray diffraction (XRD). x‐ray photoelectron spectroscopy (XPS) results corroborate the presence of carbon and CoS bonding. The prepared CoS2@Co@C anode reveals high performance where it shows a capacity of 712 mA h g−1 at 0.05 C rate. The CoS2@Co@C electrode exhibits exceptional high rate capability where it exhibits a capacity of 260 mA h g−1 at elevated rate of 10.0 C. The cyclability of CoS2@Co@C anode is tested at 0.05 C and 0.5 C rates where the electrode shows 78% and 45% capacity retention of stabilized capacity. The reaction mechanism of the CoS2@Co@C electrode is determined using x‐ray absorption spectroscopy (XAS) and the results show reversibility of the material. [ABSTRACT FROM AUTHOR]

Summary: In order to prohibit the shuttle influence of lithium polysulfides in lithium sulfur battery, a kind of graphene oxide (GO) coated γ‐MnS@KB‐S (GO@MKB‐S) composite cathode material was successfully fabricated. First of all, the γ‐MnS@KB (MKB) composite powders were prepared via a solvothermal reaction, then a spray drying method was used to obtain GO@MKB‐S composites, which displays core/shell nanostructure. SEM, TEM, XRD as well as Raman spectrum are implemented to look into the microstructures and the functions of the 2D nanosheet‐like γ‐MnS in setting in KB on the battery performance were carefully analyzed. It is demonstrated that electrochemical discharge capacity and rate performance are clearly improved by using GO@MKB‐S composites compared to the cathode electrode of the GO coated KB‐S (GO@KB‐S). With a sulfur loading of 5 mg cm−2, the cathode electrode of GO@MKB‐S shows a considerable discharge capacity of 749.9 mAh g−1 at 0.36 C. Additionally, the Li‐S battery cycle retention of GO@MKB‐S sample maintains 97.36% after 100 cycles and 78.69% after 200 cycles. [ABSTRACT FROM AUTHOR]

Summary: The heterostructural construction of metal disulfide/oxide is essential in the electrochemical performance as anode material for lithium‐ and sodium‐ion batteries (LIBs and SIBs). In this work, an integrated composite of molybdenum disulfide (MoS2) and hexagonal molybdenum dioxide (MoO2) together enwrapped in reduced graphene oxide (rGO) is synthesized under hydrothermal condition. In the pelletizing MoS2‐MoO2/rGO composite, rGO as substrate effectively prevents the restacking and pulverization of MoS2‐MoO2 during a long cycling process. Meanwhile, the synergistic effect among the MoS2, MoO2, and rGO components are responsible for abundant active sites and shorten ionic transport channels. When evaluating as anode material for LIB, MoS2‐MoO2/rGO sample presents excellent cyclic performance and still delivers a high capacity of 1062.3 mA h g−1 after 120 cycles at 0.2 A g−1; evaluating in a SIB at 0.04 A g−1, it presents excellent cyclic performance and delivers 430 mA h g−1 at the 80th cycle. The heterostructural composite MoS2‐MoO2/rGO is one of the candidate anode materials for high‐performance LIB and SIB. [ABSTRACT FROM AUTHOR]

Summary: A carbonized cotton that is coated by pyrocarbon of Polyvinylidene Fluoride (PVDF) (HC/P) was synthesized by a facile method. Its microstructure and electrochemical performances as anode for Li‐ion batteries were characterized by X‐Ray Diffraction (XRD), Raman, X‐ray photoelectron spectrometer (XPS), Scanning Electron Microscope (SEM), and other means. It is found that coating process does not affect the phase structure but influences the morphology, specific area, and electrochemical performances. HC/P series have abundant pores with diameter of 2 to 5 nm and small‐size particles; thus, they have much more lithium storage position or charge/discharge capacity than pristine hard carbon (HC). Besides, Cyclic Voltammetry (CV) curves of HC/P‐2 proved that the irreversible side reactions of Li+ with surface functional groups were reduced, which can explain the advancement of initial coulomb efficiency. Among three HC/P samples, HC/P‐2 owns the best electrochemical performances. It delivered 520 mAh/g under current density of 20 mA/g and kept 95.9% retention rates of capacity after 100 cycles under 200 mA/g of current density. [ABSTRACT FROM AUTHOR]

In this study, a two-step process involving a sol-gel and microwave-assisted hydrothermal (MH) techniques has been used to synthesize a novel TiO2 structure, namely, TiO2 mesoporous beads. Various hydrothermal synthesis parameters were investigated to study their effects on the resulting beads. It was found that within the processing conditions used, the TiO2 beads have similar sizes (~325 nm) and contain uniform-sized anatase TiO2 nanoparticles (<10 nm), which are single crystals. Crystalline TiO2 beads are obtained in as short as 15 min at a low temperature of only 140 °C without any post-process calcination. Less surface oxygen vacancies was obtained at a higher MH temperature. Compare to the commercial P-25 TiO2 powders and conventional hydrothermal synthesized TiO2 beads, MH synthesized TiO2 beads exhibit much higher values of specific surface areas, pore volumes, and porosities. The use of TiO2 beads as photocatalyst and photoelectrode for dye-sensitized solar cells has also been investigated. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Thermal instability and poor electrochemical activity of copper-ceria-YSZ anodes at the solid oxide fuel cells (SOFCs) operation temperature (>700 °C) necessitates the use of new strategy to improve the performance of respective anodes for direct hydrocarbon SOFCs. In the present study, iron is incorporated into copper-ceria-YSZ anodes in order to investigate the structural, morphological, and electrochemical properties by using various techniques such as X-ray diffraction, elemental mapping, current-voltage testing, and electrochemical impedance spectroscopy. X-ray diffraction shows that copper promotes the reduction of iron oxide, and formation of cubic phase of copper-iron metals is observed after reduction in H2 at 800 °C. Elemental mapping shows better distribution of metal catalyst inside the pores of copper-ceria-YSZ anodes at 800 °C in the presence of iron. The maximum power densities of copper-ceria-YSZ anodes and copper-iron-ceria-YSZ anodes are observed to be 140 and 195 mW cm−2 in H2 fuel and 70 and 90 mW cm−2 in CH4 fuel at 800 °C. The maximum power density increases with the increase in Cu-Fe metal loading, temperature and with the addition of 1-wt% Pd in copper-iron-ceria-YSZ anodes. The decrease in performance from 125 to 100 mW cm−2 is observed during the exposure of CH4 fuel for 46 h. Electrochemical impedance spectra show an increase in ohmic and total resistance of cell because of sintering and carbon formation, which affects the catalytic activity of anode lowering the performance of SOFC as suggested by post SEM analysis. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Copper (Cu)-catalyzed carbon nanofibers (CNFs) were used as an alternative of the conventional platinum-noble-metal-based catalyst at the counter electrode (CE) of a dye-sensitized solar cell (DSSC). The CNFs were grown on activated carbon microfiber powder (PACF) using chemical vapor deposition (CVD) and the Cu nanoparticles (NPs). The Cu NPs served simultaneous roles: (i) as the CVD catalyst for the growth of the CNFs; (ii) as an enhancer of the electrode conductivity; and (iii) as a catalyst for the reduction reaction. The Cu-CNF composite was applied as a thin layer on the fluorine-doped tin oxide glass using the simple doctor blade method. The prepared Cu-NP-dispersed PACF/CNF composite was characterized using various spectroscopic techniques, including scanning electron microscopy, Fourier transform infrared ray, X-ray diffraction, Raman spectroscopy, and transmission electron microscopy. The electrochemical tests showed that the Cu-PACF/CNFs had a high electrocatalytic activity and low charge transfer resistance (1.26 Ω cm2), using the cyclic voltammetry and electrochemical impedance spectroscopy measurements. The DSSC fabricated with Cu-PACFs/CNFs exhibited a power conversion efficiency value of 4.36%, open circuit voltage of 0.75 V, short circuit current density of 11.12 mA cm−2, and fill factor of 54%. The prepared transition metal-CNF composite was simple to develop and can potentially be used as an efficient catalyst at the CE of DSSCs. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Platinum (Pt) is the most commonly used catalyst in fuel cell systems because of its high efficiency. However, pure Pt is poisoned by carbon monoxide, which is an intermediate reaction product in fuel cell systems. Although PtRu alloys are considered to be promising anodic catalysts for commercial direct methanol fuel cells (DMFC), they are limited by slow reaction kinetics, which reduces the performance of the fuel cells and increases cost. Thus, the main objective of this study is to investigate the addition of potential metals to PtRu, specifically, nickel, Ni, and iron, Fe, to improve the reaction kinetics. This study analyzes the nano-catalyst structures using Materials Studio DMol3. The adsorption energy, free energy, vibrational frequencies and total electronic charge density were also calculated as a function of ground-state properties using the density functional theory (DFT). The simulation results indicate that PtRuNiFe has the potential to improve the performance of the catalyst due to the lower calculated adsorption energies and the presence of Fe2+ and Ni2+ ions, which increases the electron density. Finally, this study concludes that PtRuFeNi/multi-walled carbon nanotube (MWCNT) shows a comparable performance to PtRu. However, it is observed that PtRuFeNi/MWCNT is more stable and has a higher reaction rate than PtRu. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

SUMMARY A four-cell direct methanol fuel cell (DMFC) stack with an air-breathing cathode with an active area of 0.48 cm2 for each cell is designed, fabricated and tested. A pure copper sheet 300 µm thick with innovative perforated flow plates (dendrite type) is fabricated and used for the cathode. For the anode, conventional serpentine flow channels made of pure copper sheets 250 µm thick are used. An extensive parametric study is conducted to determine the optimum working conditions for the fuel flow rate (anode), methanol solution concentration, channel-to-land ratio and stack temperature. Comparisons are made with conventional serpentine flow channels. In addition, CO2 (water) bubbles in the anode (cathode) channels are visualized, and the results are presented and discussed. It is found that the maximum stack power of the four-cell μDMFC stack is up to 40 mW/cm2 with a limiting current density of 335 mA/cm2 at a maximum volumetric and gravimetric power density of 11.16 mW/cm3 and 3.13 W/kg, respectively. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]